Science.gov

Sample records for absorption spectral measurements

  1. Plasma absorption evidence via chirped pulse spectral transmission measurements

    SciTech Connect

    Jedrkiewicz, Ottavia; Minardi, Stefano; Couairon, Arnaud; Jukna, Vytautas; Selva, Marco; Di Trapani, Paolo

    2015-06-08

    This work aims at highlighting the plasma generation dynamics and absorption when a Bessel beam propagates in glass. We developed a simple diagnostics allowing us to retrieve clear indications of the formation of the plasma in the material, thanks to transmission measurements in the angular and wavelength domains. This technique featured by the use of a single chirped pulse having the role of pump and probe simultaneously leads to results showing the plasma nonlinear absorption effect on the trailing part of the pulse, thanks to the spectral-temporal correspondence in the measured signal, which is also confirmed by numerical simulations.

  2. Spectral absorption and backscatter measurements of suspended particles

    SciTech Connect

    Wouts, R.; Warnock, R.; Baker, S.; Kromkamp, J.

    1997-06-01

    Three different methods for determining light attenuation by suspended particles under laboratory conditions are compared. One method, a direct application of Gershun`s equation, by measuring scalar irradiance and the gradient of the net-vector irradiance, allows one to determine the spectral absorption by the particles. Another method, measuring radiance attenuation in an isotropic light field, measures the sum of absorption and backscatter by the particles. The difference gives an estimate for the backscatter. The results were compared with an estimate based on an adaptation of the filterpad method that measures absorption by particles. We found that the filterpad measurements depend heavily on the filter load and the scattering characteristics of the particles involved. Increasing backscatter makes the measurements less reliable. It is argued that the filterpad method should not be used to obtain sea truth data for remote sensing measurements in coastal areas. These measurements were performed in a laboratory scale enclosure (volume 250 liters) on samples of natural silt and/or algal cultures grown in the tank. In our laboratory setup we have put special emphasis on measuring inherent optical properties of natural ({open_quotes}Wester Scheldt{close_quotes} estuary, The Netherlands) silt. Together with available (non-spectral) measurements of the volume scattering function of silt, this information can be used to test models for radiative transfer.

  3. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption in Xianghe, SE of Beijing, China

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2005-12-01

    China's rapid industrialization over the last few decades has affected air quality in many regions of China, and even the regional climate. As a part of the EAST-AIRE (East Asian Study of Tropospheric Aerosols: an International Regional Experiment) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals since January 2005 at Xianghe, about 70 km southeast of Beijing. Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations during the winter months (January-March) ranged from 9 to 459 μg/m3 in the coarse mode with an average concentration of 122 μg/m3, and from 11 to 203 μg/m3 in the fine mode with an average concentration of 45 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Absorption efficiency measurements at 550 nm show very high values compared to measurements performed in the United States during the CLAMS experiment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in refractive indices from the several collected species and particle size effects. The absorption properties from aerosols measured in China show large absorption efficiencies, compared to aerosols measured in the US, possibly linked to different technology practices used in these countries. For organic plus black carbon aerosols, where the refractive index seems to be relatively constant, the absorption efficiency spectral dependence for fine mode aerosols falls between 1/λ and 1/λ2. The coarse mode absorption shows much less spectral dependence.

  4. Effect of differential spectral reflectance on DIAL measurements using topographic targets. [Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Grant, W. B.

    1982-01-01

    Differential absorption lidar (DIAL) measurements of atmospheric gases and temperature made using topographic targets to provide the backscattered signal are subject to errors from the differential spectral reflectance of the target materials. The magnitude of this effect is estimated for a number of DIAL measurements reported in the literature. Calculations are presented for several topographic targets. In general the effect on a DIAL measurement increases directly with increasing wavelength and laser line separation, and inversely with differential absorption coefficient and distance to the target. The effect can be minimized by using tunable or isotope lasers to reduce the laser line separation or by using additional reference wavelengths to determine the surface differential spectral reflectance.

  5. Retrieval of absorptive gas columnar amounts using atmospheric hyper-spectral irradiance measurements within visible spectrum

    NASA Astrophysics Data System (ADS)

    Xu, Hua; Li, Zhengqiang; Li, Donghui; Xie, Yisong; Li, Kaitao; Qie, Lili; Zhang, Ying; Chen, Xingfeng; Zheng, Xiaobin; Li, Xin; Zhang, Yanna

    2015-10-01

    A hyper spectral ground-based instrument named Atmosphere-Surface Radiation Automatic Instrument (ASRAI) has been developed for the purpose of in-situ calibration of satellites. The apparatus has both upward and downward looking views, and thus can observe both the atmosphere and land surface. The solar transmitted irradiance can be derived from the measured full spectral irradiance and diffused spectral irradiance of atmosphere within visible spectrum (0.4-1.0μm). A method similar to that of King et al. which originally intended to apply to multi-wavelength measurements, is adopted to determine absorptive gaseous columnar amount from hyper spectrum. The solar irradiance at top of atmosphere and absorption coefficients of water vapor (H2O), ozone (O3), oxygen (O2) and nitrogen dioxide (NO2) are recalculated at an instrumental spectral resolution by convolution method. Based on the gaseous characteristics of absorption, the total columnar amounts of water vapor and oxygen are first inferred from solar transmitted irradiance at strong absorption wavelength of 0.934μm and 0.763μm respectively. The total columnar amounts of ozone and nitrogen dioxide, together with aerosol optical depth, are determined by a nonlinear least distance fitting method which minimizes a χ2 statistic to obtain optimal solutions. ASRAI was deployed for observation in Dunhuang site in China in August of 2014. Our results demonstrate that the algorithm is reasonable. Although the validation is preliminary, the hyper spectrum measured by ASRAI exhibits good ability to retrieve the abundance of absorptive gases and aerosols.

  6. Measuring high spectral resolution specific absorption coefficients for use with hyperspectral imagery

    SciTech Connect

    Keller, M.; Bostater, C.

    1997-06-01

    A portable, long path length (50 cm), flow through, absorption tube system is utilized to obtain in-situ specific absorption coefficients from various water environments consisting of both clear and turbid water conditions from an underway ship or vessel. The high spectral resolution absorption signatures can be obtained and correlated with measured water quality parameters along a ship track. The long path cuvette system is capable of measuring important water quality parameters such as chlorophyll-a, seston or total suspended matter, tannins, humics, fulvic acids, or dissolved organic matter (dissolved organic carbon, DOC). The various concentrations of these substances can be determined and correlated with laboratory measurements using the double inflection ratio (DIR) of the spectra based upon derivative spectroscopy. The DIR is determined for all of the possible combinations of the bands ranging from 362-1115 nm using 252 channels, as described previously by Bostater. The information gathered from this system can be utilized in conjunction with hyperspectral imagery that allows one to relate reflectance and absorption to water quality of a particular environment. A comparison is made between absorption signatures and reflectance obtained from the Banana River, Florida.

  7. Collisional Induced Absorption (CIA) bands measured in the IR spectral range .

    NASA Astrophysics Data System (ADS)

    Stefani, S.; Piccioni, G.; Snels, M.; Adriani, A.; Grassi, D.

    In this work we present two experimental setup able to characterize the optical properties of gases, in particular CO_2 and H_2, at typically planetary conditions. The apparatus consists of a Fourier Transform InfraRed (FT-IT) interferometer able to work in a wide spectral range, from 350 to 25000 cm-1 (0.4 to 29 mu m ) with a relatively high spectral resolution, from 10 to 0.07 cm-1. Two dedicated gas cells have been integrated with the FT-IR. The first, called High Pressure High Temperature (HP-HT), can support pressures up to 300 bar, temperatures up to 300oC and is characterized by an optical path of 2 cm. The second one, a Multi Pass (MP) absorption gas cell, is designed to have a variable optical path, from 2.5 to 30 m, can be heated up to 200o and operate at pressures up to 10 bar. In this paper, measurements of Collision-Induced Absorption (CIA) bands in carbon dioxide and hydrogen recorded in the InfraRed spectral range will be presented. In principle, linear symmetric molecules such as CO_2 and H_2 possess no dipole moment, but, even when the pressure is only a few bar, we have observed the Collisional Induced Absorption (CIA) bands. This absorption results from a short-time collisional interaction between molecules. The band integrated intensity shows a quadratic dependence versus density opposed to the absorption by isolated molecules, which follows Beer's law \\citep{Beer's}. This behaviour suggests an absorption by pairs rather than by individual molecules. The bands integrated intensities show a linear dependence vs square density according to \\citep {CIA Shape} and \\citep{CIA posi}. For what concerns the H_2 CIA bands, a preliminary comparison between simulated data obtained with the model described in \\citep{CIA H2}and measured, shows a good agreement. These processes are very relevant in the dense atmospheres of planets, such as those of Venus and Jupiter and also in extrasolar planets. A detailed knowledge of these contributions is very

  8. Spectral fluorescence signature techniques and absorption measurements for continuous monitoring of biofuel-producing microalgae cultures

    NASA Astrophysics Data System (ADS)

    Martín de la Cruz, M. C.; Gonzalez Vilas, L.; Yarovenko, N.; Spyrakos, E.; Torres Palenzuela, J. M.

    2013-08-01

    Biofuel production from microalgae can be both sustainable and economically viable. Particularly in the case of algal growth in wastewater an extra benefit is the removal or biotransformation of pollutants from these types of waters. A continuous monitoring system of the microalgae status and the concentration of different wastewater contaminants could be of great help in the biomass production and the water characterisation. In this study we present a system where spectral fluorescence signature (SFS) techniques are used along with absorption measurements to monitor microalgae cultures in wastewater and other mediums. This system aims to optimise the microalgae production for biofuel applications or other uses and was developed and tested in prototype indoor photo-bioreactors at the University of Vigo. SFS techniques were applied using the fluorescence analyser INSTAND-SCREENER developed by Laser Diagnostic Instruments AS. INSTAND-SCREENER permits wavelength scanning in two modes, one in UV and another in VIS. In parallel, it permits the on-line monitoring and rapid analysis of both water quality and phytoplankton status without prior treatment of the sample. Considering that different contaminants and microalgae features (density, status etc.) have different spectral signatures of fluorescence and absorption properties, it is possible to characterise them developing classification libraries. Several algorithms were used for the classification. The implementation of this system in an outdoor raceway reactor in a Spanish wastewater treatment plant is also discussed. This study was part of the Project EnerBioAlgae (http://www.enerbioalgae.com/), which was funded by the Interreg SUDOE and led by the University of Vigo.

  9. Measurement of the Spectral Absorption of Liquid Water in Melting Snow With an Imaging Spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Dozier, Jeff

    1995-01-01

    Melting of the snowpack is a critical parameter that drives aspects of the hydrology in regions of the Earth where snow accumulates seasonally. New techniques for measurement of snow melt over regional scales offer the potential to improve monitoring and modeling of snow-driven hydrological processes. In this paper we present the results of measuring the spectral absorption of liquid water in a melting snowpack with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS data were acquired over Mammoth Mountain, in east central California on 21 May 1994 at 18:35 UTC. The air temperature at 2926 m on Mammoth Mountain at site A was measured at 15-minute intervals during the day preceding the AVIRIS data acquisition. At this elevation. the air temperature did not drop below freezing the night of the May 20 and had risen to 6 degrees Celsius by the time of the overflight on May 21. These temperature conditions support the presence of melting snow at the surface as the AVIRIS data were acquired.

  10. Measurement of the spectral absorption of liquid water in melting snow with an imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Dozier, Jeff

    1995-01-01

    Melting of the snowpack is a critical parameter that drives aspects of the hydrology in regions of the earth where snow accumulates seasonally. New techniques for measurement of snow melt over regional scales offer the potential to improve monitoring and modeling of snow-driven hydrological processes. We present the results of measuring the spectral absorption of liquid water in a melting snowpack with the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). AVIRIS data were acquired over Mammoth Mountain, in east central California on 21 May 1994 at 18:35 UTC. The air temperature at 2926 m on Mammoth Mountain at site A was measured at 15-minute intervals during the day preceding the AVIRIS data acquisition. At this elevation, the air temperature did not drop below freezing the night of May 20 and had risen to 6 degrees Celsius by the time of the overflight on May 21. These temperature conditions support the presence of melting snow at the surface as the AVIRIS data were acquired.

  11. Quantitative filter technique measurements of spectral light absorption by aquatic particles using a portable integrating cavity absorption meter (QFT-ICAM).

    PubMed

    Röttgers, Rüdiger; Doxaran, David; Dupouy, Cecile

    2016-01-25

    The accurate determination of light absorption coefficients of particles in water, especially in very oligotrophic oceanic areas, is still a challenging task. Concentrating aquatic particles on a glass fiber filter and using the Quantitative Filter Technique (QFT) is a common practice. Its routine application is limited by the necessary use of high performance spectrophotometers, distinct problems induced by the strong scattering of the filters and artifacts induced by freezing and storing samples. Measurements of the sample inside a large integrating sphere reduce scattering effects and direct field measurements avoid artifacts due to sample preservation. A small, portable, Integrating Cavity Absorption Meter setup (QFT-ICAM) is presented, that allows rapid measurements of a sample filter. The measurement technique takes into account artifacts due to chlorophyll-a fluorescence. The QFT-ICAM is shown to be highly comparable to similar measurements in laboratory spectrophotometers, in terms of accuracy, precision, and path length amplification effects. No spectral artifacts were observed when compared to measurement of samples in suspension, whereas freezing and storing of sample filters induced small losses of water-soluble pigments (probably phycoerythrins). Remaining problems in determining the particulate absorption coefficient with the QFT-ICAM are strong sample-to-sample variations of the path length amplification, as well as fluorescence by pigments that is emitted in a different spectral region than that of chlorophyll-a.

  12. Spectral Signature of Column Solar Radiation Absorption During the Atmospheric Radiation Measurement Enhanced Shortwave Experiment (ARESE). Revision

    SciTech Connect

    O'Hirok, William; Gautier, Catherine; Ricchiazzi, Paul

    1999-11-01

    Spectral and broadband shortwave radiative flux data obtained from the Atmospheric Radiation Measurement Enhanced Shortwave Experiment (ARESE) are compared with 3-D radiative transfer computations for the cloud field of October 30, 1995. Because the absorption of broadband solar radiation in the cloudy atmosphere deduced from observations and modeled differ by 135 Wm{sup -2}, we performed a consistency analysis using spectral observations and the model to integrate for wavelengths between the spectral observations. To match spectral measurements, aerosols need a reduction in both single scattering albedo (from 0.938 to 0.82) and asymmetry factor (from 0.67 to 0.61), and cloud droplets require a three-fold increase in co-albedo. Even after modifying the model inputs and microphysics the difference in total broadband absorption is still of the order of 75Wm{sup -2}. Finally, an unexplained absorber centered around 1.06 {micro}m appears in the comparison that is much too large to be explained by dimers.

  13. Broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

    NASA Astrophysics Data System (ADS)

    Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Zarzana, K. J.; Rudich, Y.; Brown, S. S.

    2016-01-01

    Formaldehyde (CH2O) is the most abundant aldehyde in the atmosphere, and it strongly affects photochemistry through its photolysis. We describe simultaneous measurements of CH2O and nitrogen dioxide (NO2) using broadband cavity-enhanced absorption spectroscopy in the ultraviolet spectral region. The light source consists of a continuous-wave diode laser focused into a Xenon bulb to produce a plasma that emits high-intensity, broadband light. The plasma discharge is optically filtered and coupled into a 1 m optical cavity. The reflectivity of the cavity mirrors is 0.99930 ± 0.00003 (1- reflectivity = 700 ppm loss) at 338 nm, as determined from the known Rayleigh scattering of He and zero air. This mirror reflectivity corresponds to an effective path length of 1.43 km within the 1 m cell. We measure the cavity output over the 315-350 nm spectral region using a grating monochromator and charge-coupled device array detector. We use published reference spectra with spectral fitting software to simultaneously retrieve CH2O and NO2 concentrations. Independent measurements of NO2 standard additions by broadband cavity-enhanced absorption spectroscopy and cavity ring-down spectroscopy agree within 2 % (slope for linear fit = 1.02 ± 0.03 with r2 = 0.998). Standard additions of CH2O measured by broadband cavity-enhanced absorption spectroscopy and calculated based on flow dilution are also well correlated, with r2 = 0.9998. During constant mixed additions of NO2 and CH2O, the 30 s measurement precisions (1σ) of the current configuration were 140 and 210 pptv, respectively. The current 1 min detection limit for extinction measurements at 315-350 nm provides sufficient sensitivity for measurement of trace gases in laboratory experiments and ground-based field experiments. Additionally, the instrument provides highly accurate, spectroscopically based trace gas detection that may complement higher precision techniques based on non

  14. High-accuracy measurement of low-water-content in liquid using NIR spectral absorption method

    NASA Astrophysics Data System (ADS)

    Peng, Bao-Jin; Wan, Xu; Jin, Hong-Zhen; Zhao, Yong; Mao, He-Fa

    2005-01-01

    Water content measurement technologies are very important for quality inspection of food, medicine products, chemical products and many other industry fields. In recent years, requests for accurate low-water-content measurement in liquid are more and more exigent, and great interests have been shown from the research and experimental work. With the development and advancement of modern production and control technologies, more accurate water content technology is needed. In this paper, a novel experimental setup based on near-infrared (NIR) spectral technology and fiber-optic sensor (OFS) is presented. It has a good measurement accuracy about -/+ 0.01%, which is better, to our knowledge, than most other methods published until now. It has a high measurement resolution of 0.001% in the measurement range from zero to 0.05% for water-in-alcohol measurement, and the water-in-oil measurement is carried out as well. In addition, the advantages of this method also include pollution-free to the measured liquid, fast measurement and so on.

  15. Precise methane absorption measurements in the 1.64 μm spectral region for the MERLIN mission

    NASA Astrophysics Data System (ADS)

    Delahaye, T.; Maxwell, S. E.; Reed, Z. D.; Lin, H.; Hodges, J. T.; Sung, K.; Devi, V. M.; Warneke, T.; Spietz, P.; Tran, H.

    2016-06-01

    In this article we describe a high-precision laboratory measurement targeting the R(6) manifold of the 2ν3 band of 12CH4. High-fidelity modeling of this absorption spectrum for atmospheric temperature and pressure conditions will be required by the Franco-German, Methane Remote Sensing LIDAR (MERLIN) space mission for retrievals of atmospheric methane. The analysis uses the Hartmann-Tran profile for modeling line shape and also includes line-mixing effects. To this end, six high-resolution and high signal-to-noise ratio absorption spectra of air-broadened methane were recorded using a frequency-stabilized cavity ring-down spectroscopy apparatus. Sample conditions corresponded to room temperature and spanned total sample pressures of 40 hPa-1013 hPa with methane molar fractions between 1 µmol mol-1 and 12 µmol mol-1. All spectroscopic model parameters were simultaneously adjusted in a multispectrum nonlinear least squares fit to the six measured spectra. Comparison of the fitted model to the measured spectra reveals the ability to calculate the room temperature, methane absorption coefficient to better than 0.1% at the online position of the MERLIN mission. This is the first time that such fidelity has been reached in modeling methane absorption in the investigated spectral region, fulfilling the accuracy requirements of the MERLIN mission. We also found excellent agreement when comparing the present results with measurements obtained over different pressure conditions and using other laboratory techniques. Finally, we also evaluated the impact of these new spectral parameters on atmospheric transmissions spectra calculations.

  16. A critical review of measurements of water vapor absorption in the 840 to 1100 cm(-1) spectral region

    NASA Technical Reports Server (NTRS)

    Grant, William B.

    1987-01-01

    A set of eleven measurements of the water vapor continuum absorption in the 840 to 1100 sq cm spectral region is reviewed and compared with spectral models maintained by the Air Force Geophysics Laboratory. The measurements were made in four different ways: spectrometer with a White cell, CO2 laser with a White cell, CO2 laser with a spectrophone, and broadband radiation source over a long atmospheric path. Where possible, the data were selected at a water vapor partial pressure of ten torr buffered to 760 torr with N2 or synthetic air and a temperature of between 296 and 300 K. The intercomparison of the data leads to several observations and conclusions. First, there are four sets of laboratory data taken with nitrogen as the buffer gas which generally agree well mutually and with AFGL's HITRAN code. Second, there is one set of laboratory data that shows that using air as the buffer gas gives a few percent decrease in the water vapor continuum compared with using nitrogen as the buffer gas. Third, the atmospheric long-path measurements for water vapor partial pressure below about 12 torr are roughly grouped within 20 percent of the HITRAN values. Fourth, there are three sets of spectrophone data for water vapor in synthetic air which are significantly higher than any of the other measurements. This discrepancy is attributed to the effects of impurity gases in the cell.

  17. Measurements of mesospheric water vapour, aerosols and temperatures with the Spectral Absorption Line Imager (SALI-AT)

    NASA Astrophysics Data System (ADS)

    Shepherd, M. G.; Mullins, M.; Brown, S.; Sargoytchev, S. I.

    2001-08-01

    Water vapour concentration is one of the most important, yet one of the least known quantities of the mesosphere. Knowledge of water vapour concentration is the key to understanding many mesospheric processes, including the one that is primary focus of our investigation, mesospheric clouds (MC). The processes of formation and occurrence parameters of MC constitute an interesting problem in their own right, but recently evidence has been provided which suggests that they are a critical indicator of atmospheric change. The aim of the SALI-AT experiment is to make simultaneous (although not strictly collocated) measurements of water vapour, aerosols and temperature in the mesosphere and the mesopause region under twilight condition in the presence of mesospheric clouds. The water vapour will be measured in the regime of solar occultation utilizing a water vapour absorption band at 936 nm wavelength employing the SALI (Spectral Absorption Line Imager) instrument concept. A three-channel zenith photometer, AT-3, with wavelengths of 385 nm, 525 nm, and 1040 nm will measure Mie and Rayleigh scattering giving both mesospheric temperature profiles and the particle size distribution. Both instruments are small, low cost and low mass. It is envisioned that the SALI-AT experiment be flown on a small rocket - the Improved Orion/Hotel payload configuration, from the Andoya Rocket range, Norway. Alternatively the instrument can be flown as a "passenger" on larger rocket carrying other experiments. In either case flight costs are relatively low. Some performance simulations are presented showing that the instrument we have designed will be sufficiently sensitive to measure water vapor in concentrations that are expected at the summer mesopause, about 85 km height.

  18. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption at Three Location in and Around Mexico City

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2006-12-01

    As a result of population growth and increasing industrialization, air pollution in heavily populated urban areas is one of the central environmental problems of the century. As a part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals at three location in Mexico during March, 2006. Sampling stations were located at the Instituto Mexicano del Petroleo (T0), at the Rancho La Bisnago in the State of Hidalgo (T2) and along the Gulf Coast in Tampico (Tam). Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations at T0 ranged from 47 to 179 μg/m3 for PM10 with an average concentration of 96 μg/m3, and from 20 to 93 μg/m3 for PM2.5 with an average concentration of 41 μg/m3. Mass concentrations at T2 ranged from 12 to 154 μg/m3 for PM10 with an average concentration of 51 μg/m3, and from 7 to 50 μg/m3 for PM2.5 with an average concentration of 25 μg/m3. Mass concentrations at Tam ranged from 34 to 80 μg/m3 for PM10 with an average concentration of 52 μg/m3, and from 8 to 23 μg/m3 for PM2.5 with an average concentration of 13 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Each of the sampling stations experienced a unique atmospheric condition. The site at T0 was influenced by urban air pollution and dust storms, the site at T2 was significantly less affected by air pollution but more affected by regional dust storms and local dust devils while Tam was influenced by air pollution, dust storms and the natural marine environment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in

  19. Airborne Differential Absorption and High Spectral Resolution Lidar Measurements for Cirrus Cloud Studies

    NASA Astrophysics Data System (ADS)

    Gross, Silke; Schaefler, Andreas; Wirth, Martin; Fix, Andreas

    2016-06-01

    Aerosol and water vapor measurements were performed with the lidar system WALES of the German Aerospace Center (DLR) onboard the German research aircraft G550-HALO during the HALO Techno-Mission in October and November 2010 and during the ML-Cirrus mission in March and April 2014 over Central Europe and the North Atlantic region. Curtains composed of lidar profiles beneath the aircraft show the water vapor mixing ratio and the backscatter ratio. Temperature data from ECMWF model analysis are used to calculate the relative humidity above ice (RHi) in the 2-D field along the flight track to study the RHi distribution inside and outside of cirrus clouds at different stages of cloud evolution.

  20. SPECTRAL RELATIVE ABSORPTION DIFFERENCE METHOD

    SciTech Connect

    Salaymeh, S.

    2010-06-17

    When analyzing field data, the uncertainty in the background continuum emission produces the majority of error in the final gamma-source analysis. The background emission typically dominates an observed spectrum in terms of counts and is highly variable spatially and temporally. The majority of the spectral shape of the background continuum is produced by combinations of cosmic rays, {sup 40}K, {sup 235}U, and {sup 220}Rn, and the continuum is similar in shape to the 15%-20% level for most field observations. However, the goal of spectroscopy analysis is to pick up subtle peaks (<%5) upon this large background. Because the continuum is falling off as energy increases, peak detection algorithms must first define the background surrounding the peak. This definition is difficult when the range of background shapes is considered. The full spectral template matching algorithms are heavily weighted to solving for the background continuum as it produces significant counts over much of the energy range. The most appropriate background mitigation technique is to take a separate background observation without the source of interest. But, it is frequently not possible to record a background observation in the exact location before (or after) a source has been detected. Thus, one uses approximate backgrounds that rely on spatially nearby locations or similar environments. Since the error in many field observations is dominated by the background, a technique that is less sensitive to the background would be quite beneficial. We report the result of an initial investigation into a novel observation scheme for gamma-emission detection in high background environments. Employing low resolution, NaI, detectors, we examine the different between the direct emission and the 'spectral-shadow' that the gamma emission produces when passed through a thin absorber. For this detection scheme to be competitive, it is required to count and analyze individual gamma-events. We describe the

  1. Spectral particle absorption coefficients, single scattering albedos and imaginary parts of refractive indices from ground based in situ measurements at Cape Verde Island during SAMUM-2

    NASA Astrophysics Data System (ADS)

    Müller, T.; Schladitz, A.; Kandler, K.; Wiedensohler, A.

    2011-09-01

    During the SAMUM-2 experiment, spectral absorption coefficients, single scattering albedos and imaginary parts of refractive indices of mineral dust particles were investigated at the Cape Verde Islands. Main absorbing constituents of airborne samples were mineral dust and soot. PM10 spectral absorption coefficients were measured using a Spectral Optical Absorption Photometer (SOAP) covering the wavelength range from 300 to 960 nm with a resolution of 25 nm. From SOAP, also information on the particle scattering coefficients could be retrieved. Spectral single scattering albedos were obtained in the wavelength range from 350 to 960 nm. Imaginary parts of the refractive index were inferred from measured particle number size distributions and absorption coefficients using Mie scattering theory. Imaginary parts for a dust case were 0.012, 0.0047 and 0.0019 at the wavelengths 450, 550 and 950 nm, respectively, and the single scattering albedos were 0.91, 0.96 and 0.98 at the same wavelengths. During a marine case, the imaginary parts of the refractive indices were 0.0045, 0.0040 and 0.0036 and single scattering albedos were 0.93, 0.95 and 0.96 at the wavelengths given above.

  2. Frequency-domain method for measuring spectral properties in multiple-scattering media: methemoglobin absorption spectrum in a tissuelike phantom

    NASA Astrophysics Data System (ADS)

    Fishkin, Joshua B.; So, Peter T. C.; Cerussi, Albert E.; Gratton, Enrico; Fantini, Sergio; Franceschini, Maria Angela

    1995-03-01

    We have measured the optical absorption and scattering coefficient spectra of a multiple-scattering medium (i.e., a biological tissue-simulating phantom comprising a lipid colloid) containing methemoglobin by using frequency-domain techniques. The methemoglobin absorption spectrum determined in the multiple-scattering medium is in excellent agreement with a corrected methemoglobin absorption spectrum obtained from a steady-state spectrophotometer measurement of the optical density of a minimally scattering medium. The determination of the corrected methemoglobin absorption spectrum takes into account the scattering from impurities in the methemoglobin solution containing no lipid colloid. Frequency-domain techniques allow for the separation of the absorbing from the scattering properties of multiple-scattering media, and these techniques thus provide an absolute

  3. Collisional Induced Absorption (CIA) bands of CO2 and H2 measured in the IR spectral range

    NASA Astrophysics Data System (ADS)

    Stefani, S.; Piccioni, G.; Snels, M.; Adriani, A.; Grassi, D.

    2015-10-01

    In this paper we present the results on the Collisional Induced Absorption (CIA) bands of CO2 and H2 measured employing two different experimental setup. Each of them allows us to reproduce typical planetary conditions, at a pressure and temperature from 1 up to 50 bar and from 298 up to 500 K respectively. A detailed study on the temperature dependence of the CO2 CIA absorption bands will be presented.

  4. Wavelength-resolved optical extinction measurements of aerosols using broad-band cavity-enhanced absorption spectroscopy over the spectral range of 445-480 nm.

    PubMed

    Zhao, Weixiong; Dong, Meili; Chen, Weidong; Gu, Xuejun; Hu, Changjin; Gao, Xiaoming; Huang, Wei; Zhang, Weijun

    2013-02-19

    Despite the significant progress in the measurements of aerosol extinction and absorption using spectroscopy approaches such as cavity ring-down spectroscopy (CRDS) and photoacoustic spectroscopy (PAS), the widely used single-wavelength instruments may suffer from the interferences of gases absorption present in the real environment. A second instrument for simultaneous measurement of absorbing gases is required to characterize the effect of light extinction resulted from gases absorption. We present in this paper the development of a blue light-emitting diode (LED)-based incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach for broad-band measurements of wavelength-resolved aerosol extinction over the spectral range of 445-480 nm. This method also allows for simultaneous measurement of trace gases absorption present in the air sample using the same instrument. On the basis of the measured wavelength-dependent aerosol extinction cross section, the real part of the refractive index (RI) can be directly retrieved in a case where the RI does not vary strongly with the wavelength over the relevant spectral region. Laboratory-generated monodispersed aerosols, polystyrene latex spheres (PSL) and ammonium sulfate (AS), were employed for validation of the RI determination by IBBCEAS measurements. On the basis of a Mie scattering model, the real parts of the aerosol RI were retrieved from the measured wavelength-resolved extinction cross sections for both aerosol samples, which are in good agreement with the reported values. The developed IBBCEAS instrument was deployed for simultaneous measurements of aerosol extinction coefficient and NO(2) concentration in ambient air in a suburban site during two representative days. PMID:23320530

  5. Spectral dependence of aerosol light absorption over the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Correia, A. L.; Artaxo, P.; Procópio, A. S.; Andreae, M. O.

    2011-09-01

    In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia) and at a primary forest site (Cuieiras Reserve, Amazonas), from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30) that covers the visible (VIS) to near-infrared (NIR) spectral range, and a 2-wavelength Aethalometer (AE20) that measures absorption in the UV and in the NIR. As a consequence of biomass burning emissions, about 10 times greater absorption values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the absorption Ångström exponent, defined as the negative slope of absorption versus wavelength in a log-log plot. At the pasture site, about 70 % of the absorption Ångström exponents fell between 1.5 and 2.5 during the dry season, indicating that biomass burning aerosols have a stronger spectral dependence than soot carbon particles. Ångström exponents decreased from the dry to the wet season, in agreement with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. The lowest absorption Ångström exponents (90 % of data below 1.5) were observed at the forest site during the dry season. Also, results indicate that low absorption coefficients were associated with low Ångström exponents. This finding suggests that biogenic aerosols from Amazonia have a weaker spectral dependence for absorption than biomass burning aerosols, contradicting our expectations of biogenic particles behaving as brown carbon. In a first order assessment, results indicate a small (<1 %) effect of variations in absorption Ångström exponents on 24-h aerosol forcings, at least in the spectral

  6. Spectral dependence of aerosol light absorption over the Amazon Basin

    NASA Astrophysics Data System (ADS)

    Rizzo, L. V.; Correia, A. L.; Artaxo, P.; Procópio, A. S.; Andreae, M. O.

    2011-04-01

    In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia) and at a primary forest site (Cuieiras Reserve, Amazonas), from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30) that covers the visible (VIS) to near-infrared (NIR) spectral range, and a 2-wavelength Aethalometer (AE20) that measures absorption in the UV and in the visible. As a consequence of biomass burning emissions, about 10 times greater absorption values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the Ångström exponent for absorption, defined as the negative slope of absorption vs. wavelength in a log-log plot. At the pasture site, about 70% of the Ångström exponents fell between 1.5 and 2.5 during the dry season, indicating that biomass burning aerosols have a stronger spectral dependence than soot carbon particles. Ångström exponents decreased from the dry to the wet season, in agreement with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. The lowest Ångström exponents (90% of data below 1.5) were observed at the forest site during the dry season. Also, results indicate that low absorption coefficients were associated with Ångström exponents below 1.0. This finding suggests that biogenic aerosols from Amazonia may have a weak spectral dependence for absorption, contradicting our expectations of biogenic particles behaving as brown carbon. Nevertheless, additional measurements should be taken in the future, to provide a complete picture of biogenic aerosol absorption spectral characteristics from different seasons and geographic locations. The

  7. Correction of pathlength amplification in the filter-pad technique for measurements of particulate absorption coefficient in the visible spectral region.

    PubMed

    Stramski, Dariusz; Reynolds, Rick A; Kaczmarek, Sławomir; Uitz, Julia; Zheng, Guangming

    2015-08-01

    Spectrophotometric measurement of particulate matter retained on filters is the most common and practical method for routine determination of the spectral light absorption coefficient of aquatic particles, ap(λ), at high spectral resolution over a broad spectral range. The use of differing geometrical measurement configurations and large variations in the reported correction for pathlength amplification induced by the particle/filter matrix have hindered adoption of an established measurement protocol. We describe results of dedicated laboratory experiments with a diversity of particulate sample types to examine variation in the pathlength amplification factor for three filter measurement geometries; the filter in the transmittance configuration (T), the filter in the transmittance-reflectance configuration (T-R), and the filter placed inside an integrating sphere (IS). Relationships between optical density measured on suspensions (ODs) and filters (ODf) within the visible portion of the spectrum were evaluated for the formulation of pathlength amplification correction, with power functions providing the best functional representation of the relationship for all three geometries. Whereas the largest uncertainties occur in the T method, the IS method provided the least sample-to-sample variability and the smallest uncertainties in the relationship between ODs and ODf. For six different samples measured with 1 nm resolution within the light wavelength range from 400 to 700 nm, a median error of 7.1% is observed for predicted values of ODs using the IS method. The relationships established for the three filter-pad methods are applicable to historical and ongoing measurements; for future work, the use of the IS method is recommended whenever feasible. PMID:26368092

  8. Photovoltaic spectral responsivity measurements

    SciTech Connect

    Emery, K.; Dunlavy, D.; Field, H.; Moriarty, T.

    1998-09-01

    This paper discusses the various elemental random and nonrandom error sources in typical spectral responsivity measurement systems. The authors focus specifically on the filter and grating monochrometer-based spectral responsivity measurement systems used by the Photovoltaic (PV) performance characterization team at NREL. A variety of subtle measurement errors can occur that arise from a finite photo-current response time, bandwidth of the monochromatic light, waveform of the monochromatic light, and spatial uniformity of the monochromatic and bias lights; the errors depend on the light source, PV technology, and measurement system. The quantum efficiency can be a function of he voltage bias, light bias level, and, for some structures, the spectral content of the bias light or location on the PV device. This paper compares the advantages and problems associated with semiconductor-detector-based calibrations and pyroelectric-detector-based calibrations. Different current-to-voltage conversion and ac photo-current detection strategies employed at NREL are compared and contrasted.

  9. Optical absorption measurement system

    DOEpatents

    Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.

    1989-01-01

    The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

  10. Backscattering measurements of atmospheric aerosols at CO2 laser wavelengths: implications of aerosol spectral structure on differential-absorption lidar retrievals of molecular species.

    PubMed

    Ben-David, A

    1999-04-20

    The volume backscattering coefficients of atmospheric aerosol were measured with a tunable CO2 lidar system at various wavelengths in Utah (a desert environment) along a horizontal path a few meters above the ground. In deducing the aerosol backscattering, a deconvolution (to remove the smearing effect of the long CO2 lidar pulse and the lidar limited bandwidth) and a constrained-slope method were employed. The spectral shape beta(lambda) was similar for all the 13 measurements during a 3-day period. A mean aerosol backscattering-wavelength dependence beta(lambda) was computed from the measurements and used to estimate the error Delta(CL) (concentration-path-length product) in differential-absorption lidar measurements for various gases caused by the systematic aerosol differential backscattering and the error that is due to fluctuations in the aerosol backscattering. The water-vapor concentration-path-length product CL and the average concentration C = /L for a path length L computed from the range-resolved lidar measurements is consistently in good agreement with the water-vapor concentration measured by a meteorological station. However, I was unable to deduce, reliably, the range-resolved water-vapor concentration C(r), which is the derivative of the range-dependent product CL, because of the effect of residual noise caused mainly by errors in the deconvolved lidar measurements.

  11. Molecular absorption in transition region spectral lines

    NASA Astrophysics Data System (ADS)

    Schmit, D. J.; Innes, D.; Ayres, T.; Peter, H.; Curdt, W.; Jaeggli, S.

    2014-09-01

    Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra. Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence. Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary. The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales and introduces a new complexity into our understanding of solar thermal structure. It lends credence to previous numerical studies that found evidence for elevated pockets of cool gas in the chromosphere. Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org

  12. Characterization of Spectral Absorption Properties of Aerosols Using Satellite Observations

    NASA Technical Reports Server (NTRS)

    Torres, O.; Jethva, H.; Bhartia, P. K.; Ahn, C.

    2012-01-01

    The wavelength-dependence of aerosol absorption optical depth (AAOD) is generally represented in terms of the Angstrom Absorption Exponent (AAE), a parameter that describes the dependence of AAOD with wavelength. The AAE parameter is closely related to aerosol composition. Black carbon (BC) containing aerosols yield AAE values near unity whereas Organic carbon (OC) aerosol particles are associated with values larger than 2. Even larger AAE values have been reported for desert dust aerosol particles. Knowledge of spectral AAOD is necessary for the calculation of direct radiative forcing effect of aerosols and for inferring aerosol composition. We have developed a satellitebased method of determining the spectral AAOD of absorbing aerosols. The technique uses high spectral resolution measurements of upwelling radiation from scenes where absorbing aerosols lie above clouds as indicated by the UV Aerosol Index. For those conditions, the satellite measured reflectance (rho lambda) is approximately given by Beer's law rho lambda = rho (sub 0 lambda) e (exp -mtau (sub abs lambda)) where rho(sub 0 lambda) is the cloud reflectance, m is the geometric slant path and tau (sub abs lambda) is the spectral AAOD. The rho (sub 0 lambda) term is determined by means of radiative transfer calculations using as input the cloud optical depth derived as described in Torres et al. [JAS, 2012] that accounts for the effects of aerosol absorption. In the second step, corrections for molecular and aerosol scattering effects are applied to the cloud reflectance term, and the spectral AAOD is then derived by inverting the equation above. The proposed technique will be discussed in detail and application results will be presented. The technique can be easily applied to hyper-spectral satellite measurements that include UV such as OMI, GOME and SCIAMACHY, or to multi-spectral visible measurements by other sensors provided that the aerosol-above-cloud events are easily identified.

  13. A wide spectral range photoacoustic aerosol absorption spectrometer.

    PubMed

    Haisch, C; Menzenbach, P; Bladt, H; Niessner, R

    2012-11-01

    A photoacoustic spectrometer for the measurement of aerosol absorption spectra, based on the excitation of a pulsed nanosecond optical parametrical oscillator (OPO), will be introduced. This spectrometer is working at ambient pressure and can be used to detect and characterize different classes of aerosols. The spectrometer features a spectral range of 410 to 2500 nm and a sensitivity of 2.5 × 10(-7) m(-1) at 550 nm. A full characterization of the system in the visible spectral range is demonstrated, and the potential of the system for near IR measurement is discussed. In the example of different kinds of soot particles, the performance of the spectrometer was assessed. As we demonstrate, it is possible to determine a specific optical absorption per particle by a combination of the new spectrometer with an aerosol particle counter. PMID:23035870

  14. A wide spectral range photoacoustic aerosol absorption spectrometer.

    PubMed

    Haisch, C; Menzenbach, P; Bladt, H; Niessner, R

    2012-11-01

    A photoacoustic spectrometer for the measurement of aerosol absorption spectra, based on the excitation of a pulsed nanosecond optical parametrical oscillator (OPO), will be introduced. This spectrometer is working at ambient pressure and can be used to detect and characterize different classes of aerosols. The spectrometer features a spectral range of 410 to 2500 nm and a sensitivity of 2.5 × 10(-7) m(-1) at 550 nm. A full characterization of the system in the visible spectral range is demonstrated, and the potential of the system for near IR measurement is discussed. In the example of different kinds of soot particles, the performance of the spectrometer was assessed. As we demonstrate, it is possible to determine a specific optical absorption per particle by a combination of the new spectrometer with an aerosol particle counter.

  15. Aerosol Absorption Measurements in MILAGRO.

    NASA Astrophysics Data System (ADS)

    Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

    2007-12-01

    During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due

  16. A High Spectral Resolution Lidar Based on Absorption Filter

    NASA Technical Reports Server (NTRS)

    Piironen, Paivi

    1996-01-01

    A High Spectral Resolution Lidar (HSRL) that uses an iodine absorption filter and a tunable, narrow bandwidth Nd:YAG laser is demonstrated. The iodine absorption filter provides better performance than the Fabry-Perot etalon that it replaces. This study presents an instrument design that can be used a the basis for a design of a simple and robust lidar for the measurement of the optical properties of the atmosphere. The HSRL provides calibrated measurements of the optical properties of the atmospheric aerosols. These observations include measurements of aerosol backscatter cross sections, optical depth, backscatter phase function depolarization, and multiple scattering. The errors in the HSRL data are discussed and the effects of different errors on the measured optical parameters are shown.

  17. Vegetation species composition and canopy architecture information expressed in leaf water absorption measured in the 1000 nm and 2200 spectral region by an imaging spectrometer

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Roberts, Dar A.

    1995-01-01

    Plant species composition and plant architectural attributes are critical parameters required for the measuring, monitoring, and modeling of terrestrial ecosystems. Remote sensing is commonly cited as an important tool for deriving vegetation properties at an appropriate scale for ecosystem studies, ranging from local to regional and even synoptic scales. Classical approaches rely on vegetation indices such as the normalized difference vegetation index (NDVI) to estimate biophysical parameters such as leaf area index or intercepted photosynthetically active radiation (IPAR). Another approach is to apply a variety of classification schemes to map vegetation and thus extrapolate fine-scale information about specific sites to larger areas of similar composition. Imaging spectrometry provides additional information that is not obtainable through broad-band sensors and that may provide improved inputs both to direct biophysical estimates as well as classification schemes. Some of this capability has been demonstrated through improved discrimination of vegetation, estimates of canopy biochemistry, and liquid water estimates from vegetation. We investigate further the potential of leaf water absorption estimated from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data as a means for discriminating vegetation types and deriving canopy architectural information. We expand our analysis to incorporate liquid water estimates from two spectral regions, the 1000-nm region and the 2200-nm region. The study was conducted in the vicinity of Jasper Ridge, California, which is located on the San Francisco peninsula to the west of the Stanford University campus. AVIRIS data were acquired over Jasper Ridge, CA, on June 2, 1992, at 19:31 UTC. Spectra from three sites in this image were analyzed. These data are from an area of healthy grass, oak woodland, and redwood forest, respectively. For these analyses, the AVIRIS-measured upwelling radiance spectra for the entire Jasper

  18. QEPAS detector for rapid spectral measurements

    NASA Astrophysics Data System (ADS)

    Kosterev, A. A.; Buerki, P. R.; Dong, L.; Reed, M.; Day, T.; Tittel, F. K.

    2010-07-01

    A quartz enhanced photoacoustic spectroscopy sensor designed for fast response was used in combination with a pulsed external cavity quantum cascade laser to rapidly acquire gas absorption data over the 1196-1281 cm-1 spectral range. The system was used to measure concentrations of water vapor, pentafluoroethane (freon-125), acetone, and ethanol both individually and in combined mixtures. The precision achieved for freon-125 concentration in a single 1.1 s long spectral scan is 13 ppbv.

  19. CCN Spectral Measurements

    SciTech Connect

    Hudson, James G.

    2009-02-27

    Detailed aircraft measurements were made of cloud condensation nuclei (CCN) spectra associated with extensive cloud systems off the central California coast in the July 2005 MASE project. These measurements include the wide supersaturation (S) range (2-0.01%) that is important for these polluted stratus clouds. Concentrations were usually characteristic of continental/anthropogenic air masses. The most notable feature was the consistently higher concentrations above the clouds than below. CCN measurements are so important because they provide a link between atmospheric chemistry and cloud-climate effects, which are the largest climate uncertainty. Extensive comparisons throughout the eleven flights between two CCN spectrometers operated at different but overlapping S ranges displayed the precision and accuracy of these difficult spectral determinations. There are enough channels of resolution in these instruments to provide differential spectra, which produce more rigorous and precise comparisons than traditional cumulative presentations of CCN concentrations. Differential spectra are also more revealing than cumulative spectra. Only one of the eleven flights exhibited typical maritime concentrations. Average below cloud concentrations over the two hours furthest from the coast for the 8 flights with low polluted stratus was 614?233 at 1% S, 149?60 at 0.1% S and 57?33 at 0.04% S cm-3. Immediately above cloud average concentrations were respectively 74%, 55%, and 18% higher. Concentration variability among those 8 flights was a factor of two. Variability within each flight excluding distances close to the coast ranged from 15-56% at 1% S. However, CN and probably CCN concentrations sometimes varied by less than 1% over distances of more than a km. Volatility and size-critical S measurements indicated that the air masses were very polluted throughout MASE. The aerosol above the clouds was more polluted than the below cloud aerosol. These high CCN concentrations from

  20. [Spectral calibration for space-borne differential optical absorption spectrometer].

    PubMed

    Zhou, Hai-Jin; Liu, Wen-Qing; Si, Fu-Qi; Zhao, Min-Jie; Jiang, Yu; Xue, Hui

    2012-11-01

    Space-borne differential optical absorption spectrometer is used for remote sensing of atmospheric trace gas global distribution. This instrument acquires high accuracy UV/Vis radiation scattered or reflected by air or earth surface, and can monitor distribution and variation of trace gases based on differential optical absorption spectrum algorithm. Spectral calibration is the premise and base of quantification of remote sensing data of the instrument, and the precision of calibration directly decides the level of development and application of the instrument. Considering the characteristic of large field, wide wavelength range, high spatial and spectral resolution of the space-borne differential optical absorption spectrometer, a spectral calibration method is presented, a calibration device was built, the equation of spectral calibration was calculated through peak searching and regression analysis, and finally the full field spectral calibration of the instrument was realized. The precision of spectral calibration was verified with Fraunhofer lines of solar light.

  1. [Decomposing total suspended particle absorption based on the spectral correlation relationship].

    PubMed

    Wang, Gui-Fen; Cao, Wen-Xi; Yang, Ding-Tian; Zhao, Jun

    2009-01-01

    A model for estimating the contributions of phytoplankton and nonalgal particles to the total particulate absorption coefficient was developed based on their separate spectral relationships, and a constrained nonlinear optimization code was used to realize the spectral decomposition. The spectral absorption of total particulate matter including phytoplankton and nonalgal particles was measured using the filter-pad method during two cruises in autumn in Northern South China Sea. Using the dataset collected in 2004, the spectral relationships of particle absorption coefficients were examined and the results showed that the phytoplankton absorption coefficients at various wavebands could be well expressed by aph (443) as the second-order quadratic equations; and the nonalgal particle absorption (aNAP(lambda)) could be successfully modeled with the simple exponential function. Based on these spectral relationships, we developed this partition model. The model was tested using the independently measured absorption by phytoplankton and nonalgal materials which were obtained in 2005 from the same area. The test results showed that the computed spectral absorption coefficients of phytoplankton and nonalgal particles were consistent with in situ measurement. Good correlations were fo und between the comput ed phytoplankton absorption coefficient and the measured value,with the determination coefficients (r2) being higher than 0.97 and slopes being around 1.0; and the RMSE values could be controlled within 17% over the main absorption wavebands such as 443, 490 and 683 nm. Compared with the other two existing models from Bricaud et al. and Oubelkheir et al., this method shows many advantages for local applications. Moreover, this model does not need any information about pigment concentrations and the selected spectral bands are consistent with the ocean color satellite sensor. This method could also be used in the total absorption coefficient decomposition which provides

  2. Determination of the in-flight spectral calibration of AVIRIS using atmospheric absorption features

    NASA Technical Reports Server (NTRS)

    Green, Robert O.

    1995-01-01

    Spectral calibration of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) as data are acquired in flight is essential to quantitative analysis of the measured upwelling spectral radiance. In each spectrum measured by AVIRIS in flight, there are numerous atmospheric gas absorption bands that drive this requirement for accurate spectral calibration. If the surface and atmospheric properties are measured independently, these atmospheric absorption bands may be used to deduce the in-flight spectral calibration of an imaging spectrometer. Both the surface and atmospheric characteristics were measured for a calibration target during an in-flight calibration experiment held at Lunar Lake, Nevada on April 5, 1994. This paper uses upwelling spectral radiance predicted for the calibration target with the MODTRAN radiative transfer code to validate the spectral calibration of AVIRIS in flight.

  3. Spectral properties of molecular iodine in absorption cells filled to specified saturation pressure.

    PubMed

    Hrabina, Jan; Šarbort, Martin; Acef, Ouali; Burck, Frédéric Du; Chiodo, Nicola; Holá, Miroslava; Číp, Ondřej; Lazar, Josef

    2014-11-01

    We present the results of measurement and evaluation of spectral properties of iodine absorption cells filled at certain saturation pressure. A set of cells made of borosilicate glass instead of common fused silica was tested for their spectral properties in greater detail with special care for the long-term development of the absorption media purity. The results were compared with standard fused silica cells and the high quality of iodine was verified. A measurement method based on an approach relying on measurement of linewidth of the hyperfine transitions is proposed as a novel technique for iodine cell absorption media purity evaluation. A potential application in laser metrology of length is also discussed.

  4. Light absorption measurements: new techniques.

    PubMed

    Hänel, G; Busen, R; Hillenbrand, C; Schloss, R

    1982-02-01

    A new radiometer is described which simplifies measurement of the radiation supply of solar wavelengths. Two methods of measuring the radiant energy absorbed by aerosol particles are described: A photometric technique is used for particles collected on filters, and a calorimetric technique is used for in situ measurements. Data collected with the radiometer and the light absorption techniques yield the heating rate of the atmosphere due to light absorption by the particles. Sample measurements show substantial atmospheric temperature increases due to absorption, especially in industrial regions.

  5. The Zugspitze radiative closure experiment for quantifying water vapor absorption over the terrestrial and solar infrared - Part 2: Accurate calibration of high spectral-resolution infrared measurements of surface solar radiation

    NASA Astrophysics Data System (ADS)

    Reichert, Andreas; Rettinger, Markus; Sussmann, Ralf

    2016-09-01

    Quantitative knowledge of water vapor absorption is crucial for accurate climate simulations. An open science question in this context concerns the strength of the water vapor continuum in the near infrared (NIR) at atmospheric temperatures, which is still to be quantified by measurements. This issue can be addressed with radiative closure experiments using solar absorption spectra. However, the spectra used for water vapor continuum quantification have to be radiometrically calibrated. We present for the first time a method that yields sufficient calibration accuracy for NIR water vapor continuum quantification in an atmospheric closure experiment. Our method combines the Langley method with spectral radiance measurements of a high-temperature blackbody calibration source (< 2000 K). The calibration scheme is demonstrated in the spectral range 2500 to 7800 cm-1, but minor modifications to the method enable calibration also throughout the remainder of the NIR spectral range. The resulting uncertainty (2σ) excluding the contribution due to inaccuracies in the extra-atmospheric solar spectrum (ESS) is below 1 % in window regions and up to 1.7 % within absorption bands. The overall radiometric accuracy of the calibration depends on the ESS uncertainty, on which at present no firm consensus has been reached in the NIR. However, as is shown in the companion publication Reichert and Sussmann (2016), ESS uncertainty is only of minor importance for the specific aim of this study, i.e., the quantification of the water vapor continuum in a closure experiment. The calibration uncertainty estimate is substantiated by the investigation of calibration self-consistency, which yields compatible results within the estimated errors for 91.1 % of the 2500 to 7800 cm-1 range. Additionally, a comparison of a set of calibrated spectra to radiative transfer model calculations yields consistent results within the estimated errors for 97.7 % of the spectral range.

  6. Multi-decade Measurements of the Long-Term Trends of Atmospheric Species by High-Spectral-Resolution Infrared Solar Absorption Spectroscopy

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Chiou, Linda; Goldman, Aaron; Hannigan, James W.

    2010-01-01

    Solar absorption spectra were recorded for the first time in 5 years with the McMath Fourier transform spectrometer at the US National solar Observatory on Kitt Peak in southern Arizona, USA (31.91 N latitude, 111.61 W longitude, 2.09 km altitude). The solar absorption spectra cover 750-1300 and 1850-5000 cm(sup -1) and were recorded on 20 days during March-June 2009. The measurements mark the continuation of a long-term record of atmospheric chemical composition measurements that have been used to quantify seasonal cycles and long-term trends of both tropospheric and stratospheric species from observations that began i 1977. Fits to the measured spectra have been performed, and they indicate the spectra obtained since return to operational status are nearly free of channeling and the instrument line shape function is well reproduced taking into account the measurement parameters. We report updated time series measurements of total columns for six atmospheric species and their analysis for seasonal cycles and long-term trends. An sn example, the time series fit shows a decrease in the annual increase rate i Montreal-Protocol-regulated chlorofluorocarbon CCL2F2 from 1.51 plus or minus 0.38% yr(sup -1) at the beginning of the time span to -1.54 plus or minus 1.28 yr(sup -1) at the end of the time span, 1 sigma, and hence provides evidence for the impact of those regulations on the trend.

  7. Cirrus cloud optical and microphysical property retrievals from eMAS during SEAC4RS using bi-spectral reflectance measurements within the 1.88 µm water vapor absorption band

    NASA Astrophysics Data System (ADS)

    Meyer, Kerry; Platnick, Steven; Arnold, G. Thomas; Holz, Robert E.; Veglio, Paolo; Yorks, John; Wang, Chenxi

    2016-04-01

    Previous bi-spectral imager retrievals of cloud optical thickness (COT) and effective particle radius (CER) based on the Nakajima and King (1990) approach, such as those of the operational MODIS cloud optical property retrieval product (MOD06), have typically paired a non-absorbing visible or near-infrared wavelength, sensitive to COT, with an absorbing shortwave or mid-wave infrared wavelength sensitive to CER. However, in practice it is only necessary to select two spectral channels that exhibit a strong contrast in cloud particle absorption. Here it is shown, using eMAS observations obtained during NASA's SEAC4RS field campaign, that selecting two absorbing wavelength channels within the broader 1.88 µm water vapor absorption band, namely the 1.83 and 1.93 µm channels that have sufficient differences in ice crystal single scattering albedo, can yield COT and CER retrievals for thin to moderately thick single-layer cirrus that are reasonably consistent with other solar and IR imager-based and lidar-based retrievals. A distinct advantage of this channel selection for cirrus cloud retrievals is that the below-cloud water vapor absorption minimizes the surface contribution to measured cloudy top-of-atmosphere reflectance, in particular compared to the solar window channels used in heritage retrievals such as MOD06. This reduces retrieval uncertainty resulting from errors in the surface reflectance assumption and reduces the frequency of retrieval failures for thin cirrus clouds.

  8. Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: Spectroscopic in situ nanotube detection using spectral absorption and surface temperature measurements by black body emission

    NASA Technical Reports Server (NTRS)

    DeBoer, Gary D.

    2005-01-01

    Carbon nanotubes hold great promise for material advancements in the areas of composites and electronics. The advancement of research in these areas is dependent upon the availability of carbon nanotubes to a broad spectrum of academic and industrial researchers. Although there has been much progress made in reducing the costs of carbon nanotubes and increasing the quality and purity of the products, an increase in demand for still less expensive and specific nanotubes types has also grown. This summer's work has involved two experiments that have been designed to further the understanding of the dynamics and chemical mechanisms of carbon nanotube formation. It is expected that a better understanding of the process of formation of nanotubes will aid current production designs and stimulate ideas for future production designs increasing the quantity, quality, and production control of carbon nanotubes. The first experiment involved the measurement of surface temperature of the target as a function of time with respect to the ablation lasers. A peak surface temperature of 5000 K was determined from spectral analysis of black body emission from the target surface. The surface temperature as a function of various changes in operating parameters was also obtained. This data is expected to aid the modeling of ablation and plume dynamics. The second experiment involved a time and spatial measurement of the spectrally resolved absorbance of the laser produced plume. This experiment explored the possibility of developing absorbance and fluorescence to detect carbon nanotubes during production. To attain control over the production of nanotubes with specific properties and reduce costs, a real time in situ diagnostics method would be very beneficial. Results from this summer's work indicate that detection of nanotubes during production may possibly be used for production feed back control.

  9. Inherent optical properties of the ocean: retrieval of the absorption coefficient of chromophoric dissolved organic matter from airborne laser spectral fluorescence measurements

    NASA Astrophysics Data System (ADS)

    Hoge, Frank E.; Vodacek, Anthony; Swift, Robert N.; Yungel, James K.; Blough, Neil V.

    1995-10-01

    The absorption coefficient of chromophoric dissolved organic matter (CDOM) at 355 nm has been retrieved from airborne laser-induced and water Raman-normalized CDOM fluorescence. Four combined airborne and ship field experiments have demonstrated that (1) the airborne CDOM fluorescence-to--water Raman ratio is linearly related to concurrent quinine-sulfate-standardized CDOM shipboard fluorescence measurements over a wide range of water masses (coastal to blue water); (2) the vicarious calibration of the airborne fluorosensor in units traceable to a fluorescence standard can be established and then maintained over an extended time period by tungsten lamp calibration; (3) the vicariously calibrated airborne CDOM fluorescence-to-water Raman ratio can be directly applied to previously developed

  10. Comparison between different spectral models of the diffuse attenuation and absorption coefficients of seawater

    NASA Astrophysics Data System (ADS)

    Kopelevich, Oleg V.; Filippov, Yuri V.

    1994-10-01

    The goal of this work is to verify different spectral models of the diffuse attenuation and absorption coefficients of sea water and to work out a recommendation for their use. It is shown that the spectral models of the diffuse attenuation coefficient Kd((lambda) ) developed by Austin, Petzold, 1984 and by Volynsky, Sud'bin, 1992 correspond with each other, as well the models of Ivanov, Shemshura, 1973 and of Kopelevich, Shemshura, 1988 for calculation of the spectral absorption coefficient a((lambda) ) on the values of Kd((lambda) ). Theoretical foundation of the relation between a((lambda) ) and Kd((lambda) ) is given. The up-to-date physical model of the sea water light absorption is considered and checked by means of comparison with measured values of the attenuation coefficient at the ultraviolet and visible spectral ranges.

  11. Spectral absorption coefficients and imaginary parts of refractive indices of Saharan dust during SAMUM-1

    NASA Astrophysics Data System (ADS)

    Müller, T.; Schladitz, A.; Massling, A.; Kaaden, N.; Kandler, K.; Wiedensohler, A.

    2009-02-01

    ABSTRACT During the SAMUM-1 experiment, absorption coefficients and imaginary parts of refractive indices of mineral dust particles were investigated in southern Morocco. Main absorbing constituents of airborne samples were identified to be iron oxide and soot. Spectral absorption coefficients were measured using a spectral optical absorption photometer (SOAP) in the wavelength range from 300 to 800 nm with a resolution of 50 nm. A new method that accounts for a loading-dependent correction of fibre filter based absorption photometers, was developed. The imaginary part of the refractive index was determined using Mie calculations from 350 to 800 nm. The spectral absorption coefficient allowed a separation between dust and soot absorption. A correlation analysis showed that the dust absorption coefficient is correlated (R2 up to 0.55) with the particle number concentration for particle diameters larger than 0.5 μm, whereas the coefficient of determination R2 for smaller particles is below 0.1. Refractive indices were derived for both the total aerosol and a dust aerosol that was corrected for soot absorption. Average imaginary parts of refractive indices of the entire aerosol are 7.4 × 10-3, 3.4 × 10-3 and 2.0 × 10-3 at wavelengths of 450, 550 and 650 nm. After a correction for the soot absorption, imaginary parts of refractive indices are 5.1 × 10-3, 1.6 × 10-3 and 4.5 × 10-4.

  12. Guided-wave approaches to spectrally selective energy absorption

    NASA Technical Reports Server (NTRS)

    Stegeman, G. I.; Burke, J. J.

    1987-01-01

    Results of experiments designed to demonstrate spectrally selective absorption in dielectric waveguides on semiconductor substrates are reported. These experiments were conducted with three waveguides formed by sputtering films of PSK2 glass onto silicon-oxide layers grown on silicon substrates. The three waveguide samples were studied at 633 and 532 nm. The samples differed only in the thickness of the silicon-oxide layer, specifically 256 nm, 506 nm, and 740 nm. Agreement between theoretical predictions and measurements of propagation constants (mode angles) of the six or seven modes supported by these samples was excellent. However, the loss measurements were inconclusive because of high scattering losses in the structures fabricated (in excess of 10 dB/cm). Theoretical calculations indicated that the power distribution among all the modes supported by these structures will reach its steady state value after a propagation length of only 1 mm. Accordingly, the measured loss rates were found to be almost independent of which mode was initially excited. The excellent agreement between theory and experiment leads to the conclusion that low loss waveguides confirm the predicted loss rates.

  13. Radar spectral measurements of vegetation

    NASA Technical Reports Server (NTRS)

    Ulaby, F. T.; Moore, R. K.

    1973-01-01

    Spectral data of 4-8 GHz radar backscatter were gathered during the 1972 growing season at look angles between 0 and 70 deg and for all four possible polarization linear combinations. The data covers four crop types (corn, milo, alfalfa, and soybeans) and a wide range of soil moisture content. To insure statistical representation of the results, measurements were conducted over 128 fields corresponding to a total of about 40,000 data points. The use of spectral response signatures to separate different crop types and to separate healthy corn from blighted corn was investigated.

  14. Multi-spectral optical absorption in substrate-free nanowire arrays

    SciTech Connect

    Zhang, Junpeng; Chia, Andrew; Boulanger, Jonathan; LaPierre, Ray; Dhindsa, Navneet; Khodadad, Iman; Saini, Simarjeet

    2014-09-22

    A method is presented of fabricating gallium arsenide (GaAs) nanowire arrays of controlled diameter and period by reactive ion etching of a GaAs substrate containing an indium gallium arsenide (InGaP) etch stop layer, allowing the precise nanowire length to be controlled. The substrate is subsequently removed by selective etching, using the same InGaP etch stop layer, to create a substrate-free GaAs nanowire array. The optical absorptance of the nanowire array was then directly measured without absorption from a substrate. We directly observe absorptance spectra that can be tuned by the nanowire diameter, as explained with rigorous coupled wave analysis. These results illustrate strong optical absorption suitable for nanowire-based solar cells and multi-spectral absorption for wavelength discriminating photodetectors. The solar-weighted absorptance above the bandgap of GaAs was 94% for a nanowire surface coverage of only 15%.

  15. Evolution of macromolecular dust: Far-ultraviolet spectral dust extinction and gas absorption of stellar light as measured with the Hopkins Ultraviolet Telescope

    NASA Astrophysics Data System (ADS)

    Buss, Richard H., Jr.; Allen, Marsha; McCandliss, Stephan; Kruk, Jeffrey; Liu, Ji-Cheng; Brown, Tom

    1994-08-01

    From far-ultraviolet (FUV) spectra of B stars taken with the Hopkins Ultraviolet Telescope (HUT) and Voyager space observations, we determine the far-ultraviolet extinction by Galactic dust and hydrogen absorption in the local spiral-arm clouds towards HD 25443 (B0.5 III), HD 37903 (B1.5 V), and HD 200775 (B3 Ve). We find that the (n (H)) = 1.3 cu cm and number fraction (f = 0.31) of H atoms in molecular hydrogen relative to the total hydrogen indicates a mostly diffuse medium toward HD 25443. We also determine f = 0.56 for the gas in the photodissociation region (PDR) in front of HD 37903 and f approximately equals 0.36 for the HD 200775 PDR. The inferred ratios of N(H2)/I(CO) = 2.4 to 2.8 x 1020/K(km/s)/sq cm for cool gas in dark clouds agree with previous canonical estimates of N(H2)/I(CO) = 2 to 3 x 1020/K(km/s)/sq cm and support the use of the ratio for determining masses of molecular clouds. We find that the shape and strength of the HD 25443 FUV extinction is the same as a diffuse-medium mean extinction (Rnu = 2.95) extrapolated from mid-UV wavelengths (normal). The HD 37903 FUV extinction through a bright H2 photodissociation region is higher than a mean FUV extinction(Rnu = 4.11), as is the HD 200775 extinction. Another star from the literature rho Oph, probes the dense medium and exhibits an FUV extinction of normal mean strength (Rnu = 4.55) but steeper shape. The normal FUV -extinction of HD 25443 implies that the small FUV-extinction dust in the diffuse medium forms in p art from larger grains as the grains shatter under shocks. The normal strength of the rho Oph FUV-extinction indicates that the minute dust condenses onto or coagulates into larger grains in the dense medium. The high extinction deviation of the HD 37903 PDR (and HD 200775 PDR) shows that FUV radiation from hot stars with Teff approximately equals 20,000 to 23,000 K in PDRs can evaporate some of the FUV-extinction dust from grain surfaces. In contrast, previously measured extinctions

  16. Evolution of macromolecular dust: Far-ultraviolet spectral dust extinction and gas absorption of stellar light as measured with the Hopkins Ultraviolet Telescope

    NASA Technical Reports Server (NTRS)

    Buss, Richard H., Jr.; Allen, Marsha; Mccandliss, Stephan; Kruk, Jeffrey; Liu, Ji-Cheng; Brown, Tom

    1994-01-01

    From far-ultraviolet (FUV) spectra of B stars taken with the Hopkins Ultraviolet Telescope (HUT) and Voyager space observations, we determine the far-ultraviolet extinction by Galactic dust and hydrogen absorption in the local spiral-arm clouds towards HD 25443 (B0.5 III), HD 37903 (B1.5 V), and HD 200775 (B3 Ve). We find that the (n (H)) = 1.3 cu cm and number fraction (f = 0.31) of H atoms in molecular hydrogen relative to the total hydrogen indicates a mostly diffuse medium toward HD 25443. We also determine f = 0.56 for the gas in the photodissociation region (PDR) in front of HD 37903 and f approximately equals 0.36 for the HD 200775 PDR. The inferred ratios of N(H2)/I(CO) = 2.4 to 2.8 x 10(exp 20)/K(km/s)/sq cm for cool gas in dark clouds agree with previous canonical estimates of N(H2)/I(CO) = 2 to 3 x 10(exp 20)/K(km/s)/sq cm and support the use of the ratio for determining masses of molecular clouds. We find that the shape and strength of the HD 25443 FUV extinction is the same as a diffuse-medium mean extinction (R(sub nu) = 2.95) extrapolated from mid-UV wavelengths (normal). The HD 37903 FUV extinction through a bright H2 photodissociation region is higher than a mean FUV extinction(R(sub nu) = 4.11), as is the HD 200775 extinction. Another star from the literature rho Oph, probes the dense medium and exhibits an FUV extinction of normal mean strength (R(sub nu) = 4.55) but steeper shape. The normal FUV -extinction of HD 25443 implies that the small FUV-extinction dust in the diffuse medium forms in p art from larger grains as the grains shatter under shocks. The normal strength of the rho Oph FUV-extinction indicates that the minute dust condenses onto or coagulates into larger grains in the dense medium. The high extinction deviation of the HD 37903 PDR (and HD 200775 PDR) shows that FUV radiation from hot stars with T(sub eff) approximately equals 20,000 to 23,000 K in PDRs can evaporate some of the FUV-extinction dust from grain surfaces. In

  17. Spectral calibration of hyperspectral imagery using atmospheric absorption features.

    PubMed

    Guanter, Luis; Richter, Rudolf; Moreno, José

    2006-04-01

    One of the initial steps in the preprocessing of remote sensing data is the atmospheric correction of the at-sensor radiance images, i.e., radiances recorded at the sensor aperture. Apart from the accuracy in the estimation of the concentrations of the main atmospheric species, the retrieved surface reflectance is also influenced by the spectral calibration of the sensor, especially in those wavelengths mostly affected by gaseous absorptions. In particular, errors in the surface reflectance appear when a systematic shift in the nominal channel positions occurs. A method to assess the spectral calibration of hyperspectral imaging spectrometers from the acquired imagery is presented in this paper. The fundamental basis of the method is the calculation of the value of the spectral shift that minimizes the error in the estimates of surface reflectance. This is performed by an optimization procedure that minimizes the deviation between a surface reflectance spectrum and a smoothed one resulting from the application of a low-pass filter. A sensitivity analysis was performed using synthetic data generated with the MODTRAN4 radiative transfer code for several values of the spectral shift and the water vapor column content. The error detected in the retrieval is less than +/- 0.2 nm for spectral shifts smaller than 2 nm, and less than +/- 1.0 nm for extreme spectral shifts of 5 nm. A low sensitivity to uncertainties in the estimation of water vapor content was found, which reinforces the robustness of the algorithm. The method was successfully applied to data acquired by different hyperspectral sensors. PMID:16608005

  18. Spectral absorption characteristics of the major components of dust clouds.

    PubMed

    Flanigan, D F; Delong, H P

    1971-01-01

    It is well known that dust clouds selectively absorb radiation in the 700-1300 cm(-1) atmospheric window region. Studies have shown that dust clouds are composed of the same minerals as surface soils, although in different proportion. We have examined seventy soil samples from a number of locations around the world to determine their compositions and spectral characteristics. The results indicate that there are five major components which selectively absorb radiation in the 700-1300 cm(-1) region. These are three clay minerals, silica, and calcium carbonate. Absorptivity coefficient spectra of representative soil samples are given.

  19. [Study of the Detecting System of CH4 and SO2 Based on Spectral Absorption Method and UV Fluorescence Method].

    PubMed

    Wang, Shu-tao; Wang, Zhi-fang; Liu, Ming-hua; Wei, Meng; Chen, Dong-ying; Wang, Xing-long

    2016-01-01

    According to the spectral absorption characteristics of polluting gases and fluorescence characteristics, a time-division multiplexing detection system is designed. Through this system we can detect Methane (CH4) and sulfur dioxide (SO2) by using spectral absorption method and the SO2 can be detected by using UV fluorescence method. The system consists of four parts: a combination of a light source which could be switched, the common optical path, the air chamber and the signal processing section. The spectral absorption characteristics and fluorescence characteristics are measured first. Then the experiment of detecting CH4 and SO2 through spectral absorption method and the experiment of detecting SO2 through UV fluorescence method are conducted, respectively. Through measuring characteristics of spectral absorption and fluorescence, we get excitation wavelengths of SO2 and CH4 measured by spectral absorption method at the absorption peak are 280 nm and 1.64 μm, respectively, and the optimal excitation wavelength of SO2 measured by UV fluorescence method is 220 nm. we acquire the linear relation between the concentration of CH4 and relative intensity and the linear relation between the concentration of SO2 and output voltage after conducting the experiment of spectral absorption method, and the linearity are 98.7%, 99.2% respectively. Through the experiment of UV fluorescence method we acquire that the relation between the concentration of SO2 and the voltage is linear, and the linearity is 99.5%. Research shows that the system is able to be applied to detect the polluted gas by absorption spectrum method and UV fluorescence method. Combing these two measurement methods decreases the costing and the volume, and this system can also be used to measure the other gases. Such system has a certain value of application. PMID:27228784

  20. [Study of the Detecting System of CH4 and SO2 Based on Spectral Absorption Method and UV Fluorescence Method].

    PubMed

    Wang, Shu-tao; Wang, Zhi-fang; Liu, Ming-hua; Wei, Meng; Chen, Dong-ying; Wang, Xing-long

    2016-01-01

    According to the spectral absorption characteristics of polluting gases and fluorescence characteristics, a time-division multiplexing detection system is designed. Through this system we can detect Methane (CH4) and sulfur dioxide (SO2) by using spectral absorption method and the SO2 can be detected by using UV fluorescence method. The system consists of four parts: a combination of a light source which could be switched, the common optical path, the air chamber and the signal processing section. The spectral absorption characteristics and fluorescence characteristics are measured first. Then the experiment of detecting CH4 and SO2 through spectral absorption method and the experiment of detecting SO2 through UV fluorescence method are conducted, respectively. Through measuring characteristics of spectral absorption and fluorescence, we get excitation wavelengths of SO2 and CH4 measured by spectral absorption method at the absorption peak are 280 nm and 1.64 μm, respectively, and the optimal excitation wavelength of SO2 measured by UV fluorescence method is 220 nm. we acquire the linear relation between the concentration of CH4 and relative intensity and the linear relation between the concentration of SO2 and output voltage after conducting the experiment of spectral absorption method, and the linearity are 98.7%, 99.2% respectively. Through the experiment of UV fluorescence method we acquire that the relation between the concentration of SO2 and the voltage is linear, and the linearity is 99.5%. Research shows that the system is able to be applied to detect the polluted gas by absorption spectrum method and UV fluorescence method. Combing these two measurement methods decreases the costing and the volume, and this system can also be used to measure the other gases. Such system has a certain value of application.

  1. Characterizing Quasar Outflows I: Sample, Spectral Measurements

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Christenson, D. H.; Richmond, J. M.; Derseweh, J. A.; Robbins, J. M.; Townsend, S. L.; Stark, M. A.

    2012-05-01

    Galaxy evolution models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 11000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) measurements of UV emission line and continuum parameters. In this poster, we subjectively divide these quasars into four categories: broad absorption-line quasars (2700 objects), associated absorption-line quasars (1700 objects), reddened quasars (160 objects), and unabsorbed/unreddened quasars (6300 objects). We present measurements of the absorption (velocities, velocity widths, equivalent widths), composite spectral profiles of outflows as a function of velocity, as well as measurements of the continuum and CIV, MgII, and FeII emission-line properties. In accompanying posters, we add photometry from the rest-frame X-ray (ROSAT and Chandra), EUV (GALEX), optical (2MASS), and infrared (WISE) bands to complete the SED. The continuum and emission-line measurements from the SDSS spectra and accompanying photometry provides estimates on the black hole masses, bolometric luminsosities, and SED. We consider empirically how these affect the outflow properties. This material is based upon work supported by the National Aeronautics and Space Administration under

  2. In situ correlative measurements for the ultraviolet differential absorption lidar and the high spectral resolution lidar air quality remote sensors: 1980 PEPE/NEROS program

    NASA Technical Reports Server (NTRS)

    Gregory, G. L.; Beck, S. M.; Mathis, J. J., Jr.

    1981-01-01

    In situ correlative measurements were obtained with a NASA aircraft in support of two NASA airborne remote sensors participating in the Environmental Protection Agency's 1980persistent elevated pollution episode (PEPE) and Northeast regional oxidant study (NEROS) field program in order to provide data for evaluating the capability of two remote sensors for measuring mixing layer height, and ozone and aerosol concentrations in the troposphere during the 1980 PEPE/NEROS program. The in situ aircraft was instrumented to measure temperature, dewpoint temperature, ozone concentrations, and light scattering coefficient. In situ measurements for ten correlative missions are given and discussed. Each data set is presented in graphical and tabular format aircraft flight plans are included.

  3. Absorption coefficients and frequency shifts measurement in the spectral range of 1071.88-1084.62 cm-1 vs. pressure for chlorodifluoromethane (CHClF2) using tunable CW CO2 laser

    NASA Astrophysics Data System (ADS)

    Al-Hawat, Sharif

    2013-02-01

    Infrared (IR) absorption in the spectral range of (1071.88-1084.62 cm-1) vs. pressure in chlorodifluoromethane (CFC-22, F-22, and CHClF2) was studied using a tunable continuous wave (CW) CO2 laser radiation on 9R branch lines with a maximum output power of about 2.12 W, provided with an absorber cell located outside the laser cavity. The absorption coefficients were determined vs. the gas pressure between 0.2 mbar and 170 mbar at lines from 9R branch for CFC-22. The frequency shifts of the absorption lines of CFC-22 in relative to the central frequencies of laser lines were calculated vs. the pressure on the basis of these absorption coefficients. The chosen lines were selected according to IR spectrum of the studied gas given by HITRAN cross section database. So the absorption was achieved for CFC-22 at the spectral lines of 9R branch situated from 9R (10) to 9R (30) emitted by a tunable CW CO2 laser. The absorption cross sections of CFC-22 determined in this work were compared with the relevant data given by HITRAN cross section database and a reasonable agreement was observed.

  4. Vegetation Species Composition and Canopy Architecture Information Expressed in Leaf Water Absorption Measured in the 1000nm and 2200 nm Spectral Region by an Imaging Spectometer

    NASA Technical Reports Server (NTRS)

    Green, R. O.; Roberts, D. A.

    1994-01-01

    Plant species composition and plant architectural attributes are critical parameters required for the measuring, monitoring and modeling of terrestrial ecosystems. Remote sensing is commonly cited as an important tool for deriving vegetation properties at an appropriate scale for ecosystem studies, ranging from local, to regional and even synoptic scales (e.g. Wessman 1992).

  5. Spectral control of an alexandrite laser for an airborne water-vapor differential absorption lidar system

    NASA Technical Reports Server (NTRS)

    Ponsardin, Patrick; Grossmann, Benoist E.; Browell, Edward V.

    1994-01-01

    A narrow-linewidth pulsed alexandrite laser has been greatly modified for improved spectral stability in an aircraft environment, and its operation has been evaluated in the laboratory for making water-vapor differential absorption lidar measurements. An alignment technique is described to achieve the optimum free spectral range ratio for the two etalons inserted in the alexandrite laser cavity, and the sensitivity of this ratio is analyzed. This technique drastically decreases the occurrence of mode hopping, which is commonly observed in a tunable, two-intracavity-etalon laser system. High spectral purity (greater than 99.85%) at 730 nm is demonstrated by the use of a water-vapor absorption line as a notch filter. The effective cross sections of 760-nm oxygen and 730-nm water-vapor absorption lines are measured at different pressures by using this laser, which has a finite linewidth of 0.02 cm(exp -1) (FWHM). It is found that for water-vapor absorption linewidths greater than 0.04 cm(exp -1) (HWHM), or for altitudes below 10 km, the laser line can be considered monochromatic because the measured effective absorption cross section is within 1% of the calculated monochromatic cross section. An analysis of the environmental sensitivity of the two intracavity etalons is presented, and a closed-loop computer control for active stabilization of the two intracavity etalons in the alexandrite laser is described. Using a water-vapor absorption line as a wavelength reference, we measure a long-term frequency drift (approximately 1.5 h) of less than 0.7 pm in the laboratory.

  6. Water vapor absorption coefficients in the 8-13-micron spectral region - A critical review

    NASA Technical Reports Server (NTRS)

    Grant, William B.

    1990-01-01

    Measurements of water vapor absorption coefficients in the thermal IR atmospheric window (8-13 microns) during the past 20 years obtained by a variety of techniques are reviewed for consistency and compared with computed values based on the AFGL spectral data tapes. The methods of data collection considered were atmospheric long path absorption with a CO2 laser or a broadband source and filters, a White cell and a CO2 laser or a broadband source and a spectrometer, and a spectrophone with a CO2 laser. Advantages and disadvantages of each measurement approach are given as a guide to further research. Continuum absorption has apparently been measured accurately to about the 5-10 percent level in five of the measurements reported.

  7. Diode laser-based sensor system for long-path absorption measurements of atmospheric concentration and near-IR molecular spectral parameters

    SciTech Connect

    Goldstein, N.; Lee, J.; Adler-Golden, S.M.; Bien, F.

    1993-12-31

    Line-locked near-IR diode lasers and a simple retroreflector/telescope system were used for remote sensing of atmospheric constituents over long atmospheric paths. The experimental configuration used in preliminary measurements of atmospheric water vapor and oxygen with AlGaAs diode lasers is presented. A prototype field sensor system currently under development shares the same basic configuration but incorporates interchangeable AlGaAs and InGaAsP diode-laser modules for monitoring a variety of atmospheric gases.

  8. Using high spectral resolution spectrophotometry to study broad mineral absorption features on Mars

    NASA Technical Reports Server (NTRS)

    Blaney, D. L.; Crisp, D.

    1993-01-01

    Traditionally telescopic measurements of mineralogic absorption features have been made using relatively low to moderate (R=30-300) spectral resolution. Mineralogic absorption features tend to be broad so high resolution spectroscopy (R greater than 10,000) does not provide significant additional compositional information. Low to moderate resolution spectroscopy allows an observer to obtain data over a wide wavelength range (hundreds to thousands of wavenumbers) compared to the several wavenumber intervals that are collected using high resolution spectrometers. However, spectrophotometry at high resolution has major advantages over lower resolution spectroscopy in situations that are applicable to studies of the Martian surface, i.e., at wavelengths where relatively weak surface absorption features and atmospheric gas absorption features both occur.

  9. [Superhigh spectral resolution measurement of spectrometer].

    PubMed

    Liu, Sheng-Gang; Weng, Ji-Dong; Tao, Tian-Jiong

    2013-04-01

    The spectral resolution is one of the most important indexes of spectrometer. A new method is put forward for measuring the superhigh spectral resolution based on the Rayleigh criterion and the optical heterodyne, and the uncertainty of this method is analyzed. The spectral resolution of some spectrometer was measured using this method, and the experimental results show that the spectral resolution is higher than 18.9 pm, and the standard uncertainty is 2.3 pm. When showed using wave number, the spectral resolution is higher than 0.078 8 cm(-1), and the standard uncertainty is 0.009 6 cm(-1).

  10. Light fluence correction for quantitative determination of tissue absorption coefficient using multi-spectral optoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Brochu, Frederic M.; Joseph, James; Tomaszewski, Michal; Bohndiek, Sarah E.

    2015-07-01

    MultiSpectral Optoacoustic Tomography (MSOT) is a fast developing imaging modality, combining the high resolution and penetration depth of ultrasound with the excellent contrast from optical imaging of tissue. Absorption and scattering of the near infrared excitation light modulates the spectral profile of light as it propagates deep into biological tissue, meaning the images obtained provide only qualitative insight into the distribution of tissue chromophores. The goal of this work is to accurately recover the spectral profile of excitation light by modelling light fluence in the data reconstruction, to enable quantitative imaging. We worked with a commercial small animal MSOT scanner and developed our light fluence correction for its' cylindrical geometry. Optoacoustic image reconstruction pinpoints the sources of acoustic waves detected by the transducers and returns the initial pressure amplitude at these points. This pressure is the product of the dimensionless Grüneisen parameter, the absorption coefficient and the light fluence. Under the condition of constant Grüneisen parameter and well modelled light fluence, there is a linear relationship between the initial pressure amplitude measured in the optoacoustic image and the absorption coefficient. We were able to reproduce this linear relationship in different physical regions of an agarose gel phantom containing targets of known optical absorption coefficient, demonstrating that our light fluence model was working. We also demonstrate promising results of light fluence correction effects on in vivo data.

  11. ABSORPTION MEASURE DISTRIBUTION IN Mrk 509

    SciTech Connect

    Adhikari, T. P.; Różańska, A.; Sobolewska, M.; Czerny, B.

    2015-12-20

    In this paper we model the observed absorption measure distribution (AMD) in Mrk 509, which spans three orders of magnitude in ionization level with a single-zone absorber in pressure equilibrium. AMD is usually constructed from observations of narrow absorption lines in radio-quiet active galaxies with warm absorbers. We study the properties of the warm absorber in Mrk 509 using recently published broadband spectral energy distribution observed with different instruments. This spectrum is an input in radiative transfer computations with full photoionization treatment using the titan code. We show that the simplest way to fully reproduce the shape of AMD is to assume that the warm absorber is a single zone under constant total pressure. With this assumption, we found theoretical AMD that matches the observed AMD determined on the basis of the 600 ks reflection grating spectrometer XMM-Newton spectrum of Mrk 509. The softness of the source spectrum and the important role of the free–free emission breaks the usual degeneracy in the ionization state calculations, and the explicit dependence of the depths of AMD dips on density open a new path to the density diagnostic for the warm absorber. In Mrk 509, the implied density is of the order of 10{sup 8} cm{sup −3}.

  12. Absorption spectroscopy setup for determination of whole human blood and blood-derived materials spectral characteristics

    NASA Astrophysics Data System (ADS)

    Wróbel, M. S.; Gnyba, M.; Milewska, D.; Mitura, K.; Karpienko, K.

    2015-09-01

    A dedicated absorption spectroscopy system was set up using tungsten-halogen broadband source, optical fibers, sample holder, and a commercial spectrometer with CCD array. Analysis of noise present in the setup was carried out. Data processing was applied to the absorption spectra to reduce spectral noise, and improve the quality of the spectra and to remove the baseline level. The absorption spectra were measured for whole blood samples, separated components: plasma, saline, washed erythrocytes in saline and human whole blood with biomarkers - biocompatible nanodiamonds (ND). Blood samples had been derived from a number of healthy donors. The results prove a correct setup arrangement, with adequate preprocessing of the data. The results of blood-ND mixtures measurements show no toxic effect on blood cells, which proves the NDs as a potential biocompatible biomarkers.

  13. Remote and Ground Truth Spectral Measurement Comparisons

    NASA Technical Reports Server (NTRS)

    Abercromby, Kira Jorgensen; Hamada, Kris; Guyote, Michael; Okada, Jennifer; Barker, Edwin

    2007-01-01

    FORMOSAT III are a set of six research satellites from Taiwan that were launched in April 2006. The satellites are in 800 km, 71 degree inclination orbits and separated by 24 degrees in ascending node. Ground truth spectral measurements were taken of outer surface materials on FORMOSAT III. From those measurements, a computer model was built to predict the spectral reflectance, which included phase angle and orientation of the spacecraft relative to the observer. However, materials exposed to the space environment have exhibited spectral changes including a darkening and a reddening of the spectra. This reddening was seen as an increase in slope of the reflectance as the wavelength increases. Therefore, the model of pristine materials was augmented to include the space weathering effects. Remote data were collected on two of the six FORMOSAT satellites using the 1.6 meter telescope at AMOS (Air Force Maui Optical and Supercomputing) site with the Spica spectrometer. Due to the separation in ascending node, observations were made on whichever one of the six satellites was visible on that specific night. Three nights of data were collected using the red (6000 9500 angstroms) filter and two nights of data were collected using the blue (3200 -6600 angstroms) filter. A comparison of the data showed a good match to the pristine model for the blue filter region. The absorption feature near 5500 angstroms due to the copper colored Kapton multi-layer insulation (MLI) was very apparent in the remote samples and a good fit to the data was seen in both satellites observed. The features in the red filter regime agreed with the pristine model up through 7000 angstroms where the reddening begins and the slope of the remote sample increases. A comparison of the two satellites showed similar features in the red and blue filter regions, i.e. the satellites were aging at the same rate. A comparison of the pristine model to the first month of remote measurements showed the amount by

  14. Remote and Ground Truth Spectral Measurement Comparisons

    NASA Astrophysics Data System (ADS)

    Abercromby, K.; Hamada, K.; Guyote, M.; Okada, J.; Barker, E.

    FORMOSAT III are a set of six research satellites from Taiwan that were launched in April 2006. The satellites are in 800 km, 71 degree inclination orbits and separated by 24 degrees in ascending node. Laboratory spectral measurements were taken of outer surface materials on FORMOSAT III. From those measurements, a computer model was built to predict the spectral reflectance accounting for both solar phase angle and orientation of the spacecraft relative to the observer. However, materials exposed to the space environment have exhibited spectral changes including a darkening and a "reddening" of the spectra. This "reddening" is characterized by an increase in slope of the reflectance as the wavelength increases. Therefore, the model of pre-flight materials was augmented to include the presumed causative agent: space weathering effects. Remote data were collected on two of the six FORMOSAT satellites using the 1.6 meter telescope at the AMOS (Air Force Maui Optical and Supercomputing) site with the Spica spectrometer. Due to the separation in ascending node, observations were acquired of whichever one of the six satellites was visible on that specific night. Three nights of data were collected using the red (6000 - 9500 angstroms) filter and five nights of data were collected using the blue (3200 -6600 angstroms) filter. A comparison of the data showed a good match to the pre-flight models for the blue filter region. The absorption feature near 5500 angstroms due to the copper colored Kapton multi-layer insulation (MLI) was very apparent in the remote samples and a good fit to the data was seen in all satellites observed. The features in the red filter regime agreed with the pre-flight model up through 7000 angstroms where the reddening begins and the slope of the remote sample increases. A comparison of the satellites showed similar features in the red and blue filter regions, i.e. the satellite surfaces were aging at the same rate. A comparison of the pre

  15. Atmospheric Measurements by Cavity Enhanced Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yi, Hongming; Wu, Tao; Coeur-Tourneur, Cécile; Fertein, Eric; Gao, Xiaoming; Zhao, Weixiong; Zhang, Weijun; Chen, Weidong

    2015-04-01

    Since the last decade, atmospheric environmental monitoring has benefited from the development of novel spectroscopic measurement techniques owing to the significant breakthroughs in photonic technology from the UV to the infrared spectral domain [1]. In this presentation, we will overview our recent development and applications of cavity enhanced absorption spectroscopy techniques for in situ optical monitoring of chemically reactive atmospheric species (such as HONO, NO3, NO2, N2O5) in intensive campaigns [2] and/or in smog chamber studies [3]. These field deployments demonstrated that modern photonic technologies (newly emergent light sources combined with high sensitivity spectroscopic techniques) can provide a useful tool to improve our understanding of tropospheric chemical processes which affect climate, air quality, and the spread of pollution. Experimental detail and preliminary results will be presented. Acknowledgements. The financial support from the French Agence Nationale de la Recherche (ANR) under the NexCILAS (ANR-11-NS09-0002) and the CaPPA (ANR-10-LABX-005) contracts is acknowledged. References [1] X. Cui, C. Lengignon, T. Wu, W. Zhao, G. Wysocki, E. Fertein, C. Coeur, A. Cassez,L. Croisé, W. Chen, et al., "Photonic Sensing of the Atmosphere by absorption spectroscopy", J. Quant. Spectrosc. Rad. Transfer 113 (2012) 1300-1316 [2] T. Wu, Q. Zha, W. Chen, Z. XU, T. Wang, X. He, "Development and deployment of a cavity enhanced UV-LED spectrometer for measurements of atmospheric HONO and NO2 in Hong Kong", Atmos. Environ. 95 (2014) 544-551 [3] T. Wu, C. Coeur-Tourneur, G. Dhont,A. Cassez, E. Fertein, X. He, W. Chen,"Application of IBBCEAS to kinetic study of NO3 radical formation from O3 + NO2 reaction in an atmospheric simulation chamber", J. Quant. Spectrosc. Rad. Transfer 133 (2014)199-205

  16. Spectral Absorption By Particulate Impurities in Snow Determined By Photometric Analysis Of Filters

    NASA Astrophysics Data System (ADS)

    Grenfell, T. C.; Doherty, S. J.; Clarke, A. D.

    2009-12-01

    Our work is motivated by the 1983-84 survey by Clarke and Noone (Atmos. Environ., 1985) of soot in Arctic snow. Our objective is to resurvey the original area they covered and to extend the observations around the entire Arctic Basin under the auspices of the IPY program. We use the filtering and integrating sandwich techniques developed by Clarke and Noone to process the snow samples. Among the advantages of this method are that (a) it provides a direct measure of light absorption and the result is closely related to the actual absorption of sunlight in the snow or ice, (b) processing and filtering of the snow samples can be carried out in remote locations and (c) it is not necessary to transport large quantities of snow back to our home laboratory. Here we describe the construction, calibration, and some applications of an integrating sphere spectrophotometer system designed to take advantage of recent advances in instrumentation to improve the accuracy of measurements of absorption by particulate impurities collected on nuclepore filters used in our survey. Filter loading in terms of effective black carbon (BC) amount is determined together with the ratio of non-BC to BC concentrations using a set of reference filters with known loadings of Monarch 71 BC prepared by A. D. Clarke. The new spectrophotometer system has (a) system stability of approximately 0.5%; (b) precision relative to ADC standards of 3-4% for filter loadings greater than about 0.5 microgm Carbon/cm2. (c) We can distinguish BC from non-BC from relative spectral shapes of the energy absorption curves with an accuracy that depends on our knowledge of the spectral absorption curves of the non-BC components; and (d) by-eye estimates are consistent with spectrophotometric results. The major outstanding uncertainty is the appropriate value to use for the mass absorption efficiency for BC.

  17. Interactions of praseodymium and neodymium with nucleosides and nucleotides: absorption difference and comparative absorption spectral study.

    PubMed

    Misra, S N; Anjaiah, K; Joseph, G; Abdi, S H

    1992-02-01

    The interactions of praseodymium(III) and neodymium(III) with nucleosides and nucleotides have been studied in different stoichiometry in water and water-DMF mixtures by employing absorption difference and comparative absorption spectrophotometry. The 4f-4f bands were analysed by linear curve analysis followed by gaussian curve analysis, and various spectral parameters were computed, using partial and multiple regression method. The magnitude of changes in both energy interaction and intensity were used to explore the degree of outer and inner sphere coordination, incidence of covalency and the extent of metal 4f-orbital involvement in chemical bonding. Crystalline complexes of the type [Ln(nucleotide)2(H2O)2]- (where nucleotide--GMP or IMP) were characterized by IR, 1H NMR, 31P NMR data. These studies indicated that the binding of the nucleotide is through phosphate oxygen in a bidentate manner and the complexes undergo substantial ionisation in aqueous medium, thereby supporting the observed weak 4f-4f bands and lower values for nephelauxetic effect (1-beta), bonding (b) and covalency (delta) parameters derived from coulombic and spin orbit interaction parameters.

  18. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    NASA Astrophysics Data System (ADS)

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10‑3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10‑27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  19. Determination of the concentration of mineral particles and suspended organic substance based on their spectral absorption

    NASA Astrophysics Data System (ADS)

    Konovalov, B. V.; Kravchishina, M. D.; Belyaev, N. A.; Novigatsky, A. N.

    2014-09-01

    A method to determine the concentrations of the particulate mineral matter ( C PMM) and the particulate organic matter ( C POM) is suggested. The values of C PMM and C POM are calculated from the measurements of the spectral coefficients of the light absorption a POM(440) and a PMM(750) using empirical equations. The latter have been obtained by comparing the concentrations of the suspended solids measured by means of the gravimetric method with the spectral values of the optical density of the suspended matter settled on membrane filters. The data used are typical of the coastal waters of inland and marginal seas and the open ocean and cover the range of three and two orders of magnitude for the concentrations of C PMM and C POM, respectively.

  20. Limits of spectral resolution in optical measurements

    NASA Astrophysics Data System (ADS)

    Marques, Manuel B.

    2014-08-01

    Nowadays a growing number of scientists relies on optical spectral measurements for their research. The market is full of new plug-and-play equipment for spectral analysis that take the fuss out of the measurements. As with other instruments (computers, lasers, etc.) the researcher doesńt need any longer to work with someone with a post-graduate formation on the technology to be able to do excellent research. But, as in every instrument, there are limitations on the instrument use that affect its precision and resolution. Currently there is in the market a large variety of equipment for spectral measurements. They range from the huge long focal length double pass monochromators to the small pocket size USB connected array spectrometers. The different configurations have different sensitivities on the light input system, light intensity, coherence, polarization, etc. In this talk we will discuss a few of the limitations in spectral measurements that can be found in experimental setups.

  1. Spectral variation of scattering and absorption by cirrus

    NASA Technical Reports Server (NTRS)

    Hein, Paul F.; Davis, John M.; Cox, Stephen K.

    1993-01-01

    The impact of cirrus clouds on the radiative budget of the earth depends on the microphysics and scattering properties of the clouds. Cirrus clouds have been especially difficult to observe because of their high altitude and complex tenuous structure. Observations by Abakumova et. al. (1991) show that the near infrared wavelengths are more sensitive to the cirrus cloud properties than the shorter ultraviolet wavelengths. Anikin (1991) was able to show that collimated spectral measurements can be used to determine an effective particle size of the cirrus clouds. Anikin (1991) also showed that the effect of scattering through cloud causes the apparent optical depth of a 10 degrees field of view pyrheliometer to be roughly half the actual optical depth. Stackhouse and Stephens (1991) have shown that the existence of small ice crystals do dramatically affect the radiative properties of the cirrus, though observations taken during the 1986 FIRE were not totally explained by their presence.

  2. Spectral response measurements with white light bias

    NASA Technical Reports Server (NTRS)

    Devaney, W.; Lorenz, S.; Meakin, J. D.

    1976-01-01

    The spectral response of solar cells such as the CdS/Cu2S cell is non-linear with distinct quenching and enhancement bands. One possible technique to produce standardized solar efficiencies is to fold in spectral response with a standard solar spectrum. The spectral response of a cell was measured in a way which matched cell behavior under white light illumination. A technique was developed to measure the response of a cell to low intensity chopped monochromatic light while the cell is also illuminated with a white light bias corresponding to AMI.

  3. Differential optical absorption spectrometer for measurement of tropospheric pollutants

    NASA Astrophysics Data System (ADS)

    Evangelisti, F.; Baroncelli, A.; Bonasoni, P.; Giovanelli, G.; Ravegnani, F.

    1995-05-01

    Our institute has recently developed a differential optical absorption spectrometry system called the gas analyzer spectrometer correlating optical absorption differences (GASCOAD), which features as a detector a linear image sensor that uses an artificial light source for long-path tropospheric-pollution monitoring. The GASCOAD, its method of eliminating interference from background sky light, and subsequent spectral analysis are reported and discussed. The spectrometer was used from 7 to 22 February 1993 in Milan, a heavily polluted metropolitan area, to measure the concentrations of SO2, NO2, O3, and HNO2 averaged over a 1.7-km horizontal light path. The findings are reported and briefly discussed.

  4. Spectral reflectance measurements in the genus Sphagnum

    SciTech Connect

    Vogelmann, J.E.; Moss, D.M. . Complex Systems/Institute for the Study of Earth Oceans and Space)

    1993-09-01

    High-spectral resolution reflectance data were acquired in the laboratory for four species of Sphagnum (peat moss): S. cuspidatum, S. papillosum, S. fallax, and S. capillifolium. All four species had different spectral reflectance properties. Species differences were noted especially in the visible portion of the spectrum from 0.45 [mu]m to 0.70 [mu]m; some major spectral differences were also noted in the near infrared. Samples analyzed had much lower reflectance than typical green vegetation in the midinfrared region of the spectrum from 1.30 [mu]m to 2.40 [mu]m. In addition, Sphagnum had very pronounced water-related absorption features at about 1.00m [mu] and 1.20 [mu]m, unlike typical green vegetation. Spectral data acquired as samples were dried indicated large spectral increases with increasing dryness, especially in the midinfrared. Simulated Landsat Thematic Mapper 5/4 band ratio data were linearly related to the log of wet weight/dry weight. Reflectance from vegetation in the midinfrared region of the electromagnetic spectrum is strongly modified by water content. Peatlands are major sources of global methane and it has been found that methane evolution within these peatlands is related to water status within these peatlands is related to water status within the wetland. It may be possible to indirectly estimate methane flux using remote sensing data.

  5. A new method to retrieve spectral absorption coefficient of highly-scattering and weakly-absorbing materials

    NASA Astrophysics Data System (ADS)

    Dombrovsky, Leonid A.

    2016-03-01

    A significant uncertainty in the absorption coefficient of highly scattering dispersed materials is typical in the spectral ranges of very weak absorption. The traditional way to identify the main absorption and scattering characteristics of semi-transparent materials is based on spectral measurements of normal-hemispherical reflectance and transmittance for the material sample. Unfortunately this way cannot be used in the case of in vivo measurements of optical properties of biological tissues. A method suggested in the present paper is based on thermal response to the periodic radiative heating of the open surface of a semi-transparent material. It is shown that the period of a variation of the surface temperature is sensitive to the value of an average absorption coefficient in the surface layer. As a result, the monochromatic external irradiation combined with the surface temperature measurements can be used to retrieve the spectral values of absorption coefficient. Possible application of this method to porous semi-transparent ceramics is considered. An example problem is also solved to illustrate the applicability of this method to human skin. The approach suggested enables one to estimate an average absorption coefficient of human skin of a patient just before the thermal processing.

  6. Spectral Absorption of Solar Radiation by Aerosols during ACE-Asia

    NASA Technical Reports Server (NTRS)

    Bergstrom, R. W.; Pilewskie, P.; Pommier, J.; Rabbette, M.; Russell, P. B.; Schmid, B.; Redermann, J.; Higurashi, A.; Nakajima, T.; Quinn, P. K.

    2004-01-01

    As part of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia), the upward and downward spectral solar radiant fluxes were measured with the Spectral Solar Flux Radiometer (SSFR), and the aerosol optical depth was measured with the Ames Airborne Tracking Sunphotometer (AATS-14) aboard the Center for INterdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter aircraft. IN this paper, we examine the data obtained for two cases: a moderately thick aerosol layer, 12 April, and a relatively thin aerosol case, 16 April 2001. ON both days, the Twin Otter flew vertical profiles in the Korean Strait southeast of Gosan Island. For both days we determine the aerosol spectral absorption of the layer and estimate the spectral aerosol absorption optical depth and single-scattering albedo. The results for 12 April show that the single-scattering albedo increases with wavelength from 0.8 at 400 nm to 0.95 at 900 nm and remains essentially constant from 950 to 1700 nm. On 16 April the amount of aerosol absorption was very low; however, the aerosol single-scattering albedo appears to decrease slightly with wavelength in the visible region. We interpret these results in light of the two absorbing aerosol species observed during the ACE-asia study: mineral dust and black carbon. The results for 12 April are indicative of a mineral dust-black carbon mixture. The 16 April results are possibly caused by black carbon mixed with nonabsorbing pollution aerosols. For the 12 April case we attempt to estimate the relative contributions of the black carbon particles and the mineral dust particles. We compare our results with other estimates of the aerosol properties from a Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) satellite analysis and aerosol measurements made aboard the Twin Otter, aboard the National Oceanic and Atmospheric Administration Ronald H Brown ship, and at ground sites in Gosan and Japan. The results indicate a relatively complicated aerosol

  7. Differences in spectral absorption properties between active neovascular macular degeneration and mild age related maculopathy.

    PubMed

    Balaskas, Konstantinos; Nourrit, Vincent; Dinsdale, Michelle; Henson, David B; Aslam, Tariq

    2013-05-01

    This study examines the differences in spectral absorption properties between the maculae of patients with active neovascular macular degeneration and those with early age related maculopathy (ARM). Patients attending for management of neovascular age related macular degeneration (AMD) underwent multispectral imaging with a system comprising of a modified digital fundus camera coupled with a 250-W tungsten-halogen lamp and a liquid crystal fast-tuneable filter. Images were obtained at 8 wavelengths between 496 and 700 nm. Aligned images were used to generate a DLA (differential light absorption, a measure of spectral absorption properties) map of the macular area. DLA maps were generated for both eyes of 10 sequential patients attending for anti-vascular endothelial growth factor injections. Each of these patients had active leaking neovascular AMD in one eye and early ARM or milder disease in the fellow eye. Eyes with neovascular AMD demonstrated lower average levels of DLA compared with their fellow eyes with early ARM (p=0.037, t test). The significant difference in DLA demonstrates the potential of multispectral imaging for differentiating the two pathologies non-invasively. PMID:23137662

  8. Solar spectral measurements and modeling

    SciTech Connect

    Bird, R.E.; Hulstrom, R.L.

    1981-01-01

    A newly developed spectroradiometer for routine measurement of the solar spectra is described. This instrument measures the solar spectrum between 300 and 2500 nm in less than 2.5 min, with 0.7-nm resolution in the visible and 10-nm resolution in the infrared. Many examples of global, direct, and diffuse spectra are illustrated for Bedford, Mass. and Golden, Colo. The effects of air mass, turbidity, and sun tracking on the spectrum are presented, and radiative transfer modeling capabilities and comparisons between models and between models and experiment are discussed.

  9. Measurement of atmospheric precipitable water using a solar radiometer. [water vapor absorption effects

    NASA Technical Reports Server (NTRS)

    Pitts, D. E.; Dillinger, A. E.; Mcallum, W. E.

    1974-01-01

    A technique is described and tested that allows the determination of atmospheric precipitable water from two measurements of solar intensity: one in a water-vapor absorption band and another in a nearby spectral region unaffected by water vapor.

  10. Glue Film Thickness Measurements by Spectral Reflectance

    SciTech Connect

    B. R. Marshall

    2010-09-20

    Spectral reflectance was used to determine the thickness of thin glue layers in a study of the effect of the glue on radiance and reflectance measurements of shocked-tin substrates attached to lithium fluoride windows. Measurements based on profilometry of the components were found to be inaccurate due to flatness variations and deformation of the tin substrate under pressure during the gluing process. The accuracy of the spectral reflectance measurements were estimated to be ±0.5 μm, which was sufficient to demonstrate a convincing correlation between glue thickness and shock-generated light.

  11. Study on the Relationship between the Depth of Spectral Absorption and the Content of the Mineral Composition of Biotite.

    PubMed

    Yang, Chang-bao; Zhang, Chen-xi; Liu, Fang; Jiang, Qi-gang

    2015-09-01

    The mineral composition of rock is one of the main factors affecting the spectral reflectance characteristics, and it's an important reason for generating various rock characteristic spectra. This study choose the rock samples provided by Jet Propulsion Laboratory (JPL) (including all kinds of mineral percentage of rocks, and spectral reflectances range from 0.35 to 2.50 μm wavelength measured by ASD spectrometer), and the various types of mineral spectral reflectances contained within the rocks are the essential data. Using the spectral linear mixture model of rocks and their minerals, firstly, a simulation study on the mixture of rock and mineral composition is achieved, the experimental results indicate that rock spectral curves using the model which based on the theory of the linear mixture are able to simulate better and preserve the absorption characteristics of various mineral components well. Then, 8 samples which contain biotite mineral are picked from the rock spectra of igneous, biotite contents and the absorption depth characteristics of spectral reflection at 2.332 μm, furthermore, a variety of linear and nonlinear normal statistical models are used to fit the relationship between the depth of absorption spectra and the content of the mineral composition of biotite, finally, a new simulation model is build up with the Growth and the Exponential curve model, and a statistical response relationship between the spectral absorption depth and the rock mineral contents is simulated by using the new model, the fitting results show that the correlation coefficient reaches 0.9984 and the standard deviation is 0.572, although the standard deviation using Growth and Exponential model is less than the two model combined with the new model fitting the standard deviation, the correlation coefficient of the new model had significantly increased, which suggesting that the, new model fitting effect is closer to the measured values of samples, it proves that the

  12. Study on the Relationship between the Depth of Spectral Absorption and the Content of the Mineral Composition of Biotite.

    PubMed

    Yang, Chang-bao; Zhang, Chen-xi; Liu, Fang; Jiang, Qi-gang

    2015-09-01

    The mineral composition of rock is one of the main factors affecting the spectral reflectance characteristics, and it's an important reason for generating various rock characteristic spectra. This study choose the rock samples provided by Jet Propulsion Laboratory (JPL) (including all kinds of mineral percentage of rocks, and spectral reflectances range from 0.35 to 2.50 μm wavelength measured by ASD spectrometer), and the various types of mineral spectral reflectances contained within the rocks are the essential data. Using the spectral linear mixture model of rocks and their minerals, firstly, a simulation study on the mixture of rock and mineral composition is achieved, the experimental results indicate that rock spectral curves using the model which based on the theory of the linear mixture are able to simulate better and preserve the absorption characteristics of various mineral components well. Then, 8 samples which contain biotite mineral are picked from the rock spectra of igneous, biotite contents and the absorption depth characteristics of spectral reflection at 2.332 μm, furthermore, a variety of linear and nonlinear normal statistical models are used to fit the relationship between the depth of absorption spectra and the content of the mineral composition of biotite, finally, a new simulation model is build up with the Growth and the Exponential curve model, and a statistical response relationship between the spectral absorption depth and the rock mineral contents is simulated by using the new model, the fitting results show that the correlation coefficient reaches 0.9984 and the standard deviation is 0.572, although the standard deviation using Growth and Exponential model is less than the two model combined with the new model fitting the standard deviation, the correlation coefficient of the new model had significantly increased, which suggesting that the, new model fitting effect is closer to the measured values of samples, it proves that the

  13. Measurement and modeling of terahertz spectral signatures from layered material

    NASA Astrophysics Data System (ADS)

    Kniffin, G. P.; Schecklman, S.,; Chen, J.; Henry, S. C.; Zurk, L. M.; Pejcinovic, B.; Timchenko, A. I.

    2010-04-01

    Many materials such as drugs and explosives have characteristic spectral signatures in the terahertz (THz) band. These unique signatures hold great promise for potential detection utilizing THz radiation. While such spectral features are most easily observed in transmission,real life imaging systems will need to identify materials of interest from reflection measurements,often in non-ideal geometries. In this work we investigate the interference effects introduced by layered materials,whic h are commonly encountered in realistic sensing geometries. A model for reflection from a layer of material is presented,along with reflection measurements of single layers of sample material. Reflection measurements were made to compare the response of two materials; α-lactose monohydrate which has sharp absorption features,and polyethylene which does not. Finally,the model is inverted numerically to extract material parameters from the measured data as well as simulated reflection responses from the explosive C4.

  14. Identification of key aerosol populations through their size and composition resolved spectral scattering and absorption

    NASA Astrophysics Data System (ADS)

    Costabile, F.; Barnaba, F.; Angelini, F.; Gobbi, G. P.

    2013-03-01

    Characterizing chemical and physical aerosol properties is important to understand their sources, effects, and feedback mechanisms in the atmosphere. This study proposes a scheme to classify aerosol populations based on their spectral optical properties (absorption and scattering). The scheme is obtained thanks to the outstanding set of information on particle size and composition these properties contain. The spectral variability of the aerosol single scattering albedo (dSSA), and the extinction, scattering and absorption Angstrom exponents (EAE, SAE and AAE, respectively) were observed on the basis of two-year measurements of aerosol optical properties (scattering and absorption coefficients at blue, green and red wavelengths) performed in the suburbs of Rome (Italy). Optical measurements of various aerosol types were coupled to measurements of particle number size distributions and relevant optical properties simulations (Mie theory). These latter allowed the investigation of the role of the particle size and composition in the bulk aerosol properties observed. The combination of simulations and measurements suggested a general "paradigm" built on dSSA, SAE and AAE to optically classify aerosols. The paradigm proved suitable to identify the presence of key aerosol populations, including soot, biomass burning, organics, dust and marine particles. The work highlights that (i) aerosol populations show distinctive combinations of SAE and dSSA times AAE, these variables being linked by a linear inverse relation varying with varying SSA; (ii) fine particles show EAE > 1.5, whilst EAE < 2 is found for both coarse particles and ultrafine soot-rich aerosols; (iii) fine and coarse particles both show SSA > 0.8, whilst ultrafine urban Aitken mode and soot particles show SSA < 0.8. The proposed paradigm agrees with aerosol observations performed during past major field campaigns, this indicating that relations concerning the paradigm have a general validity.

  15. Directional spectral emissivity measurement system

    NASA Technical Reports Server (NTRS)

    Halyo, Nesim (Inventor); Pandey, Dhirendra K. (Inventor)

    1992-01-01

    Apparatus and process for determining the emissivity of a test specimen including an integrated sphere having two concentric walls with a coolant circulating therebetween, and disposed within a chamber which may be under ambient, vacuum or inert gas conditions. A reference sample is disposed within the sphere with a monochromatic light source in optical alignment therewith. A pyrometer is in optical alignment with the test sample for obtaining continuous test sample temperature measurements during a test. An arcuate slit port is provided through the spaced concentric walls of the integrating sphere with a movable monochromatic light source extending through and movable along the arcuate slit port. A detector system extends through the integrating sphere for continuously detecting an integrated signal indicative of all radiation within its field of view, as a function of the emissivity of the test specimen at various temperatures and various angle position of the monochromatic light source. A furnace for heating the test sample to approximately 3000 K. and control mechanism for transferring the heated sample from the furnace to the test sample port in the integrating sphere is also contained within the chamber.

  16. Spectral properties of microwave graphs with local absorption.

    PubMed

    Allgaier, Markus; Gehler, Stefan; Barkhofen, Sonja; Stöckmann, H-J; Kuhl, Ulrich

    2014-02-01

    The influence of absorption on the spectra of microwave graphs has been studied experimentally. The microwave networks were made up of coaxial cables and T junctions. First, absorption was introduced by attaching a 50Ω load to an additional vertex for graphs with and without time-reversal symmetry. The resulting level-spacing distributions were compared with a generalization of the Wigner surmise in the presence of open channels proposed recently by Poli et al. [Phys. Rev. Lett. 108, 174101 (2012)]. Good agreement was found using an effective coupling parameter. Second, absorption was introduced along one individual bond via a variable microwave attenuator, and the influence of absorption on the length spectrum was studied. The peak heights in the length spectra corresponding to orbits avoiding the absorber were found to be independent of the attenuation, whereas, the heights of the peaks belonging to orbits passing the absorber once or twice showed the expected decrease with increasing attenuation.

  17. Spectral absorption index in hyperspectral image analysis for predicting moisture contents in pork longissimus dorsi muscles.

    PubMed

    Ma, Ji; Sun, Da-Wen; Pu, Hongbin

    2016-04-15

    Spectral absorption index was proposed to extract the morphological features of the spectral curves in pork meat samples (longissimus dorsi) under the conditions including fresh, frozen-thawed, heated-dehydrated and brined-dehydrated. Savitzky-Golay (SG) smoothing and multiplicative scatter correction (MSC) were used for calibrating both the spectral reflectance and absorbance values. The absorption values were better than the reflectance values and the calibrated spectra by MSC were better than the raw and SG smoothing corrected spectra in building moisture content predictive models. The optimized partial least square regression (PLSR) model attained good results with the MSC calibrated spectral absorption values based on the spectral absorption index features (R(2)P=0.952, RMSEP=1.396) and the optimal wavelengths selected by regression coefficients (R(2)P=0.966, RMSEP=0.855), respectively. The models proved spectral absorption index was promising in spectral analysis to predict moisture content in pork samples using HSI techniques for the first time.

  18. High temperature measurement of water vapor absorption

    NASA Technical Reports Server (NTRS)

    Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

    1985-01-01

    An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

  19. Modeling the spectral absorption by CDOM in Meiliang Bay, Taihu Lake

    NASA Astrophysics Data System (ADS)

    Fu, Qinghua; Wang, Shixin; Zhou, Yi; Yan, Fuli; Wang, Jingjing

    2007-06-01

    The interpretation of remotely sensed images of turbid coastal waters or inland lake waters is more difficult than case 1 water, because their optical properties are complex, and their optical constituents are independent of phytoplankton concentrations. In recent years significant efforts have been made to develop ocean color satellite missions with improved spectral and radiometric performance, and in the same time, techniques for constituent retrieval have evolved from empirical towards analytical algorithms. Analytical models can be developed and inverted to yield concentrations (Carder et al. 1999) of substances in the water from reflectance measurements, which require a suitable parameterization of the optically active constituents and their optical properties. This paper focused on absorption by chromophoric dissolved organic matter (CDOM; also Gelbstoff or yellow substances), which was the pool of absorbing substances in water and one of the main optically active constituents in Case 2 waters. The absorption of CDOM is generally considered as the exponential form model, which have three important main parameters, S, a(λ 0), λ 0. The S results got from the exponential form model fit using CDOM normalization absorptions by 350nm, or 400nm, or 440nm absorption were the same, and the final value of S for CDOM in Meiliang Bay, Taihu Lake was 0.0106, namely the mean of S for all samples; Normally, a(λ 0) is simply taken to be the mean of the absorption coefficient of CDOM of field samples in the reference wavelength, however, this study found that a(λ 0) a varied greatly between samples ( λ 0 = 400, 1.93

  20. Atmospheric Temperature Profile Measurements Using Mobile High Spectral Resolution Lidar

    NASA Astrophysics Data System (ADS)

    Razenkov, Ilya I.; Eloranta, Edwin W.

    2016-06-01

    The High Spectral Resolution Lidar (HSRL) designed at the University of Wisconsin-Madison discriminates between Mie and Rayleigh backscattering [1]. It exploits the Doppler effect caused by thermal motion of molecules, which broadens the spectrum of the transmitted laser light. That allows for absolute calibration of the lidar and measurements of the aerosol volume backscatter coefficient. Two iodine absorption filters with different absorption line widths (a regular iodine vapor filter and Argon buffered iodine filter) allow for atmospheric temperature profile measurements. The sensitivity of the measured signal-to-air temperature ratio is around 0.14%/K. The instrument uses a shared telescope transmitter-receiver design and operates in eyesafe mode (the product of laser average power and telescope aperture equals 0.1 Wm2 at 532 nm).

  1. Spectral interferometric microscopy reveals absorption by individual optical nanoantennas from extinction phase

    PubMed Central

    Gennaro, Sylvain D.; Sonnefraud, Yannick; Verellen, Niels; Van Dorpe, Pol; Moshchalkov, Victor V.; Maier, Stefan A.; Oulton, Rupert F.

    2014-01-01

    Optical antennas transform light from freely propagating waves into highly localized excitations that interact strongly with matter. Unlike their radio frequency counterparts, optical antennas are nanoscopic and high frequency, making amplitude and phase measurements challenging and leaving some information hidden. Here we report a novel spectral interferometric microscopy technique to expose the amplitude and phase response of individual optical antennas across an octave of the visible to near-infrared spectrum. Although it is a far-field technique, we show that knowledge of the extinction phase allows quantitative estimation of nanoantenna absorption, which is a near-field quantity. To verify our method we characterize gold ring-disk dimers exhibiting Fano interference. Our results reveal that Fano interference only cancels a bright mode’s scattering, leaving residual extinction dominated by absorption. Spectral interference microscopy has the potential for real-time and single-shot phase and amplitude investigations of isolated quantum and classical antennas with applications across the physical and life sciences. PMID:24781663

  2. Spectral interferometric microscopy reveals absorption by individual optical nanoantennas from extinction phase.

    PubMed

    Gennaro, Sylvain D; Sonnefraud, Yannick; Verellen, Niels; Van Dorpe, Pol; Moshchalkov, Victor V; Maier, Stefan A; Oulton, Rupert F

    2014-04-30

    Optical antennas transform light from freely propagating waves into highly localized excitations that interact strongly with matter. Unlike their radio frequency counterparts, optical antennas are nanoscopic and high frequency, making amplitude and phase measurements challenging and leaving some information hidden. Here we report a novel spectral interferometric microscopy technique to expose the amplitude and phase response of individual optical antennas across an octave of the visible to near-infrared spectrum. Although it is a far-field technique, we show that knowledge of the extinction phase allows quantitative estimation of nanoantenna absorption, which is a near-field quantity. To verify our method we characterize gold ring-disk dimers exhibiting Fano interference. Our results reveal that Fano interference only cancels a bright mode's scattering, leaving residual extinction dominated by absorption. Spectral interference microscopy has the potential for real-time and single-shot phase and amplitude investigations of isolated quantum and classical antennas with applications across the physical and life sciences.

  3. Relative spectral absorption of solar radiation by water vapor and cloud droplets

    NASA Technical Reports Server (NTRS)

    Davies, R.; Ridgway, W. L.

    1983-01-01

    A moderate (20/cm) spectral resolution model which accounts for both the highly variable spectral transmission of solar radiation through water vapor within and above cloud, as well as the more slowly varying features of absorption and anisotropic multiple scattering by the cloud droplets, is presented. Results from this model as applied to the case of a typical 1 km thick stratus cloud in a standard atmosphere, with cloud top altitude of 2 km and overhead sun, are discussed, showing the relative importance of water vapor above the cloud, water vapor within the cloud, and cloud droplets on the spectral absorption of solar radiation.

  4. Tunable diode laser measurements of HO2NO2 absorption coefficients near 12.5 microns

    NASA Technical Reports Server (NTRS)

    May, R. D.; Molina, L. T.; Webster, C. R.

    1988-01-01

    A tunable diode laser spectrometer has been used to measure absorption coefficients of peroxynitric acid (HO2NO2) near the 803/cm Q branch. HO2NO2 concentrations in a low-pressure flowing gas mixture were determined from chemical titration procedures and UV absorption spectroscopy. The diode laser measured absorption coefficients, at a spectral resolution of better than 0.001/cm, are about 10 percent larger than previous Fourier transform infrared measurements made at a spectral resolution of 0.06/cm.

  5. Recovery of x-ray absorption spectral profile in etched TiO{sub 2} thin films

    SciTech Connect

    Sano, Keiji; Niibe, Masahito; Kawakami, Retsuo; Nakano, Yoshitaka

    2015-05-15

    Near edge x-ray absorption fine structure (NEXAFS) spectra of plasma-etched TiO{sub 2} thin films were observed using the total fluorescence yield method involving visible emission. The disrupted spectrum recovered its as-grown (nonetched) profile, upon soft x-ray (SX) irradiation. This recovery was investigated by ultraviolet (UV) irradiation, spatial distribution measurements, exposing recovered samples to air, and NEXAFS measurements of ultrafine TiO{sub 2} particles. The spectral profile recovered upon UV irradiation, and at sample positions outside of the SX irradiation site. The recovered spectral profiles were disrupted again, upon exposure to air. Nonetched ultrafine TiO{sub 2} particles also exhibited a disrupted spectral profile, which was recovered upon SX irradiation. The spectral recovery is explained by a model involving electrons trapped in oxygen vacancies generated by etching.

  6. Ranging of Extensive Airshowers by Spectral Measurements

    NASA Astrophysics Data System (ADS)

    Paul, T.; Reucroft, S.; Swain, J.

    We study the feasibility of measuring the distance to an extensive air shower using the fact that shorter wavelengths undergo more scattering than longer ones. In principle measuring the spectral distribution of light arriving at a detector provides information about the distance to the shower independent of its brightness or other features. Such measurements may also provide event-by-event measurements of atmospheric properties along the line of sight. We discuss how such measurements could be done with very fast Geiger-mode avalanche photodiodes.

  7. Aerosol optical absorption measurements with photoacoustic spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Kun; Wang, Lei; Liu, Qiang; Wang, Guishi; Tan, Tu; Zhang, Weijun; Chen, Weidong; Gao, Xiaoming

    2015-04-01

    Many parameters related to radiative forcing in climate research are known only with large uncertainties. And one of the largest uncertainties in global radiative forcing is the contribution from aerosols. Aerosols can scatter or absorb the electromagnetic radiation, thus may have negative or positive effects on the radiative forcing of the atmosphere, respectively [1]. And the magnitude of the effect is directly related to the quantity of light absorbed by aerosols [2,3]. Thus, sensitivity and precision measurement of aerosol optical absorption is crucial for climate research. Photoacoustic spectroscopy (PAS) is commonly recognized as one of the best candidates to measure the light absorption of aerosols [4]. A PAS based sensor for aerosol optical absorption measurement was developed. A 532 nm semiconductor laser with an effective power of 160 mW was used as a light source of the PAS sensor. The PAS sensor was calibrated by using known concentration NO2. The minimum detectable optical absorption coefficient (OAC) of aerosol was determined to be 1 Mm-1. 24 hours continues measurement of OAC of aerosol in the ambient air was carried out. And a novel three wavelength PAS aerosol OAC sensor is in development for analysis of aerosol wavelength-dependent absorption Angstrom coefficient. Reference [1] U. Lohmann and J. Feichter, Global indirect aerosol effects: a review, Atmos. Chem. Phys. 5, 715-737 (2005) [2] M. Z. Jacobson, Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols, Nature 409, 695-697 (2001) [3] V. Ramanathan and G. Carmichae, Global and regional climate changes due to black carbon, nature geoscience 1, 221-227 (2008) [4] W.P Arnott, H. Moosmuller, C. F. Rogers, T. Jin, and R. Bruch, Photoacoustic spectrometer for measuring light absorption by aerosol: instrument description. Atmos. Environ. 33, 2845-2852 (1999).

  8. Feature-enhanced spectral similarity measure for the analysis of hyperspectral imagery

    NASA Astrophysics Data System (ADS)

    Li, Qingbo; Niu, Chunyang

    2015-01-01

    In hyperspectral remote sensing, the surface compositional material can be identified by means of spectral matching algorithms. In many cases, the importance of each spectral band to measure spectral similarity is different, whereas the traditional spectral matching algorithms implicitly assume all wavelength-dependent absorption features are equal. This may yield an unsatisfactory performance for spectral matching. To remedy this deficiency, we propose methods called feature-enhanced spectral similarity measures. They are hybrids of the spectral matching algorithms combined with a feature-enhanced space projection, termed feature-enhanced spectral angle measure, feature-enhanced Euclidean distance measure, feature-enhanced spectral correlation measure, and feature-enhanced spectral information divergence. The proposed methods creatively project the original spectra into spectral feature-enhanced space, in which important features for measuring the spectral similarity will be increased to a high degree, whereas features of low importance will be suppressed. In order to demonstrate the effectiveness of the proposed approaches, performances are compared on real hyperspectral image data from Airborne Visible Infrared Imaging Spectrometer. The proposed methods are found to possess significant improvements over the original four spectral matching algorithms.

  9. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite

    NASA Astrophysics Data System (ADS)

    Reddy, S. Lakshmi; Fayazuddin, Md.; Frost, Ray L.; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals.

  10. Electron paramagnetic resonance and optical absorption spectral studies on chalcocite.

    PubMed

    Reddy, S Lakshmi; Fayazuddin, Md; Frost, Ray L; Endo, Tamio

    2007-11-01

    A chalcocite mineral sample of Shaha, Congo is used in the present study. An electron paramagnetic resonance (EPR) study on powdered sample confirms the presence of Mn(II), Fe(III) and Cu(II). Optical absorption spectrum indicates that Fe(III) impurity is present in octahedral structure whereas Cu(II) is present in rhombically distorted octahedral environment. Mid-infrared results are due to water and sulphate fundamentals. PMID:17324611

  11. Atmospheric effect on spectral signature - measurements

    NASA Astrophysics Data System (ADS)

    Kaufman, Yoram J.

    In order to improve the quality of remote sensing there is a need to estimate the atmospheric effect on the remotely sensed image, from the image itself. This can be done by recognition of some surface features with known radiative characteristics. For this purpose measurements of the atmospheric effect on the spectral signature of surface cover were conducted during hazy conditions. Simultaneous measurements of the aerosol optical thickness and its vertical distribution were carried. The results of the measurements are used here to study the spectral dependence of the atmospheric effect on remote sensing of vegetated fields (forest, corn field etc.) and water bodies, and to verify theoretical predictions. It is suggested that the radiances over dark areas (e.g. water in the near IR and forest in the visible) can be used to derive the aerosol optical thickness. Combined with climatological information, the derived optical thickness can be used to perform corrections of the atmospheric effect (not given here).

  12. [The effect of spectral range on the measurement of ozone in the atmosphere by DOAS].

    PubMed

    Fu, Qiang; Peng, Fu-Min; Liu, Wen-Qing; Xie, Pin-Hua; Luo, Tao; Si, Fu-Qi; Li, Su-Wen

    2009-08-01

    Ozone (O3) often serves as the benchmark for the overall pollution level of a given airshed and it is critical that the measurement technique be accurate and precise, In the DOAS measurement, the accuracy of O3 concentration is determined by the selected spectral range. The present paper focuses on the effect of spectral range on the detected characteristic absorption structure of O3, and the variation of differential cross section of O3 with the change in spectral range and the source of interference in different spectral range. The effect of practical atmospheric light extinction on the light intensities of different spectral ranges was deduced; the effect of spectral range on the accuracy was determined by detecting the standard gases at different concentration and different spectral resolution. The optimized spectral range was determined for O3, which can yield high sensitivity, good selectivity and a reasonable time resolution for the accurate qualitative and quantitative analysis of O3. PMID:19839323

  13. Mixing state and spectral absorption of atmospheric aerosols observed at a marine background site

    NASA Astrophysics Data System (ADS)

    Cayetano, M. G.; Lee, K. Y.; Kim, Y. J.

    2011-12-01

    Mineral dust and sea salt particles are portions of atmospheric aerosols in Korea due to the periodic transport of loess dust particles from Gobi and Taklimakan deserts in west China, as well as the sea salt enrichment of atmospheric particles from the seas surrounding the Korean peninsula [Kim et al., 2009; Sahu et al., 2009]. Carbonaceous particles and secondary inorganic aerosols (sulphates and nitrates) are ubiquitous due to the proliferating biomass burning [Ryu et al., 2004], as well as the increasing use of fossil fuels locally and by regional transport from neighbouring countries. Collectively, when these aerosols are transported, their compositions are further modified due to the aging process, impacting their physico-chemical properties including spectral absorption. In order to investigate the spectral response of the absorption under different ambient aerosol conditions, measurements have been conducted at a marine background site in Korea (Deokjeok Island. 37° 13' 33" N, 126° 8' 51" E) during the spring (13 days) and fall (8 days) seasons of 2009 using an aethalometer (Magee AE31), a nephelometer (Optec NGN2a) and other supporting instruments (PILS-IC, PM2.5 cyclone samplers for off-line OC/EC measurements). It has been found that spring aerosols were dominated by sulphate-rich and carbonaceous-rich fractions (21.4%±8.0% and 28.8%±7.9%, respectively), with an Angström exponent of absorption, αabs = 1.3±0.1 at 370-950 nm. The fall season aerosols were grouped based on their chemical composition as acidic aerosols, dust-enriched, and seasalt-enriched aerosols. Angström exponent of absorption, αabs for acidic aerosols was obtained to be 1.3±0.2 at 370-950 nm. However, dust enriched aerosols showed increased absorption in the short UV-Vis range (370-590 nm), which can be attributed to their mixing with light absorbing aerosols. Different types of aerosols exhibit different spectral absorption characteristics depending on their composition and

  14. Uncertainty evaluation of spectral UV irradiance measurements

    NASA Astrophysics Data System (ADS)

    Cordero, Raul R.; Seckmeyer, Gunther; Pissulla, Darius; Da Silva, Luis; Labbe, Fernando

    2008-04-01

    The reference instruments to measure the surface UV irradiance are based on a double monochromator system. The spectral irradiance yielded by these instruments is influenced by temporal instabilities and nonlinearities in the signal, the cosine error as well as uncertainties introduced in the needed prior calibrations. In this paper, we have carried out an uncertainty analysis of the spectral irradiances measured by using a mobile spectroradiometer that complies with the requirements of the Network for the Detection of Atmospheric Composition Change (NDACC). The spectral measurements were performed on 9th June 2005 (cloudless sky conditions) at the Izaña Observatory (28.3° N, 16.5° E, 2367 m above sea level, Tenerife, Spain), during an international intercomparison campaign organized in the framework of the project Quality Assurance of Spectral Ultraviolet Measurements in Europe (QASUME). At solar zenith angles smaller than 30°, we found that despite the variations due to wavelength shifts induced by the high environmental temperature the relative expanded uncertainty was about 7% in the UV-A part of the spectrum; an increment was observed at wavelengths shorter than 315 nm such that the expanded uncertainty of the UV-B irradiance at 300 nm wavelength was about 9%. The measurements of the other five teams that participated in the campaign were within the bound specified by these expanded uncertainties. We also found that, regardless of the influence of the cosine error, the uncertainties involved in the absolute calibration procedure accounted for about 65% of the irradiance uncertainty. Although only a double monochromator was used in this work, the methodology applied to evaluate the uncertainty is general and it agrees with recommendations of the ISO Guide to the Expression of Uncertainty in Measurement.

  15. Measurements of spectral attenuation coefficients in the lower Chesapeake Bay

    NASA Technical Reports Server (NTRS)

    Houghton, W. M.

    1983-01-01

    The spectral transmission was measured for water samples taken in the lower Chesapeake Bay to allow characterization of several optical properties. The coefficients of total attenuation, particle attenuation, and absorption by dissolved organic matter were determined over a wavelength range from 3500 A to 8000 A. The data were taken over a 3 year period and at a number of sites so that an indication of spatial and temporal variations could be obtained. The attenuations determined in this work are, on the average, 10 times greater than those obtained by Hulburt in 1944, which are commonly accepted in the literature for Chesapeake Bay attenuation.

  16. Absorption technique for OH measurements and calibration

    NASA Technical Reports Server (NTRS)

    Bakalyar, D. M.; James, J. V.; Wang, C. C.

    1982-01-01

    An absorption technique is described which utilizes a stabilized frequency-doubled tunable dye laser and a long-path White cell with high mirror reflectivities both in the red and UV. In laboratory conditions it has been possible to routinely obtain a detection sensitivity of 3 parts in 1,000,000 over absorption paths less than 1 m in length and a detection sensitivity of approximately 6 parts in 100,000 over an absorption path of the order of 1 km. The latter number corresponds to 3,000,000 OH molecules/cu cm, and therefore the technique should be particularly useful for calibration the fluorescence instrument for OH measurements. However, the presence of atmospheric fluctuations coupled with intensity variation accompanying frequency scanning appears to degrade the detection sensitivity in outdoor ambient conditions, thus making it unlikely that this technique can be employed for direct OH monitoring.

  17. Detector absorptivity measuring method and apparatus

    NASA Technical Reports Server (NTRS)

    Sheets, R. E. (Inventor)

    1976-01-01

    A method and apparatus for measuring the absorptivity of a radiation detector by making the detector an integral part of a cavity radiometer are described. By substituting the detector for the surface of the cavity upon which the radiation first impinges a comparison is made between the quantity of radiation incident upon the detector and the quantity reflected from the detector. The difference between the two is a measurement of the amount of radiation absorbed by the detector.

  18. Scintillation detectors in gamma spectral logging; geometry, absorption and calibration

    USGS Publications Warehouse

    Schimschal, Ulrich

    1980-01-01

    The theory for the evaluation of the effects of geometry in gamma ray absorption is developed for cylindrical scintillation detectors as applicable to borehole gamma spectrometry. The results of a laboratory experiment are shown for comparison. A calibration procedure to determine detector efficiency is given for application to borehole probes. It is shown that the response of a crystal can be separated in terms of geometric effects and instrumentation effects. It is also shown that approximating crystal detectors with point detectors in mathematical theory is grossly oversimplified. (USGS)

  19. Fiberoptic probe and system for spectral measurements

    DOEpatents

    Dai, S.; Young, J.P.

    1998-10-13

    A fused fiberoptic probe, a system, method and embodiments thereof for conducting spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferably silica. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0{degree}, an inverted cone-shaped probe tip, and a lens head. 12 figs.

  20. Fiberoptic probe and system for spectral measurements

    DOEpatents

    Dai, Sheng; Young, Jack P.

    1998-01-01

    A fused fiberoptic probe, a system, method and embodiments thereof for conducting spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferrably silica. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0.degree., an inverted cone-shaped probe tip, and a lens head.

  1. Revealing spectral features in two-photon absorption spectrum of Hoechst 33342: a combined experimental and quantum-chemical study.

    PubMed

    Olesiak-Banska, Joanna; Matczyszyn, Katarzyna; Zaleśny, Robert; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Bartkowiak, Wojciech; Samoc, Marek

    2013-10-10

    We present the results of wide spectral range Z-scan measurements of the two-photon absorption (2PA) spectrum of the Hoechst 33342 dye. The strongest 2PA of the dye in aqueous solution is found at 575 nm, and the associated two-photon absorption cross section is 245 GM. A weak but clearly visible 2PA band at ∼850 nm is also observed, a feature that could not be anticipated from the one-photon absorption spectrum. On the basis of the results of hybrid quantum mechanics/molecular mechanics calculations, we put forward a notion that the long-wavelength feature observed in the two-photon absorption spectrum of Hoechst 33342 is due to the formation of dye aggregates. PMID:24016295

  2. Spectral Light Absorption and Scattering by Aerosol Particles in Central Amazonia

    NASA Astrophysics Data System (ADS)

    Artaxo, P.; Holanda, B. A.; Ferreira De Brito, J.; Carbone, S.; Barbosa, H. M.; Rizzo, L. V.; Cirino, G. G.; Andreae, M. O.; Saturno, J.; Pöhlker, C.; Martin, S. T.; Holben, B. N.; Schafer, J.

    2015-12-01

    As part of the GoAmazon2014/5, a detailed characterization of spectral light absorption and light scattering was performed at four research sites located in the central Amazon forest at different distances upwind and downwind of Manaus. The sites ATTO (T0a) and Embrapa (T0e) are located upwind of Manaus where it is possible to observe very pristine atmospheric conditions in wet season. The site Tiwa (T2) is being operated under the direct influence of the Manaus plume at 5 km downwind of Manaus and, finally, the Manacapuru (T3) site is located at about 60 km downwind of Manaus. The spectral dependence of light absorption and light scattering were measured using Aethalometers (7-wavelengths) and Nephelometers (3-wavelengths), respectively. By calculating the Absorption Angstrom Exponent (AAE), it was possible to get information about the source of the aerosol whereas the Scattering Angstrom Exponent (SAE) gives information about its size distribution. Sunphotometers from the AERONET network were set up at T3 and T0e sites to measure column Aerosol Optical Depth (AOD). For all the stations, much higher absorption and scattering coefficients were observed during the dry season in comparison to the wet season, as a result of the larger concentration of BC and OC present in the biomass burning events. Additionally, we also observed Manaus plume pollution that alters the BC signal. There is also an increase of the AAE during the dry season due to the larger amount of aerosols from biomass burning compared with urban pollution. High values of AAE are also observed during the wet season, attributed to the presence of long-range transport of aerosols from Africa. The SAE for all the sites are lower during the wet season, with the dominance of large biological particles, and increases during the dry season as a consequence of fine particles emitted from both biomass and fossil fuel burning. The AOD at T0e and T3 (Jan-Jun/2014) showed very similar values ranging from 0.05 to

  3. Temperature and salinity correction coefficients for light absorption by water in the visible to infrared spectral region.

    PubMed

    Röttgers, Rüdiger; McKee, David; Utschig, Christian

    2014-10-20

    The light absorption coefficient of water is dependent on temperature and concentration of ions, i.e. the salinity in seawater. Accurate knowledge of the water absorption coefficient, a, and/or its temperature and salinity correction coefficients, Ψ(T) and Ψ(S), respectively, is essential for a wide range of optical applications. Values are available from published data only at specific narrow wavelength ranges or at single wavelengths in the visible and infrared regions. Ψ(T) and Ψ(S) were therefore spectrophotometrically measured throughout the visible, near, and short wavelength infrared spectral region (400 to ~2700 nm). Additionally, they were derived from more precise measurements with a point-source integrating-cavity absorption meter (PSICAM) for 400 to 700 nm. When combined with earlier measurements from the literature in the range of 2600 - 14000 nm (wavenumber: 3800 - 700 cm(-1)), the coefficients are provided for 400 to 14000 nm (wavenumber: 25000 to 700 cm(-1)).

  4. Absorption and scattering imaging of tissue with steady-state second-differential spectral-analysis tomography.

    PubMed

    Xu, Heng; Pogue, Brian W; Dehghani, Hamid; Paulsen, Keith D

    2004-09-01

    A novel approach to reconstructing both the absorption and the scattering properties of a turbid medium simultaneously from steady-state broadband spectral measurements is presented that utilizes second-differential fitting to the water spectrum to estimate the optical path length in tissue. Theoretical and experimental evidence is provided to demonstrate the robust accuracy of the spectroscopy approach and reconstructed absorption images. The steady-state broadband CCD system has the potential to provide accurate chromophore imaging without the technological complexity of time- or frequency-domain systems.

  5. Absorption and fluorescent spectral studies of imidazophenazine derivatives.

    PubMed

    Ryazanova, O A; Zozulya, V N; Voloshin, I M; Karachevtsev, V A; Makitruk, V L; Stepanian, S G

    2004-07-01

    Absorption and fluorescent spectra as well as fluorescence polarization degree of imidazo-[4,5-d]-phenazine (F1) and its two modified derivatives, 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F2) and 1,2,3-triazole-[4,5-d]-phenazine (F3), were investigated in organic solvents of various polarities and hydrogen bonding abilities. Extinction coefficients of F2 and F3 are increased, their fluorescence Stokes shifts are reduced in comparison with those for unmodified imidazophenazine. For F3 a red shift of the longwave absorption band is observed by 15-20 nm. Modifications of imidazophenazine have led to a sufficient increase of fluorescence polarization degrees that enables to use F2 and F3 as promising fluorescent probes with polarization method application. The configuration, atomic charge distribution and dipole moments of the isolated dye molecules in the ground state were calculated by the DFT method. The computation has revealed that ground state dipole moments of F1, F2, and F3 differ slightly and are equal to 3.5, 3.2, and 3.7D, respectively. The changes in dipole moments upon the optical excitation for all derivatives estimated using Lippert equation were found to be Deltamu = 9 D. The energies of the electronic S1<--S0 transition in solvents of different proton donor abilities were determined, and energetic diagram illustrating the substituent effect was plotted. For nucleoside analogs of these compounds, covalently incorporated into a nucleotide chain, we have considered a possibility to use them as fluorescent reporters of hybridization of antisense oligonucleotides, as well as molecular anchors for its stabilization. PMID:15248979

  6. Dynamics of CO(2) laser pulse filamentation in air influenced by spectrally selective molecular absorption.

    PubMed

    Geints, Yuri E; Zemlyanov, Alexander A

    2014-09-01

    The theoretical aspects of self-focusing and filamentation of high-power pulsed CO(2) laser radiation with carrier wavelength 10.6 μm in air are considered. The spectrally selective molecular absorption of realistic atmospheric air is included in the theoretical model. In the conditions of strong pulse self-phase modulation and pulse spectral broadening, the supercontinual radiation spectrum is substantially influenced by the selective atmospheric absorption that destabilizes the filamentation process and results in considerable shortening of the filamentation length. PMID:25321358

  7. Spectral slopes of the absorption coefficient of colored dissolved and detrital material inverted from UV-visible remote sensing reflectance

    NASA Astrophysics Data System (ADS)

    Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy

    2016-03-01

    The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), Scdm (units: nm-1), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving Scdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360-500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized dataset to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of Scdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors.

  8. Linking CDOM spectral absorption to dissolved organic carbon concentrations and loadings in boreal estuaries

    NASA Astrophysics Data System (ADS)

    Asmala, Eero; Stedmon, Colin A.; Thomas, David N.

    2012-10-01

    The quantity of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) in three Finnish estuaries (Karjaanjoki, Kyrönjoki and Kiiminkijoki) was investigated, with respect to predicting DOC concentrations and loadings from spectral CDOM absorption measurements. Altogether 87 samples were collected from three estuarine transects which were studied in three seasons, covering a salinity range between 0 and 6.8, and DOC concentrations from 1572 μmol l-1 in freshwater to 222 μmol l-1 in coastal waters. CDOM absorption coefficient, aCDOM(375) values followed the trend in DOC concentrations across the salinity gradient and ranged from 1.67 to 33.4 m-1. The link between DOC and CDOM was studied using a range of wavelengths and algorithms. Wavelengths between 250 and 270 nm gave the best predictions with single linear regression. Total dissolved iron was found to influence the prediction in wavelengths above 520 nm. Despite significant seasonal and spatial differences in DOC-CDOM models, a universal relationship was tested with an independent data set and found to be robust. DOC and CDOM yields (loading/catchment area) from the catchments ranged from 1.98 to 5.44 g C m-2 yr-1, and 1.67 to 11.5 aCDOM(375) yr-1, respectively.

  9. Retrieval interval mapping, a tool to optimize the spectral retrieval range in differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Vogel, L.; Sihler, H.; Lampel, J.; Wagner, T.; Platt, U.

    2012-06-01

    Remote sensing via differential optical absorption spectroscopy (DOAS) has become a standard technique to identify and quantify trace gases in the atmosphere. The technique is applied in a variety of configurations, commonly classified into active and passive instruments using artificial and natural light sources, respectively. Platforms range from ground based to satellite instruments and trace-gases are studied in all kinds of different environments. Due to the wide range of measurement conditions, atmospheric compositions and instruments used, a specific challenge of a DOAS retrieval is to optimize the parameters for each specific case and particular trace gas of interest. This becomes especially important when measuring close to the detection limit. A well chosen evaluation wavelength range is crucial to the DOAS technique. It should encompass strong absorption bands of the trace gas of interest in order to maximize the sensitivity of the retrieval, while at the same time minimizing absorption structures of other trace gases and thus potential interferences. Also, instrumental limitations and wavelength depending sources of errors (e.g. insufficient corrections for the Ring effect and cross correlations between trace gas cross sections) need to be taken into account. Most often, not all of these requirements can be fulfilled simultaneously and a compromise needs to be found depending on the conditions at hand. Although for many trace gases the overall dependence of common DOAS retrieval on the evaluation wavelength interval is known, a systematic approach to find the optimal retrieval wavelength range and qualitative assessment is missing. Here we present a novel tool to determine the optimal evaluation wavelength range. It is based on mapping retrieved values in the retrieval wavelength space and thus visualize the consequence of different choices of retrieval spectral ranges, e.g. caused by slightly erroneous absorption cross sections, cross correlations and

  10. Absorption cross-sections of ozone in the ultraviolet and visible spectral regions: Status report 2015

    NASA Astrophysics Data System (ADS)

    Orphal, Johannes; Staehelin, Johannes; Tamminen, Johanna; Braathen, Geir; De Backer, Marie-Renée; Bais, Alkiviadis; Balis, Dimitris; Barbe, Alain; Bhartia, Pawan K.; Birk, Manfred; Burkholder, James B.; Chance, Kelly; von Clarmann, Thomas; Cox, Anthony; Degenstein, Doug; Evans, Robert; Flaud, Jean-Marie; Flittner, David; Godin-Beekmann, Sophie; Gorshelev, Viktor; Gratien, Aline; Hare, Edward; Janssen, Christof; Kyrölä, Erkki; McElroy, Thomas; McPeters, Richard; Pastel, Maud; Petersen, Michael; Petropavlovskikh, Irina; Picquet-Varrault, Benedicte; Pitts, Michael; Labow, Gordon; Rotger-Languereau, Maud; Leblanc, Thierry; Lerot, Christophe; Liu, Xiong; Moussay, Philippe; Redondas, Alberto; Van Roozendael, Michel; Sander, Stanley P.; Schneider, Matthias; Serdyuchenko, Anna; Veefkind, Pepijn; Viallon, Joële; Viatte, Camille; Wagner, Georg; Weber, Mark; Wielgosz, Robert I.; Zehner, Claus

    2016-09-01

    The activity "Absorption Cross-Sections of Ozone" (ACSO) started in 2008 as a joint initiative of the International Ozone Commission (IO3C), the World Meteorological Organization (WMO) and the IGACO ("Integrated Global Atmospheric Chemistry Observations") O3/UV subgroup to study, evaluate, and recommend the most suitable ozone absorption cross-section laboratory data to be used in atmospheric ozone measurements. The evaluation was basically restricted to ozone absorption cross-sections in the UV range with particular focus on the Huggins band. Up until now, the data of Bass and Paur published in 1985 (BP, 1985) are still officially recommended for such measurements. During the last decade it became obvious that BP (1985) cross-section data have deficits for use in advanced space-borne ozone measurements. At the same time, it was recognized that the origin of systematic differences in ground-based measurements of ozone required further investigation, in particular whether the BP (1985) cross-section data might contribute to these differences. In ACSO, different sets of laboratory ozone absorption cross-section data (including their dependence on temperature) of the group of Reims (France) (Brion et al., 1993, 1998, 1992, 1995, abbreviated as BDM, 1995) and those of Serdyuchenko et al. (2014), and Gorshelev et al. (2014), (abbreviated as SER, 2014) were examined for use in atmospheric ozone measurements in the Huggins band. In conclusion, ACSO recommends: The spectroscopic data of BP (1985) should no longer be used for retrieval of atmospheric ozone measurements. For retrieval of ground-based instruments of total ozone and ozone profile measurements by the Umkehr method performed by Brewer and Dobson instruments data of SER (2014) are recommended to be used. When SER (2014) is used, the difference between total ozone measurements of Brewer and Dobson instruments are very small and the difference between Dobson measurements at AD and CD wavelength pairs are diminished

  11. Modeling optical absorption for thermoreflectance measurements

    NASA Astrophysics Data System (ADS)

    Yang, Jia; Ziade, Elbara; Schmidt, Aaron J.

    2016-03-01

    Optical pump-probe techniques based on thermoreflectance, such as time domain thermoreflectance and frequency domain thermoreflectance (FDTR), have been widely used to characterize the thermal conductivity of thin films and the thermal conductance across interfaces. These techniques typically use a transducer layer to absorb the pump light and improve the thermoreflectance signal. The transducer, however, complicates the interpretation of the measured signal because the approximation that all the energy from the pump beam is deposited at the transducer surface is not always accurate. In this paper, we consider the effect of laser absorption in the top layer of a multilayer sample, and derive an analytical solution for the thermoreflectance signal in the diffusion regime based on volumetric heating. We analyze the measurement sensitivity to the pump absorption depth for transducers with different thermal conductivities, and investigate the additional effect of probe laser penetration depth on the measured signal. We validate our model using FDTR measurements on 490 nm thick amorphous silicon films deposited on fused silica and silicon substrates.

  12. Spectral shape of the UV ionizing background and He II absorption at redshifts 1.8 < z < 2.9

    NASA Astrophysics Data System (ADS)

    Agafonova, I. I.; Levshakov, S. A.; Reimers, D.; Fechner, C.; Tytler, D.; Simcoe, R. A.; Songaila, A.

    2007-01-01

    Aims:The shape of the UV ionizing background is reconstructed from optically thin metal absorption-line systems identified in spectra of HE 2347-4342, Q 1157+3143, and HS 1700+6416 in the redshift interval 1.8 < z < 2.9. Methods: The systems are analyzed by means of the Monte Carlo Inversion method completed with the spectral shape recovering procedure. Results: The UVB spectral shape fluctuates at 2.4 < z < 2.9 mostly due to radiative transfer processes in the clumpy IGM. At z ⪉ 1.8, the IGM becomes almost transparent both in the H I and He II Lyman continua and the variability of the spectral shape comes from diversity of spectral indices describing the QSO/AGN intrinsic radiation. At z > 2.4, the recovered spectral shapes show intensity depression between 3 and 4 Ryd due to He II Lyα absorption in the IGM clouds (line blanketing) and continuous medium (true Gunn-Petersen effect). The mean He II Lyα opacity estimated from the depth of this depression corresponds within 1-2σ to the values directly measured from the H I/He II Lyα forest towards the quasars studied. The observed scatter in η = N(He II)/N(H I) and anti-correlation between N(H I) and η can be explained by the combined action of variable spectral softness and differences in the mean gas density between the absorbing clouds. Neither of the recovered spectral shapes show features which can be attributed to the putative input of radiation from soft sources like starburst galaxies.

  13. Extreme ultraviolet spectral irradiance measurements since 1946

    NASA Astrophysics Data System (ADS)

    Schmidtke, G.

    2015-03-01

    In the physics of the upper atmosphere the solar extreme ultraviolet (EUV) radiation plays a dominant role controlling most of the thermospheric/ionospheric (T/I) processes. Since this part of the solar spectrum is absorbed in the thermosphere, platforms to measure the EUV fluxes became only available with the development of rockets reaching altitude levels exceeding 80 km. With the availability of V2 rockets used in space research, recording of EUV spectra started in 1946 using photographic films. The development of pointing devices to accurately orient the spectrographs toward the sun initiated intense activities in solar-terrestrial research. The application of photoelectric recording technology enabled the scientists placing EUV spectrometers aboard satellites observing qualitatively strong variability of the solar EUV irradiance on short-, medium-, and long-term scales. However, as more measurements were performed more radiometric EUV data diverged due to the inherent degradation of the EUV instruments with time. Also, continuous recording of the EUV energy input to the T/I system was not achieved. It is only at the end of the last century that there was progress made in solving the serious problem of degradation enabling to monitore solar EUV fluxes with sufficient radiometric accuracy. The data sets available allow composing the data available to the first set of EUV data covering a period of 11 years for the first time. Based on the sophisticated instrumentation verified in space, future EUV measurements of the solar spectral irradiance (SSI) are promising accuracy levels of about 5% and less. With added low-cost equipment, real-time measurements will allow providing data needed in ionospheric modeling, e.g., for correcting propagation delays of navigation signals from space to earth. Adding EUV airglow and auroral emission monitoring by airglow cameras, the impact of space weather on the terrestrial T/I system can be studied with a spectral terrestrial

  14. Infrared spectral measurement of space shuttle glow

    SciTech Connect

    Ahmadijian, M.

    1992-01-01

    Infrared spectral measurements of the space shuttle glow were successfully conducted during the STS-39 space shuttle mission. Analysis indicates that NO, NO[sup +], OH, and CO are among the molecules associated with the infrared glow phenomenon. During orbiter thruster firings the glow intensities in the infrared are enhanced by factors of 10x to 100x with significant changes in spectral distribution. These measurements were obtained with the Spacecraft Kinetic Infrared Test (SKIRT) payload which included a cryogenic infrared circular variable filter (CVF) spectrometer (0.6 [mu]m to 5.4 [mu]) and a number of infrared, visible, and ultraviolet radiometers (0.2 [mu]m to 5.4 [mu]m and 9.9 [mu]m to 10.4 [mu]m). In addition, glow measurements were unsuccessfully attempted with the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) with its 2.5 [mu]m to 25 [mu]m Fourier transform interferometer. SKIRT CVF obtained over 14,000 spectra of quiescent shuttle glow, thruster enhanced shuttle glow, upper atmosphere airglow, aurora, orbiter environment, and deep space non-glow backgrounds during its eight day mission. The SKIRT radiometers operated almost continuously throughout the mission to provide a detailed history of the IR/VIS/UV optical environment associated with the operation of large spacecraft structures in low earth orbit. This dissertation will primarily address those measurements conducted by the SKIRT spectrometer as they relate to space shuttle glow in the infrared. The STS-39 Space Shuttle Discovery was launched from the NASA Kennedy Space Center on 28 April 1991 into a 57 degree inclination circular orbit at an altitude of 260 km.

  15. [The linearity analysis of ultrahigh temperature FTIR spectral emissivity measurement system].

    PubMed

    Wang, Zong-wei; Dai, Jing-min; He, Xiao-wa; Yang, Chun-ling

    2012-02-01

    To study thermal radiation properties of special materials at high temperature in aerospace fields, the ultrahigh temperature spectral emissivity measurement system with Fourier spectrometer has been established. The linearity of system is the guarantee of emissivity measurement precision. Through measuring spectral radiation signals of a blackbody source at different temperatures, the function relations between spectral signal values and blackbody spectral radiation luminance of every spectrum points were calculated with the method of multi-temperature and multi-spectrum linear fitting. The spectral radiation signals of blackbody were measured between 1 000 degrees C and 2 000 degrees C in the spectral region from 3 to 20 microm. The linear relations between spectral signal and theory line at wavelength of 4 microm were calculated and introduced. The spectral response is well good between 4 and 18 microm, the spectral linearity are less than 1% except CO2 strong absorption spectrum regions. The results show that when the errors of measured spectrum radiation and linear fitting theory lines are certain, the higher the temperature, the smaller the spectral errors on emissivity. The linearity analysis of spectrum response is good at eliminating errors caused by individual temperature' disturbance to the spectra.

  16. Airborne Spectral Measurements of Ocean Directional Reflectance

    NASA Technical Reports Server (NTRS)

    Gatebe, Charles K.; King, Michael D.; Lyapustin, Alexei; Arnold, G. Thomas; Redemann, Jens

    2004-01-01

    During summer of 2001 NASA's Cloud Absorption Radiometer (CAR) obtained measurement of ocean angular distribution of reflected radiation or BRDF (bidirectional reflectance distribution function) aboard the University of Washington Convair CV-580 research aircraft under cloud-free conditions. The measurements took place aver the Atlantic Ocean off the eastern seaboard of the U.S. in the vicinity of the Chesapeake Light Tower and at nearby National Oceanic and Atmospheric Administration (NOAA) Buoy Stations. The measurements were in support of CLAMS, Chesapeake Lighthouse and Aircraft Measurements for Satellites, field campaign that was primarily designed to validate and improve NASA's Earth Observing System (EOS) satellite data products being derived from three sensors: MODIS (MODerate Resolution Imaging Spectro-Radiometer), MISR (Multi-angle Imaging Spectro-Radiometer) and CERES (Clouds and Earth s Radiant Energy System). Because of the high resolution of the CAR measurements and its high sensitivity to detect weak ocean signals against a noisy background, results of radiance field above the ocean are seen in unprecedented detail. The study also attempts to validate the widely used Cox-Munk model for predicting reflectance from a rough ocean surface.

  17. Enhanced plasmonic light absorption engineering of graphene: simulation by boundary-integral spectral element method.

    PubMed

    Niu, Jun; Luo, Ma; Zhu, Jinfeng; Liu, Qing Huo

    2015-02-23

    Graphene's relatively poor absorption is an essential obstacle for designing graphene-based photonic devices with satisfying photo-responsivity. To enhance the tunable light absorption of graphene, appropriate excitation of localized surface plasmon resonance is considered as a promising approach. In this work, the strategy of incorporating periodic cuboid gold nanoparticle (NP) cluster arrays and cylindrical gold NP arrays with Bragg reflectors into graphene-based photodetectors are theoretically studied by the boundary-integral spectral element method (BI-SEM). With the BI-SEM, the models can be numerically analyzed with excellent accuracy and efficiency. Numerical simulation shows that the proposed structures can effectively engineer the light absorption in graphene by tuning plasmon resonance. In the spectra of 300 nm to 1000 nm, a maximum light absorption of 67.54% is observed for the graphene layer with optimal parameters of the photodetector model.

  18. Spectral Absorption Depth Profile: A Step Forward to Plasmonic Solar Cell Design

    NASA Astrophysics Data System (ADS)

    Hossain, Mohammad K.; Mukhaimer, Ayman W.; Drmosh, Qasem A.

    2016-11-01

    Absorption depth profile, a deterministic and key factor that defines the quality of excitons generation rate in optoelectronic devices, is numerically predicted using finite different time domain analysis. A typical model, nanoparticles array on silicon slab, was devised considering the concept of plasmonic solar cell design. The trend of spectral absorption depth profile distributions at various wavelengths of the solar spectrum, 460 nm, 540 nm, 650 nm, 815 nm, and 1100 nm, was obtained. A stronger and well-distributed absorption profile was obtained at ˜650 nm of the solar spectrum (i.e. ˜1.85 eV, c-Si bandgap), although the absorbing layer was affected more than a half micron depth at shorter wavelengths. Considering the observations obtained from this simulation, we have shown a simple two-step method in fabricating ultra-pure silver (Ag) nanoparticles that can be used as plasmonic nanoscatterers in a thin film solar cell. The morphology and elemental analysis of as-fabricated Ag nanoparticles was confirmed by field emission scanning electron microscope (FESEM) and FESEM-coupled electron diffraction spectroscopy. The size of the as-fabricated Ag nanoparticles was found to range from 50 nm to 150 nm in diameter. Further investigations on structural and optical properties of the as-fabricated specimen were carried out using ultraviolet-visible (UV-Vis) absorption, photoluminesce, and x-ray diffraction (XRD). Preferential growth of ZnO along {002} was confirmed by XRD pattern that was more intense and broadened at increasing annealing temperatures. The lattice parameter c was found to increase, whereas grain size increased with increasing annealing temperature. The optical bandgap was also observed to decrease from 3.31 eV to 3.25 eV at increasing annealing temperatures through UV-Vis measurements. This parallel investigation on optical properties by simulation is in line with experimental studies and, in fact, facilitates devising optimum process cost for

  19. Spectral Absorption Depth Profile: A Step Forward to Plasmonic Solar Cell Design

    NASA Astrophysics Data System (ADS)

    Hossain, Mohammad K.; Mukhaimer, Ayman W.; Drmosh, Qasem A.

    2016-07-01

    Absorption depth profile, a deterministic and key factor that defines the quality of excitons generation rate in optoelectronic devices, is numerically predicted using finite different time domain analysis. A typical model, nanoparticles array on silicon slab, was devised considering the concept of plasmonic solar cell design. The trend of spectral absorption depth profile distributions at various wavelengths of the solar spectrum, 460 nm, 540 nm, 650 nm, 815 nm, and 1100 nm, was obtained. A stronger and well-distributed absorption profile was obtained at ˜650 nm of the solar spectrum (i.e. ˜1.85 eV, c-Si bandgap), although the absorbing layer was affected more than a half micron depth at shorter wavelengths. Considering the observations obtained from this simulation, we have shown a simple two-step method in fabricating ultra-pure silver (Ag) nanoparticles that can be used as plasmonic nanoscatterers in a thin film solar cell. The morphology and elemental analysis of as-fabricated Ag nanoparticles was confirmed by field emission scanning electron microscope (FESEM) and FESEM-coupled electron diffraction spectroscopy. The size of the as-fabricated Ag nanoparticles was found to range from 50 nm to 150 nm in diameter. Further investigations on structural and optical properties of the as-fabricated specimen were carried out using ultraviolet-visible (UV-Vis) absorption, photoluminesce, and x-ray diffraction (XRD). Preferential growth of ZnO along {002} was confirmed by XRD pattern that was more intense and broadened at increasing annealing temperatures. The lattice parameter c was found to increase, whereas grain size increased with increasing annealing temperature. The optical bandgap was also observed to decrease from 3.31 eV to 3.25 eV at increasing annealing temperatures through UV-Vis measurements. This parallel investigation on optical properties by simulation is in line with experimental studies and, in fact, facilitates devising optimum process cost for

  20. Near-infrared spectral methods for noninvasively measuring blood glucose

    NASA Astrophysics Data System (ADS)

    Fei, Sun; Kong, Deyi; Mei, Tao; Tao, Yongchun

    2004-05-01

    Determination of blood glucose concentrations in diabetic patients is a frequently occurring procedure and an important tool for diabetes management. Use of noninvasive detection techniques can relieve patients from the pain of frequent finger pokes and avoid the infection of disease via blood. This thesis discusses current research and analyzes the advantages and shortages of different measurement methods, including: optical methods (Transmission, Polarimetry and scattering), then, we give emphasis to analyze the technology of near-infrared (NIR) spectra. NIR spectral range 700 nm ~2300 nm was used because of its good transparency for biological tissue and presence of glucose absorption band. In this work, we present an outline of noninvasive blood glucose measurement. A near-infrared light beam is passed through the finger, and the spectral components of the emergent beam are measured using spectroscopic techniques. The device includes light sources having the wavelengths of 600 nm - 1800 nm to illuminate the tissue. Receptors associated with the light sources for receiving light and generating a transmission signal representing the light transmitted are also provided. Once a transmission signal is received by receptors, and the high and low values from each of the signals are stored in the device. The averaged values are then analyzed to determine the glucose concentration, which is displayed on the device.

  1. Spectral density measurements of gyro noise

    NASA Technical Reports Server (NTRS)

    Truncale, A.; Koenigsberg, W.; Harris, R.

    1972-01-01

    Power spectral density (PSD) was used to analyze the outputs of several gyros in the frequency range from 0.01 to 200 Hz. Data were accumulated on eight inertial quality instruments. The results are described in terms of input angle noise (arcsec 2/Hz) and are presented on log-log plots of PSD. These data show that the standard deviation of measurement noise was 0.01 arcsec or less for some gyros in the passband from 1 Hz down 10 0.01 Hz and probably down to 0.001 Hz for at least one gyro. For the passband between 1 and 100 Hz, uncertainties in the 0.01 and 0.05 arcsec region were observed.

  2. Gas-phase absorption cross sections of 24 monocyclic aromatic hydrocarbons in the UV and IR spectral ranges

    NASA Astrophysics Data System (ADS)

    Etzkorn, Thomas; Klotz, Björn; Sørensen, Søren; Patroescu, Iulia V.; Barnes, Ian; Becker, Karl H.; Platt, Ulrich

    Absorption cross sections of 24 volatile and non-volatile derivatives of benzene in the ultraviolet (UV) and the infrared (IR) regions of the electromagnetic spectrum have been determined using a 1080 l quartz cell. For the UV a 0.5 m Czerny-Turner spectrometer coupled with a photodiode array detector (spectral resolution 0.15 nm) was used. IR spectra were recorded with an FT-IR spectrometer (Bruker IFS-88, spectral resolution 1 cm -1). Absolute absorption cross sections and the instrument function are given for the UV, while for the IR, absorption cross sections and integrated band intensities are reported. The study focused primarily on the atmospherically relevant methylated benzenes (benzene, toluene, o-xylene, m-xylene, p-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, ethylbenzene, styrene) and their ring retaining oxidation products (benzaldehyde, o-tolualdehyde, m-tolualdehyde, p-tolualdehyde, phenol, o-cresol, m-cresol, p-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol, 2,4,6-trimethylphenol and ( E,Z)- and ( E,E)-2,4-hexadienedial). The UV absorption cross sections reported here can be used for the evaluation of DOAS spectra (Differential Optical Absorption Spectroscopy) for measurements of the above compounds in the atmosphere and in reaction chambers, while the IR absorption cross sections will primarily be useful in laboratory studies on atmospheric chemistry, where FT-IR spectrometry is an important tool.

  3. Nonlinear optical absorption and fluorescence of phosphine-substituted bithiophenes in the violet-blue spectral region

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Zhao, Qun; Lawson, Christopher M.; Gray, Gary M.

    2011-06-01

    The nonlinear optical absorptions of two 5,5‧-bis(diphenylphosphino)-2,2‧-bithiophene derivatives, Ph2(X)P(C4H2S)2P(X)Ph2 (X = O, 1; S, 2), have been investigated by direct transmission measurement with both picosecond and nanosecond laser pulses from 420 nm to 480 nm. Saturated dichloromethane solutions of 1 and 2 exhibit strong nonlinear optical absorptions in this violet-blue spectral region with that of 2 being stronger at all wavelengths. In the picosecond regime, at 420 nm, the transmittance rapidly falls to 50% when the incident fluence is 0.22 J/cm2 for 1 and 0.11 J/cm2 for 2. Two-photon absorption appears to be the primary mechanism for this nonlinear absorption. The two-photon absorption coefficients β for 1 (2.1 cm/GW) and 2 (4.4 cm/GM) were obtained by fitting the measurement of transmittance as the function of incident beam intensity at 420 nm. These β values are comparable with some of the best results obtained for organic materials in the green, red and infrared spectral region. Both compounds also show fluorescence with an emission peak at 390 nm for 1 and 400 nm for 2. The fluorescence of 1 is considerably stronger than is that of 2. The combination of the wide band gap and strong fluorescence emission of 1 makes it a promising candidate as a host material for blue organic light emitting diodes.

  4. Infrared Spectroscopy of Explosives Residues: Measurement Techniques and Spectral Analysis

    SciTech Connect

    Phillips, Mark C.; Bernacki, Bruce E.

    2015-03-11

    Infrared laser spectroscopy of explosives is a promising technique for standoff and non-contact detection applications. However, the interpretation of spectra obtained in typical standoff measurement configurations presents numerous challenges. Understanding the variability in observed spectra from explosives residues and particles is crucial for design and implementation of detection algorithms with high detection confidence and low false alarm probability. We discuss a series of infrared spectroscopic techniques applied toward measuring and interpreting the reflectance spectra obtained from explosives particles and residues. These techniques utilize the high spectral radiance, broad tuning range, rapid wavelength tuning, high scan reproducibility, and low noise of an external cavity quantum cascade laser (ECQCL) system developed at Pacific Northwest National Laboratory. The ECQCL source permits measurements in configurations which would be either impractical or overly time-consuming with broadband, incoherent infrared sources, and enables a combination of rapid measurement speed and high detection sensitivity. The spectroscopic methods employed include standoff hyperspectral reflectance imaging, quantitative measurements of diffuse reflectance spectra, reflection-absorption infrared spectroscopy, microscopic imaging and spectroscopy, and nano-scale imaging and spectroscopy. Measurements of explosives particles and residues reveal important factors affecting observed reflectance spectra, including measurement geometry, substrate on which the explosives are deposited, and morphological effects such as particle shape, size, orientation, and crystal structure.

  5. Spectral signatures of fluorescence and light absorption to identify crude oils found in the marine environment

    NASA Astrophysics Data System (ADS)

    Baszanowska, E.; Otremba, Z.

    2014-08-01

    To protect the natural marine ecosystem, it is necessary to continuously enhance knowledge of environmental contamination, including oil pollution. Therefore, to properly track the qualitative and quantitative changes in the natural components of seawater, a description of the essential spectral features describing petroleum products is necessary. This study characterises two optically-different types of crude oils (Petrobaltic and Romashkino) - substances belonging to multi-fluorophoric systems. To obtain the spectral features of crude oils, the excitation-emission spectroscopy technique was applied. The fluorescence and light absorption properties for various concentrations of oils at a stabilised temperature are described. Both excitation-emission spectra (EEMs) and absorption spectra of crude oils are discussed. Based on the EEM spectra, both excitation end emission peaks for the wavelengthindependent fluorescence maximum (Exmax/ Emmax) - characteristic points for each type of oil - were identified and compared with the literature data concerning typical marine chemical structures.

  6. Spectral ratio method for measuring emissivity

    USGS Publications Warehouse

    Watson, K.

    1992-01-01

    The spectral ratio method is based on the concept that although the spectral radiances are very sensitive to small changes in temperature the ratios are not. Only an approximate estimate of temperature is required thus, for example, we can determine the emissivity ratio to an accuracy of 1% with a temperature estimate that is only accurate to 12.5 K. Selecting the maximum value of the channel brightness temperatures is an unbiased estimate. Laboratory and field spectral data are easily converted into spectral ratio plots. The ratio method is limited by system signal:noise and spectral band-width. The images can appear quite noisy because ratios enhance high frequencies and may require spatial filtering. Atmospheric effects tend to rescale the ratios and require using an atmospheric model or a calibration site. ?? 1992.

  7. Multi-wavelength differential absorption measurements of chemical species

    NASA Astrophysics Data System (ADS)

    Brown, David M.

    The probability of accurate detection and quantification of airborne species is enhanced when several optical wavelengths are used to measure the differential absorption of molecular spectral features. Characterization of minor atmospheric constituents, biological hazards, and chemical plumes containing multiple species is difficult when using current approaches because of weak signatures and the use of a limited number of wavelengths used for identification. Current broadband systems such as Differential Optical Absorption Spectroscopy (DOAS) have either limitations for long-range propagation, or require transmitter power levels that are unsafe for operation in urban environments. Passive hyperspectral imaging systems that utilize absorption of solar scatter at visible and infrared wavelengths, or use absorption of background thermal emission, have been employed routinely for detection of airborne chemical species. Passive approaches have operational limitations at various ranges, or under adverse atmospheric conditions because the source intensity and spectrum is often an unknown variable. The work presented here describes a measurement approach that uses a known source of a low transmitted power level for an active system, while retaining the benefits of broadband and extremely long-path absorption operations. An optimized passive imaging system also is described that operates in the 3 to 4 mum window of the mid-infrared. Such active and passive instruments can be configured to optimize the detection of several hydrocarbon gases, as well as many other species of interest. Measurements have provided the incentive to develop algorithms for the calculations of atmospheric species concentrations using multiple wavelengths. These algorithms are used to prepare simulations and make comparisons with experimental results from absorption data of a supercontinuum laser source. The MODTRAN model is used in preparing the simulations, and also in developing additional

  8. Spectral Fingerprinting of Individual Cells Visualized by Cavity-Reflection-Enhanced Light-Absorption Microscopy

    PubMed Central

    Arai, Yoshiyuki; Yamamoto, Takayuki; Minamikawa, Takeo; Takamatsu, Tetsuro; Nagai, Takeharu

    2015-01-01

    The absorption spectrum of light is known to be a “molecular fingerprint” that enables analysis of the molecular type and its amount. It would be useful to measure the absorption spectrum in single cell in order to investigate the cellular status. However, cells are too thin for their absorption spectrum to be measured. In this study, we developed an optical-cavity-enhanced absorption spectroscopic microscopy method for two-dimensional absorption imaging. The light absorption is enhanced by an optical cavity system, which allows the detection of the absorption spectrum with samples having an optical path length as small as 10 μm, at a subcellular spatial resolution. Principal component analysis of various types of cultured mammalian cells indicates absorption-based cellular diversity. Interestingly, this diversity is observed among not only different species but also identical cell types. Furthermore, this microscopy technique allows us to observe frozen sections of tissue samples without any staining and is capable of label-free biopsy. Thus, our microscopy method opens the door for imaging the absorption spectra of biological samples and thereby detecting the individuality of cells. PMID:25950513

  9. Spectral fingerprinting of individual cells visualized by cavity-reflection-enhanced light-absorption microscopy.

    PubMed

    Arai, Yoshiyuki; Yamamoto, Takayuki; Minamikawa, Takeo; Takamatsu, Tetsuro; Nagai, Takeharu

    2015-01-01

    The absorption spectrum of light is known to be a "molecular fingerprint" that enables analysis of the molecular type and its amount. It would be useful to measure the absorption spectrum in single cell in order to investigate the cellular status. However, cells are too thin for their absorption spectrum to be measured. In this study, we developed an optical-cavity-enhanced absorption spectroscopic microscopy method for two-dimensional absorption imaging. The light absorption is enhanced by an optical cavity system, which allows the detection of the absorption spectrum with samples having an optical path length as small as 10 μm, at a subcellular spatial resolution. Principal component analysis of various types of cultured mammalian cells indicates absorption-based cellular diversity. Interestingly, this diversity is observed among not only different species but also identical cell types. Furthermore, this microscopy technique allows us to observe frozen sections of tissue samples without any staining and is capable of label-free biopsy. Thus, our microscopy method opens the door for imaging the absorption spectra of biological samples and thereby detecting the individuality of cells.

  10. Airborne Spectral Measurements of Ocean Anisotropy during CLAMS

    NASA Technical Reports Server (NTRS)

    Gatebe, C. K.; King, M. D.; Arnold, G. T.; Lau, William K. M. (Technical Monitor)

    2002-01-01

    The Cloud Absorption Radiometer (CAR) aboard the University of Washington Convair CV-580 research aircraft obtained bidirectional reflectance-distribution function (BRDF) of Atlantic Ocean and Dismal Swamp between July 10 and August 2, 2001. The BRDF measurements (15 in total, 8 uncontaminated by clouds) obtained under a variety of sun angles and wind conditions, will be used to characterize ocean anisotropy in support of Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRDF models of the ocean. In this paper we present results of BRDF of the Ocean under different sun angles and wind conditions. The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 micron), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 micron). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. At an altitude of 600 m above the targeted surface area and

  11. Airborne Spectral Measurements of Ocean Anisotropy during CLAMS

    NASA Astrophysics Data System (ADS)

    Gatebe, C. K.; King, M. D.; Arnold, G. T.

    2002-05-01

    The Cloud Absorption Radiometer (CAR) aboard the University of Washington Convair CV-580 research aircraft obtained bidirectional reflectance-distribution function (BRDF) of Atlantic ocean off eastern USA and Dismal Swamp between July 10 and August 2, 2001. The BRDF measurements (15 in total, 8 uncontaminated by clouds) obtained under a variety of sun angles and wind conditions, will be used to characterize ocean anisotropy in support of Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRDF models of the ocean. In this paper we present results of BRDF of the Ocean under different sun angles and wind conditions. The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 μ m), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 μ m). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and atmospheric inhomogeneities. For example, at an altitude of 600 m above the

  12. [Analyses of spectral emissivity in radiation temperature measurement].

    PubMed

    Fu, Tai-Ran; Cheng, Xiao-Fang; Zhong, Mao-Hua; Yang, Zang-Jian

    2008-01-01

    The complexity of the spectral emissivity of actual surfaces is the key point in the research and applications of radiation temperature measurement, resulting in the difficulty in the achievement of the temperature measurement. In the present paper, based on the discussions of the Taylor expansion, the non-dimension wavelength and the exponent, the authors describe the mathematical expression of the spectral emissivity of actual surfaces, and establish the general spectral emissivity function. Through the fitting of experimental data of the spectral emissivities of different metals at different temperatures, the applicability of the spectral emissivity function is verified which especially becomes the fundamental in the research of primary spectrum pyrometry.

  13. Spectroradiometric pyrometry of shock-heated gases by infrared emission and absorption measurements.

    PubMed

    Penzias, G J; Dolin, S A; Kruegle, H A

    1966-02-01

    A spectroradiometric pyrometer was developed to measure temperatures of shock-heated gases with time resolution of about 10 microsec. Gas temperatures in shock-heated CO(2)-N(2) mixtures and in self-sustaining detonations were determined by simultaneously measuring infrared spectral radiance and absorptance at selected wavelengths in CO(2) and H(2)O band spectra. By Kirchhoff's law, the ratio (radiance/absorptance) equals the Planck blackbody radiance, from which the temperature is easily found. The measured temperatures agreed with values calculated from the measured shock velocities. PMID:20048824

  14. Surface ozone measurements using differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Jain, Sohan L.; Arya, B. C.; Ghude, Sachin D.; Arora, Arun K.; Sinha, Randhir K.

    2005-01-01

    Human activities have been influencing the global atmosphere since the beginning of the industrial era, causing shifts from its natural state. The measurements have shown that tropospheric ozone is increasing gradually due to anthropogenic activities. Surface ozone is a secondary pollutant, its concentration in lower troposphere depends upon its precursors (CO, CH4, non methane hydrocarbons, NOx) as well as weather and transport phenomenon. The surface ozone exceeding the ambient air quality standard is health hazard to human being, animal and vegetation. The regular information of its concentrations on ground levels is needed for setting ambient air quality objectives and understanding photo chemical air pollution in urban areas. A Differential Absorption Lidar (DIAL) using a tunable CO2 laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor water vapour, surface ozone, ammonia, ethylene etc. Some times ethylene and surface ozone was found to be more than 40 ppb and 140 ppb respectively which is a health hazard. Seasonal variation in ozone concentrations shows maximum in the months of summer and autumn and minimum in monsoon and winter months. In present communication salient features of experimental set up and results obtained will be presented in detail.

  15. Absorption of Solar Radiation by the Cloudy Atmosphere Interpretations of Collocated Aircraft Measurements

    NASA Technical Reports Server (NTRS)

    Valero, Francisco P. J.; Cess, Robert D.; Zhang, Minghua; Pope, Shelly K.; Bucholtz, Anthony; Bush, Brett; Vitko, John, Jr.

    1997-01-01

    As part of the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE), we have obtained and analyzed measurements made from collocated aircraft of the absorption of solar radiation within the atmospheric column between the two aircraft. The measurements were taken during October 1995 at the ARM site in Oklahoma. Relative to a theoretical radiative transfer model, we find no evidence for excess solar absorption in the clear atmosphere and significant evidence for its existence in the cloudy atmosphere. This excess cloud solar absorption appears to occur in both visible (0.224-0.68 microns) and near-infrared (0.68-3.30 microns) spectral regions, although not at 0.5 microns for the visible contribution, and it is shown to be true absorption rather than an artifact of sampling errors caused by measuring three-dimensional clouds.

  16. Spectral-based inferential measurement of grey-body's temperature

    NASA Astrophysics Data System (ADS)

    Zheng, Feng; Liu, Liying; Zhu, Lingxi; Huan, Kewei; Li, Ye; Shi, Xiaoguang

    2015-11-01

    Aiming at the problems of temperature measurement and the defects of radiance thermometry theory, one method of spectral-based inferential measurement is proposed, which adopts the Empirical Risk Minimization (ERM) functional model as the temperature measurement model. Then, the radiance thermometry theory and inferential measurement technology are discussed comparatively. Temperatures of some targets, such and tungsten lamp and solar surface, are measured by spectral-based inferential measurement.

  17. ON NEUTRAL ABSORPTION AND SPECTRAL EVOLUTION IN X-RAY BINARIES

    SciTech Connect

    Miller, J. M.; Cackett, E. M.; Reis, R. C.

    2009-12-10

    Current X-ray observatories make it possible to follow the evolution of transient and variable X-ray binaries across a broad range in luminosity and source behavior. In such studies, it can be unclear whether evolution in the low-energy portion of the spectrum should be attributed to evolution in the source, or instead to evolution in neutral photoelectric absorption. Dispersive spectrometers make it possible to address this problem. We have analyzed a small but diverse set of X-ray binaries observed with the Chandra High Energy Transmission Grating Spectrometer across a range in luminosity and different spectral states. The column density in individual photoelectric absorption edges remains constant with luminosity, both within and across source spectral states. This finding suggests that absorption in the interstellar medium strongly dominates the neutral column density observed in spectra of X-ray binaries. Consequently, evolution in the low-energy spectrum of X-ray binaries should properly be attributed to evolution in the source spectrum. We discuss our results in the context of X-ray binary spectroscopy with current and future X-ray missions.

  18. Linearity Study of a Spectral Emissivity Measurement Facility

    NASA Astrophysics Data System (ADS)

    Yuan, Z.; Zhang, J.; Zhao, J.; Liang, Y.; Duan, Y.

    2009-02-01

    Linearity is one of the important characteristics of a spectral radiation measurement facility. Basically, it depends on the linearity of the spectral responsivity of the detector and amplifier at different wavelengths. As spectral emissivity is measured over wide wavelength and temperature ranges and the detection system has significant drift and noise, it is not easy to measure the linearity of this facility accurately using only one standard radiator. A simple double-blackbody method has been adopted to simulate reference emissivity samples and test the linearity of the spectral emissivity measurement facility developed at the National Institute of Metrology. Good linearity results were obtained from 3 μm to 15 μm. This method minimizes the influence of drift on the emissivity measurement over a wide ratio of measurement signals and wide spectral range.

  19. Interaction of some fluorinated nucleic acid components with praseodymium: an absorption spectral approach.

    PubMed

    Misra, S N

    1990-10-01

    Absorption difference and comparative absorption spectrophotometric studies on praseodymium(III) and fluorouracil, fluorocytosine, fluoroadenine, fluorothymine, fluorouridine, fluorocytidine, fluoroadenosine and fluorothymidine systems at pH approximately 5.5 and in different stoichiometries in 80% DMF medium have been carried out. Magnitudes of spectral parameters, viz. Coulombic (Fk), spin-orbit (zeta 4f), nephelauxetic (beta), bonding (b), intensity (T lambda Judd-Ofelt), and oscillator strength (P) and their variation have provided information on the binding mode of these biomolecules in terms of outer and inner sphere complexation, degree of covalency and extent of 4f orbital involvement. Preliminary ultrasonic studies have indicated that these biomolecules behave as structure breakers, hence weak ligands in aqueous medium, while strengthening water structure in semi-nonaqueous medium. The analysis of the isolated solid complexes has suggested octa- and nona-coordination for praseodymium(III) in fluorinated nucleic bases and fluorinated nucleoside complexes.

  20. Re-Evaluation of Dust Radiative Forcing Using Remote Measurements of Dust Absorption

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Tanre, Didier; Karnieli, Arnon; Remer, Lorraine A.

    1998-01-01

    Spectral remote observations of dust properties from space and from the ground creates a powerful tool for determination of dust absorption of solar radiation with an unprecedented accuracy. Absorption is a key component in understanding dust impact on climate. We use Landsat spaceborne measurements at 0.47 to 2.2 microns over Senegal with ground based sunphotometers to find that Saharan dust absorption of solar radiation is two to four times smaller than in models. Though dust absorbs in the blue, almost no absorption was found for wavelengths greater 0.6 microns. The new finding increases by 50% recent estimated solar radiative forcing by dust and decreases the estimated dust heating of the lower troposphere. Dust transported from Asia shows slightly higher absorption probably due to the presence of black carbon from populated regions. Large scale application of this method to satellite data from the Earth Observing System can reduce significantly the uncertainty in the dust radiative effects.

  1. Accurate Measurements of Spectral Reflectance in Picasso's Guernica Painting.

    PubMed

    de Luna, Javier Muñoz; Fernandez-Balbuena, Antonio Alvarez; Vázquez, Daniel; Melgosa, Manuel; Durán, Humberto; García, Jorge; Muro, Carmen

    2016-01-01

    The use of non-invasive spectral measurements to control the conservation status is a part of the preventive conservation of artworks which nowadays is becoming increasingly interesting. This paper describes how to use a spectral measuring device and an illumination system specifically designed for such a task in a very large dimension artwork painting (7.8 m wide × 3.5 m high). The system, controlled by a Cartesian robot, allows spectral measurements in a spectral range of 400-780 nm. The measured data array has a total of 2201 circular regions with 5.5 mm spot diameter placed on a square grid. Colorimetric calculations performed from these spectral measurements may be used to characterize color shifts related to reflectance changes in specific areas of the paint. A color shifting from the expected gray has been shown.

  2. Accurate Measurements of Spectral Reflectance in Picasso's Guernica Painting.

    PubMed

    de Luna, Javier Muñoz; Fernandez-Balbuena, Antonio Alvarez; Vázquez, Daniel; Melgosa, Manuel; Durán, Humberto; García, Jorge; Muro, Carmen

    2016-01-01

    The use of non-invasive spectral measurements to control the conservation status is a part of the preventive conservation of artworks which nowadays is becoming increasingly interesting. This paper describes how to use a spectral measuring device and an illumination system specifically designed for such a task in a very large dimension artwork painting (7.8 m wide × 3.5 m high). The system, controlled by a Cartesian robot, allows spectral measurements in a spectral range of 400-780 nm. The measured data array has a total of 2201 circular regions with 5.5 mm spot diameter placed on a square grid. Colorimetric calculations performed from these spectral measurements may be used to characterize color shifts related to reflectance changes in specific areas of the paint. A color shifting from the expected gray has been shown. PMID:26767640

  3. Remote and Ground Truth Spectral Measurement Comparisons of FORMOSAT III

    NASA Technical Reports Server (NTRS)

    Abercromby, Kira Jorgensen; Hamada, Kris; Guyote, Michael; Okada, Jennifer; Barker, Edwin

    2007-01-01

    FORMOSAT III are a set of six research satellites from Taiwan that were launched in April 2006. The satellites are in 800 km, 71 degree inclination orbits and separated by 24 degrees in ascending node. Laboratory spectral measurements were taken of outer surface materials on FORMOSAT III. From those measurements, a computer model was built to predict the spectral reflectance accounting for both solar phase angle and orientation of the spacecraft relative to the observer. However, materials exposed to the space environment have exhibited spectral changes including a darkening and a "reddening" of the spectra. This "reddening" is characterized by an increase in slope of the reflectance as the wavelength increases. Therefore, the model of pre-flight materials was augmented to include the presumed causative agent: space weathering effects. Remote data were collected on two of the six FORMOSAT satellites using the 1.6 meter telescope at the AMOS (Air Force Maui Optical and Supercomputing) site with the Spica spectrometer. Due to the separation in ascending node, observations were acquired of whichever one of the six satellites was visible on that specific night. Three nights of data were collected using the red (6000 - 9500 angstroms) filter and five nights of data were collected using the blue (3200 - 6600 angstroms) filter. A comparison of the data showed a good match to the pre-flight models for the blue filter region. The absorption feature near 5500 angstroms due to the copper colored Kapton multi-layer insulation (MLI) was very apparent in the remote samples and a good fit to the data was seen in all satellites observed. The features in the red filter regime agreed with the pre-flight model up through 7000 angstroms where the reddening begins and the slope of the remote sample increases. A comparison of the satellites showed similar features in the red and blue filter regions, i.e. the satellite surfaces were aging at the same rate. A comparison of the pre

  4. Maximum a posteriori estimation of spectral reflectance from color image and multipoint spectral measurements.

    PubMed

    Murakami, Yuri; Ietomi, Kunihiko; Yamaguchi, Masahiro; Ohyama, Nagaaki

    2007-10-01

    Accurate color image reproduction under arbitrary illumination can be realized if the spectral reflectance functions in a scene are obtained. Although multispectral imaging is one of the promising methods to obtain the reflectance of a scene, it is expected to reduce the number of color channels without significant loss of accuracy. This paper presents what we believe to be a new method for estimating spectral reflectance functions from color image and multipoint spectral measurements based on maximum a posteriori (MAP) estimation. Multipoint spectral measurements are utilized as auxiliary information to improve the accuracy of spectral reflectance estimated from image data. Through simulations, it is confirmed that the proposed method improves the estimation accuracy, particularly when a scene includes subjects that belong to various categories.

  5. Measuring black carbon spectral extinction in the visible and infrared

    NASA Astrophysics Data System (ADS)

    Smith, A. J. A.; Peters, D. M.; McPheat, R.; Lukanihins, S.; Grainger, R. G.

    2015-09-01

    This work presents measurements of the spectral extinction of black carbon aerosol from 400 nm to 15 μm. The aerosol was generated using a Miniature Combustion Aerosol Standard soot generator and then allowed to circulate in an aerosol cell where its extinction was measured using a grating spectrometer in the visible and a Fourier transform spectrometer in the infrared. Size distribution, number concentration, and mass extinction cross sections have also been obtained using single-particle aerosol samplers. A mean mass extinction cross section at 550 nm of 8.3 ± 1.6 m2 g-1 is found which, assuming a reasonable single scatter albedo of 0.2, corresponds to a mass absorption cross section of 6.6 ± 1.3 m2 g-1. This compares well with previously reported literature values. Computer analysis of electron microscope images of the particles provides independent confirmation of the size distribution as well as fractal parameters of the black carbon aerosol. The aerosol properties presented in this work are representative of very fresh, uncoated black carbon aerosol. After atmospheric processing of such aerosols (which could include mixing with other constituents and structural changes), different optical properties would be expected.

  6. Absolute Rovibrational Intensities of C-12O2-16 Absorption Bands in the 3090-3850/ CM Spectral Region

    NASA Technical Reports Server (NTRS)

    Devi, V. Malathy; Benner, D. Chris; Rinsland, Curtis P.; Smith, Mary Ann H.

    1998-01-01

    A multispectrum nonlinear least-squares fitting technique has been used to determine the absolute intensities for approximately 1500 spectral lines in 36 vibration - rotation bands Of C-12O2-16 between 3090 and 3850/ cm. A total of six absorption spectra of a high- purity (99.995% minimum) natural sample of carbon dioxide were used in the analysis. The spectral data (0.01/cm resolution) were recorded at room temperature and low pressure (1 to 10 Torr) using the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak. The absorption path lengths for these spectra varied between 24.86 and 385.76 m. The first experimental determination of the intensity of the theoretically predicted 2(nu)(sub 2, sup 2) + nu(sub 3) "forbidden" band has been made. The measured line intensities obtained for each band have been analyzed to determine the vibrational band intensity, S(sub nu), in /cm/( molecule/sq cm) at 296 K, square of the rotationless transition dipole moment |R|(exp 2) in Debye, as well as the nonrigid rotor coefficients. The results are compared to the values listed in the 1996 HITRAN database which are obtained using the direct numerical diagonalization (DND) technique as well as to other published values where available.

  7. Variability of light absorption by aquatic particles in the near-infrared spectral region

    NASA Astrophysics Data System (ADS)

    Tassan, Stelvio; Ferrari, Giovanni M.

    2003-08-01

    We have measured the light absorption of a set of particle suspensions of varying nature (pure minerals, particulate standards, aquatic particles) using a double-beam spectrophotometer with a 15-cm-diameter integrating sphere. The sample was located inside the sphere so as to minimize the effect of light scattering by the particles. The results obtained showed highly variable absorption in the near-IR region of the wavelength spectrum. The same particle samples were deposited on glass-fiber filters, and their absorption was measured by the transmittance-reflectance method, based on a theoretical model that corrects for the effect of light scattering. The good agreement found between the results of the measurements carried out inside the sphere and by the transmittance-reflectance method confirms the validity of the scattering correction included in the above method.

  8. Depth-resolved water column spectral absorption of sunlight by phytoplankon during the Southern Ocean Gas Exchange (SOGasEx) Lagrangian tracer experiments

    NASA Astrophysics Data System (ADS)

    Hargreaves, B. R.

    2008-12-01

    Optical measurements made during gas exchange tracer experiments in the Southern Ocean, Atlantic sector near 51°S, 38°W from March-April 2008 (SOGasEx) were used to develop daily integrated depth- resolved PAR absorbed by phytoplankton. Particulate and phytoplankton pigment spectral absorption coefficients (ap and aph), and methanol-extracted chlorophyll-a concentrations (chl-a) from discrete samples within and below the upper mixed layer (40 stations) were combined with data from optical casts where chlorophyll-a and cdom fluorescence and PAR scalar irradiance were measured (11 stations), PAR Kd was measured from a buoy free of ship shadow for 0-5m (11 stations), and Wetlabs AC-9 whole water absorption coefficients to 150m were measured (14 stations, with 3 in common with fluorescence data) to estimate depth-resolved values for both total spectral absorption and spectral PAR irradiance. By combining depth-adjusted spectral absorption of phytoplankton pigments (aph) with depth-adjusted PAR spectral irradiance we estimated depth-resolved daily PAR irradiance absorbed by photosynthetic pigments. These data can be compared with time-integrated primary production measurements conducted on deck where solar exposure or lamp exposure was modified to simulate a range of depths. Such a synthesis should improve our estimates of depth-integrated daily primary production, and ultimately contribute to refining estimates of carbon export rates to be incorporated into a carbon budget and CO2 air-sea flux models for the SOGasEx experiments.

  9. Investigation of the formaldehyde differential absorption cross section at high and low spectral resolution in the simulation chamber SAPHIR

    NASA Astrophysics Data System (ADS)

    Brauers, T.; Bossmeyer, J.; Dorn, H.-P.; Schlosser, E.; Tillmann, R.; Wegener, R.; Wahner, A.

    2007-07-01

    The results from a simulation chamber study on the formaldehyde (HCHO) absorption cross section in the UV spectral region are presented. We performed 4 experiments at ambient HCHO concentrations with simultaneous measurements of two DOAS instruments in the atmosphere simulation chamber SAPHIR in Jülich. The two instruments differ in their spectral resolution, one working at 0.2 nm (broad-band, BB-DOAS), the other at 2.7 pm (high-resolution, HR-DOAS). Both instruments use dedicated multi reflection cells to achieve long light path lengths of 960 m and 2240 m, respectively, inside the chamber. During two experiments HCHO was injected into the clean chamber by thermolysis of well defined amounts of para-formaldehyde reaching mixing rations of 30 ppbV at maximum. The HCHO concentration calculated from the injection and the chamber volume agrees with the BB-DOAS measured value when the absorption cross section of Meller and Moortgat (2000) and the temperature coefficient of Cantrell (1990) were used for data evaluation. In two further experiments we produced HCHO in-situ from the ozone + ethene reaction which was intended to provide an independent way of HCHO calibration through the measurements of ozone and ethene. However, we found an unexpected deviation from the current understanding of the ozone + ethene reaction when CO was added to suppress possible oxidation of ethene by OH radicals. The reaction of the Criegee intermediate with CO could be 240 times slower than currently assumed. Based on the BB-DOAS measurements we could deduce a high-resolution cross section for HCHO which was not measured directly so far.

  10. Inversion of the volume scattering function and spectral absorption in coastal waters with biogeochemical implications

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Huot, Y.; Gray, D. J.; Weidemann, A.; Rhea, W. J.

    2013-06-01

    In the aquatic environment, particles can be broadly separated into phytoplankton (PHY), non-algal particle (NAP) and dissolved (or very small particle, VSP) fractions. Typically, absorption spectra are inverted to quantify these fractions, but volume scattering functions (VSFs) can also be used. Both absorption spectra and VSFs were used to calculate particle fractions for an experiment in Chesapeake Bay. A complete set of water inherent optical properties was measured using a suite of commercial instruments and a prototype Multispectral Volume Scattering Meter (MVSM); the chlorophyll concentration, [Chl] was determined using the HPLC method. The total scattering coefficient (measured by an ac-s) and the VSF (at a few backward angles, measured by a HydroScat 6 and an ECO-VSF) agreed with the LISST and MVSM data within 5%, thus indicating inter-instrument consistency. The size distribution and scattering parameters for PHY, NAP and VSP were inverted from measured VSFs. For the absorption inversion, the "dissolved" absorption spectra were measured for filtrate passing through a 0.2 μm filter, whereas [Chl] and NAP absorption spectra were inverted from the particulate fraction. Even though the total scattering coefficient showed no correlation with [Chl], estimates of [Chl] from the VSF-inversion agreed well with the HPLC measurements (r = 0.68, mean relative error s = -20%). The scattering associated with NAP and VSP both correlated well with the NAP and "dissolved" absorption coefficients, respectively. While NAP dominated forward, and hence total, scattering, our results also suggest that the scattering by VSP was far from negligible and dominated backscattering.

  11. Optoacoustic measurements of water vapor absorption at selected CO laser wavelengths in the 5-micron region

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1976-01-01

    Measurements of water vapor absorption were taken with a resonant optoacoustical detector (cylindrical pyrex detector, two BaF2 windows fitted into end plates at slight tilt to suppress Fabry-Perot resonances), for lack of confidence in existing spectral tabular data for the 5-7 micron region, as line shapes in the wing regions of water vapor lines are difficult to characterize. The measurements are required for air pollution studies using a CO laser, to find the differential absorption at the wavelengths in question due to atmospheric constituents other than water vapor. The design and performance of the optoacoustical detector are presented. Effects of absorption by ambient NO are considered, and the fixed-frequency discretely tunable CO laser is found suitable for monitoring urban NO concentrations in a fairly dry climate, using the water vapor absorption data obtained in the study.

  12. Pressure Measurements Using an Airborne Differential Absorption Lidar. Part 1; Analysis of the Systematic Error Sources

    NASA Technical Reports Server (NTRS)

    Flamant, Cyrille N.; Schwemmer, Geary K.; Korb, C. Laurence; Evans, Keith D.; Palm, Stephen P.

    1999-01-01

    Remote airborne measurements of the vertical and horizontal structure of the atmospheric pressure field in the lower troposphere are made with an oxygen differential absorption lidar (DIAL). A detailed analysis of this measurement technique is provided which includes corrections for imprecise knowledge of the detector background level, the oxygen absorption fine parameters, and variations in the laser output energy. In addition, we analyze other possible sources of systematic errors including spectral effects related to aerosol and molecular scattering interference by rotational Raman scattering and interference by isotopic oxygen fines.

  13. Effect of differential spectral reflectance on DIAL measurements using topographic targets.

    PubMed

    Grant, W B

    1982-07-01

    Differential absorption lidar (DIAL) measurements of atmospheric gases and temperature made using topographic targets to provide the backscattered signal are subject to errors from the differential spectral reflectance of the target materials. The magnitude of this effect is estimated for a number of DIAL measurements reported in the literature. Calculations are presented for several topographic targets. In general the effect on a DIAL measurement increases directly with increasing wavelength and laser line separation, and inversely with differential absorption coefficient and distance to the target. The effect can be minimized by using tunable or isotope lasers to reduce the laser line separation or by using additional reference wavelengths to determine the surface differential spectral reflectance. PMID:20396041

  14. X-ray absorption fine structure measurement with a 9 V electric battery x-ray emitter

    SciTech Connect

    Mitsuya, Shota; Ishii, Hideshi; Kawai, Jun; Tanaka, Keiichi

    2006-09-25

    X-ray absorption spectral analysis is a well known technique for analyzing the chemical environment of an element in a specimen. It has been believed that high intensity and monochromatized x rays such as the synchrotron radiation are required for an x-ray absorption experiment. In the present study, however, we demonstrate that the x-ray absorption spectral measurement of transition metal foils with an energy resolution of 10 eV is possible with a combination of a 9 V dry electric battery pyroelectric x-ray generator and a superconducting microcalorimeter.

  15. Ultrafast transient absorption revisited: Phase-flips, spectral fingers, and other dynamical features.

    PubMed

    Cina, Jeffrey A; Kovac, Philip A; Jumper, Chanelle C; Dean, Jacob C; Scholes, Gregory D

    2016-05-01

    We rebuild the theory of ultrafast transient-absorption/transmission spectroscopy starting from the optical response of an individual molecule to incident femtosecond pump and probe pulses. The resulting description makes use of pulse propagators and free molecular evolution operators to arrive at compact expressions for the several contributions to a transient-absorption signal. In this alternative description, which is physically equivalent to the conventional response-function formalism, these signal contributions are conveniently expressed as quantum mechanical overlaps between nuclear wave packets that have undergone different sequences of pulse-driven optical transitions and time-evolution on different electronic potential-energy surfaces. Using this setup in application to a simple, multimode model of the light-harvesting chromophores of PC577, we develop wave-packet pictures of certain generic features of ultrafast transient-absorption signals related to the probed-frequency dependence of vibrational quantum beats. These include a Stokes-shifting node at the time-evolving peak emission frequency, antiphasing between vibrational oscillations on opposite sides (i.e., to the red or blue) of this node, and spectral fingering due to vibrational overtones and combinations. Our calculations make a vibrationally abrupt approximation for the incident pump and probe pulses, but properly account for temporal pulse overlap and signal turn-on, rather than neglecting pulse overlap or assuming delta-function excitations, as are sometimes done. PMID:27155654

  16. Temperature dependent measurement of absorption and emission cross sections for various Yb3+ doped laser materials

    NASA Astrophysics Data System (ADS)

    Körner, J.; Hein, J.; Kahle, M.; Liebetrau, H.; Lenski, M.; Kaluza, M.; Loeser, M.; Siebold, M.

    2011-06-01

    For laser performance simulations, optical properties of applied active materials have to be exactly known. Here we report on temperature dependent emission and absorption cross section measurements for Yb:YAG, Yb:CaF2 and Yb:FP15-glass. The temperature of the samples was aligned in steps of 20 K between 100 K and room temperature with a liquid nitrogen driven cryostat. Absorption spectra were obtained with a fiber coupled white light source and fluorescence spectra by excitation with a fiber coupled 10W laser diode at 970 nm. All spectral measurements were performed with a scanning spectrum analyzer, providing a spectral resolution down to 0.05 nm. By applying the McCumber relation in combination with the Fuchtbauer-Ladenburg method, we were able to obtain a valid emission cross section over the whole range of interest from the measured data.

  17. Spectral infrared hemispherical reflectance measurements for LDEF tray clamps

    NASA Technical Reports Server (NTRS)

    Wood, Bobby E.; Cromwell, Brian K.; Pender, Charles W.; Shepherd, Seth D.

    1992-01-01

    This paper describes infrared hemispherical reflectance measurements (2-15 microns) that were made on 58 chromic acid anodized tray clamps retrieved from the LDEF spacecraft. These clamps were used for maintaining the experiments in place and were located at various locations about the spacecraft. Changes in reflectance of the tray clamps at these locations were compared with atomic oxygen fluxes at the same locations. A decrease in absorption band depth was seen for the surfaces exposed to space indicating that there was some surface layer erosion. In all of the surfaces measured, little evidence of contamination was observed and none of the samples showed evidence of the brown nicotine stain that was so prominent in other experiments. Total emissivity values were calculated for both exposed and unexposed tray clamp surfaces. Only small differences, usually less than 1 percent, were observed. The spectral reflectances were measured using a hemi-ellipsoidal mirror reflectometer matched with an interferometer spectrometer. The rapid scanning capability of the interferometer allowed the reflectance measurements to be made in a timely fashion. The ellipsoidal mirror has its two foci separated by 2 inches and located on the major axis. A blackbody source was located at one focus while the tray clamp samples were located at the conjugate focus. The blackbody radiation was modulated and then focused by the ellipsoid onto the tray clamps. Radiation reflected from the tray clamp was sampled by the interferometer by viewing through a hole in the ellipsoid. A gold mirror (reflectance approximately 98 percent) was used as the reference surface.

  18. Temperature-dependent spectral weight transfer in YBa2Cu3Ox probed by x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Lin, J.-Y.

    2010-03-01

    The x-ray absorption spectroscopy was utilized to critically examine the temperature dependency of the spectral weight in YBa2Cu3Ox. Large excess spectral weight for the Zhang- Rice singlet due to dynamics of holes is found with its doping dependence showing similar doom-like shape as that for Tc. Furthermore, appreciable spectral weight transfer from the upper Hubbard band to Zhang-Rice singlet was observed as the temperature acrosses the onset temperature for the pseudogap. The observed spectral weight transfer follows the change of the pseudogap, indicating a strong link between pseudogap and the upper Hubbard band.

  19. Measurement of Broad Absorption Features Using a Tunable External Cavity Quantum Cascade Laser

    SciTech Connect

    Phillips, Mark C.; Myers, Tanya L.; Wojcik, Michael D.; Cannon, Bret D.; Taubman, Matthew S.; Scott, David C.

    2007-09-25

    We demonstrate the use of a tunable external cavity quantum cascade laser system for measurement of broad absorption features in the mid-infrared spectral region. The thermoelectrically cooled external cavity laser was tuned over a 65 cm-1 range centered at 8.7 microns using stepper motor control. Pulsing the laser at a high duty cycle provided 3-5 mW average output power over the tuning range, and enabled phase-sensitive detection of amplitude-modulated signals. We used the laser system to measure the absorption spectra of Freon-125 using a Herriott cell. In addition, the absorption spectrum of water in the laboratory air was measured. The measurements showed excellent agreement with reference spectra, in both wavelength and amplitude. The measured scan resolution of 0.14 cm-1 is suitable for measurement of the absorption features of complex molecules as well as simple molecules with atmospherically broadened lines. We discuss the limits to the scan resolution due to effects of spectral chirp and mode-hops during pulsed operation.

  20. Measurement of broad absorption features using a tunable external cavity quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Phillips, Mark C.; Myers, Tanya L.; Wojcik, Michael D.; Cannon, Bret D.; Taubman, Matthew S.; Scott, David C.

    2007-09-01

    We demonstrate the use of a tunable external cavity quantum cascade laser system for measurement of broad absorption features in the mid-infrared spectral region. The thermoelectrically cooled external cavity laser was tuned over a 65 cm -1range centered at 8.7 microns using stepper motor control. Pulsing the laser at a high duty cycle provided 2-4.5 mW average output power over the tuning range, and enabled phase-sensitive detection of amplitude-modulated signals. We used the laser system to measure the absorption spectra of Freon-125 using a Herriott cell. In addition, the absorption spectrum of water in the laboratory air was measured. The measurements showed excellent agreement with reference spectra, in both wavelength and amplitude. The measured scan resolution of 0.14 cm -1 is suitable for measurement of the absorption features of complex molecules as well as simple molecules with atmospherically broadened lines. We discuss the limits to the scan resolution due to effects of spectral chirp and mode-hops during pulsed operation.

  1. Examination of the Measurement of Absorption Using the Reverberant Room Method for Highly Absorptive Acoustic Foam

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.; Chris Nottoli; Eric Wolfram

    2015-01-01

    The absorption coefficient for material specimens are needed to quantify the expected acoustic performance of that material in its actual usage and environment. The ASTM C423-09a standard, "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberant Room Method" is often used to measure the absorption coefficient of material test specimens. This method has its basics in the Sabine formula. Although widely used, the interpretation of these measurements are a topic of interest. For example, in certain cases the measured Sabine absorption coefficients are greater than 1.0 for highly absorptive materials. This is often attributed to the diffraction edge effect phenomenon. An investigative test program to measure the absorption properties of highly absorbent melamine foam has been performed at the Riverbank Acoustical Laboratories. This paper will present and discuss the test results relating to the effect of the test materials' surface area, thickness and edge sealing conditions. A follow-on paper is envisioned that will present and discuss the results relating to the spacing between multiple piece specimens, and the mounting condition of the test specimen.

  2. Remote sensing of forage nutrients: Combining ecological and spectral absorption feature data

    NASA Astrophysics Data System (ADS)

    Knox, Nichola M.; Skidmore, Andrew K.; Prins, Herbert H. T.; Heitkönig, Ignas M. A.; Slotow, Rob; van der Waal, Cornelis; de Boer, William F.

    2012-08-01

    Forage quality in grassland-savanna ecosystems support high biomass of both wild ungulates and domestic livestock. Forage quality is however variable in both space and time. In this study findings from ecological and laboratory studies, focused on assessing forage quality, are combined to evaluate the feasibility of a remote sensing approach for predicting the spatial and temporal variations in forage quality. Spatially available ecological findings (ancillary data), and physically linked spectral data (absorption data) are evaluated in this study and combined to create models which predict forage quality (nitrogen, phosphorus and fibre concentrations) of grasses collected in the Kruger National Park, South Africa, and analysed in both dry and wet seasons. Models were developed using best subsets regression modelling. Ancillary data alone, could predict forage components, with a higher goodness of fit and predictive capability, than absorption data (Ancillary: Radj2=0.42-0.74 compared with absorption: Radj2=0.11-0.51, and lower RMSE values for each nutrient produced by the ancillary models). Plant species and soil classes were found to be ecological variables most frequently included in prediction models of ancillary data. Models in which both ancillary and absorption variables were included, had the highest predictive capabilities ( Radj2=0.49-0.74 and lowest RMSE values) compared to models where data sources were derived from only one of the two groups. This research provides an important step in the process of creating biochemical models for mapping forage nutrients in savanna systems that can be generalised seasonally over large areas.

  3. Method and apparatus for measuring film spectral properties

    DOEpatents

    Forrest, Stephen R.; Burrows, Paul E.; Garbuzov, Dmitri Z.; Bulovic, Vladimir

    1999-12-21

    Film spectral properties are measured by projecting chopped monochromatic light onto a luminescent film sample deposited on a substrate, and coupling through use of immersion oil the reflection of light therefrom to a light detector.

  4. Temporal spectral measurements of corn and soybean crops

    NASA Technical Reports Server (NTRS)

    Tucker, C. J.; Elgin, J. H., Jr.; Mcmurtrey, J. E., III

    1979-01-01

    A ground-based, hand-held radiometer, configured to measure red and photographic infrared spectral radiances, was successfully used to collect in situ temporal spectral measurements of corn and soybean crops. Significant relationships were found between the radiance data and the biomass, plant height, percentage crop cover, percentage crop chlorosis, and percentage leaf loss. The results of this experiment show conclusively that hand-held radiometers can be used to collect spectral data that are highly correlated to several agronomic variables. These findings suggest approaches for agronomic research, and confirm the value of remote sensing of agricultural targets.

  5. Indoor and Outdoor Spectroradiometer Intercomparison for Spectral Irradiance Measurement

    SciTech Connect

    Habte, A.; Andreas, A.; Ottoson, L.; Gueymard, C.; Fedor, G.; Fowler, S.; Peterson, J.; Naranen, R.; Kobashi, T.; Akiyama, A.; Takagi, S.

    2014-05-01

    This report details the global spectral irradiance intercomparison using spectroradiometers that was organized by the National Renewable Energy Laboratory's Solar Radiation Research Laboratory. The intercomparison was performed both indoors and outdoors on September 17, 2013. Five laboratories participated in the intercomparison using 10 spectroradiometers, and a coordinated measurement setup and a common platform were employed to compare spectral irradiances under both indoor and outdoor conditions. The intercomparison aimed to understand the performance of the different spectroradiometers and to share knowledge in making spectral irradiance measurements. This intercomparison was the first of its kind in the United States.

  6. High Spectral Resolution Lidar Measurements of Extinction and Particle Size in Clouds

    NASA Technical Reports Server (NTRS)

    Eloranta, E. W.; Piirronen, P.

    1996-01-01

    The University of Wisconsin High Spectral Resolution Lidar (HSRL) measures optical properties of the atmosphere by separating the Doppler broadened molecular backscatter return from the unbroadened aerosol return. In the past, the HSRL employed a 150 mm diameter Fabry-Perot etalon to separate the aerosol and molecular signals. The replacement of the etalon with an I2 absorption filter significantly improved the ability of the HSRL to separate weak molecular signals inside dense clouds.

  7. [Gas Concentration Measurement Based on the Integral Value of Absorptance Spectrum].

    PubMed

    Liu, Hui-jun; Tao, Shao-hua; Yang, Bing-chu; Deng, Hong-gui

    2015-12-01

    The absorptance spectrum of a gas is the basis for the qualitative and quantitative analysis of the gas by the law of the Lambert-Beer. The integral value of the absorptance spectrum is an important parameter to describe the characteristics of the gas absorption. Based on the measured absorptance spectrum of a gas, we collected the required data from the database of HIT-RAN, and chose one of the spectral lines and calculated the integral value of the absorptance spectrum in the frequency domain, and then substituted the integral value into Lambert-Beer's law to obtain the concentration of the detected gas. By calculating the integral value of the absorptance spectrum we can avoid the more complicated calculation of the spectral line function and a series of standard gases for calibration, so the gas concentration measurement will be simpler and faster. We studied the changing trends of the integral values of the absorptance spectrums versus temperature. Since temperature variation would cause the corresponding variation in pressure, we studied the changing trends of the integral values of the absorptance spectrums versus both the pressure not changed with temperature and changed with the temperature variation. Based on the two cases, we found that the integral values of the absorptance spectrums both would firstly increase, then decrease, and finally stabilize with temperature increasing, but the ranges of specific changing trend were different in the two cases. In the experiments, we found that the relative errors of the integrated values of the absorptance spectrum were much higher than 1% and still increased with temperature when we only considered the change of temperature and completely ignored the pressure affected by the temperature variation, and the relative errors of the integrated values of the absorptance spectrum were almost constant at about only 1% when we considered that the pressure were affected by the temperature variation. As the integral value

  8. [Gas Concentration Measurement Based on the Integral Value of Absorptance Spectrum].

    PubMed

    Liu, Hui-jun; Tao, Shao-hua; Yang, Bing-chu; Deng, Hong-gui

    2015-12-01

    The absorptance spectrum of a gas is the basis for the qualitative and quantitative analysis of the gas by the law of the Lambert-Beer. The integral value of the absorptance spectrum is an important parameter to describe the characteristics of the gas absorption. Based on the measured absorptance spectrum of a gas, we collected the required data from the database of HIT-RAN, and chose one of the spectral lines and calculated the integral value of the absorptance spectrum in the frequency domain, and then substituted the integral value into Lambert-Beer's law to obtain the concentration of the detected gas. By calculating the integral value of the absorptance spectrum we can avoid the more complicated calculation of the spectral line function and a series of standard gases for calibration, so the gas concentration measurement will be simpler and faster. We studied the changing trends of the integral values of the absorptance spectrums versus temperature. Since temperature variation would cause the corresponding variation in pressure, we studied the changing trends of the integral values of the absorptance spectrums versus both the pressure not changed with temperature and changed with the temperature variation. Based on the two cases, we found that the integral values of the absorptance spectrums both would firstly increase, then decrease, and finally stabilize with temperature increasing, but the ranges of specific changing trend were different in the two cases. In the experiments, we found that the relative errors of the integrated values of the absorptance spectrum were much higher than 1% and still increased with temperature when we only considered the change of temperature and completely ignored the pressure affected by the temperature variation, and the relative errors of the integrated values of the absorptance spectrum were almost constant at about only 1% when we considered that the pressure were affected by the temperature variation. As the integral value

  9. Measurements of Soot Mass Absorption Coefficients from 300 to 660 nm

    NASA Astrophysics Data System (ADS)

    Renbaum-Wolff, Lindsay; Fisher, Al; Helgestad, Taylor; Lambe, Andrew; Sedlacek, Arthur; Smith, Geoffrey; Cappa, Christopher; Davidovits, Paul; Onasch, Timothy; Freedman, Andrew

    2016-04-01

    Soot, a product of incomplete combustion, plays an important role in the earth's climate system through the absorption and scattering of solar radiation. In particular, the assumed mass absorption coefficient (MAC) of soot and its variation with wavelength presents a significant uncertainty in the calculation of radiative forcing in global climate change models. As part of the fourth Boston College/Aerodyne soot properties measurement campaign, we have measured the mass absorption coefficient of soot produced by an inverted methane diffusion flame over a spectral range of 300-660 nm using a variety of optical absorption techniques. Extinction and absorption were measured using a dual cavity ringdown photoacoustic spectrometer (CRD-PAS, UC Davis) at 405 nm and 532 nm. Scattering and extinction were measured using a CAPS PMssa single scattering albedo monitor (Aerodyne) at 630 nm; the absorption coefficient was determined by subtraction. In addition, the absorption coefficients in 8 wavelength bands from 300 to 660 nm were measured using a new broadband photoacoustic absorption monitor (UGA). Soot particle mass was quantified using a centrifugal particle mass analyzer (CPMA, Cambustion), mobility size with a scanning mobility particle sizer (SMPS, TSI) and soot concentration with a CPC (Brechtel). The contribution of doubly charged particles to the sample mass was determined using a Single Particle Soot Photometer (DMT). Over a mass range of 1-8 fg, corresponding to differential mobility diameters of ~150 nm to 550 nm, the value of the soot MAC proved to be independent of mass for all wavelengths. The wavelength dependence of the MAC was best fit to a power law with an Absorption Ångstrom Coefficient slightly greater than 1.

  10. Solar absorption by elemental and brown carbon determined from spectral observations

    PubMed Central

    Bahadur, Ranjit; Praveen, Puppala S.; Xu, Yangyang; Ramanathan, V.

    2012-01-01

    Black carbon (BC) is functionally defined as the absorbing component of atmospheric total carbonaceous aerosols (TC) and is typically dominated by soot-like elemental carbon (EC). However, organic carbon (OC) has also been shown to absorb strongly at visible to UV wavelengths and the absorbing organics are referred to as brown carbon (BrC), which is typically not represented in climate models. We propose an observationally based analytical method for rigorously partitioning measured absorption aerosol optical depths (AAOD) and single scattering albedo (SSA) among EC and BrC, using multiwavelength measurements of total (EC, OC, and dust) absorption. EC is found to be strongly absorbing (SSA of 0.38) whereas the BrC SSA varies globally between 0.77 and 0.85. The method is applied to the California region. We find TC (EC + BrC) contributes 81% of the total absorption at 675 nm and 84% at 440 nm. The BrC absorption at 440 nm is about 40% of the EC, whereas at 675 nm it is less than 10% of EC. We find an enhanced absorption due to OC in the summer months and in southern California (related to forest fires and secondary OC). The fractions and trends are broadly consistent with aerosol chemical-transport models as well as with regional emission inventories, implying that we have obtained a representative estimate for BrC absorption. The results demonstrate that current climate models that treat OC as nonabsorbing are underestimating the total warming effect of carbonaceous aerosols by neglecting part of the atmospheric heating, particularly over biomass-burning regions that emit BrC. PMID:23045698

  11. Solar absorption by elemental and brown carbon determined from spectral observations.

    PubMed

    Bahadur, Ranjit; Praveen, Puppala S; Xu, Yangyang; Ramanathan, V

    2012-10-23

    Black carbon (BC) is functionally defined as the absorbing component of atmospheric total carbonaceous aerosols (TC) and is typically dominated by soot-like elemental carbon (EC). However, organic carbon (OC) has also been shown to absorb strongly at visible to UV wavelengths and the absorbing organics are referred to as brown carbon (BrC), which is typically not represented in climate models. We propose an observationally based analytical method for rigorously partitioning measured absorption aerosol optical depths (AAOD) and single scattering albedo (SSA) among EC and BrC, using multiwavelength measurements of total (EC, OC, and dust) absorption. EC is found to be strongly absorbing (SSA of 0.38) whereas the BrC SSA varies globally between 0.77 and 0.85. The method is applied to the California region. We find TC (EC + BrC) contributes 81% of the total absorption at 675 nm and 84% at 440 nm. The BrC absorption at 440 nm is about 40% of the EC, whereas at 675 nm it is less than 10% of EC. We find an enhanced absorption due to OC in the summer months and in southern California (related to forest fires and secondary OC). The fractions and trends are broadly consistent with aerosol chemical-transport models as well as with regional emission inventories, implying that we have obtained a representative estimate for BrC absorption. The results demonstrate that current climate models that treat OC as nonabsorbing are underestimating the total warming effect of carbonaceous aerosols by neglecting part of the atmospheric heating, particularly over biomass-burning regions that emit BrC.

  12. Continuous hyperspectral absorption measurements of colored dissolved organic material in aquatic systems

    NASA Astrophysics Data System (ADS)

    Kirkpatrick, Gary J.; Orrico, Cristina; Moline, Mark A.; Oliver, Matthew; Schofield, Oscar M.

    2003-11-01

    The majority of organic carbon in the oceans is present as dissolved organic matter (DOM) therefore understanding the distribution and dynamics of DOM is central to understanding global carbon cycles. Describing the time-space variability in colored dissolved organic matter (CDOM) has been difficult, as standard spectrophotometric methods for CDOM determination are laborious and susceptible to methodological biases. Previously, measurements of CDOM absorption in discrete water samples by use of a liquid-waveguide capillary cell (LWCC) compared favorably with measurements made with a benchtop spectrophotometer. Given this, we focused on automating the LWCC technique to improve our spatial and temporal sampling capabilities for CDOM. We found strong correlations between CDOM absorption spectra collected from discrete water samples using standard methods and selected corresponding CDOM spectra collected by the automated LWCC system. The near-continuous measurements by the LWCC system made it possible to map the temporal, spatial, and spectral variability of CDOM absorption along the ship track.

  13. Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements

    NASA Technical Reports Server (NTRS)

    Chen, Jeffrey R.; Numata, Kenji; Wu, Stewart T.

    2012-01-01

    We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

  14. Error reduction methods for integrated-path differential-absorption lidar measurements.

    PubMed

    Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

    2012-07-01

    We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

  15. Calculation of UV attenuation and colored dissolved organic matter absorption spectra from measurements of ocean color

    NASA Astrophysics Data System (ADS)

    Johannessen, S. C.; Miller, W. L.; Cullen, J. J.

    2003-09-01

    The absorption of ultraviolet and visible radiation by colored or chromophoric dissolved organic matter (CDOM) drives much of marine photochemistry. It also affects the penetration of ultraviolet radiation (UV) into the water column and can confound remote estimates of chlorophyll concentration. Measurements of ocean color from satellites can be used to predict UV attenuation and CDOM absorption spectra from relationships between visible reflectance, UV attenuation, and absorption by CDOM. Samples were taken from the Bering Sea and from the Mid-Atlantic Bight, and water types ranged from turbid, inshore waters to the Gulf Stream. We determined the following relationships between in situ visible radiance reflectance, Lu/Ed (λ) (sr-1), and diffuse attenuation of UV, Kd(λ) (m-1): Kd(323nm) = 0.781[Lu/Ed(412)/Lu/Ed(555)]-1.07; Kd(338nm) = 0.604[Lu/Ed(412)/Lu/Ed(555)]-1.12; Kd(380 nm) = 0.302[Lu/Ed(412)/Lu/Ed(555)]-1.24. Consistent with published observations, these empirical relationships predict that the spectral slope coefficient of CDOM absorption increases as diffuse attenuation of UV decreases. Excluding samples from turbid bays, the ratio of the CDOM absorption coefficient to Kd is 0.90 at 323 nm, 0.86 at 338 nm, and 0.97 at 380 nm. We applied these relationships to SeaWiFS images of normalized water-leaving radiance to calculate the CDOM absorption and UV attenuation in the Mid-Atlantic Bight in May, July, and August 1998. The images showed a decrease in UV attenuation from May to August of approximately 50%. We also produced images of the areal distribution of the spectral slope coefficient of CDOM absorption in the Georgia Bight. The spectral slope coefficient increased offshore and changed with season.

  16. Numerical calculations of spectral turnover and synchrotron self-absorption in CSS and GPS radio sources

    NASA Astrophysics Data System (ADS)

    Jeyakumar, S.

    2016-06-01

    The dependence of the turnover frequency on the linear size is presented for a sample of Giga-hertz Peaked Spectrum and Compact Steep Spectrum radio sources derived from complete samples. The dependence of the luminosity of the emission at the peak frequency with the linear size and the peak frequency is also presented for the galaxies in the sample. The luminosity of the smaller sources evolve strongly with the linear size. Optical depth effects have been included to the 3D model for the radio source of Kaiser to study the spectral turnover. Using this model, the observed trend can be explained by synchrotron self-absorption. The observed trend in the peak-frequency-linear-size plane is not affected by the luminosity evolution of the sources.

  17. Gas concentration measurement by optical similitude absorption spectroscopy: methodology and experimental demonstration.

    PubMed

    Anselmo, Christophe; Welschinger, Jean-Yves; Cariou, Jean-Pierre; Miffre, Alain; Rairoux, Patrick

    2016-06-13

    We propose a new methodology to measure gas concentration by light-absorption spectroscopy when the light source spectrum is larger than the spectral width of one or several molecular gas absorption lines. We named it optical similitude absorption spectroscopy (OSAS), as the gas concentration is derived from a similitude between the light source and the target gas spectra. The main OSAS-novelty lies in the development of a robust inversion methodology, based on the Newton-Raphson algorithm, which allows retrieving the target gas concentration from spectrally-integrated differential light-absorption measurements. As a proof, OSAS is applied in laboratory to the 2ν3 methane absorption band at 1.66 µm with uncertainties revealed by the Allan variance. OSAS has also been applied to non-dispersive infra-red and the optical correlation spectroscopy arrangements. This all-optics gas concentration retrieval does not require the use of a gas calibration cell and opens new tracks to atmospheric gas pollution and greenhouse gases sources monitoring.

  18. Gas concentration measurement by optical similitude absorption spectroscopy: methodology and experimental demonstration.

    PubMed

    Anselmo, Christophe; Welschinger, Jean-Yves; Cariou, Jean-Pierre; Miffre, Alain; Rairoux, Patrick

    2016-06-13

    We propose a new methodology to measure gas concentration by light-absorption spectroscopy when the light source spectrum is larger than the spectral width of one or several molecular gas absorption lines. We named it optical similitude absorption spectroscopy (OSAS), as the gas concentration is derived from a similitude between the light source and the target gas spectra. The main OSAS-novelty lies in the development of a robust inversion methodology, based on the Newton-Raphson algorithm, which allows retrieving the target gas concentration from spectrally-integrated differential light-absorption measurements. As a proof, OSAS is applied in laboratory to the 2ν3 methane absorption band at 1.66 µm with uncertainties revealed by the Allan variance. OSAS has also been applied to non-dispersive infra-red and the optical correlation spectroscopy arrangements. This all-optics gas concentration retrieval does not require the use of a gas calibration cell and opens new tracks to atmospheric gas pollution and greenhouse gases sources monitoring. PMID:27410280

  19. Minute Concentration Measurements of Simple Hydrocarbon Species Using Supercontinuum Laser Absorption Spectroscopy.

    PubMed

    Yoo, Jihyung; Traina, Nicholas; Halloran, Michael; Lee, Tonghun

    2016-06-01

    Minute concentration measurements of simple hydrocarbon gases are demonstrated using near-infrared supercontinuum laser absorption spectroscopy. Absorption-based gas sensors, particularly when combined with optical fiber components, can significantly enhance diagnostic capabilities to unprecedented levels. However, these diagnostic techniques are subject to limitations under certain gas sensing applications where interference and harsh conditions dominate. Supercontinuum laser absorption spectroscopy is a novel laser-based diagnostic technique that can exceed the above-mentioned limitations and provide accurate and quantitative concentration measurement of simple hydrocarbon species while maintaining compatibility with telecommunications-grade optical fiber components. Supercontinuum radiation generated using a highly nonlinear photonic crystal fiber is used to probe rovibrational absorption bands of four hydrocarbon species using full-spectral absorption diagnostics. Absorption spectra of methane (CH4), acetylene (C2H2), and ethylene (C2H4) were measured in the near-infrared spectrum at various pressures and concentrations to determine the accuracy and feasibility of the diagnostic strategy. Absorption spectra of propane (C3H8) were subsequently probed between 1650 nm and 1700 nm, to demonstrate the applicability of the strategy. Measurements agreed very well with simulated spectra generated using the HITRAN database as well as with previous experimental results. Absorption spectra of CH4, C2H2, and C2H4 were then analyzed to determine their respective measurement accuracy and detection limit. Concentration measurements integrated from experimental results were in very good agreement with independent concentration measurements. Calculated detection limits of CH4, C2H2, and C2H4 at room temperature and atmospheric pressure are 0.1%, 0.09%, and 0.17%, respectively. PMID:27091905

  20. Presence of terrestrial atmospheric gas absorption bands in standard extraterrestrial solar irradiance curves in the near-infrared spectral region.

    PubMed

    Gao, B C; Green, R O

    1995-09-20

    The solar irradiance curves compiled by Wehrli [Physikalisch-Meteorologisches Observatorium Publ. 615 (World Radiation Center, Davosdorf, Switzerland, 1985)] and by Neckel and Labs [Sol. Phys. 90, 205 (1984)] are widely used. These curves were obtained based on measurements of solar radiation from the ground and from aircraft platforms. Contaminations in these curves by atmospheric gaseous absorptions were inevitable. A technique for deriving the transmittance spectrum of the Sun's atmosphere from high-resolution (0.01 cm(-1)) solar occultation spectra measured above the Earth's atmosphere by the use of atmospheric trace molecule spectroscopy (ATMOS) aboard the space shuttle is described. The comparisons of the derived ATMOS solar transmittance spectrum with the two solar irradiance curves show that he curve derived by Wehrli contains many absorption features in the 2.0-2.5-µm region that are not of solar origin, whereas the curve obtained by Neckel and Labs is completely devoid of weak solar absorption features that should be there. An Earth atmospheric oxygen band at 1.268 µm and a water-vapor band near 0.94 µm are likely present in the curve obtained by Wehrli. It is shown that the solar irradiance measurement errors in some narrow spectral intervals can be as large as 20%. An improved solar irradiance spectrum is formed by the incorporation of the solar transmittance spectrum derived from the ATMOS data into the solar irradiance spectrum from Neckel and Labs. The availability of a new solar spectrum from 50 to 50 000 cm(-1) from the U.S. Air Force Phillips Laboratory is also discussed.

  1. Spectral measurements of the cosmic microwave background

    SciTech Connect

    Kogut, A.J.

    1989-04-01

    Three experiments have measured the intensity of the Cosmic Microwave Background (CMB) at wavelengths 4.0, 3.0, and 0.21 cm. The measurement at 4.0 cm used a direct-gain total-power radiometer to measure the difference in power between the zenith sky and a large cryogenic reference target. Foreground signals are measured with the same instrument and subtracted from the zenith signal, leaving the CMB as the residual. The reference target consists of a large open-mouth cryostat with a microwave absorber submerged in liquid helium; thin windows block the radiative heat load and prevent condensation atmospheric gases within the cryostat. The thermodynamic temperature of the CMB at 4.0 cm is 2.59 +- 0.07 K. The measurement at 3.0 cm used a superheterodyne Dicke-switched radiometer with a similar reference target to measure the zenith sky temperature. A rotating mirror allowed one of the antenna beams to be redirected to a series of zenith angles, permitting automated atmospheric measurements without moving the radiometer. A weighted average of 5 years of data provided the thermodynamic temperature of the CMB at 3.0 cm of 2.62 +- 0.06 K. The measurement at 0.21 cm used Very Large Array observations of interstellar ortho-formaldehyde to determine the CMB intensity in molecular clouds toward the giant HII region W51A (G49.5-0.4). Solutions of the radiative transfer problem in the context of a large velocity gradient model provided estimates of the CMB temperature within the foreground clouds. Collisional excitation from neutral hydrogen molecules within the clouds limited the precision of the result. The thermodynamic temperature of the CMB at 0.21 cm is 3.2 +- 0.9 K. 72 refs., 27 figs., 38 tabs.

  2. Molar absorptivity (ε) and spectral characteristics of cyanidin-based anthocyanins from red cabbage.

    PubMed

    Ahmadiani, Neda; Robbins, Rebecca J; Collins, Thomas M; Giusti, M Monica

    2016-04-15

    Red cabbage extract contains mono and di-acylated cyanidin (Cy) anthocyanins and is often used as food colorants. Our objectives were to determine the molar absorptivity (ε) of different red cabbage Cy-derivatives and to evaluate their spectral behaviors in acidified methanol (MeOH) and buffers pH 1-9. Major red cabbage anthocyanins were isolated using a semi-preparatory HPLC, dried and weighed. Pigments were dissolved in MeOH and diluted with either MeOH (0.1% HCl) or buffers to obtain final concentrations between 5×10(-5) and 1×10(-3) mol/L. Spectra were recorded and ε calculated using Lambert-Beer's law. The ε in acidified MeOH and buffer pH 1 ranged between ~16,000-30,000 and ~13,000-26,000 L/mol cm, respectively. Most pigments showed higher ε in pH 8 than pH 2, and lowest ε between pH 4 and 6. There were bathochromic shifts (81-105 nm) from pH 1 to 8 and hypsochromic shifts from pH 8 to 9 (2-19 nm). Anthocyanins molecular structures and the media were important variables which greatly influenced their ε and spectral behaviors. PMID:26617032

  3. Molar absorptivity (ε) and spectral characteristics of cyanidin-based anthocyanins from red cabbage.

    PubMed

    Ahmadiani, Neda; Robbins, Rebecca J; Collins, Thomas M; Giusti, M Monica

    2016-04-15

    Red cabbage extract contains mono and di-acylated cyanidin (Cy) anthocyanins and is often used as food colorants. Our objectives were to determine the molar absorptivity (ε) of different red cabbage Cy-derivatives and to evaluate their spectral behaviors in acidified methanol (MeOH) and buffers pH 1-9. Major red cabbage anthocyanins were isolated using a semi-preparatory HPLC, dried and weighed. Pigments were dissolved in MeOH and diluted with either MeOH (0.1% HCl) or buffers to obtain final concentrations between 5×10(-5) and 1×10(-3) mol/L. Spectra were recorded and ε calculated using Lambert-Beer's law. The ε in acidified MeOH and buffer pH 1 ranged between ~16,000-30,000 and ~13,000-26,000 L/mol cm, respectively. Most pigments showed higher ε in pH 8 than pH 2, and lowest ε between pH 4 and 6. There were bathochromic shifts (81-105 nm) from pH 1 to 8 and hypsochromic shifts from pH 8 to 9 (2-19 nm). Anthocyanins molecular structures and the media were important variables which greatly influenced their ε and spectral behaviors.

  4. Spectral Similarity Assessment Based on a Spectrum Reflectance-Absorption Index and Simplified Curve Patterns for Hyperspectral Remote Sensing

    PubMed Central

    Ma, Dan; Liu, Jun; Huang, Junyi; Li, Huali; Liu, Ping; Chen, Huijuan; Qian, Jing

    2016-01-01

    Hyperspectral images possess properties such as rich spectral information, narrow bandwidth, and large numbers of bands. Finding effective methods to retrieve land features from an image by using similarity assessment indices with specific spectral characteristics is an important research question. This paper reports a novel hyperspectral image similarity assessment index based on spectral curve patterns and a reflection-absorption index. First, some spectral reflection-absorption features are extracted to restrict the subsequent curve simplification. Then, the improved Douglas-Peucker algorithm is employed to simplify all spectral curves without setting the thresholds. Finally, the simplified curves with the feature points are matched, and the similarities among the spectral curves are calculated using the matched points. The Airborne Visible Infrared Imaging Spectrometer (AVIRIS) and Reflective Optics System Imaging Spectrometer (ROSIS) hyperspectral image datasets are then selected to test the effect of the proposed index. The practical experiments indicate that the proposed index can achieve higher precision and fewer points than the traditional spectral information divergence and spectral angle match. PMID:26821030

  5. Spectral Similarity Assessment Based on a Spectrum Reflectance-Absorption Index and Simplified Curve Patterns for Hyperspectral Remote Sensing.

    PubMed

    Ma, Dan; Liu, Jun; Huang, Junyi; Li, Huali; Liu, Ping; Chen, Huijuan; Qian, Jing

    2016-01-01

    Hyperspectral images possess properties such as rich spectral information, narrow bandwidth, and large numbers of bands. Finding effective methods to retrieve land features from an image by using similarity assessment indices with specific spectral characteristics is an important research question. This paper reports a novel hyperspectral image similarity assessment index based on spectral curve patterns and a reflection-absorption index. First, some spectral reflection-absorption features are extracted to restrict the subsequent curve simplification. Then, the improved Douglas-Peucker algorithm is employed to simplify all spectral curves without setting the thresholds. Finally, the simplified curves with the feature points are matched, and the similarities among the spectral curves are calculated using the matched points. The Airborne Visible Infrared Imaging Spectrometer (AVIRIS) and Reflective Optics System Imaging Spectrometer (ROSIS) hyperspectral image datasets are then selected to test the effect of the proposed index. The practical experiments indicate that the proposed index can achieve higher precision and fewer points than the traditional spectral information divergence and spectral angle match. PMID:26821030

  6. Spectral Similarity Assessment Based on a Spectrum Reflectance-Absorption Index and Simplified Curve Patterns for Hyperspectral Remote Sensing.

    PubMed

    Ma, Dan; Liu, Jun; Huang, Junyi; Li, Huali; Liu, Ping; Chen, Huijuan; Qian, Jing

    2016-01-01

    Hyperspectral images possess properties such as rich spectral information, narrow bandwidth, and large numbers of bands. Finding effective methods to retrieve land features from an image by using similarity assessment indices with specific spectral characteristics is an important research question. This paper reports a novel hyperspectral image similarity assessment index based on spectral curve patterns and a reflection-absorption index. First, some spectral reflection-absorption features are extracted to restrict the subsequent curve simplification. Then, the improved Douglas-Peucker algorithm is employed to simplify all spectral curves without setting the thresholds. Finally, the simplified curves with the feature points are matched, and the similarities among the spectral curves are calculated using the matched points. The Airborne Visible Infrared Imaging Spectrometer (AVIRIS) and Reflective Optics System Imaging Spectrometer (ROSIS) hyperspectral image datasets are then selected to test the effect of the proposed index. The practical experiments indicate that the proposed index can achieve higher precision and fewer points than the traditional spectral information divergence and spectral angle match.

  7. Experimental investigation of X-ray spectral absorption coefficients in heated Al and Ge on the Iskra-5 laser facility

    NASA Astrophysics Data System (ADS)

    Bondarenko, S. V.; Garanin, Sergey G.; Zhidkov, N. V.; Pinegin, A. V.; Suslov, N. A.

    2012-01-01

    We set forth the data of experimental investigation of X-ray spectral absorption coefficients in the 1.1 — 1.6 keV photon energy range for Al and Ge specimens bulk heated by soft X-ray radiation. Two experimental techniques are described: with the use of one facility channel and the heating of specimens by the X-ray radiation from a plane burnthrough target, as well as with the use of four channels and the heating by the radiation from two cylindrical targets with internal input of laser radiation. The X-ray radiation absorption coefficients were studied by way of transmission absorption spectroscopy using backlighting X-ray radiation from a point source. The results of investigation of X-ray spectral absorption coefficients on the 1s — 2p transitions in Al atoms and the 2p — 3d transitions in Ge atoms are presented.

  8. Temperature dependence of aggregated structure of β-carotene by absorption spectral experiment and simulation.

    PubMed

    Lu, Liping; Wu, Jie; Wei, Liangshu; Wu, Fang

    2016-12-01

    β-carotene can self-assemble to form J- or H-type aggregate in hydrophilic environments, which is crucial for the proper functioning of biological system. Although several ways controlling the formation of the two types of aggregate in hydrated ethanol have been investigated in recent years, our study provided another way to control whether J- or H- β-carotene was formed and presented a method to investigate the aggregated structure. For this purpose, the aggregates of β-carotene formed at different temperatures were studied by UV-Vis spectra and a computational method based on Frenkel exciton was applied to simulate the absorption spectra to obtain the aggregated structure of the β-carotene. The analysis showed that β-carotene formed weakly coupled H-aggregate at 15°C in 1:1 ethanol-water solvent, and with the increase of temperature it tended to form J-type of aggregate. The absorption spectral simulation based on one-dimensional Frenkel exciton model revealed that good fit with the experiment was obtained with distance between neighbor molecules r=0.82nm, disorder of the system D=1500cm(-1) for H-type and r=1.04nm, D=1800cm(-1) for J-type. PMID:27348046

  9. Temperature dependence of aggregated structure of β-carotene by absorption spectral experiment and simulation

    NASA Astrophysics Data System (ADS)

    Lu, Liping; Wu, Jie; Wei, Liangshu; Wu, Fang

    2016-12-01

    β-carotene can self-assemble to form J- or H-type aggregate in hydrophilic environments, which is crucial for the proper functioning of biological system. Although several ways controlling the formation of the two types of aggregate in hydrated ethanol have been investigated in recent years, our study provided another way to control whether J- or H- β-carotene was formed and presented a method to investigate the aggregated structure. For this purpose, the aggregates of β-carotene formed at different temperatures were studied by UV-Vis spectra and a computational method based on Frenkel exciton was applied to simulate the absorption spectra to obtain the aggregated structure of the β-carotene. The analysis showed that β-carotene formed weakly coupled H-aggregate at 15 °C in 1:1 ethanol-water solvent, and with the increase of temperature it tended to form J-type of aggregate. The absorption spectral simulation based on one-dimensional Frenkel exciton model revealed that good fit with the experiment was obtained with distance between neighbor molecules r = 0.82 nm, disorder of the system D = 1500 cm- 1 for H-type and r = 1.04 nm, D = 1800 cm- 1 for J-type.

  10. Differential absorption lidar measurements of atmospheric temperature and pressure profiles

    NASA Technical Reports Server (NTRS)

    Korb, C. L.

    1981-01-01

    The theory and methodology of using differential absorption lidar techniques for the remote measurement of atmospheric pressure profiles, surface pressure, and temperature profiles from ground, air, and space-based platforms are presented. Pressure measurements are effected by means of high resolution measurement of absorption at the edges of the oxygen A band lines where absorption is pressure dependent due to collisional line broadening. Temperature is assessed using measurements of the absorption at the center of the oxygen A band line originating from a quantum state with high ground state energy. The population of the state is temperature dependent, allowing determination of the temperature through the Boltzmann term. The results of simulations of the techniques using Voigt profile and variational analysis are reported for ground-based, airborne, and Shuttle-based systems. Accuracies in the 0.5-1.0 K and 0.1-0.3% range are projected.

  11. Inferring brown carbon content from UV aerosol absorption measurements during biomass burning season

    NASA Astrophysics Data System (ADS)

    Mok, J.; Krotkov, N. A.; Arola, A. T.; Torres, O.; Jethva, H. T.; Andrade, M.; Labow, G. J.; Eck, T. F.; Li, Z.; Dickerson, R. R.; Stenchikov, G. L.; Osipov, S.

    2015-12-01

    Measuring spectral dependence of light absorption by colored organic or "brown" carbon (BrC) is important, because of its effects on photolysis rates of ozone and surface ultraviolet (UV) radiation. Enhanced UV spectral absorption by BrC can in turn be exploited for simultaneous retrievals of BrC and black carbon (BC) column amounts in field campaigns. We present an innovative ground-based retrieval of BC and BrC volume fractions and their mass absorption efficiencies during the biomass burning season in Santa Cruz, Bolivia in September-October 2007. Our method combines retrieval of BC volume fraction using AERONET inversion in visible wavelengths with the inversion of total BC+BrC absorption (i.e., column effective imaginary refractive index, kmeas) using Diffuse/Direct irradiance measurements in UV wavelengths. First, we retrieve BrC volume fraction by fitting kmeas at 368nm using Maxwell-Garnett (MG) mixing rules assuming: (1) flat spectral dependence of kBC, (2) known value of kBrC at 368nm from laboratory absorption measurements or smoke chamber experiments, and (3) known BC volume fraction from AERONET inversion. Next, we derive kBrC in short UVB wavelengths by fitting kmeas at 305nm, 311nm, 317nm, 325nm, and 332nm using MG mixing rules and fixed volume fractions of BC and BrC. Our retrievals show larger than expected spectral dependence of kBrC in UVB wavelengths, implying reduced surface UVB irradiance and inhibited photolysis rates of surface ozone destruction. We use a one-dimensional chemical box model to show that the observed strong wavelength dependence of BrC absorption leads to inhibited photolysis of ozone to O(1D), a loss mechanism, while having little impact or even accelerating photolysis of NO2, an ozone production mechanism. Although BC only absorption in biomass burning aerosols is important for climate radiative forcing in the visible wavelengths, additional absorption by BrC is important because of its impact on surface UVB radiation

  12. Tomographic retrieval for scattered light limb measurements: multiple spectral fit windows to improve the spatial resolution

    NASA Astrophysics Data System (ADS)

    Pukite, Janis; Dörner, Steffen; Wagner, Thomas

    2015-04-01

    The Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite probed the atmosphere at the day side of Earth in alternating sequences of nadir and limb measurements from August 2002 to April 2012. Limb measurements allow the retrieval of stratospheric profiles of various trace gases on a global scale. It has been shown that combining measurements of the same air volume from different viewing positions along the orbit, 2D distribution fields of stratospheric trace gases can be acquired in one inversion step. Since the atmospheric scattering and absorption processes are wavelength dependent, the spatial sensitivity for limb observations also varies with wavelength. In general, for longer wavelengths, photons from more remote areas along the line of sight are contributing stronger to the measurement than for shorter wavelengths because of the lower probability of Rayleigh scattering. In addition, the radiative transfer is modified by the ozone absorption structures making longer light paths less probable within strong ozone absorption bands. In this study, additional information on the spatial distribution of NO2 is investigated by analysing results obtained by Differential Optical Absorption Spectroscopy (DOAS) in various spectral fit windows. Combing the fit results in one profile retrieval algorithm helps to improve the spatial sensitivity and resolution of the measurements. The largest improvements for the spatial resolution and sensitivity are expected for the upper troposphere/ lower stratosphere (UTLS) region where the variation of the spatial sensitivity with wavelength is strongest.

  13. Neutron spectral measurements in the upper atmosphere

    NASA Technical Reports Server (NTRS)

    Zobel, W.; Love, T. A.; Delorenzo, J. T.; Mcnew, C. O.

    1972-01-01

    An experiment to measure neutrons in the upper atmosphere was performed on a balloon flight from Palestine, Texas, at an altitude of about 32 km. The experimental arrangement is discussed briefly, and results of a preliminary analysis of the data for neutrons in the energy range 3 to 30 MeV are given.

  14. Information Retrieval from SAGE II and MFRSR Multi-Spectral Extinction Measurements

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew A.; Hansen, James E. (Technical Monitor)

    2001-01-01

    Direct beam spectral extinction measurements of solar radiation contain important information on atmospheric composition in a form that is essentially free from multiple scattering contributions that otherwise tend to complicate the data analysis and information retrieval. Such direct beam extinction measurements are available from the solar occultation satellite-based measurements made by the Stratospheric and Aerosol Gas Experiment (SAGE II) instrument and by ground-based Multi-Filter Shadowband Radiometers (MFRSRs). The SAGE II data provide cross-sectional slices of the atmosphere twice per orbit at seven wavelengths between 385 and 1020 nm with approximately 1 km vertical resolution, while the MFRSR data provide atmospheric column measurements at six wavelengths between 415 and 940 nm but at one minute time intervals. We apply the same retrieval technique of simultaneous least-squares fit to the observed spectral extinctions to retrieve aerosol optical depth, effective radius and variance, and ozone, nitrogen dioxide, and water vapor amounts from the SAGE II and MFRSR measurements. The retrieval technique utilizes a physical model approach based on laboratory measurements of ozone and nitrogen dioxide extinction, line-by-line and numerical k-distribution calculations for water vapor absorption, and Mie scattering constraints on aerosol spectral extinction properties. The SAGE II measurements have the advantage of being self-calibrating in that deep space provides an effective zero point for the relative spectral extinctions. The MFRSR measurements require periodic clear-day Langley regression calibration events to maintain accurate knowledge of instrument calibration.

  15. Localization of subsurface fluorescent lesions using surface spectral measurements

    NASA Astrophysics Data System (ADS)

    Kolste, Kolbein

    Localization of Subsurface Fluorescent Lesions using Surface Spectral Measurements Sponsored by the National Institute of Health, Bethesda, Maryland Kolbein Kolste, Ph.D. Keith Paulsen In neurosurgical tumor resection, maximizing extent of resection plays a major role in the care of cancer patients. To date, ALA is being researched as a technique to guide tumor resection by inducing the accumulation of the endogenous fluorophore PpIX. Most research has focused on the use of blue light excitation of PpIX to visual the tumor. However, due to the high attenuation of blue light by in vivo chromophores, such as oxy- and deoxy-hemoglobin, the source of collected fluorescence emissions is confined to the top layer of cells, and the signal is subject to masking by blood on the surface of the surgical field of view. This issue is particularly a problem at the end of the resection, when the surgeon is evaluating the margin for remaining tumor, but the blue-signal is insensitive to residual tumor that may be located several millimeters beneath the surface. PpIX has an absorption band in the near infrared (NIR), where the absorption due to blood is orders of magnitude lower, enabling the excitation of a fluorophore at depth. In this work, we created a hyperspectral imaging system that attaches to a neurosurgical microscope and is capable of detecting PpIX fluorescence that has been excited at 635 nm. We utilize a dual-waveband technique from the hyperspectral to estimate depth of fluorescence origin and characterize the inherent limitations of the estimated depth. One of the major benefits of this technique is that the estimation is independent of the concentration and size of the fluorophore. This is first demonstrated in phantom studies, where the depths of multiple separate inclusions at various depths are accurately estimated. The technique is verified in animal tumor models and translated into the clinical theater, with pilot data showing the first estimation of depth of

  16. Modified thermal-optical analysis using spectral absorption selectivity to distinguish black carbon from pyrolized organic carbon

    SciTech Connect

    Hadley, Odelle; Hadley, O.L.; Corrigan, C.E.; Kirchstetter, T.W.

    2008-04-14

    Black carbon (BC), a main component of combustion-generated soot, is a strong absorber of sunlight and contributes to climate change. Measurement methods for BC are uncertain, however. This study presents a method for analyzing the BC mass loading on a quartz fiber filter using a modified thermal-optical analysis method, wherein light transmitted through the sample is measured over a spectral region instead of at a single wavelength as the sample is heated. Evolution of the spectral light transmission signal depends on the relative amounts of light-absorbing BC and char, the latter of which forms when organic carbon in the sample pyrolyzes during heating. Absorption selectivities of BC and char are found to be distinct and are used to apportion the amount of light attenuated by each component in the sample. Light attenuation is converted to mass concentration based on derived mass attenuation efficiencies (MAE) of BC and char. The fraction of attenuation due to each component are scaled by their individual MAE values and added together as the total mass of light absorbing carbon (LAC). An iterative algorithm is used to find the MAE values for both BC and char that provide the best fit to the carbon mass remaining on the filter (derived from direct measurements of thermally evolved CO{sub 2}) at temperatures higher than 480 C. This method was applied to measure the BC concentration in precipitation samples collected from coastal and mountain sites in Northern California. The uncertainty in measured BC concentration of samples that contained a high concentration of organics susceptible to char ranged from 12 to 100 percent, depending on the mass loading of BC on the filter. The lower detection limit for this method was approximately 0.35 {micro}g BC and uncertainty approached 20 percent for BC mass loading greater than 1.0 {micro}g BC.

  17. Approach for determining the contributions of phytoplankton, colored organic material, and nonalgal particles to the total spectral absorption in marine waters.

    PubMed

    Lin, Junfang; Cao, Wenxi; Wang, Guifeng; Hu, Shuibo

    2013-06-20

    Using a data set of 1333 samples, we assess the spectral absorption relationships of different wave bands for phytoplankton (ph) and particles. We find that a nonlinear model (second-order quadratic equations) delivers good performance in describing their spectral characteristics. Based on these spectral relationships, we develop a method for partitioning the total absorption coefficient into the contributions attributable to phytoplankton [a(ph)(λ)], colored dissolved organic material [CDOM; a(CDOM)(λ)], and nonalgal particles [NAP; a(NAP)(λ)]. This method is validated using a data set that contains 550 simultaneous measurements of phytoplankton, CDOM, and NAP from the NASA bio-Optical Marine Algorithm Dataset. We find that our method is highly efficient and robust, with significant accuracy: the relative root-mean-square errors (RMSEs) are 25.96%, 38.30%, and 19.96% for a(ph)(443), a(CDOM)(443), and the CDOM exponential slope, respectively. The performance is still satisfactory when the method is applied to water samples from the northern South China Sea as a regional case. The computed and measured absorption coefficients (167 samples) agree well with the RMSEs, i.e., 18.50%, 32.82%, and 10.21% for a(ph)(443), a(CDOM)(443), and the CDOM exponential slope, respectively. Finally, the partitioning method is applied directly to an independent data set (1160 samples) derived from the Bermuda Bio-Optics Project that contains relatively low absorption values, and we also obtain good inversion accuracy [RMSEs of 32.37%, 32.57%, and 11.52% for a(ph)(443), a(CDOM)(443), and the CDOM exponential slope, respectively]. Our results indicate that this partitioning method delivers satisfactory performance for the retrieval of a(ph), a(CDOM), and a(NAP). Therefore, this may be a useful tool for extracting absorption coefficients from in situ measurements or remotely sensed ocean-color data. PMID:23842167

  18. Approach for determining the contributions of phytoplankton, colored organic material, and nonalgal particles to the total spectral absorption in marine waters.

    PubMed

    Lin, Junfang; Cao, Wenxi; Wang, Guifeng; Hu, Shuibo

    2013-06-20

    Using a data set of 1333 samples, we assess the spectral absorption relationships of different wave bands for phytoplankton (ph) and particles. We find that a nonlinear model (second-order quadratic equations) delivers good performance in describing their spectral characteristics. Based on these spectral relationships, we develop a method for partitioning the total absorption coefficient into the contributions attributable to phytoplankton [a(ph)(λ)], colored dissolved organic material [CDOM; a(CDOM)(λ)], and nonalgal particles [NAP; a(NAP)(λ)]. This method is validated using a data set that contains 550 simultaneous measurements of phytoplankton, CDOM, and NAP from the NASA bio-Optical Marine Algorithm Dataset. We find that our method is highly efficient and robust, with significant accuracy: the relative root-mean-square errors (RMSEs) are 25.96%, 38.30%, and 19.96% for a(ph)(443), a(CDOM)(443), and the CDOM exponential slope, respectively. The performance is still satisfactory when the method is applied to water samples from the northern South China Sea as a regional case. The computed and measured absorption coefficients (167 samples) agree well with the RMSEs, i.e., 18.50%, 32.82%, and 10.21% for a(ph)(443), a(CDOM)(443), and the CDOM exponential slope, respectively. Finally, the partitioning method is applied directly to an independent data set (1160 samples) derived from the Bermuda Bio-Optics Project that contains relatively low absorption values, and we also obtain good inversion accuracy [RMSEs of 32.37%, 32.57%, and 11.52% for a(ph)(443), a(CDOM)(443), and the CDOM exponential slope, respectively]. Our results indicate that this partitioning method delivers satisfactory performance for the retrieval of a(ph), a(CDOM), and a(NAP). Therefore, this may be a useful tool for extracting absorption coefficients from in situ measurements or remotely sensed ocean-color data.

  19. Optical reflectance of pyrheliometer absorption cavities: progress toward SI-traceable measurements of solar irradiance.

    PubMed

    Patrick, Heather J; Germer, Thomas A; Zarobila, Clarence J; Cooksey, Catherine C; Yoon, Howard W

    2016-08-10

    We have accurately determined the absorptance of three pyrheliometer cavities at 532 nm by measuring the residual reflectance using an angle-resolved bidirectional reflectometer. Measurements were performed at a normal incidence as a function of the viewing angle and position on the cavity cone. By numerically integrating the measured angle-resolved scatter over both the direction and position and accounting for an obstructed view of the cavity, we determined that the effective cavity reflectance was between 8×10-4 and 9×10-4. Thus, the absorptance of the three cavities ranged from 0.99909±0.00014 to 0.99922±0.00012 (k=2 combined expanded uncertainties). These measurements, when extended over the spectral range of operation of the pyrheliometer, are required to establish SI traceability for absolute solar irradiance measurements. PMID:27534478

  20. Prototype simulates remote sensing spectral measurements on fruits and vegetables

    NASA Astrophysics Data System (ADS)

    Hahn, Federico

    1998-09-01

    A prototype was designed to simulate spectral packinghouse measurements in order to simplify fruit and vegetable damage assessment. A computerized spectrometer is used together with lenses and an externally controlled illumination in order to have a remote sensing simulator. A laser is introduced between the spectrometer and the lenses in order to mark the zone where the measurement is being taken. This facilitates further correlation work and can assure that the physical and remote sensing measurements are taken in the same place. Tomato ripening and mango anthracnose spectral signatures are shown.

  1. Testing tripartite Mermin inequalities by spectral joint measurements of qubits

    SciTech Connect

    Huang, J. S.; Oh, C. H.; Wei, L. F.

    2011-06-15

    Using spectral joint measurements of the qubits, we propose a scheme to test the tripartite Mermin inequality with three qubits dispersively coupled to a driven cavity. First, we show how to generate a three-qubit Greenberger-Horne-Zeilinger (GHZ) state by only one-step quantum operation. Then spectral joint measurements are introduced to directly confirm such tripartite entanglement. Assisted by a series of single-qubit operations, these measurements are further utilized to test the Mermin inequality. The feasibility of the proposal is robustly demonstrated by the present numerical experiments.

  2. Spectral measurements of asymmetrically irradiated capsule backlighters

    NASA Astrophysics Data System (ADS)

    Keiter, P. A.; Drake, R. P.

    2016-11-01

    Capsule backlighters provide a quasi-continuum x-ray spectrum over a wide range of photon energies [J. F. Hansen et al., Rev. Sci. Instrum. 79, 013504 (2008)]. Ideally one irradiates the capsule backlighter symmetrically, however, in complex experimental geometries, this is not always possible. In recent experiments we irradiated capsule backlighters asymmetrically and measured the x-ray spectrum from multiple directions. We will present time-integrated spectra over the photon energy range of 2-13 keV and time-resolved spectra over the photon energy range of 2-3 keV. We will compare the spectra from different lines of sight to determine if the laser asymmetry results in an angular dependence in the x-ray emission.

  3. Broad spectral range measurement of chromatic dispersion of polarization modes in holey fibers using spectral interferometry

    NASA Astrophysics Data System (ADS)

    Hlubina, P.; Ciprian, D.; Martynkien, T.; Mergo, P.; Urbańczyk, W.

    2011-05-01

    Chromatic dispersion of polarization modes in holey fibers is measured over a broad spectral range (e.g. 500-1600 nm) using two white-light spectral interferometric techniques. First, a technique employing an unbalanced Mach-Zehnder interferometer with a fiber in the test arm is used to measure the wavelength dependence of the differential group effective index, or equivalently the chromatic dispersion of one polarization mode supported by the fiber. Second, a technique employing a tandem configuration of a Michelson interferometer and the optical fiber under test is used to measure the group modal birefringence in the fiber. From these measurements, the chromatic dispersion of the other polarization mode supported by the fiber is retrieved. We measured by these techniques the chromatic dispersion of polarization modes in four air-silica holey fibers and revealed the dependence of zero-dispersion wavelength on the geometry of the holey fiber.

  4. A New Measurement of the Absolute Spectral Reflectance of the Moon

    NASA Technical Reports Server (NTRS)

    Lawrence, S. J.; Lau, E.; Steutel, D.; Stopar, J. D.; Wilcox, B. B.; Lucey, P. G.

    2003-01-01

    The spectral reflectance of the Moon is an important property for studies of lunar geology, quantitative physical modeling of the moon, and in-flight calibration of spacecraft sensors. Previous studies have claimed that telescopic absolute reflectance values for the Moon are greater than laboratory reflectance measurements by a factor of two. In order to confirm these results, we performed ground-based observations of the lunar surface using a visible/near-infrared spectroradiometer and compared the measured lunar surface radiance to solar radiance corrected for atmospheric scattering and absorption. These data were compared to previously obtained laboratory reflectance measurements from Apollo soil samples.

  5. Drizzle Measurements Using High Spectral Resolution Lidar and Radar Data

    NASA Astrophysics Data System (ADS)

    Eloranta, Edwin W.

    2016-06-01

    The ratio of millimeter radar and High Spectral Resolution Lidar (HSRL) backscatter are used to determine drizzle rates which are compared to conventional ground based measurements. The robustly calibrated HSRL backscatter cross section provides advantages over measurements made with traditional lidars.

  6. Spectral Measurements of Meteorite Powders: Implications for 433 Eros

    NASA Technical Reports Server (NTRS)

    Burbine, T. H.; McCoy, T. J.; Jarosewich, E.; Sunshine, J. M.

    2002-01-01

    We are re-examining the regions defined by different meteorite classes in Band Area Ratio plots by measuring more meteorite samples. These data will allow us to better determine asteroid compositions from spectral measurements. Additional information is contained in the original extended abstract.

  7. Absolute measurements of nonlinear absorption near LIDT at 193 nm

    NASA Astrophysics Data System (ADS)

    Blaschke, Holger; Ristau, Detlev; Welsch, Eberhard; Apel, Oliver

    2001-04-01

    Previous investigations indicate that oxide coatings exhibit non-linear absorption phenomena below 200 nm. Hereby, absorption data of Al2O3 thin film coatings has been determined absolutely by laser calorimetry (LCA) at 193 nm in the low fluence regime. As an alternative, on the basis of the pulsed surface thermal lens technique (STL), photothermal measurements allow to determine the absorption relatively at fluence levels both in the subdamage fluence range far from the damage onset and close to the LIDT. By combining the two measurement techniques, the absolute determination of linear as well as multiphoton absorption can be achieved also in the vicinity of the laser damage fluences. This is of crucial interest because the initiation of damage onset can be observed immediately. Absolute absorption data of Al2O3 coatings at different laser fluences stating of some mJoule/cm2 will be presented for the wavelength 193 nm. Thus, the correlation between the increase of absorption and the onset of breakdown can be illustrated impressively. The evaluation and discussion of the experimental results are focused on the degree of non-linearity of the investigated absorption behavior of oxide single layers initiating the optical breakdown of UV oxide coatings.

  8. Variability, absorption features, and parent body searches in "spectrally featureless" meteorite reflectance spectra: Case study - Tagish Lake

    NASA Astrophysics Data System (ADS)

    Izawa, M. R. M.; Craig, M. A.; Applin, D. M.; Sanchez, J. A.; Reddy, V.; Le Corre, L.; Mann, P.; Cloutis, E. A.

    2015-07-01

    Reflectance spectra of many asteroids and other Solar System bodies are commonly reported as "featureless". Here, we show that weak but consistently detectable absorption bands are observable in 200-2500 nm spectra of the Tagish Lake meteorite, a likely compositional and spectral analogue for low-albedo, "spectrally-featureless" asteroids. Tagish Lake presents a rare opportunity to study multiple lithologies within a single meteorite. Reflectance spectra of Tagish Lake display significant variation between different lithologies. The spectral variations are due in part to mineralogical variations between different Tagish Lake lithologies. Ultraviolet reflectance spectra (200-400 nm), few of which have been reported in the literature to date, reveal albedo and spectral ratio variations as a function of mineralogy. Similarly visible-near infrared reflectance spectra reveal variations in albedo, spectral slope, and the presence of weak absorption features that persist across different lithologies and can be attributed to various phases present in Tagish Lake. These observations demonstrate that significant spectral variability may exist between different lithologies of Tagish Lake, which may affect the interpretation of potential source body spectra. It is also important to consider the spectral variability within the meteorite before excluding compositional links between possible parent bodies in the main belt and Tagish Lake. Tagish Lake materials may also be spectral-compositional analogues for materials on the surfaces of other dark asteroids, including some that are targets of upcoming spacecraft missions. Tagish Lake has been proposed as a spectral match for 'ultra-primitive' D or P-type asteroids, and the variability reported here may be reflected in spatially or rotationally-resolved spectra of possible Tagish Lake parent bodies and source objects in the Near-Earth Asteroid population. A search for objects with spectra similar to Tagish Lake has been carried

  9. Field measurements of the spectral response of natural waters

    NASA Technical Reports Server (NTRS)

    Bartolucci, L. A.; Robinson, B. F.; Silva, L. F.

    1977-01-01

    The spectral response (air-water interface reflectance and water-volume scattering) of turbid river water (99 mg/liter suspended solids) and relatively clear lake water (10 mg/liter suspended solids) was measured in situ with a field spectroradiometer. The influence of the river bottom on the spectral response of the water also was determined by using a modified Secchi disc approach. The results indicated that turbid river water had a higher spectral response than clear lake water (about 6 percent) in the red (0.6-0.7 micron) and near-infrared (0.7-0.9 micron) portions of the spectrum. Also, the reflectance characteristics of the river bottom did not influence the spectral response of the turbid river water when the water was deeper than 30 cm

  10. Inclusion Analysis and Absorption Measurement in Nonlinear Crystals

    SciTech Connect

    Smith, L L

    2005-08-26

    Yttrium calcium oxyborate (YCOB) is a newly developed nonlinear optical crystal used for second harmonic generation in the Mercury laser. As with any new crystal, optical characterization of the material properties needs to be fully investigated. We are developing two new techniques to detect inclusions and measure optical absorption. With the side illuminating detection examination (SIDE) method, we hope to identify and map the size, density, and the morphology of inclusions. The multi-pass absorption technique (MPAT) will be used to help determine the absorption coefficient of various finished crystalline pieces at near-infrared wavelengths.

  11. Orthogonal spectra and cross sections: Application to optimization of multi-spectral absorption and fluorescence lidar

    SciTech Connect

    Shokair, I.R.

    1997-09-01

    This report addresses the problem of selection of lidar parameters, namely wavelengths for absorption lidar and excitation fluorescence pairs for fluorescence lidar, for optimal detection of species. Orthogonal spectra and cross sections are used as mathematical representations which provide a quantitative measure of species distinguishability in mixtures. Using these quantities, a simple expression for the absolute error in calculated species concentration is derived and optimization is accomplished by variation of lidar parameters to minimize this error. It is shown that the optimum number of wavelengths for detection of a species using absorption lidar (excitation fluorescence pairs for fluorescence lidar) is the same as the number of species in the mixture. Each species present in the mixture has its own set of optimum wavelengths. There is usually some overlap in these sets. The optimization method is applied to two examples, one using absorption and the other using fluorescence lidar, for analyzing mixtures of four organic compounds. The effect of atmospheric attenuation is included in the optimization process. Although the number of optimum wavelengths might be small, it is essential to do large numbers of measurements at these wavelengths in order to maximize canceling of statistical errors.

  12. Spectral Measurements of Meteorite Powders: Implications for 433 Eros

    NASA Technical Reports Server (NTRS)

    Burbine, T. H.; McCoy, T. J.; Jarosewich, E.; Sunshine, J. M.

    2001-01-01

    One of the goals of the NEAR-Shoemaker mission to 433 Eros was to determine if it has a meteoritic analog. The primary means of making such a link are the X-ray/gamma-ray spectrometers, which measure elemental compositions of the surface, and the multi-spectral imager (MSI) and near-infrared spectrometer (NIS), which measure spectral reflectance. For determining meteoritic analogs using the X-ray/gamma-ray spectrometer data, the primary data used for comparison is the set of bulk chemical analyses of meteorites done by Jarosewich. These bulk chemical analyses were done on samples now found in the Smithsonian's Analyzed Meteorite Powder collection (USNM 7073). For determining meteoritic analogs using MSI/NIS spectral data, the primary data used for comparison is the set of meteoritic spectra compiled by Gaffey. To expand the set of meteoritic spectra available to the scientific community, we have initiated a spectral study of over 70 samples (primarily ordinary chondrites) found in the Smithsonian's Analyzed Meteorite Powder collection and an electron microprobe study of their corresponding thin sections. This set of spectral and compositional data should allow for better constraints on the distribution of meteorites in plots of band area ratios versus Band I centers and the usefulness of equations for deriving mineralogic compositions from band parameters. These spectral data can also be combined with previous spectral studies of other meteorite types such as the primitive achondrites, eucrites, and angrites to determine how useful the derived band parameters are for differentiating between different meteorite classes. These spectral data can also be used for testing the Modified Gaussian Model (MGM) for determining modal abundances and mafic mineral chemistries from reflectance spectra.

  13. A high spectral resolution VLA search for H I absorption towards A496, A1795, and A2584

    NASA Technical Reports Server (NTRS)

    O'Dea, Christopher P.; Gallimore, Jack F.; Baum, Stefi A.

    1995-01-01

    In this paper, we present the results of a Very Large Array (VLA) search for H I absorption with high spectral resolution (1.6 km/s) towards A496, A1795, A2584, and A2597. These observations are well matched to the properties of cold, optically thick H I clouds, where the line width is given by the width of an individual cloud rather than the dispersion in an ensemble of clouds. We do not detect any H I absorption with narrow linewidths in these clusters. Our limits mainly apply to clouds which are larger than a few tenths parsec-i.e., if the clouds are much smaller than the background radio source and have a low covering factor in velocity space, they could still escape detection. The estimated limits on column density (for clouds in this regime of parameter space) are 2-3 orders of magnitude less than the 10(exp 21)/sq cm required to explain the x-ray absorption seen in some cooling flow clusters. The combination of our high spectral resolution H I absorption searches with the existing lower spectral resolution H I absorption searches and the searches for H I emission makes it unlikely that atomic hydrogen is the dominant component of the cold x-ray absorbing gas in the inter-cloud medium (ICM).

  14. Dual-peak dose measurement for radiochromic films by a newly developed spectral microdensitometer

    SciTech Connect

    Lee, K.Y.; Fung, K.K.L.; Kwok, C.S.

    2005-06-15

    Radiochromic film (RCF) dosimetry is usually based on densitometric methods which use an analyzing light source of a fixed or a broad spectrum of wavelengths. These methods have not exploited the sensitivity of the dose response of the RCF otherwise attainable by using a light source with wavelengths peaked at the two absorption peaks in the absorption spectrum of the RCF. A new algorithm of dual-peak dose measurement for the RCF has been proposed in this paper to make use of these dual absorption peaks to achieve the maximum attainable sensitivity. This technique relies on the measurement of the transmittance of the RCF at the wavelength of the major and minor absorption peaks, respectively. The dual-peak dose measurement is accomplished with the aid of a novel spectral microdensitometer developed in our Institute. The microdensitometer utilizes a monochromator to provide a light source of which the wavelength can be matched precisely to the wavelength of the absorption peaks of the RCF. The doses obtained at these wavelengths are fed into a weighted objective function and an optimum dose is searched by minimizing the objective function to give the best estimate of the dose deposited on the film. An initial test shows that there is a good agreement between the estimated and actual dose deposited; and the maximum discrepancy was found to be less than 1%.

  15. Spectral measurements of ocean-dumped wastes tested in the marine upwelled spectral signature laboratory

    NASA Technical Reports Server (NTRS)

    Witte, W. G.; Usry, J. W.; Whitlock, C. H.; Gurganus, E. A.

    1979-01-01

    Transmission and inherent upwelled radiance measurements were made of various mixtures of three ocean-dumped industrial plant wastes in artificial seawater. Laboratory analyses were made of the physical and chemical properties of the various mixtures. These results and the laboratory measurements of beam attenuation and inherent upwelled radiance indicate a variety of chemical and spectral responses when industrial wastes are added to artificial seawater. In particular, increased levels of turbidity did not always cause increased levels of inherent reflectance.

  16. Stabilization and spectral characterization of an alexandrite laser for water vapor lidar measurements

    NASA Technical Reports Server (NTRS)

    Ponsardin, Patrick; Higdon, Noah S.; Grossman, Benoist E.; Browell, Edward V.

    1991-01-01

    A description of an optical system used to lock the alexandrite laser frequency on a water vapor absorption line is presented. The laser spectral characteristics, which include the spectral purity, the effect of the laser linewidth on the absorption, and the laser wavelength stability, are evaluated.

  17. Inferring surface solar absorption from broadband satellite measurements

    NASA Technical Reports Server (NTRS)

    Cess, Robert D.; Vulis, Inna L.

    1989-01-01

    An atmospheric solar radiation model and surface albedo models that include wavelength dependence and surface anisotropy are combined to study the possibility of inferring the surface solar absorption from satellite measurements. The model includes ocean, desert, pasture land, savannah, and bog surface categories. Problems associated with converting narrowband measurements to broadband quantities are discussed, suggesting that it would be easier to infer surface solar absorption from broadband measurements directly. The practice of adopting a linear relationship between planetary and surface albedo to estimate surface albedos from satellite measurements is examined, showing that the linear conversion between broadband planetary and surface albedos is strongly dependent on vegetation type. It is suggested that there is a linear slope-offset relationship between surface and surface-atmosphere solar absorption.

  18. Rapid microscopy measurement of very large spectral images.

    PubMed

    Lindner, Moshe; Shotan, Zav; Garini, Yuval

    2016-05-01

    The spectral content of a sample provides important information that cannot be detected by the human eye or by using an ordinary RGB camera. The spectrum is typically a fingerprint of the chemical compound, its environmental conditions, phase and geometry. Thus measuring the spectrum at each point of a sample is important for a large range of applications from art preservation through forensics to pathological analysis of a tissue section. To date, however, there is no system that can measure the spectral image of a large sample in a reasonable time. Here we present a novel method for scanning very large spectral images of microscopy samples even if they cannot be viewed in a single field of view of the camera. The system is based on capturing information while the sample is being scanned continuously 'on the fly'. Spectral separation implements Fourier spectroscopy by using an interferometer mounted along the optical axis. High spectral resolution of ~5 nm at 500 nm could be achieved with a diffraction-limited spatial resolution. The acquisition time is fairly high and takes 6-8 minutes for a sample size of 10mm x 10mm measured under a bright-field microscope using a 20X magnification. PMID:27137565

  19. Toward improved spectral measures of /s/: Results from adolescents

    PubMed Central

    Koenig, Laura L.; Shadle, Christine H.; Preston, Jonathan L.; Mooshammer, Christine R.

    2014-01-01

    Purpose To introduce theoretically-driven acoustic measures of /s/ that reflect aerodynamic and articulatory conditions. The measures were evaluated by assessing whether they revealed expected changes over time and labiality effects, along with possible gender differences suggested by past work. Method Productions of /s/ were extracted from various speaking tasks from typically-speaking adolescents (6 boys; 6 girls). Measures were made of relative spectral energies in low- (550–3000 Hz), mid- (3000–7000 Hz), and high-frequency regions (7000–11025 Hz); the mid-frequency amplitude peak; and temporal changes in these parameters. Spectral moments were also obtained to permit comparison with existing work. Results Spectral balance measures in low–mid and mid–high frequency bands varied over the time course of /s/, capturing the development of sibilance at mid-fricative along with showing some effects of gender and labiality. The mid-frequency spectral peak was significantly higher in non-labial contexts, and in girls. Temporal variation in the mid-frequency peak differentiated ±labial contexts while normalizing over gender. Discussion The measures showed expected patterns, supporting their validity. Comparison of these data with studies of adults suggests some developmental patterns that call for further study. The measures may also serve to differentiate some cases of typical and misarticulated /s/. PMID:23785194

  20. Picosecond absorption relaxation measured with nanosecond laser photoacoustics

    NASA Astrophysics Data System (ADS)

    Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

    2010-10-01

    Picosecond absorption relaxation—central to many disciplines—is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural—including strongly scattering and nonfluorescent—materials.

  1. Deriving brown carbon from multiwavelength absorption measurements: Method and application to AERONET and Aethalometer observations

    DOE PAGES

    Wang, X.; Heald, C. L.; Sedlacek, A.; de Sa, S. S.; Martin, S. T.; Alexander, M. L.; Watson, T. B.; Aiken, A. C.; Springston, S. R.; Artaxo, P.

    2016-10-13

    The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However the absorption properties of BrC are poorly understood leading to large uncertainties in modelling studies. To obtain observational constraints from measurements, a simple Absorption Ångström Exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regardingmore » the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new method that decreases the uncertainties associated with estimating BrC absorption. By applying this method to multi-wavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites, we estimate that BrC globally contributes 6-40% of the absorption at 440nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with BC/OA mass ratio. Based on the variability of BC properties and BC/OA emission ratio, we estimate a range of 0.05-1.2 m2/g for OA-MAC at 440nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388/440nm for BrC is generally ~4 world-wide, with a smaller value in Europe (< 2). Our analyses of two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of Manaus, Brazil) reveal no significant relationship between BrC absorptivity and photochemical aging in typical urban influenced conditions. However, the absorption of BrC measured during the biomass burning season near Manaus is found to decrease with photochemical aging with a lifetime of ~1 day. This lifetime is comparable to

  2. Precise Measurement of Lunar Spectral Irradiance at Visible Wavelengths

    PubMed Central

    Cramer, CE; Lykke, KR; Woodward, JT; Smith, AW

    2013-01-01

    We report a measurement of lunar spectral irradiance with an uncertainty below 1 % from 420 nm to 1000 nm. This measurement uncertainty meets the stability requirement for many climate data records derived from satellite images, including those for vegetation, aerosols, and snow and ice albedo. It therefore opens the possibility of using the Moon as a calibration standard to bridge gaps in satellite coverage and validate atmospheric retrieval algorithms. Our measurement technique also yields detailed information about the atmosphere at the measurement site, suggesting that lunar observations are a possible solution for aerosol monitoring during the polar winter and can provide nighttime measurements to complement aerosol data collected with sun photometers. Our measurement, made with a novel apparatus, is an order of magnitude more accurate than the previous state-of-the-art and has continuous spectral coverage, removing the need to interpolate between filter passbands. PMID:26401440

  3. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols

    NASA Technical Reports Server (NTRS)

    Carter, Arlen F.; Allen, Robert J.; Mayo, M. Neale; Butler, Carolyn F.; Grossman, Benoist E.; Ismail, Syed; Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Mayor, Shane D.; Ponsardin, Patrick; Hueser, Alene W.

    1994-01-01

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H2O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and greater than 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H2O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H2O absorption-line parameters were performed to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H2O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H2O radiosondes. The H2O distributions measured with the DIAL system differed by less than 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  4. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  5. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions. PMID:20941181

  6. [Physical meaning of temperature measured by spectral line intensity method].

    PubMed

    Zhao, Wen-Hua; Tang, Huang-Zai; Shen, Yan; Shi, Yong; Hou, Ling-Yun

    2007-11-01

    The difference between electron temperature and excitation temperature is analyzed in the aspect of statistics thermodynamics. It is presented clearly that the temperature acquired by spectral line intensity method is not free electron temperature, but internal electronic excitation temperature of heavy particle. Under thermal equilibrium condition, the excitation temperature is equal to the electron temperature, while under non-thermal equilibrium condition, the excitation temperature is not equal to the electron temperature. In the study of arc jet plume in vacuum chamber, spectral line intensity method was employed to measure the apparent excitation temperature of arc jet plume, and Langmuir probe was employed to measure the electron temperature of arcjet plume. The big difference between the excitation temperature and the electron temperature proved that the temperature acquired by spectral line intensity method is not free electron temperature.

  7. International Photolysis Frequency Measurement and Model Intercomparison (IPMMI): Spectral actinic solar flux measurements and modeling

    NASA Astrophysics Data System (ADS)

    Bais, A. F.; Madronich, S.; Crawford, J.; Hall, S. R.; Mayer, B.; van Weele, M.; Lenoble, J.; Calvert, J. G.; Cantrell, C. A.; Shetter, R. E.; Hofzumahaus, A.; Koepke, P.; Monks, P. S.; Frost, G.; McKenzie, R.; Krotkov, N.; Kylling, A.; Swartz, W. H.; Lloyd, S.; Pfister, G.; Martin, T. J.; Roeth, E.-P.; Griffioen, E.; Ruggaber, A.; Krol, M.; Kraus, A.; Edwards, G. D.; Mueller, M.; Lefer, B. L.; Johnston, P.; Schwander, H.; Flittner, D.; Gardiner, B. G.; Barrick, J.; Schmitt, R.

    2003-08-01

    The International Photolysis Frequency Measurement and Model Intercomparison (IPMMI) took place in Boulder, Colorado, from 15 to 19 June 1998, aiming to investigate the level of accuracy of photolysis frequency and spectral downwelling actinic flux measurements and to explore the ability of radiative transfer models to reproduce the measurements. During this period, 2 days were selected to compare model calculations with measurements, one cloud-free and one cloudy. A series of ancillary measurements were also performed and provided parameters required as input to the models. Both measurements and modeling were blind, in the sense that no exchanges of data or calculations were allowed among the participants, and the results were objectively analyzed and compared by two independent referees. The objective of this paper is, first, to present the results of comparisons made between measured and modeled downwelling actinic flux and irradiance spectra and, second, to investigate the reasons for which some of the models or measurements deviate from the others. For clear skies the relative agreement between the 16 models depends strongly on solar zenith angle (SZA) and wavelength as well as on the input parameters used, like the extraterrestrial (ET) solar flux and the absorption cross sections. The majority of the models (11) agreed to within about ±6% for solar zenith angles smaller than ˜60°. The agreement among the measured spectra depends on the optical characteristics of the instruments (e.g., slit function, stray light rejection, and sensitivity). After transforming the measurements to a common spectral resolution, two of the three participating spectroradiometers agree to within ˜10% for wavelengths longer than 310 nm and at all solar zenith angles, while their differences increase when moving to shorter wavelengths. Most models agree well with the measurements (both downwelling actinic flux and global irradiance), especially at local noon, where the agreement

  8. Measurements of scattering and absorption in mammalian cell suspensions

    SciTech Connect

    Mourant, J.R.; Johnson, T.M.; Freyer, J.P.

    1996-03-01

    During the past several years a range of spectroscopies, including fluorescence and elastic-scatter spectroscopy, have been investigated for optically based detection of cancer and other tissue pathologies. Both elastic-scatter and fluorescence signals depend, in part, on scattering and absorption properties of the cells in the tissue. Therefore an understanding of the scattering and absorption properties of cells is a necessary prerequisite for understanding and developing these techniques. Cell suspensions provide a simple model with which to begin studying the absorption and scattering properties of cells. In this study we have made preliminary measurements of the scattering and absorption properties of suspensions of mouse mammary carcinoma cells (EMT6) over a broad wavelength range (380 nm to 800 nm).

  9. Simultaneous multielement graphite furnace atomic absorption measurements using a photodiode array detector

    NASA Astrophysics Data System (ADS)

    Tong, S. L.; Chin, K. S.

    1994-05-01

    A photodiode array detector multichannel analyser system has been coupled to a graphite furnace atomizer and tested for simultaneous multielement atomic absorption analysis. Multielement hollow cathode lamps are used as light sources and spectral lines are dispersed through a spectrograph with three selectable gratings. Multiple transmitted spectra are recorded to simultaneously determine the atomic absorption profiles of the analyte elements during the atomization stage. Atomic absorbance of individual elements is obtained by integrating the respective peak areas of the appropriate time-resolved atomic absorption spectra. The obtained sensitivities for Ni-Co-Fe are within the same order of magnitude as those from conventional single element determinations using photomultiplier tube detection. The system has also been applied for simultaneous multielement flame atomic absorption spectrometry (AAS) measurements and it has been demonstrated that background absorption can be readily corrected for both flame and graphite furnace AAS by a two-line method where non-atomic absorption lines can be chosen from the simultaneously recorded spectra.

  10. Measurement of atmospheric NO3 1. Improved removal of water vapour absorption features in the analysis for NO3

    NASA Astrophysics Data System (ADS)

    Aliwell, S. R.; Jones, R. L.

    Atmospheric measurements of the nitrate radical generally detect its absorption of visible radiation in the band near 662 nm. This band is negatively correlated with strong absorptions due to tropospheric water vapour which must therefore be fitted in the spectral analysis to reduce the spectral residual to the level at which sufficient sensitivity to NO3 can be obtained. Previously this had been fitted using a cross-section typically derived from spectra obtained just before sunset or just after sunrise which took no account of the diurnal variation in temperature and water vapour column amounts. An improved method of accounting for water vapour absorptions is presented here. When fitted together with their temperature dependence, water vapour cross-sections calculated using a line-by-line approach gave a more accurate fitting of water vapour absorptions, thus improving the analysis for NO3.

  11. Measurement of temperature profiles in flames by emission-absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Simmons, F. S.; Arnold, C. B.; Lindquist, G. H.

    1972-01-01

    An investigation was conducted to explore the use of infrared and ultraviolet emission-absorption spectroscopy for determination of temperature profiles in flames. Spectral radiances and absorptances were measured in the 2.7-micron H2O band and the 3064-A OH band in H2/O2 flames for several temperature profiles which were directly measured by a sodium line-reversal technique. The temperature profiles, determined by inversion of the infrared and ultraviolet spectra, showed an average disagreement with line-reversal measurements of 50 K for the infrared and 200 K for the ultraviolet at a temperature of 2600 K. The reasons for these discrepancies are discussed in some detail.

  12. Determination of aerosol size distributions from spectral attenuation measurements.

    PubMed

    Grassl, H

    1971-11-01

    An iteration method for the determination of size distributions of aerosols from spectral attenuation data, similar to the one previously published for clouds, is presented. The basis for this iteration is to consider the extinction efficiency factor of particles as a set of weighting functions covering the entire radius region of a distribution. The weighting functions were calculated exactly from the Mie theory. Aerosol distributions are shown derived from tests with analytical size distributions and also generated from measured aerosol extinction data in seven spectral channels from 0.4-microto 10-micro wavelength in continental aerosols. The influence of relative humidity on the complex index of refraction is also discussed.

  13. [Influencing factors in measuring absorption coefficient of suspended particulate matters].

    PubMed

    Yu, Xiao-long; Shen, Fang; Zhang, Jin-fang

    2013-05-01

    Absorption coefficient of suspended particulate matters in natural water is one of the key parameters in ocean color remote sensing. In order to study the influencing factors that affect the measurement, a series of experiments were designed to measure samples using transmittance method (T method), transmittance-reflectance method (T-R method) and absorptance method (A method). The results shows that absorption coefficient measured by the A method has a much lower error compared to the T method and T-R method due to influencing factors,such as filter-to-filter variations, water content of the filter, and homogeneity of filter load and so on. Another factor influence absorption coefficient is path-length amplification induced by multiple scattering inside the filter. To determine the path-length amplification, the true absorption was measured by AC-s (WetLabs). The linear fitting result shows that the mean path-length amplification is much higher for the A method than that of the T-R method and the T method (4.01 versus 2.20 and 2.32), and the corresponding correlation coefficient are 0.90, 0.87 and 0.80. For the A method and the T-R method, higher correlation coefficients are calculated when using polynomial fitting, and the value are 0.95 and 0.94. Analysis of the mean relative error caused by different influencing factors indicates that path-length amplification is the largest error source in measuring the absorption coefficient.

  14. Pulsed Airborne Lidar Measurements of C02 Column Absorption

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Weaver, Clark J.; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William E.; Rodriquez, Michael; Browell, Edward V.

    2011-01-01

    We report on airborne lidar measurements of atmospheric CO2 column density for an approach being developed as a candidate for NASA's ASCENDS mission. It uses a pulsed dual-wavelength lidar measurement based on the integrated path differential absorption (IPDA) technique. We demonstrated the approach using the CO2 measurement from aircraft in July and August 2009 over four locations. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The 2009 measurements have been analyzed in detail and the results show approx.1 ppm random errors for 8-10 km altitudes and approx.30 sec averaging times. Airborne measurements were also made in 2010 with stronger signals and initial analysis shows approx. 0.3 ppm random errors for 80 sec averaging times for measurements at altitudes> 6 km.

  15. Spectrally resolved white light interferometry to measure material dispersion over a wide spectral band in a single acquisition.

    PubMed

    Arosa, Yago; Lago, Elena López; Varela, Luis Miguel; de la Fuente, Raúl

    2016-07-25

    In this paper we apply spectrally resolved white light interferometry to measure refractive and group index over a wide spectral band from 400 to 1000 nm. The output of a Michelson interferometer is spectrally decomposed by a homemade prism spectrometer with a high resolution camera. The group index is determined directly from the phase extracted from the spectral interferogram while the refractive index is estimated once its value at a given wavelength is known. PMID:27464179

  16. Transient absorption measurement system using pulsed energetic ion

    NASA Astrophysics Data System (ADS)

    Taguchi, Mitsumasa; Baldacchino, Gérard; Kurashima, Satoshi; Kimura, Atsushi; Sugo, Yumi; Katsumura, Yosuke; Hirota, Koichi

    2009-12-01

    This article reports a highly sensitive transient absorbance measurement system using pulsed energetic ions. The ions were pulsed by a beam chopper, which was synchronized with the cyclotron, and accelerated to the desired energy around 18 MeV/u. H, He, C and Ne ions can be used for the transient absorption measurement. The optical system can measure an absorbance smaller than 1.0×10 -4 in the wavelength range of 400-740 nm.

  17. Terahertz spectral signatures :measurement and detection LDRD project 86361 final report.

    SciTech Connect

    Wanke, Michael Clement; Brener, Igal; Lee, Mark

    2005-11-01

    LDRD Project 86361 provided support to upgrade the chemical and material spectral signature measurement and detection capabilities of Sandia National Laboratories using the terahertz (THz) portion of the electromagnetic spectrum, which includes frequencies between 0.1 to 10 THz. Under this project, a THz time-domain spectrometer was completed. This instrument measures sample absorption spectra coherently, obtaining both magnitude and phase of the absorption signal, and has shown an operating signal-to-noise ratio of 10{sub 4}. Additionally, various gas cells and a reflectometer were added to an existing high-resolution THz Fourier transform spectrometer, which greatly extend the functionality of this spectrometer. Finally, preliminary efforts to design an integrated THz transceiver based on a quantum cascade laser were begun.

  18. Survey of spectral response measurements for photovoltaic devices

    SciTech Connect

    Hartman, J.S.; Lind, M.A.

    1981-11-01

    A survey of the photovoltaic community was conducted to ascertain the present state-of-the-art for PV spectral response measurements. Specific topics explored included measurement system designs, good and bad features of the systems, and problems encountered in the evaluation of specific cell structures and materials. The survey showed that most spectral response data are used in diagnostic analysis for the optimization of developmental solar cells. Measurement systems commonly utilize a chopped narrowband source in conjunction with a constant bias illumination which simulates the ambient end use environment. Researchers emphasized the importance of bias illumination for all types of cells in order to minimize the effects of nonlinearities in cell response. Not surprisingly single crystal silicon cells present the fewest measurement problems to the researcher and have been studied more thoroughly than any other type of solar cell. But, the accurate characterization of silicon cells is still difficult and laboratory intercomparison studies have yielded data scatter ranging from +-5% to +-15%. The measurement experience with other types of cells is less extensive. The development of reliable data bases for some solar cells is complicated by problems of cell nonuniformity, environmental instability, nonlinearity, etc. Cascade cells present new problems associated with their structue (multiple cells in series) which are just beginning to be understood. In addition, the importance of many measurement parameters (spectral content of bias light, bias light intensity, bias voltage, chopping frequency, etc.) are not fully understood for most types of solar cells.

  19. Imaging spectrometer measurement of water vapor in the 400 to 2500 nm spectral region

    NASA Technical Reports Server (NTRS)

    Green, Robert O.; Roberts, Dar A.; Conel, James E.; Dozier, Jeff

    1995-01-01

    The Airborne Visible-Infrared Imaging Spectrometer (AVIRIS) measures the total upwelling spectral radiance from 400 to 2500 nm sampled at 10 nm intervals. The instrument acquires spectral data at an altitude of 20 km above sea level, as images of 11 by up to 100 km at 17x17 meter spatial sampling. We have developed a nonlinear spectral fitting algorithm coupled with a radiative transfer code to derive the total path water vapor from the spectrum, measured for each spatial element in an AVIRIS image. The algorithm compensates for variation in the surface spectral reflectance and atmospheric aerosols. It uses water vapor absorption bands centered at 940 nm, 1040 nm, and 1380 nm. We analyze data sets with water vapor abundances ranging from 1 to 40 perceptible millimeters. In one data set, the total path water vapor varies from 7 to 21 mm over a distance of less than 10 km. We have analyzed a time series of five images acquired at 12 minute intervals; these show spatially heterogeneous changes of advocated water vapor of 25 percent over 1 hour. The algorithm determines water vapor for images with a range of ground covers, including bare rock and soil, sparse to dense vegetation, snow and ice, open water, and clouds. The precision of the water vapor determination approaches one percent. However, the precision is sensitive to the absolute abundance and the absorption strength of the atmospheric water vapor band analyzed. We have evaluated the accuracy of the algorithm by comparing several surface-based determinations of water vapor at the time of the AVIRIS data acquisition. The agreement between the AVIRIS measured water vapor and the in situ surface radiometer and surface interferometer measured water vapor is 5 to 10 percent.

  20. Temperature and pressure measurement based on tunable diode laser absorption spectroscopy with gas absorption linewidth detection

    NASA Astrophysics Data System (ADS)

    Meng, Yunxia; Liu, Tiegen; Liu, Kun; Jiang, Junfeng; Wang, Tao; Wang, Ranran

    2014-11-01

    A gas temperature and pressure measurement method based on Tunable Diode Laser Absorption Spectroscopy (TDLAS) detecting linewidth of gas absorption line was proposed in this paper. Combined with Lambert-Beer Law and ideal gas law, the relationship between temperature, pressure and gas linewidth with Lorentzian line shape was investigated in theory. Taking carbon monoxide (CO) at 1567.32 nm for example, the linewidths of gas absorption line in different temperatures and pressures were obtained by simulation. The relationship between the linewidth of second harmonic and temperature, pressure with the coefficient 0.025 pm/K and 0.0645 pm/kPa respectively. According to the relationship of simulation results and detected linewidth, the undefined temperature and pressure of CO gas were measured. The gas temperature and pressure measurement based on linewidth detection, avoiding the influence of laser intensity, is an effective temperature and pressure measurement method. This method also has the ability to detect temperature and pressure of other gases with Lorentzian line shape.

  1. Tone-burst technique measures high-intensity sound absorption

    NASA Technical Reports Server (NTRS)

    Powell, J. G.; Van Houten, J. J.

    1971-01-01

    Tone-burst technique, in which narrow-bandwidth, short-duration sonic pulse is propagated down a standing-wave tube, measures sound absorbing capacity of materials used in jet engine noise abatement. Technique eliminates effects of tube losses and yields normal-incidence absorption coefficient of specimen.

  2. Spectral and lifetime domain measurements of rat brain tumours

    NASA Astrophysics Data System (ADS)

    Abi Haidar, D.; Leh, B.; Allaoua, K.; Genoux, A.; Siebert, R.; Steffenhagen, M.; Peyrot, D.; Sandeau, N.; Vever-Bizet, C.; Bourg-Heckly, G.; Chebbi, I.; Collado-Hilly, M.

    2012-02-01

    During glioblastoma surgery, delineation of the brain tumour margins remains difficult especially since infiltrated and normal tissues have the same visual appearance. This problematic constitutes our research interest. We developed a fibre-optical fluorescence probe for spectroscopic and time domain measurements. First measurements of endogenous tissue fluorescence were performed on fresh and fixed rat tumour brain slices. Spectral characteristics, fluorescence redox ratios and fluorescence lifetime measurements were analysed. Fluorescence information collected from both, lifetime and spectroscopic experiments, appeared promising for tumour tissue discrimination. Two photon measurements were performed on the same fixed tissue. Different wavelengths are used to acquire two-photon excitation-fluorescence of tumorous and healthy sites.

  3. Improving spectral library search by redefining similarity measures.

    PubMed

    Garg, Ankita; Enright, Catherine G; Madden, Michael G

    2015-05-26

    Similarity plays a central role in spectral library search. The goal of spectral library search is to identify those spectra in a reference library of known materials that most closely match an unknown query spectrum, on the assumption that this will allow us to identify the main constituent(s) of the query spectrum. The similarity measures used for this task in software and the academic literature are almost exclusively metrics, meaning that the measures obey the three axioms of metrics: (1) minimality; (2) symmetry; (3) triangle inequality. Consequently, they implicitly assume that the query spectrum is drawn from the same distribution as that of the reference library. In this paper, we demonstrate that this assumption is not necessary in practical spectral library search and that in fact it is often violated in practice. Although the reference library may be constructed carefully, it is generally impossible to guarantee that all future query spectra will be drawn from the same distribution as the reference library. Before evaluating different similarity measures, we need to understand how they define the relationship between spectra. In spectral library search, we often aim to find the constituent(s) of a mixture. We propose that, rather than asking which reference library spectra are similar to the mixture, we should ask which of the reference library spectra are contained in the given query mixture. This question is inherently asymmetric. Therefore, we should adopt a nonmetric measure. To evaluate our hypothesis, we apply a nonmetric measure formulated by Tversky [Psychol. Rev. 1977, 84, 327-352] known as the Contrast Model and compare its performance to the well-known Jaccard similarity index metric on spectroscopic data sets. Our results show that the Tversky similarity measure yields better results than the Jaccard index. PMID:25902003

  4. Improving spectral library search by redefining similarity measures.

    PubMed

    Garg, Ankita; Enright, Catherine G; Madden, Michael G

    2015-05-26

    Similarity plays a central role in spectral library search. The goal of spectral library search is to identify those spectra in a reference library of known materials that most closely match an unknown query spectrum, on the assumption that this will allow us to identify the main constituent(s) of the query spectrum. The similarity measures used for this task in software and the academic literature are almost exclusively metrics, meaning that the measures obey the three axioms of metrics: (1) minimality; (2) symmetry; (3) triangle inequality. Consequently, they implicitly assume that the query spectrum is drawn from the same distribution as that of the reference library. In this paper, we demonstrate that this assumption is not necessary in practical spectral library search and that in fact it is often violated in practice. Although the reference library may be constructed carefully, it is generally impossible to guarantee that all future query spectra will be drawn from the same distribution as the reference library. Before evaluating different similarity measures, we need to understand how they define the relationship between spectra. In spectral library search, we often aim to find the constituent(s) of a mixture. We propose that, rather than asking which reference library spectra are similar to the mixture, we should ask which of the reference library spectra are contained in the given query mixture. This question is inherently asymmetric. Therefore, we should adopt a nonmetric measure. To evaluate our hypothesis, we apply a nonmetric measure formulated by Tversky [Psychol. Rev. 1977, 84, 327-352] known as the Contrast Model and compare its performance to the well-known Jaccard similarity index metric on spectroscopic data sets. Our results show that the Tversky similarity measure yields better results than the Jaccard index.

  5. Material Spectral Emissivity Measurement Based on Two Reference Blackbodies

    NASA Astrophysics Data System (ADS)

    Cai, Jing; Yang, Yongjun; Liao, Li; Lyu, Guoyi

    2015-12-01

    Spectral emissivity is one of the important physical properties of materials. Emissivity measurement is critical for accurate temperature measurements and the evaluation of the stealth performance for materials. In this paper, a Fourier transform infrared spectrometer and an energy comparison method are used to study material emissivity measurements. Two reference blackbodies are employed for real-time measurement and correction of the spectrometer background function to enhance the emissivity measurement accuracy, to improve the design of a three-parabolic-mirror optical system, and to enlarge the optical field of view to meet the measurement requirements. The linearity of the system is measured using a mercury cadmium telluride detector and a deuterated triglycine sulfate detector. The results indicate that the linear range of the system meets the emissivity measurement requirements for the temperature range from 50°C to 1000° C. The effective radiation surface is introduced as a parameter of the reference blackbodies to reduce the influence of the measurement distance. The Fourier transform infrared spectrometer is used to measure the spectral emissivity of a conductive silica film and SiC, respectively, at different temperatures in the wavelength range of 1 \\upmu m to 25 \\upmu m. The expanded uncertainty is less than 5 %.

  6. Towards higher stability of resonant absorption measurements in pulsed plasmas.

    PubMed

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-01

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source. PMID:26724013

  7. Towards higher stability of resonant absorption measurements in pulsed plasmas

    SciTech Connect

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-15

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called “dynamic source triggering,” between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

  8. Towards higher stability of resonant absorption measurements in pulsed plasmas

    NASA Astrophysics Data System (ADS)

    Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

    2015-12-01

    Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

  9. Quantum cascade laser absorption spectroscopy of UF6 at 7.74 μm for analytical uranium enrichment measurements

    NASA Astrophysics Data System (ADS)

    Lewicki, Rafal; Kosterev, Anatoliy A.; Toor, Fatima; Yao, Yu; Gmachl, Claire; Tsai, Tracy; Wysocki, Gerard; Wang, Xiaojun; Troccoli, Mariano; Fong, Mary; Tittel, Frank K.

    2010-01-01

    The ν1+ν3 combination band of uranium hexafluoride (UF6) is targeted to perform analytical enrichment measurements using laser absorption spectroscopy. A high performance widely tunable EC-QCL sources emitting radiation at 7.74 μm (1291 cm-1) is employed as an UF6-LAS optical source to measure the unresolved rotational-vibrational spectral structure of several tens of wavenumbers (cm-1). A preliminary spectroscopic measurement based on a direct laser absorption spectroscopy of methane (CH4) as an appropriate UF6 analyte simulant, was demonstrated.

  10. Absorption spectral change of peripheral-light harvesting complexes 2 induced by magnesium protoporphyrin IX monomethyl ester association.

    PubMed

    Yue, Huiying; Zhao, Chungui; Li, Kai; Yang, Suping

    2015-02-25

    Several spectrally different types of peripheral light harvesting complexes (LH) have been reported in anoxygenic phototrophic bacteria in response to environmental changes. In this study, two spectral forms of LH2 (T-LH2 and U-LH2) were isolated from Rhodobacter azotoformans. The absorption of T-LH2 was extremely similar to the LH2 isolated from Rhodobacter sphaeroides. U-LH2 showed an extra peak at ∼423 nm in the carotenoid region. To explore the spectral origin of this absorption peak, the difference in pigment compositions of two LH2 was analyzed. Spheroidene and bacteriochlorophyll aP were both contained in the two LH2. And magnesium protoporphyrin IX monomethyl ester (MPE) was only contained in U-LH2. It is known that spheroidene and bacteriochlorophyll aP do not produce ∼423 nm absorption peak either in vivo or in vitro. Whether MPE accumulation was mainly responsible for the formation of the ∼423 nm peak? The interactions between MPE and different proteins were further studied. The results showed that the maximum absorption of MPE was red-shifted from ∼415 nm to ∼423 nm when it was mixed with T-LH2 and its apoproteins, nevertheless, the Qy transitions of the bound bacteriochlorophylls in LH2 were almost unaffected, which indicated that the formation of the ∼423 nm peak was related to MPE-LH2 protein interaction. MPE did not bind to sites involved in the spectral tuning of BChls, but the conformation of integral LH2 was affected by MPE association, the alkaline stability of U-LH2 was lower than T-LH2, and the fluorescence intensity at 860 nm was decreased after MPE combination.

  11. The infrared optical constants of sulfuric acid at 250 K. [spectral reflectance measurement of aqueous solutions

    NASA Technical Reports Server (NTRS)

    Pinkley, L. W.; Williams, D.

    1976-01-01

    Results are presented for measurements of the IR spectral reflectance at near-normal incidence of aqueous solutions of sulfuric acid with acid concentrations of 75% and 95.6% by weight. Kramers-Kronig analyses of the reflectance data are employed to obtain values of the optical constants n(nu) and k(nu) in the spectral range from 400 to 6000 cm to the -1 power. The optical constants of these solutions at 250 K and 300 K are compared. It is found that in spectral regions remote from strong absorption bands, the values of the n(nu) indices obtained at 250 K agree with the values given by Lorentz-Lorenz correction of the same indices at 300 K. All absorption bands observed at 300 K are found to be present at 250 K with slight shifts in frequency and with significant differences in the k(nu) indices at the band maxima. Based on these results, it is concluded that the clouds of Venus probably consist of droplets of aqueous solutions of sulfuric acid with acid concentrations of about 75% by weight.

  12. Scalar spectral measures associated with an operator-fractal

    SciTech Connect

    Jorgensen, Palle E. T.; Kornelson, Keri A.; Shuman, Karen L.

    2014-02-15

    We study a spectral-theoretic model on a Hilbert space L{sup 2}(μ) where μ is a fixed Cantor measure. In addition to μ, we also consider an independent scaling operator U acting in L{sup 2}(μ). To make our model concrete, we focus on explicit formulas: We take μ to be the Bernoulli infinite-convolution measure corresponding to scale number 1/4 . We then define the unitary operator U in L{sup 2}(μ) from a scale-by-5 operation. The spectral-theoretic and geometric properties we have previously established for U are as follows: (i) U acts as an ergodic operator; (ii) the action of U is not spatial; and finally, (iii) U is fractal in the sense that it is unitarily equivalent to a countable infinite direct sum of (twisted) copies of itself. In this paper, we prove new results about the projection-valued measures and scalar spectral measures associated to U and its constituent parts. Our techniques make use of the representations of the Cuntz algebra O{sub 2} on L{sup 2}(μ)

  13. High spectral resolution measurements for the ARM Program

    SciTech Connect

    Revercomb, H.E.

    1992-05-22

    This report focuses on the design and fabrication of high spectral resolution FTIR (Fourier Transform Infrared) instrumentation for the CART sites of the Atmospheric Radiation Measurement (ARM) Program. The ultimate objective of this grant is to develop three different types of instruments, named the AERI, AERI-X, and SORT. The Atmospheric Emitted Radiance Interferometer (AERI) is the simplest. It will be available for early deployment at the first ARM site and will be deployable at several locations in the extended network to give horizontal coverage. The AERI will be an 0.5 cm{sup {minus}1} resolution instrument, which measures accurately calibrated radiance spectra for radiation studies and for remote sensing of atmospheric state variables. The AERI-X and the SORTI are higher spectral resolution instruments for obtaining the highest practical resolution for spectroscopy at the ARM central sites. The AERI-X, like the AERI will measure atmospheric emitted radiance, but with resolutions as high as 0.1 cm{sup {minus}1}. The Solar Radiance Transmission Interferometer will measure the total transmission of the atmosphere by tracking the sun through changes in atmospheric air mass. The large solar signal makes it practical for this instrument to offer the ultimate in spectral resolution, about 0.002 cm{sup {minus}1}.

  14. Quantitative Spectral Radiance Measurements in the HYMETS Arc Jet

    NASA Technical Reports Server (NTRS)

    Danehy, Paul M.; Hires, Drew V.; Johansen, Craig T.; Bathel, Brett F.; Jones, Stephen B.; Gragg, Jeffrey G.; Splinter, Scott C.

    2012-01-01

    Calibrated spectral radiance measurements of gaseous emission spectra have been obtained from the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. A fiber-optic coupled spectrometer collected natural luminosity from the flow. Spectral radiance measurements are reported between 340 and 1000 nm. Both Silicon Carbide (SiC) and Phenolic Impregnated Carbon Ablator (PICA) samples were placed in the flow. Test gases studied included a mostly-N2 atmosphere (95% nitrogen, 5% argon), a simulated Earth Air atmosphere (75% nitrogen, 20% oxygen, 5% argon) and a simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon). The bulk enthalpy of the flow was varied as was the location of the measurement. For the intermediate flow enthalpy tested (20 MJ/kg), emission from the Mars simulant gas was about 10 times higher than the Air flow and 15 times higher than the mostly-N2 atmosphere. Shock standoff distances were estimated from the spectral radiance measurements. Within-run, run-to-run and day-to-day repeatability of the emission were studied, with significant variations (15-100%) noted.

  15. Low-frequency sound absorption measurements in air

    NASA Technical Reports Server (NTRS)

    Zuckerwar, A. J.; Meredith, R. W.

    1984-01-01

    Thirty sets of sound absorption measurements in air at a pressure of 1 atmosphere are presented at temperatures from 10 C to 50 C, relative humidities from 0 to 100 percent, and frequencies from 10 to 2500 Hz. The measurements were conducted by the method of free decay in a resonant tube having a length of 18.261 m and bore diameter of 0.152 m. Background measurements in a gas consisting of 89.5 percent N2 and 10.5 percent Ar, a mixture which has the same sound velocity as air, permitted the wall and structural losses of the tube to be separated from the constituent absorption, consisting of classical rotational and vibrational absorption, in the air samples. The data were used to evaluate the vibrational relaxation frequencies of N2 and/or O2 for each of the 30 sets of meteorological parameters. Over the full range of humidity, the measured relaxation frequencies of N2 in air lie between those specified by ANSI Standard S1.26-1978 and those measured earlier in binary N2H2O mixtures. The measured relaxation frequencies could be determined only at very low values of humidity, reveal a significant trend away from the ANSI standard, in agreement with a prior investigation.

  16. IRCM spectral signature measurements instrumentation featuring enhanced radiometric accuracy

    NASA Astrophysics Data System (ADS)

    Lantagne, Stéphane; Prel, Florent; Moreau, Louis; Roy, Claude; Willers, Cornelius J.

    2015-10-01

    Hyperspectral Infrared (IR) signature measurements are performed in military applications including aircraft- and -naval vessel stealth characterization, detection/lock-on ranges, and flares efficiency characterization. Numerous military applications require high precision measurement of infrared signature characterization. For instance, Infrared Countermeasure (IRCM) systems and Infrared Counter-Countermeasure (IRCCM) system are continuously evolving. Infrared flares defeated IR guided seekers, IR flares became defeated by intelligent IR guided seekers and Jammers defeated the intelligent IR guided seekers [7]. A precise knowledge of the target infrared signature phenomenology is crucial for the development and improvement of countermeasure and counter-countermeasure systems and so precise quantification of the infrared energy emitted from the targets requires accurate spectral signature measurements. Errors in infrared characterization measurements can lead to weakness in the safety of the countermeasure system and errors in the determination of detection/lock-on range of an aircraft. The infrared signatures are analyzed, modeled, and simulated to provide a good understanding of the signature phenomenology to improve the IRCM and IRCCM technologies efficiency [7,8,9]. There is a growing need for infrared spectral signature measurement technology in order to further improve and validate infrared-based models and simulations. The addition of imagery to Spectroradiometers is improving the measurement capability of complex targets and scenes because all elements in the scene can now be measured simultaneously. However, the limited dynamic range of the Focal Plane Array (FPA) sensors used in these instruments confines the ranges of measurable radiance intensities. This ultimately affects the radiometric accuracy of these complex signatures. We will describe and demonstrate how the ABB hyperspectral imaging spectroradiometer features enhanced the radiometric accuracy

  17. Direct Measurement of Aerosol Absorption Using Photothermal Interferometry

    NASA Astrophysics Data System (ADS)

    Sedlacek, A. J.; Lee, J. A.

    2007-12-01

    Efforts to bound the contribution of light absorption in aerosol radiative forcing is still very much an active area of research in large part because aerosol extinction is dominated by light scattering. In response to this and other technical issues, the aerosol community has actively pursued the development of new instruments to measure aerosol absorption (e.g., photoacoustic spectroscopy (PAS) and multi-angle absorption photometer (MAAP)). In this poster, we introduce the technique of photothermal interferometry (PTI), which combines the direct measurement capabilities of photothermal spectroscopy (PTS) with high-sensitivity detection of the localized heating brought about by the PT process through interferometry. At its most fundamental level, the PTI technique measures the optical pathlength change that one arm of an interferometer (referred to as the 'probe' arm) experiences relative to the other arm of the interferometer (called the 'reference' arm). When the two arms are recombined at a beamsplitter, an interference pattern is created. If the optical pathlength in one arm of the interferometer changes, a commensurate shift in the interference pattern will take place. For the specific application of measuring light absorption, the heating of air surrounding the light- absorbing aerosol following laser illumination induces the optical pathlength change. This localized heating creates a refractive index gradient causing the probe arm of the interferometer to take a slightly different optical pathlength relative to the unperturbed reference arm. This effect is analogous to solar heating of a road causing mirages. As discussed above, this altered optical pathlength results in a shift in the interference pattern that is then detected as a change in the signal intensity by a single element detector. The current optical arrangement utilizes a folded Jamin interferometer design (Sedlacek, 2006) that provides a platform that is robust with respect to sensitivity

  18. Spectral analysis of sinus arrhythmia - A measure of mental effort

    NASA Technical Reports Server (NTRS)

    Vicente, Kim J.; Craig Thornton, D.; Moray, Neville

    1987-01-01

    The validity of the spectral analysis of sinus arrhythmia as a measure of mental effort was investigated using a computer simulation of a hovercraft piloted along a river as the experimental task. Strong correlation was observed between the subjective effort-ratings and the heart-rate variability (HRV) power spectrum between 0.06 and 0.14 Hz. Significant correlations were observed not only between subjects but, more importantly, within subjects as well, indicating that the spectral analysis of HRV is an accurate measure of the amount of effort being invested by a subject. Results also indicate that the intensity of effort invested by subjects cannot be inferred from the objective ratings of task difficulty or from performance.

  19. Solar spectral irradiance model validation using Solar Spectral Irradiance and Solar Radius measurements

    NASA Astrophysics Data System (ADS)

    Thuillier, Gérard; Zhu, Ping; Shapiro, Alexander; Sofia, Sabatino; Tagirov, Rinat; Van Ruymbeke, Michel; Schmutz, Werner

    2016-04-01

    The importance of the reliable solar spectral irradiance (SSI) data for solar and climate physics is now well acknowledged. In particular, the irradiance time series are necessary for most of the current studies concerning climate evolution. However, space instruments are vulnerable to the degradation due to the environment while ground based measurements are limited in wavelength range and need atmospheric effects corrections. This is why SSI modeling is necessary to understand the mechanism of the solar irradiance variability and to provide long and uninterrupted irradiance records to climate and Earth atmosphere scientists. Here we present COSI (COde for Solar Irradiance) model of the SSI variability. The COSI model is based on the Non local thermodynamic Equilibrium Spectral SYnthesis Code (NESSY). We validate NESSY by two independent datasets: - The SSI at solar minimum occurring in 2008, - The radius variation with wavelength and absolute values determined from PREMOS and BOS instruments onboard the PICARD spacecraft. Comparisons between modeling and measured SSI will be shown. However, since SSI measurements have an accuracy estimated between 2 to 3%, the comparison with the solar radius data provides a very important additional constrains on model. For that, 17 partial solar occultations by the Moon are used providing solar radii clearly showing the dependence of the solar radius with wavelength. These results are compared with the NESSY predictions. The agreement between NESSY and observations is within the model and measurements accuracy.

  20. Absorptance Measurements of Optical Coatings - A Round Robin

    SciTech Connect

    Chow, R; Taylor, J R; Wu, Z L; Boccara, C A; Broulik, U; Commandre, M; DiJon, J; Fleig, C; Giesen, A; Fan, Z X; Kuo, P K; Lalezari, R; Moncur, K; Obramski, H-J; Reicher, D; Ristau, D; Roche, P; Steiger, B; Thomsen, M; von Gunten, M

    2000-10-26

    An international round robin study was conducted on the absorption measurement of laser-quality coatings. Sets of optically coated samples were made by a ''reactive DC magnetron'' sputtering and an ion beam sputtering deposition process. The sample set included a high reflector at 514 nm and a high reflector for the near infrared (1030 to 1318 nm), single layers of silicon dioxide, tantalum pentoxide, and hafnium dioxide. For calibration purposes, a sample metalized with hafnium and an uncoated, superpolished fused silica substrate were also included. The set was sent to laboratory groups for absorptance measurement of these coatings. Whenever possible, each group was to measure a common, central area and another area specifically assigned to the respective group. Specific test protocols were also suggested in regards to the laser exposure time, power density, and surface preparation.

  1. Photothermal method for absorption measurements in anisotropic crystals

    NASA Astrophysics Data System (ADS)

    Stubenvoll, M.; Schäfer, B.; Mann, K.; Novak, O.

    2016-02-01

    A measurement system for quantitative determination of both surface and bulk contributions to the photo-thermal absorption has been extended to anisotropic optical media. It bases upon a highly sensitive Hartmann-Shack wavefront sensor, accomplishing precise on-line monitoring of wavefront deformations of a collimated test beam transmitted perpendicularly through the laser-irradiated side of a cuboid sample. Caused by the temperature dependence of the refractive index as well as thermal expansion, the initially plane wavefront of the test beam is distorted. Sign and magnitude depend on index change and expansion. By comparison with thermal theory, a calibration of the measurement is possible, yielding a quantitative absolute measure of bulk and surface absorption losses from the transient wavefront distortion. Results for KTP and BBO single crystals are presented.

  2. Optoelectronic set for measuring the absorption spectrum of the thin biological media

    NASA Astrophysics Data System (ADS)

    Gryko, Lukasz; Zajac, Andrzej; Gilewski, Marian

    2013-10-01

    In the paper the authors present the developed optoelectronic system for controlled, repetitive exposure by electromagnetic radiation of biological structures in the Low Level Laser (LED) Therapy procedures. The set allows for objective selection and control of the irradiation parameters by light from spectral range of the tissues transmission window. Measurements of optical parameters of thin biological medium - spectral absorption coefficient and the amount of absorbed energy - can be implemented in the measuring chamber during irradiation treatment. The radiation source is the broadband illuminator consists of set of selected high power LEDs. The maximum optical power of single source is from 80 mW to 800 mW. Illuminator is controlled and powered by the multi-channel prototype control system, which allows independently control a current of each emitter. This control allows shaping spectral emission characteristic of broadband source in range 600-1000 nm. Illuminator allows providing in the working area of 700 cm2 a uniform distribution of optical power density, of 10 mW/cm2 for maximum. Set ensure uniform distribution of the spectral power density of up to 40 mW/nm.

  3. Spectral optical layer properties of cirrus from collocated airborne measurements - a feasibility study

    NASA Astrophysics Data System (ADS)

    Finger, F.; Werner, F.; Klingebiel, M.; Ehrlich, A.; Jäkel, E.; Voigt, M.; Borrmann, S.; Spichtinger, P.; Wendisch, M.

    2015-07-01

    Spectral optical layer properties of cirrus are derived from simultaneous and vertically collocated measurements of spectral upward and downward solar irradiance above and below the cloud layer and concurrent in situ microphysical sampling. From the irradiance data spectral transmissivity, absorptivity, reflectivity, and cloud top albedo of the observed cirrus layer are obtained. At the same time microphysical properties of the cirrus were sampled. The close collocation of the radiative and microphysical measurements, above, beneath and inside the cirrus, is obtained by using a research aircraft (Learjet 35A) in tandem with a towed platform called AIRTOSS (AIRcraft TOwed Sensor Shuttle). AIRTOSS can be released from and retracted back to the research aircraft by means of a cable up to a distance of 4 km. Data were collected in two field campaigns above the North and Baltic Sea in spring and late summer 2013. Exemplary results from one measuring flight are discussed also to illustrate the benefits of collocated sampling. Based on the measured cirrus microphysical properties, radiative transfer simulations were applied to quantify the impact of cloud particle properties such as crystal shape, effective radius reff, and optical thickness τ on cirrus optical layer properties. The effects of clouds beneath the cirrus are evaluated in addition. They cause differences in the layer properties of the cirrus by a factor of 2 to 3, and for cirrus radiative forcing by up to a factor of 4. If low-level clouds below cirrus are not considered the solar cooling due to the cirrus is significantly overestimated.

  4. Mapping vegetation types with the multiple spectral feature mapping algorithm in both emission and absorption

    NASA Technical Reports Server (NTRS)

    Clark, Roger N.; Swayze, Gregg A.; Koch, Christopher; Ager, Cathy

    1992-01-01

    Vegetation covers a large portion of the Earth's land surface. Remotely sensing quantitative information from vegetation has proven difficult because in a broad sense, all vegetation is similar from a chemical viewpoint, and most healthy plants are green. Plant species are generally characterized by the leaf and flower or fruit morphology, not by remote sensing spectral signatures. But to the human eye, many plants show varying shades of green, so there is direct evidence for spectral differences between plant types. Quantifying these changes in a predictable manner has not been easy. The Clark spectral features mapping algorithm was applied to mapping spectral features in vegetation species.

  5. Uncertainty of measurements of spectral solar UV irradiance

    NASA Astrophysics Data System (ADS)

    Bernhard, G.; Seckmeyer, G.

    Most investigations on the nature and effects of solar ultraviolet (UV) radiation at the Earth's surface require measurements of high accuracy combined with well-defined procedures to assess their quality. Here we present a general evaluation of all relevant errors and uncertainties associated with measurements of spectral global irradiance in the UV. The uncertainties are quantified in terms of dependence of the characteristics of the spectroradiometer, the uncertainty of calibration standards, the solar zenith angle, and atmospheric conditions. The methodologies and equations presented can be applied to most spectroradiometers currently employed for UV research. The sources of error addressed include radiometric calibration, cosine error, spectral resolution, wavelength misalignment, stability, noise, stray light, and timing errors. The practical application of the method is demonstrated by setting up a complete uncertainty table for the mobile spectroradiometer of the Fraunhofer Institute for Atmospheric Environmental Research (IFU). This instrument has successfully participated in several international intercomparisons of UV spectroradiometers. The expanded uncertainty (coverage factor k=2) for measurements of global spectral irradiance conducted with this instrument varies between 6.3% in the UVA and 12.7% at 300 nm and 60° solar zenith angle. The expanded uncertainties in erythemally and DNA weighted irradiances are 6.1% and 6.6%, respectively. These expanded uncertainties are comparable to uncertainties at the 2σ level in conventional statistics. A substantial reduction of these uncertainties would require smaller uncertainties in the irradiance standards used to calibrate the instrument. Though uncertainties caused by wavelength misalignment and noise become prominent in the shortwave UVB, which is the most important spectral range for UV trend detection, the results indicate that the accuracy of the IFU radiometer is sufficient to detect long-term trends

  6. Visible spectral dependence of the scattering and absorption coefficients of pigmented coatings from inversion of diffuse reflectance spectra.

    PubMed

    Curiel, Fernando; Vargas, William E; Barrera, Rubén G

    2002-10-01

    A spectral-projected gradient method and an extension of the Kubelka-Munk theory are applied to obtain the relevant parameters of the theory from measured diffuse reflectance spectra of pigmented samples illuminated with visible diffuse radiation. The initial estimate of the spectral dependence of the parameters, required by a recursive spectral-projected gradient method, was obtained by use of direct measurements and up-to-date theoretical estimates. We then tested the consistency of the Kubelka-Munk theory by repeating the procedure with samples of different thicknesses.

  7. Amplified spontaneous emission measurement of a line-narrowed, tunable, Ti:Al2O3 amplifier using rubidium absorption

    NASA Technical Reports Server (NTRS)

    Barnes, James C.; Barnes, Norman P.; Lockard, George E.; Cross, Patricia L.

    1989-01-01

    Amplified spontaneous emission, ASE, generated by a Ti:Al2O3 laser amplifier has been measured as a function of pump energy, and thus gain, using the atomic absorption of rubidium, Rb, gas at 0.780 micron. By tuning the Ti:Al2O3 laser, the Rb cell could selectively absorb the narrow spectral bandwidth laser radiation while transmitting the wide spectral bandwidth ASE. Transmission of laser amplifier pulses through a Rb absorption cell, measured at various temperatures, thus allows the measurement of the weak ASE in the vicinity of the strong laser pulse. A model for the transmission of Rb as a function of temperature and wavelength has been developed. The measured transmissions are in good agreement with the transmission model predictions.

  8. On the interpretation of zenith sky absorption measurements

    NASA Astrophysics Data System (ADS)

    Solomon, Susan; Schmeltekopf, Arthur L.; Sanders, Ryan W.

    1987-07-01

    Observations of several atmospheric species can be performed by measuring the absorption of visible and near-ultraviolet light scattered from the zenith sky. The determination of vertical column abundances of molecules such as ozone and NO2 from such measurements is briefly reviewed. It is shown that the conversion of NO to NO2 can be of significance in the interpretation of measurements made near twilight. On the other hand, multiple scattering from the atmosphere or by clouds is likely to be a very small effect.

  9. [Research on New Type of Spectral Modulation Polarization Measurement Technology].

    PubMed

    Zhao, Jia; Zhou, Feng; Li, Huan; Zhao, Hai-bo

    2015-10-01

    Spectral Modulation Polarization Measurement technology (SMPM) is a new type of polarization modulation technology, with an achromatic /4 retarder, a multiple-order retarder and a polarizer the polarization information of incident light can be encoded into the spectral dimension, sinusoidal which amplitude scales with the degree of the linear polarization and phase scales with the angle of the linear polarization can be acquired directly. With a dedicated algorithm for the modulated spectrum, we can get degree and angle of the linear polarization, spectral information and radiation information of the target. This paper expounds the basic principle of SMPM and concrete implementation scheme is proposed. Demodulation algorithm is designed before experimental platform are set up. Experiment which verified the correctness on the SMPM has carried on. The experimental results show the correctness and feasibility of SMPM. Compared with traditional polarization modulate techniques no moving parts and electronic components are including in this scheme. It's also has the advantages of compact and low mass. We can get all the polarization information through one single measurement rather than get Stokes parameters for further calculations. This study provides a new kind of technological approaches for the development of new space polarization detecting sensor.

  10. [Research on New Type of Spectral Modulation Polarization Measurement Technology].

    PubMed

    Zhao, Jia; Zhou, Feng; Li, Huan; Zhao, Hai-bo

    2015-10-01

    Spectral Modulation Polarization Measurement technology (SMPM) is a new type of polarization modulation technology, with an achromatic /4 retarder, a multiple-order retarder and a polarizer the polarization information of incident light can be encoded into the spectral dimension, sinusoidal which amplitude scales with the degree of the linear polarization and phase scales with the angle of the linear polarization can be acquired directly. With a dedicated algorithm for the modulated spectrum, we can get degree and angle of the linear polarization, spectral information and radiation information of the target. This paper expounds the basic principle of SMPM and concrete implementation scheme is proposed. Demodulation algorithm is designed before experimental platform are set up. Experiment which verified the correctness on the SMPM has carried on. The experimental results show the correctness and feasibility of SMPM. Compared with traditional polarization modulate techniques no moving parts and electronic components are including in this scheme. It's also has the advantages of compact and low mass. We can get all the polarization information through one single measurement rather than get Stokes parameters for further calculations. This study provides a new kind of technological approaches for the development of new space polarization detecting sensor. PMID:26904842

  11. RAPID COMMUNICATION: Calorimetric radar absorptivity measurement using a microwave oven

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.

    1999-06-01

    The measurement of the microwave absorptivity of materials typically requires expensive and arcane equipment and methods. I show that, for moderately absorbing materials (loss tangent icons/Journals/Common/delta" ALT="delta" ALIGN="TOP"/>icons/Journals/Common/simeq" ALT="simeq" ALIGN="TOP"/>0.005 or higher), useful measurements can be easily made using a thermometer and a normal domestic microwave oven: the heat absorbed for suitably designed sample size and geometry relates directly to the absorptivity. This technique, although not supremely accurate, is quick and inexpensive and may be useful for rapid investigations, educational projects and situations in which samples are awkward to handle. I show that water ice spiked with even only 0.2% ammonia is about three orders of magnitude more absorbing than is pure ice at -80 °C.

  12. Deriving brown carbon from multiwavelength absorption measurements: method and application to AERONET and Aethalometer observations

    NASA Astrophysics Data System (ADS)

    Wang, Xuan; Heald, Colette L.; Sedlacek, Arthur J.; de Sá, Suzane S.; Martin, Scot T.; Lizabeth Alexander, M.; Watson, Thomas B.; Aiken, Allison C.; Springston, Stephen R.; Artaxo, Paulo

    2016-10-01

    The radiative impact of organic aerosols (OA) is a large source of uncertainty in estimating the global direct radiative effect (DRE) of aerosols. This radiative impact includes not only light scattering but also light absorption from a subclass of OA referred to as brown carbon (BrC). However, the absorption properties of BrC are poorly understood, leading to large uncertainties in modeling studies. To obtain observational constraints from measurements, a simple absorption Ångström exponent (AAE) method is often used to separate the contribution of BrC absorption from that of black carbon (BC). However, this attribution method is based on assumptions regarding the spectral dependence of BC that are often violated in the ambient atmosphere. Here we develop a new AAE method which improves upon previous approaches by using the information from the wavelength-dependent measurements themselves and by allowing for an atmospherically relevant range of BC properties, rather than fixing these at a single assumed value. We note that constraints on BC optical properties and mixing state would help further improve this method. We apply this method to multiwavelength absorption aerosol optical depth (AAOD) measurements at AERONET sites worldwide and surface aerosol absorption measurements at multiple ambient sites. We estimate that BrC globally contributes up to 40 % of the seasonally averaged absorption at 440 nm. We find that the mass absorption coefficient of OA (OA-MAC) is positively correlated with the BC / OA mass ratio. Based on the variability in BC properties and BC / OA emission ratio, we estimate a range of 0.05-1.5 m2 g-1 for OA-MAC at 440 nm. Using the combination of AERONET and OMI UV absorption observations we estimate that the AAE388/440 nm for BrC is generally ˜ 4 worldwide, with a smaller value in Europe (< 2). Our analyses of observations at two surface sites (Cape Cod, to the southeast of Boston, and the GoAmazon2014/5 T3 site, to the west of

  13. Measurement of microresonator frequency comb coherence by spectral interferometry.

    PubMed

    Webb, K E; Jang, J K; Anthony, J; Coen, S; Erkintalo, M; Murdoch, S G

    2016-01-15

    We experimentally investigate the spectral coherence of microresonator optical frequency combs. Specifically, we use a spectral interference method, typically used in the context of supercontinuum generation, to explore the variation of the magnitude of the complex degree of first-order coherence across the full comb bandwidth. We measure the coherence of two different frequency combs and observe wholly different coherence characteristics. In particular, we find that the observed dynamical regimes are similar to the stable and unstable modulation instability regimes reported in previous theoretical studies. Results from numerical simulations are found to be in good agreement with experimental observations. In addition to demonstrating a new technique to assess comb stability, our results provide strong experimental support for previous theoretical analyses. PMID:26766693

  14. Measuring stellar kinematics in galaxies with the near-infrared (2-0) (12) CO absorption bandhead

    NASA Technical Reports Server (NTRS)

    Gaffney, Niall I.; Lester, Dan F.; Doppmann, Gregg

    1995-01-01

    The shape and strength of the near-infrared (2-0) (12)CO absorption bandhead provide astronomers with a unique tool for measuring stellar kinematics in galaxies with strong dust obscuration. However, the asymmetric shape of the bandhead introduces complexities when extracting the kinematics from an observed spectrum. This paper discusses the benefits, drawbacks, and observational constraints associated with using this bandhead to measure kinematics in galaxies, focusing on applications in high spectral-resolution data. Additionally, we discuss techniques found useful for extracting the kinematics from the absorption feature, and outline our success with two different methods.

  15. Airborne high spectral resolution lidar for measuring aerosol extinction and backscatter coefficients.

    PubMed

    Esselborn, Michael; Wirth, Martin; Fix, Andreas; Tesche, Matthias; Ehret, Gerhard

    2008-01-20

    An airborne high spectral resolution lidar (HSRL) based on an iodine absorption filter and a high-power frequency-doubled Nd:YAG laser has been developed to measure backscatter and extinction coefficients of aerosols and clouds. The instrument was operated aboard the Falcon 20 research aircraft of the German Aerospace Center (DLR) during the Saharan Mineral Dust Experiment in May-June 2006 to measure optical properties of Saharan dust. A detailed description of the lidar system, the analysis of its data products, and measurements of backscatter and extinction coefficients of Saharan dust are presented. The system errors are discussed and airborne HSRL results are compared to ground-based Raman lidar and sunphotometer measurements.

  16. Aerosol Classification from High Spectral Resolution Lidar Measurements

    NASA Astrophysics Data System (ADS)

    Burton, S. P.; Hair, J. W.; Ferrare, R. A.; Hostetler, C. A.; Kahnert, M.; Vaughan, M. A.; Cook, A. L.; Harper, D. B.; Berkoff, T.; Seaman, S. T.; Collins, J. E., Jr.; Fenn, M. A.; Rogers, R. R.

    2015-12-01

    The NASA Langley airborne High Spectral Resolution Lidars, HSRL-1 and HSRL-2, have acquired large datasets of vertically resolved aerosol extinction, backscatter, and depolarization during >30 airborne field missions since 2006. The lidar measurements of aerosol intensive parameters like lidar ratio and color ratio embed information about intrinsic aerosol properties, and are combined to qualitatively classify HSRL aerosol measurements into aerosol types. Knowledge of aerosol type is important for assessing aerosol radiative forcing, and can provide useful information for source attribution studies. However, atmospheric aerosol is frequently not a single pure type, but instead is a mixture, which affects the optical and radiative properties of the aerosol. We show that aerosol intensive parameters measured by lidar can be understood using mixing rules for cases of external mixing. Beyond coarse classification and mixing between classes, variations in the lidar aerosol intensive parameters provide additional insight into aerosol processes and composition. This is illustrated by depolarization measurements at three wavelengths, 355 nm, 532 nm, and 1064 nm, made by HSRL-2. Particle depolarization ratio is an indicator of non-spherical particles. Three cases each have a significantly different spectral dependence of the depolarization ratio, related to the size of the depolarizing particles. For two dust cases, large non-spherical particles account for the depolarization of the lidar light. The spectral dependence reflects the size distribution of these particles and reveals differences in the transport histories of the two plumes. For a smoke case, the depolarization is inferred to be due to the presence of small coated soot aggregates. Interestingly, the depolarization at 355 nm is similar for this smoke case compared to the dust cases, having potential implications for the upcoming EarthCARE satellite, which will measure particle depolarization ratio only at 355 nm.

  17. Spectral measurements of muzzle flash with multispectral and hyperspectral sensor

    NASA Astrophysics Data System (ADS)

    Kastek, M.; Dulski, R.; Trzaskawka, P.; Piątkowski, T.; Polakowski, H.

    2011-08-01

    The paper presents some practical aspects of the measurements of muzzle flash signatures. Selected signatures of sniper shot in typical scenarios has been presented. Signatures registered during all phases of muzzle flash were analyzed. High precision laboratory measurements were made in a special ballistic laboratory and as a result several flash patterns were registered. The field measurements of a muzzle flash were also performed. During the tests several infrared cameras were used, including the measurement class devices with high accuracy and frame rates. The registrations were made in NWIR, SWIR and LWIR spectral bands simultaneously. An ultra fast visual camera was also used for visible spectra registration. Some typical infrared shot signatures were presented. Beside the cameras, the LWIR imaging spectroradiometer HyperCam was also used during the laboratory experiments and the field tests. The signatures collected by the HyperCam device were useful for the determination of spectral characteristics of the muzzle flash, whereas the analysis of thermal images registered during the tests provided the data on temperature distribution in the flash area. As a result of the measurement session the signatures of several types handguns, machine guns and sniper rifles were obtained which will be used in the development of passive infrared systems for sniper detection.

  18. Direct absorption measurements in thin rods and optical fibers

    NASA Astrophysics Data System (ADS)

    Mühlig, Christian; Bublitz, Simon; Lorenz, Martin

    2015-11-01

    We report on the first realization of direct absorption measurements in thin rods and optical fibers using the laser induced deflection (LID) technique. Typically, along the fiber processing chain more or less technology steps are able to introduce additional losses to the starting material. After the final processing, the fibers are commonly characterized regarding losses using the so-called cut-back technique in combination with spectrometers. This, however, only serves for a total loss determination. For optimization of the fiber processing, it would be of great interest to not only distinguish between different loss mechanisms but also have a better understanding of possible causes. For measuring the absorption losses along the fiber processing, a particular concept for the LID technique is introduced and requirements, calibration procedure as well as first results are presented. It allows to measure thin rods, e.g. during preform manufacturing, as well as optical fibers. In addition, the results show the prospects to also apply the new concept to topics like characterizing unwanted absorption after fiber splicing or Bragg grating inscription.

  19. Spectral optical layer properties of cirrus from collocated airborne measurements and simulations

    NASA Astrophysics Data System (ADS)

    Finger, Fanny; Werner, Frank; Klingebiel, Marcus; Ehrlich, André; Jäkel, Evelyn; Voigt, Matthias; Borrmann, Stephan; Spichtinger, Peter; Wendisch, Manfred

    2016-06-01

    Spectral upward and downward solar irradiances from vertically collocated measurements above and below a cirrus layer are used to derive cirrus optical layer properties such as spectral transmissivity, absorptivity, reflectivity, and cloud top albedo. The radiation measurements are complemented by in situ cirrus crystal size distribution measurements and radiative transfer simulations based on the microphysical data. The close collocation of the radiative and microphysical measurements, above, beneath, and inside the cirrus, is accomplished by using a research aircraft (Learjet 35A) in tandem with the towed sensor platform AIRTOSS (AIRcraft TOwed Sensor Shuttle). AIRTOSS can be released from and retracted back to the research aircraft by means of a cable up to a distance of 4 km. Data were collected from two field campaigns over the North Sea and the Baltic Sea in spring and late summer 2013. One measurement flight over the North Sea proved to be exemplary, and as such the results are used to illustrate the benefits of collocated sampling. The radiative transfer simulations were applied to quantify the impact of cloud particle properties such as crystal shape, effective radius reff, and optical thickness τ on cirrus spectral optical layer properties. Furthermore, the radiative effects of low-level, liquid water (warm) clouds as frequently observed beneath the cirrus are evaluated. They may cause changes in the radiative forcing of the cirrus by a factor of 2. When low-level clouds below the cirrus are not taken into account, the radiative cooling effect (caused by reflection of solar radiation) due to the cirrus in the solar (shortwave) spectral range is significantly overestimated.

  20. A standard for measuring metadata quality in spectral libraries

    NASA Astrophysics Data System (ADS)

    Rasaiah, B.; Jones, S. D.; Bellman, C.

    2013-12-01

    A standard for measuring metadata quality in spectral libraries Barbara Rasaiah, Simon Jones, Chris Bellman RMIT University Melbourne, Australia barbara.rasaiah@rmit.edu.au, simon.jones@rmit.edu.au, chris.bellman@rmit.edu.au ABSTRACT There is an urgent need within the international remote sensing community to establish a metadata standard for field spectroscopy that ensures high quality, interoperable metadata sets that can be archived and shared efficiently within Earth observation data sharing systems. Metadata are an important component in the cataloguing and analysis of in situ spectroscopy datasets because of their central role in identifying and quantifying the quality and reliability of spectral data and the products derived from them. This paper presents approaches to measuring metadata completeness and quality in spectral libraries to determine reliability, interoperability, and re-useability of a dataset. Explored are quality parameters that meet the unique requirements of in situ spectroscopy datasets, across many campaigns. Examined are the challenges presented by ensuring that data creators, owners, and data users ensure a high level of data integrity throughout the lifecycle of a dataset. Issues such as field measurement methods, instrument calibration, and data representativeness are investigated. The proposed metadata standard incorporates expert recommendations that include metadata protocols critical to all campaigns, and those that are restricted to campaigns for specific target measurements. The implication of semantics and syntax for a robust and flexible metadata standard are also considered. Approaches towards an operational and logistically viable implementation of a quality standard are discussed. This paper also proposes a way forward for adapting and enhancing current geospatial metadata standards to the unique requirements of field spectroscopy metadata quality. [0430] BIOGEOSCIENCES / Computational methods and data processing [0480

  1. Measurement of local chromatin compaction by spectral precision distance microscopy

    NASA Astrophysics Data System (ADS)

    Rauch, Joachim; Hausmann, Michael; Solovei, Irina; Horsthemke, Bernhard; Cremer, Thomas; Cremer, Christoph G.

    2000-12-01

    Fluorescence in situ hybridization (FISH) offers an appropriate technique to specifically label any given chromatin region by multi spectrally labeled, specific DNA probes. Using confocal laser scanning microscopy, quantitative measurements on the spatial distribution of labeling sites can be performed in 3D conserved cell nuclei. Recently, 'Spectral Precision Distance Microscopy' has been developed that allows 3D distance measurements between point-like fluorescence objects of different spectral signatures far beyond the diffraction limited resolution. In a well characterized and sequenced DNA region, the Prader- Willi/Angelman region q11-13 on chromosome 15, geometric distances between the fluorescence intensity bary centers of four different 'point-like' labeling sites were measured. More than 300 cell nuclei were evaluated with a 3D resolution equivalent better than 100 nm. The geometric bary center distances in nanometers were compared with the genomic bary center distance in kilobases (kb). A direct correlation, for instance linear correlation between geometric and genomic distances was not observed. From the measured values, a local compaction factor for the high order chromatin folding in the analyzed genome region was calculated. Along the 1000 kb chromatin segment analyzed, which spans nearly the compete Prader-Willi/Angelman region, different compaction factors were found. The compaction factor 40 typical for a straight 30 nm chromatin fiber was not observed. This shows that chromatin folding and compaction in intact nuclei may be more complex. With SPDM, however, a microscopical technique is available that can sensitively analyze chromatin organization in the 100 nm range in 3D conserved cell nuclei.

  2. Extensive goniometric spectral measurements at desert sites for military engineering

    NASA Astrophysics Data System (ADS)

    Berry, T. E.; Morgan, J. C.; Furey, J. S.; DeMoss, T. A.; Kelley, J. R.; McKenna, J. R.

    2012-10-01

    Remote-sensing technology designed to exploit disturbed earth signatures has become extremely useful in the detection of disturbed soil in military areas of operation. Soil reflectance can be exploited for this purpose and is dependent on atmospheric conditions. An understanding of the in situ soil background is vital to any type of change detection. Researchers from the Engineering Research and Development Center (ERDC) conducted OCONUS soil spectral measurements at ten sites in Afghanistan from July to November, 2011. Sampling sites were chosen on the basis of geomorphic setting, surface-soil characteristics, and field-expedient conditions. Goniometric spectral measurements at these sites have provided high quality bi-directional reflectance data, and their analyses are presented in the context of threat recognition and discrimination. These data can also provide the basis for BDRF model validation. Most spectral data were acquired under ambient solar lighting, but other data were collected at night and under artificial illumination conditions. Bidirectional measurements of soil reflectance in the VIS/NIR and SWIR were taken using the University of Lethbridge Goniometer System (ULGS) at dawn, mid-day, dusk and after sunset with a light. Soil surface roughness and reflectance varied, depending on the presence of desert varnish and desert pavement at some sites. Sun angle and dust and smoke in the atmosphere impacted soil reflectance and noise in the SWIR part of the light spectrum, in particular. The presence of minerals such as calcium carbonate, gypsum, and oxidized iron in the subsurface directly impacted reflectance measurements in disturbed soil.

  3. Supercontinuum based absorption spectrometer for cycle-resolved multiparameter measurements in a rapid compression machine.

    PubMed

    Werblinski, Thomas; Kleindienst, Stefan; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

    2016-06-10

    A broadband supercontinuum (SC) based absorption spectrometer capable of cycle-resolved multiparameter measurements at internal combustion (IC) engine conditions is presented. Three parameters, temperature, pressure and water mole fraction, were extracted from broadband near-infrared H2O absorption spectra, spanning the wavelength-range from 1340 to 1405.5 nm, which exhibits a large number of specific H2O transitions. The spectrometer is based on spatial domain detection and features a near-infrared line scan camera as a detector. Measurements were performed during a compression cycle of a rapid compression machine comprising a pressure and temperature range from 2.5 to 65 bar and 300 to 900 K, respectively. With the new spectrometer, we are for the first time, based on the authors' knowledge, able to perform measurements based on SC radiation over a complete compression and expansion stroke at measurement rates up to 50 kHz. A detailed overview is provided about the best match algorithm between theory and experiments, including parameters from two different spectral databases, namely the Barber-Tennyson database (BT2) and HITRAN2012. The results indicate that spectral broadening effects are not properly described by theory, especially at pressure levels exceeding 20 bar, which culminates in a clear underestimation of the derived pressure data by SC absorption spectroscopy. Nevertheless, temperature can be determined accurately by performing a three-parameter fit based on water mole fraction, temperature, and pressure. In contrast, making use of pressure transducer data as look-up values and varying only temperature and H2O mole fraction to find the best match leads to a clear overestimation of temperature at elevated pressures. PMID:27409013

  4. Supercontinuum based absorption spectrometer for cycle-resolved multiparameter measurements in a rapid compression machine.

    PubMed

    Werblinski, Thomas; Kleindienst, Stefan; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

    2016-06-10

    A broadband supercontinuum (SC) based absorption spectrometer capable of cycle-resolved multiparameter measurements at internal combustion (IC) engine conditions is presented. Three parameters, temperature, pressure and water mole fraction, were extracted from broadband near-infrared H2O absorption spectra, spanning the wavelength-range from 1340 to 1405.5 nm, which exhibits a large number of specific H2O transitions. The spectrometer is based on spatial domain detection and features a near-infrared line scan camera as a detector. Measurements were performed during a compression cycle of a rapid compression machine comprising a pressure and temperature range from 2.5 to 65 bar and 300 to 900 K, respectively. With the new spectrometer, we are for the first time, based on the authors' knowledge, able to perform measurements based on SC radiation over a complete compression and expansion stroke at measurement rates up to 50 kHz. A detailed overview is provided about the best match algorithm between theory and experiments, including parameters from two different spectral databases, namely the Barber-Tennyson database (BT2) and HITRAN2012. The results indicate that spectral broadening effects are not properly described by theory, especially at pressure levels exceeding 20 bar, which culminates in a clear underestimation of the derived pressure data by SC absorption spectroscopy. Nevertheless, temperature can be determined accurately by performing a three-parameter fit based on water mole fraction, temperature, and pressure. In contrast, making use of pressure transducer data as look-up values and varying only temperature and H2O mole fraction to find the best match leads to a clear overestimation of temperature at elevated pressures.

  5. Elementary reaction rate measurements at high temperatures by tunable-laser flash-absorption

    SciTech Connect

    Hessler, J.P.

    1993-12-01

    The major objective of this program is to measure thermal rate coefficients and branching ratios of elementary reactions. To perform these measurements, the authors constructed an ultrahigh-purity shock tube to generate temperatures between 1000 and 5500 K. The tunable-laser flash-absorption technique is used to measure the rate of change of the concentration of species which absorb below 50,000 cm{sup {minus}1} e.g.: OH, CH, and CH{sub 3}. This technique is being extended into the vacuum-ultraviolet spectral region where one can measure atomic species e.g.: H, D, C, O, and N; and diatomic species e.g.: O{sub 2}, CO, and OH.

  6. Pulsed airborne lidar measurements of atmospheric CO2 column absorption

    NASA Astrophysics Data System (ADS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Weaver, Clark J.; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William E.; Kawa, S. Randoph; Biraud, Sebastien

    2010-11-01

    ABSTRACT We report initial measurements of atmospheric CO2 column density using a pulsed airborne lidar operating at 1572 nm. It uses a lidar measurement technique being developed at NASA Goddard Space Flight Center as a candidate for the CO2 measurement in the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) space mission. The pulsed multiple-wavelength lidar approach offers several new capabilities with respect to passive spectrometer and other lidar techniques for high-precision CO2 column density measurements. We developed an airborne lidar using a fibre laser transmitter and photon counting detector, and conducted initial measurements of the CO2 column absorption during flights over Oklahoma in December 2008. The results show clear CO2 line shape and absorption signals. These follow the expected changes with aircraft altitude from 1.5 to 7.1 km, and are in good agreement with column number density estimates calculated from nearly coincident airborne in-situ measurements.

  7. Kr II transition probability measurements for the UV spectral region

    NASA Astrophysics Data System (ADS)

    Belmonte, M. T.; Gavanski, L.; Peláez, R. J.; Aparicio, J. A.; Djurović, S.; Mar, S.

    2016-02-01

    The determination of radiative transition probabilities or oscillator strengths is of common interest in astrophysics. The analysis of the high-resolution stellar spectra is now available in order to estimate the stellar abundances. In this paper, 93 experimentally obtained transition probability values (Aki) for singly ionized krypton spectral lines belonging to the ultraviolet (UV) wavelength region (208-360) nm are presented. These data, expressed in absolute units, were derived from the measurements of relative spectral line intensities and the values of transition probability data taken from the literature. The results obtained extend considerably the transition probability data base. As a light source, a plasma from a low-pressure pulsed arc was used. Its electron density was in the range of (1.5-3.4) × 1022 m-3, while the temperature was between 28 000 and 35 000 K. A detailed analysis of the results is also given. Only a few relative and a few absolute transition probabilities from other authors, for the mentioned spectral region, are available in the literature.

  8. Spatially resolved concentration measurements based on backscatter absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Ze; Sanders, Scott T.; Robinson, Michael A.

    2016-06-01

    We demonstrate the feasibility of spatially resolved measurements of gas properties using direct absorption spectroscopy in conjunction with backscattered signals. We report a 1-D distribution of H2O mole fraction with a spatial resolution of 5 mm. The peak and average discrepancy between the measured and expected mole fraction are 21.1 and 8.0 %, respectively. The demonstration experiment is related to a diesel aftertreatment system; a selective catalytic reduction brick made of cordierite is used. The brick causes volume scattering interference; advanced baseline fitting based on a genetic algorithm is used to reduce the effects of this interference by a factor of 2.3.

  9. Transient Infrared Measurement of Laser Absorption Properties of Porous Materials

    NASA Astrophysics Data System (ADS)

    Marynowicz, Andrzej

    2016-06-01

    The infrared thermography measurements of porous building materials have become more frequent in recent years. Many accompanying techniques for the thermal field generation have been developed, including one based on laser radiation. This work presents a simple optimization technique for estimation of the laser beam absorption for selected porous building materials, namely clinker brick and cement mortar. The transient temperature measurements were performed with the use of infrared camera during laser-induced heating-up of the samples' surfaces. As the results, the absorbed fractions of the incident laser beam together with its shape parameter are reported.

  10. Interpreting measurements obtained with the cloud absorption radiometer

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The software developed for the analysis of data from the Cloud Absorption Radiometer (CAR) is discussed. The CAR is a multichannel radiometer designed to measure the radiation field in the middle of an optically thick cloud (the diffusion domain). It can also measure the surface albedo and escape function. The instrument currently flies on a C-131A aircraft operated by the University of Washington. Most of this data was collected during the First International satellite cloud climatology project Regional Experiment (FIRE) Marine Stratocumulus Intensive Field Observation program off San Diego during July 1987. Earlier flights of the CAR have also been studied.

  11. Validity Assessment of Pixel Linear Spectral Mixing Through Laboratory Measurements

    NASA Astrophysics Data System (ADS)

    Mobasheri, M. R.; Dehnavi, S.; Maghsoudi, Y.

    2015-12-01

    In order to understand the characteristics of the data collected by hyperspectral imaging systems, it is important to discuss the physics behind the scene radiance field incident on the imaging system. A dominant effect in hyperspectral remote sensing is the mixing of radiant energies contributed from different materials present in a given pixel. The basic assumption of mixture modelling is that within a given scene, the surface is covered by a small number of distinct materials that have relatively constant spectral properties. It is most common to assume that the radiance reflected by different materials in a pixel can spectrally combine in a linear additive manner to produce the pixel radiance/reflectance, even when that might not be the case e.g. where the mixing process leads to nonlinear combinations of the radiance and where the linear assumption fails to hold. This can occur where there is significant relative three-dimensional structure within a given pixel. Without detailed knowledge of the dimensional structure, it can be very difficult to correctly ``un-mix'' the contributions of the various materials. This work aims to evaluate the correctness of the linear assumption in the mixture modelling using some laboratory measurements. Study was conducted using some sheets made of cellulose materials of different colours in 400-800 nm spectral range. Experimental results have shown that a correction term must be applied to the gains and offsets in the linear model. The obtained results can be extended to satellite sensors that acquire images in the above mentioned spectral range.

  12. The Importance of Optical Pathlength Control for Plasma Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, M.; Partridge, Harry (Technical Monitor)

    2001-01-01

    An inductively coupled GEC Cell with modified viewing ports has been used to measure in-situ absorption in CF4 plasmas via Fourier Transform Infrared Spectroscopy, and the results compared to those obtained in a standard viewport configuration. The viewing ports were modified so that the window boundary is inside, rather than outside, of the GEC cell. Because the absorption obtained is a spatially integrated absorption, measurements made represent an averaging of absorbing species inside and outside of the plasma. This modification is made to reduce this spatial averaging and thus allow a more accurate estimation of neutral species concentrations and temperatures within the plasmas. By reducing this pathlength, we find that the apparent CF4 consumption increases from 65% to 95% and the apparent vibrational temperature of CF4 rises by 50-75 K. The apparent fraction of etch product SiF4 decreases from 4% to 2%. The data suggests that these density changes may be due to significant temperature gradients between the plasma and chamber viewports.

  13. NO_2 Trace Measurements by Optical-Feedback Cavity-Enhanced Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ventrillard-Courtillot, I.; Desbois, Th.; Foldes, T.; Romanini, D.

    2009-06-01

    In order to reach the sub-ppb NO_2 detection level required for environmental applications in remote areas, we develop a spectrometer based on a technique introduced a few years ago, named Optical-Feedback Cavity-Enhanced Absorption Spectroscopy (OF-CEAS) [1]. It allows very sensitive and selective measurements, together with the realization of compact and robust set-ups as was subsequently demonstrated during measurements campaigns in harsh environments [2]. OF-CEAS benefits from the optical feedback to efficiently inject a cw-laser in a V-shaped high finesse cavity (typically 10 000). Cavity-enhanced absorption spectra are acquired on a small spectral region (˜1 cm^{-1}) that enables selective and quantitative measurements at a fast acquisition rate with a detection limit of several 10^{-10} cm^{-1} as reported in this work. Spectra are obtained with high spectral definition (150 MHz highly precisely spaced data points) and are self calibrated by cavity rind-down measurements regularly performed (typically every second). NO_2 measurements are performed with a commercial extended cavity diode laser around 411 nm, spectral region where intense electronic transitions occur. We will describe the set-up developed for in-situ measurements allowing real time concentration measurements at typically 5 Hz; and then report on the measurements performed with calibrated NO_2 reference samples to evaluate the linearity of the apparatus. The minimum detectable absorption loss is estimated by considering the standard deviation of the residual of one spectrum. We achieved 2x10^{-10} cm^{-1} for a single spectrum recorded in less than 100 ms at 100 mbar. It leads to a potential detection limit of 3x10^8 molecules/cm^3, corresponding to about 150 pptv at this pressure. [1] J. Morville, S. Kassi, M. Chenevier, and D. Romanini, Appl. Phys. B, 80, 1027 (2005). [2] D. Romanini, M. Chenevrier, S. Kassi, M. Schmidt, C. Valant, M. Ramonet, J. Lopez, and H.-J. Jost, Appl. Phys. B, 83, 659

  14. The measurement of absolute absorption of millimeter radiation in gases - The absorption of CO and O2

    NASA Technical Reports Server (NTRS)

    Read, William G.; Cohen, Edward A.; Pickett, Herbert M.; Hillig, Kurt W., II

    1988-01-01

    An apparatus is described that will measure absolute absorption of millimeter radiation in gases. The method measures the change in the quality factor of a Fabry-Perot resonator with and without gas present. The magnitude of the change is interpreted in terms of the absorption of the lossy medium inside the resonator. Experiments have been performed on the 115-GHz CO line and the 119-GHz O2 line at two different temperatures to determine the linewidth parameter and the peak absorption value. These numbers can be combined to give the integrated intensity which can be accurately calculated from results of spectroscopy measurements. The CO results are within 2 percent percent of theoretically predicted valves. Measurements on O2 have shown that absorption can be measured as accurately as 0.5 dB/km with this technique. Results have been obtained for oxygen absolute absorption in the 60-80-GHz region.

  15. Clay composition and swelling potential estimation of soils using depth of absorption bands in the SWIR (1100-2500 nm) spectral domain

    NASA Astrophysics Data System (ADS)

    Dufréchou, Grégory; Granjean, Gilles; Bourguignon, Anne

    2014-05-01

    Swelling soils contain clay minerals that change volume with water content and cause extensive and expensive damage on infrastructures. Presence of clay minerals is traditionally a good estimator of soils swelling and shrinking behavior. Montmorillonite (i.e. smectite group), illite, kaolinite are the most common minerals in soils and are usually associated to high, moderate, and low swelling potential when they are present in significant amount. Characterization of swelling potential and identification of clay minerals of soils using conventional analysis are slow, expensive, and does not permit integrated measurements. SWIR (1100-2500 nm) spectral domain are characterized by significant spectral absorption bands related to clay content that can be used to recognize main clay minerals. Hyperspectral laboratory using an ASD Fieldspec Pro spectrometer provides thus a rapid and less expensive field surface sensing that permits to measure soil spectral properties. This study presents a new laboratory reflectance spectroscopy method that used depth of clay diagnostic absorption bands (1400 nm, 1900 nm, and 2200 nm) to compare natural soils to synthetic montmorillonite-illite-kaolinite mixtures. We observe in mixtures that illite, montmorillonite, and kaolinite content respectively strongly influence the depth of absorption bands at 1400 nm (D1400), 1900 nm (D1900), and 2200 nm (D2200). To attenuate or removed effects of abundance and grain size, depth of absorption bands ratios were thus used to performed (i) 3D (using D1900/D2200, D1400/D1900, and D2200/D1400 as axis), and (ii) 2D (using D1400/D1900 and D1900/D2200 as axis) diagrams of synthetic mixtures. In this case we supposed that the overall reduction or growth of depth absorption bands should be similarly affected by the abundance and grain size of materials in soil. In 3D and 2D diagrams, the mixtures define a triangular shape formed by two clay minerals as external envelop and the three clay minerals mixtures

  16. Ultrashort coherence times in partially polarized stationary optical beams measured by two-photon absorption.

    PubMed

    Shevchenko, Andriy; Roussey, Matthieu; Friberg, Ari T; Setälä, Tero

    2015-11-30

    We measure the recently introduced electromagnetic temporal degree of coherence of a stationary, partially polarized, classical optical beam. Instead of recording the visibility of intensity fringes, the spectrum, or the polarization characteristics, we introduce a novel technique based on two-photon absorption. Using a Michelson interferometer equipped with polarizers and a specific GaAs photocount tube, we obtain the two fundamental quantities pertaining to the fluctuations of light: the degree of coherence and the degree of polarization. We also show that the electromagnetic intensity-correlation measurements with two-photon absorption require that the polarization dynamics, i.e., the time evolution of the instantaneous polarization state, is properly taken into account. We apply the technique to unpolarized and polarized sources of amplified spontaneous emission (Gaussian statistics) and to a superposition of two independent, narrow-band laser beams of different mid frequencies (non-Gaussian statistics). For these two sources femtosecond-range coherence times are found that are in good agreement with the traditional spectral measurements. Although previously employed for laser pulses, two-photon absorption provides a new physical principle to study electromagnetic coherence phenomena in classical and quantum continuous-wave light at extremely short time scales.

  17. Ultrashort coherence times in partially polarized stationary optical beams measured by two-photon absorption.

    PubMed

    Shevchenko, Andriy; Roussey, Matthieu; Friberg, Ari T; Setälä, Tero

    2015-11-30

    We measure the recently introduced electromagnetic temporal degree of coherence of a stationary, partially polarized, classical optical beam. Instead of recording the visibility of intensity fringes, the spectrum, or the polarization characteristics, we introduce a novel technique based on two-photon absorption. Using a Michelson interferometer equipped with polarizers and a specific GaAs photocount tube, we obtain the two fundamental quantities pertaining to the fluctuations of light: the degree of coherence and the degree of polarization. We also show that the electromagnetic intensity-correlation measurements with two-photon absorption require that the polarization dynamics, i.e., the time evolution of the instantaneous polarization state, is properly taken into account. We apply the technique to unpolarized and polarized sources of amplified spontaneous emission (Gaussian statistics) and to a superposition of two independent, narrow-band laser beams of different mid frequencies (non-Gaussian statistics). For these two sources femtosecond-range coherence times are found that are in good agreement with the traditional spectral measurements. Although previously employed for laser pulses, two-photon absorption provides a new physical principle to study electromagnetic coherence phenomena in classical and quantum continuous-wave light at extremely short time scales. PMID:26698754

  18. Cryogenic Far-Infrared Laser Absorptivity Measurements of the Herschel Space Observatory Telescope Mirror Coatings

    NASA Astrophysics Data System (ADS)

    Fischer, Jacqueline; Klaassen, Tjeerd; Hovenier, Niels; Jakob, Gerd; Poglitsch, Albrecht; Sternberg, Oren

    2004-07-01

    Far-infrared laser calorimetry was used to measure the absorptivity, and thus the emissivity, of aluminum-coated silicon carbide mirror samples produced during the coating qualification run of the Herschel Space Observatory telescope to be launched by the European Space Agency in 2007. The samples were measured at 77 K to simulate the operating temperature of the telescope in its planned orbit about the second Lagrangian point, L2, of the Earth-Sun system. Together, the telescope's equilibrium temperature in space and the emissivity of the mirror surfaces will determine the far-infrared-submillimeter background and thus the sensitivity of two of the three astronomical instruments aboard the observatory if stray-light levels can be kept low relative to the mirror emission. Absorptivities of both clean and dust-contaminated samples were measured at 70, 118, 184, and 496 μm. Theoretical fits to the data predict absorptivities of 0.2-0.4% for the clean sample and 0.2-0.8% for the dusty sample, over the spectral range of the Herschel Space Observatory instruments.

  19. Cryogenic Far-IR Laser Absorptivity Measurements of the Herschel Space Observatory Telescope Mirror Coatings

    NASA Astrophysics Data System (ADS)

    Fischer, J.; Klaassen, T. O.; Hovenier, J. N.; Jakob, G.; Poglitsch, A.; Sternberg, O.

    2004-05-01

    Far-infrared laser calorimetry was used to measure the absorptivity, and thus the emissivity, of aluminum-coated silicon carbide mirror samples produced during the coating qualification run of the Herschel Space Observatory telescope to be launched by the European Space Agency in 2007. The samples were measured at 77 Kelvin to simulate the operating temperature of the telescope in its planned orbit around the second Lagrangian point, L2, of the Earth-Sun system. Together, the telescope equilibrium temperature in space and the emissivity of the mirror surfaces will determine the far-infrared/submillimeter background and thus the sensitivity of two of the three astronomical instruments aboard the Observatory, if stray light levels can be kept low relative to the mirror emission. Absorptivities of both clean and dust-contaminated samples were measured at 70, 118, 184 and 496 μ m. Theoretical fits to the data predict absorptivities in the range 0.2 -- 0.4% for the clean sample and 0.2 -- 0.8% for the dusty sample, over the spectral range of the Herschel Space Observatory instruments. This work was funded by the ESA Herschel/Planck Project Office, the Office of Naval Research, and the NASA Herschel/Planck Project Office at JPL.

  20. Coherent differential absorption lidar measurements of CO2.

    PubMed

    Koch, Grady J; Barnes, Bruce W; Petros, Mulugeta; Beyon, Jeffrey Y; Amzajerdian, Farzin; Yu, Jirong; Davis, Richard E; Ismail, Syed; Vay, Stephanie; Kavaya, Michael J; Singh, Upendra N

    2004-09-10

    A differential absorption lidar has been built to measure CO2 concentration in the atmosphere. The transmitter is a pulsed single-frequency Ho:Tm:YLF laser at a 2.05-microm wavelength. A coherent heterodyne receiver was used to achieve sensitive detection, with the additional capability for wind profiling by a Doppler technique. Signal processing includes an algorithm for power measurement of a heterodyne signal. Results show a precision of the CO2 concentration measurement of 1%-2% 1sigma standard deviation over column lengths ranging from 1.2 to 2.8 km by an average of 1000 pulse pairs. A preliminary assessment of instrument sensitivity was made with an 8-h-long measurement set, along with correlative measurements with an in situ sensor, to determine that a CO2 trend could be detected.

  1. Atmospheric extinction in solar tower plants: the Absorption and Broadband Correction for MOR measurements

    NASA Astrophysics Data System (ADS)

    Hanrieder, N.; Wilbert, S.; Pitz-Paal, R.; Emde, C.; Gasteiger, J.; Mayer, B.; Polo, J.

    2015-05-01

    Losses of reflected Direct Normal Irradiance due to atmospheric extinction in concentrating solar tower plants can vary significantly with site and time. The losses of the direct normal irradiance between the heliostat field and receiver in a solar tower plant are mainly caused by atmospheric scattering and absorption by aerosol and water vapor concentration in the atmospheric boundary layer. Due to a high aerosol particle number, radiation losses can be significantly larger in desert environments compared to the standard atmospheric conditions which are usually considered in raytracing or plant optimization tools. Information about on-site atmospheric extinction is only rarely available. To measure these radiation losses, two different commercially available instruments were tested and more than 19 months of measurements were collected at the Plataforma Solar de Almería and compared. Both instruments are primarily used to determine the meteorological optical range (MOR). The Vaisala FS11 scatterometer is based on a monochromatic near-infrared light source emission and measures the strength of scattering processes in a small air volume mainly caused by aerosol particles. The Optec LPV4 long-path visibility transmissometer determines the monochromatic attenuation between a light-emitting diode (LED) light source at 532 nm and a receiver and therefore also accounts for absorption processes. As the broadband solar attenuation is of interest for solar resource assessment for Concentrating Solar Power (CSP), a correction procedure for these two instruments is developed and tested. This procedure includes a spectral correction of both instruments from monochromatic to broadband attenuation. That means the attenuation is corrected for the actual, time-dependent by the collector reflected solar spectrum. Further, an absorption correction for the Vaisala FS11 scatterometer is implemented. To optimize the Absorption and Broadband Correction (ABC) procedure, additional

  2. Determining the Uncertainty of X-Ray Absorption Measurements

    PubMed Central

    Wojcik, Gary S.

    2004-01-01

    X-ray absorption (or more properly, x-ray attenuation) techniques have been applied to study the moisture movement in and moisture content of materials like cement paste, mortar, and wood. An increase in the number of x-ray counts with time at a location in a specimen may indicate a decrease in moisture content. The uncertainty of measurements from an x-ray absorption system, which must be known to properly interpret the data, is often assumed to be the square root of the number of counts, as in a Poisson process. No detailed studies have heretofore been conducted to determine the uncertainty of x-ray absorption measurements or the effect of averaging data on the uncertainty. In this study, the Poisson estimate was found to adequately approximate normalized root mean square errors (a measure of uncertainty) of counts for point measurements and profile measurements of water specimens. The Poisson estimate, however, was not reliable in approximating the magnitude of the uncertainty when averaging data from paste and mortar specimens. Changes in uncertainty from differing averaging procedures were well-approximated by a Poisson process. The normalized root mean square errors decreased when the x-ray source intensity, integration time, collimator size, and number of scanning repetitions increased. Uncertainties in mean paste and mortar count profiles were kept below 2 % by averaging vertical profiles at horizontal spacings of 1 mm or larger with counts per point above 4000. Maximum normalized root mean square errors did not exceed 10 % in any of the tests conducted. PMID:27366627

  3. Low Temperature Measurements of HCN Broadened by N2 in the 14-micron Spectral Region

    SciTech Connect

    Smith, M.A.H.; Rinsland, Curtis P.; Blake, Thomas A.; Sams, Robert L.; Benner, D. C.; Devi, V. M.

    2008-04-01

    N2-broadening and N2-pressure-induced shift coefficients; and the temperature dependence exponent of the N2-broadening and the temperature dependent coefficients of N2-pressure-induced shifts have been measured for transitions in the v2 band of HCN from analysis of high-resolution absorption spectra recorded with two different Fourier transform spectrometers. A total of 34 laboratory spectra recorded at 0.002-0.005 cm-1 resolution and at temperatures ranging from 211 to 300 K were used in the determination of various spectral line parameters. A multispectrum nonlinear least squares curve fitting technique employing a modified Voigt line profile including speed dependence was used in the P- and R-branch measurements. In analyzing the Q branch transitions, the off-diagonal relaxation matrix element coefficients were included in analysis to fit the data. Present results are compared to previous measurements reported in the literature.

  4. CCD fiber optic spectrometer for the measurement of spectral irradiance

    NASA Astrophysics Data System (ADS)

    Morley, J. U.; McArthur, L. J. B.; Halliwell, D.; Poissant, Y.; Pelland, S.

    2010-08-01

    Recent technological advancements have made CCD spectrometers an increasingly suitable alternative to traditional monochromator-based instrumentation. The authors have developed instrumentation for the near instantaneous measurement of spectral global, direct, diffuse, reflected and southward-tilted irradiances. The system uses an AvaSpec2048TEC-2 - a dual channel thermo-electric-cooled fiber optic spectrometer from Avantes Inc. Each channel has a 2048-pixel linear array detector and the system achieves a spectral resolution of 0.0007 μm (FWHM) over the range 0.241-1.1 μm. The system also includes sensor heads, fiber optic cables and a multiplexer. Two types of sensor heads have been developed: a pyrheliometer configuration for direct beam, and a pyranometer configuration for global, diffuse, reflected and tilted measurements. Calibration uses a system of standard light sources. Cosine errors inherent to the spectralon diffusers have been characterized and corrections are applied to data from each sensor head. Accuracy of global irradiance is examined by comparing measurements against global photosynthetically active radiation (PAR) (0.395 - 0.695 μm) from Eppley red and green dome pyranometers. PAR daily totals (MJ/m2/day) and one minute averages (W/m2) are compared for 35 days in 2009 and daily totals are within +/- 10% from June to October.

  5. Retrieval of Aerosol Properties from Multi-Spectral Extinction Measurements

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew A.

    1999-01-01

    The direct-beam spectral extinction of solar radiation contains information on atmospheric composition in a form that is essentially free from the data analysis complexities that often arise from multiple scattering. Ground based Multi-Filter Shadowband Radiometer (MFRSR) measurements provide such information for the vertical atmospheric column path, while solar occultation measurements from a satellite platform provide horizontal slices through the atmosphere. We describe application of a Multi-Spectral Atmospheric Column Extinction (MACE) analysis technique used to analyze MFRSR data also to occultation measurements made by SAGE II. For analysis, we select the 1985 Nevado del Ruiz volcanic eruption period to retrieve atmospheric profiles of ozone and NO2, and changes in the stratospheric aerosol size and optical depth. The time evolution of volcanic aerosol serves as a passive tracer to study stratospheric dynamics, and changes in particle size put constraints on the sulfur chemistry modeling of volcanic aerosols. Paper presented at The '99 Kyoto Aerosol-Cloud Workshop, held Dec 1-3, 1999, Kyoto, Japan

  6. Transient absorption microscopy of gold nanorods as spectrally orthogonal labels in live cells†

    PubMed Central

    Chen, Tao; Chen, Shouhui; Zhou, Jihan; Liang, Dehai

    2015-01-01

    Gold nanorods (AuNRs) have shown great potential as bio-compatible imaging probes in various biological applications. Probing nanomaterials in live cells is essential to reveal the interaction between them. In this study, we used a transient absorption microscope to selectively image AuNRs in live cells. The transient absorption signals were monitored through lock-in amplification. This provides a new way of observing AuNRs with no interference from background autofluorescence. PMID:25098209

  7. Transient absorption microscopy of gold nanorods as spectrally orthogonal labels in live cells.

    PubMed

    Chen, Tao; Chen, Shouhui; Zhou, Jihan; Liang, Dehai; Chen, Xiaoyuan; Huang, Yanyi

    2014-09-21

    Gold nanorods (AuNRs) have shown great potential as bio-compatible imaging probes in various biological applications. Probing nanomaterials in live cells is essential to reveal the interaction between them. In this study, we used a transient absorption microscope to selectively image AuNRs in live cells. The transient absorption signals were monitored through lock-in amplification. This provides a new way of observing AuNRs with no interference from background autofluorescence.

  8. X-ray Spectral Measurements of a Dense Plasma Focus

    NASA Astrophysics Data System (ADS)

    Whitlock, Robert R.; Dozier, Charles M.; Newman, Daniel A.; Petr, Rodney A.; Freshman, Jay; Hoey, David W.; Heaton, John

    2002-10-01

    Absolute intensities of spectra in a dense-plasma-focus (DPF) source have been recorded and analyzed. This DPF source has been identified as one of the more promising sources for X-ray lithography. The source, developed by Science Research Laboratory, Inc., is currently undergoing testing and further development at BAE Systems, Inc. The DPF operates at 60 Hz and produces an average output pulse of ~5 J of X rays into 4π steradians in a continuous operation mode. In all runs, there was an initial number of pulses, typically between 30 to 40, during which the X-ray output increased and the DPF appeared to be undergoing a conditioning process, and after which a "steady-state" mode was achieved where the average X-ray power was relatively constant. Each spectral run was exposed to ~600 J of output, as measured by the PIN. The X-ray spectral region between 0.8 and 3 keV was recorded on Kodak DEF film in a potassium acid phthalate (KAP) convex curved-crystal spectrograph. The source emits neon line radiation from Ne IX and Ne X ionization stages in the 900 to 1300 eV region, suitable for lithographic exposures of photoresist. Two helium-like neon lines contribute more than 50% of the total energy. From continuum shape, plasma temperatures were found to be approximately 170-200 eV. The absolute, integrated spectral outputs were verified to within 30% by comparison with measurements by a PIN detector and a radiachromic X-ray dosimeter.

  9. Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 1. system setup and characterization.

    PubMed

    Müller, Thomas; Müller, Detlef; Dubois, René

    2005-03-20

    We describe an instrument for measuring the particle extinction coefficient at ambient conditions in the spectral range from 270 to 1000 nm. It is based on a differential optical absorption spectroscopy (DOAS) system, which was originally used for measuring trace-gas concentrations of atmospheric absorbers in the ultraviolet-visible wavelength range. One obtains the particle extinction spectrum by measuring the total atmospheric extinction and subtracting trace-gas absorption and Rayleigh scattering. The instrument consists of two nested Newton-type telescopes, which are simultaneously used for emitting and detecting light, and two arrays of retroreflectors at the ends of the two light paths. The design of this new instrument solves crucial problems usually encountered in the design of such instruments. The telescope is actively repositioned during the measurement cycle. Particle extinction is simultaneously measured at several wavelengths by the use of two grating spectrometers. Optical turbulence causes lateral movement of the spot of light in the receiver telescope. Monitoring of the return signals with a diode permits correction for this effect. Phase-sensitive detection efficiently suppresses background signals from the atmosphere as well as from the instrument itself. The performance of the instrument was tested during a measurement period of 3 months from January to March 2000. The instrument ran without significant interruption during that period. A mean accuracy of 0.032 km(-1) was found for the extinction coefficient for an 11-day period in March. PMID:15813269

  10. Spectrally resolved measurement of small optical losses by cavity enhanced spectroscopy techniques

    NASA Astrophysics Data System (ADS)

    Zeuner, T.; Paa, W.; Schmidl, G.; Mühlig, Ch.

    2011-05-01

    In general losses of optical of less than 1 % cannot be measured precisely with the best-established techniques (e.q. two-beam spectroscopy). However, it is possible to measure losses in the 0.0001 - 0.5 % range with high accuracy using cavity enhanced spectroscopy (CES) methods. Such low losses can be measured with CES, due to an increased interaction path way with the object. The Cavity Ring-Down (CRD) technique takes advantage of the CES method and transforms the optical loss information into the time domain. Two types of CRD setups for spectrally resolved loss measurement of laser mirrors will be presented. The first setup uses a tunable laser system for serial detection of the reflectivity spectra. The second method determines the spectral losses using a super continuum source. Here, simultaneous excitation and a spectrometer based camera system for separate detection of several wavelengths is used. Results will be shown and compared with direct absorption measurements of the same sample.

  11. Towards photodetection with high efficiency and tunable spectral selectivity: graphene plasmonics for light trapping and absorption engineering.

    PubMed

    Zhang, Jianfa; Zhu, Zhihong; Liu, Wei; Yuan, Xiaodong; Qin, Shiqiao

    2015-08-28

    Plasmonics can be used to improve absorption in optoelectronic devices and has been intensively studied for solar cells and photodetectors. Graphene has recently emerged as a powerful plasmonic material. It shows significantly less loss compared to traditional plasmonic materials such as gold and silver and its plasmons can be tuned by changing the Fermi energy with chemical or electrical doping. Here we propose the use of graphene plasmonics for light trapping in optoelectronic devices and show that the excitation of localized plasmons in doped, nanostructured graphene can enhance optical absorption in its surrounding medium including both bulky and two-dimensional materials by tens of times, which may lead to a new generation of photodetectors with high efficiency and tunable spectral selectivity in the mid-infrared and THz ranges.

  12. Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam

    SciTech Connect

    Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

    1996-06-01

    This work describes a pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode on the Particle Beam Fusion Accelerator II. The goal is to produce a {approximately} 10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced-fluorescence or absorption spectroscopy. A {approximately} 10 ns fwhm, 1.06 {micro}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately} 1 {micro}sec fwhm dye laser beam tuned to 5,890 {angstrom} is used for absorption measurement of the Na I resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated CCD camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately} 0.1 {angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5 to 2 eV. Laser-induced-fluorescence from {approximately} 1 {times} 10{sup 12}-cm{sup {minus}3} Na I 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately} 0.06 {angstrom} wavelength shift measurements in a mock-up of an ion diode experiment.

  13. Microplasmas as vacuum ultraviolet source for Cl-atom density measurements by resonance absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Martin, Virginie; Bauville, Gérard; Sadeghi, Nader; Puech, Vincent

    2011-11-01

    A micro-hollow cathode discharge was used to generate radiation on the chlorine atom resonance lines. Such radiation could be used to measure, by resonance absorption spectroscopy, the density of chlorine atoms in either ground state (3p5 2P3/2) or in the fine structure metastable state (3p5 2P1/2), which is located at 882.35 cm-1. Among the nine analysed lines in the 132-142 nm spectral region, only those at 137.953 and 139.653 nm, which are strong enough and are not affected by the self-absorption, can be used for the resonance absorption diagnostic of the ground state and the metastable state, respectively. The best operating conditions of the lamp source are 0.5% of Cl2 in argon at 150 mbar and 4 mA discharge current. The measured 800 ± 30 K gas temperature of the microplasma, indicates that under these specific conditions, these two lines are dominantly Doppler broadened. So their profile is Gaussian shaped with full widths at half maximum of (4.7 ± 0.1) × 10-4 nm.

  14. Decay Heat Measurements Using Total Absorption Gamma-ray Spectroscopy

    NASA Astrophysics Data System (ADS)

    Rice, S.; Valencia, E.; Algora, A.; Taín, J. L.; Regan, P. H.; Podolyák, Z.; Agramunt, J.; Gelletly, W.; Nichols, A. L.

    2012-09-01

    A knowledge of the decay heat emitted by thermal neutron-irradiated nuclear fuel is an important factor in ensuring safe reactor design and operation, spent fuel removal from the core, and subsequent storage prior to and after reprocessing, and waste disposal. Decay heat can be readily calculated from the nuclear decay properties of the fission products, actinides and their decay products as generated within the irradiated fuel. Much of the information comes from experiments performed with HPGe detectors, which often underestimate the beta feeding to states at high excitation energies. This inability to detect high-energy gamma emissions effectively results in the derivation of decay schemes that suffer from the pandemonium effect, although such a serious problem can be avoided through application of total absorption γ-ray spectroscopy (TAS). The beta decay of key radionuclei produced as a consequence of the neutron-induced fission of 235U and 239Pu are being re-assessed by means of this spectroscopic technique. A brief synopsis is given of the Valencia-Surrey (BaF2) TAS detector, and their method of operation, calibration and spectral analysis.

  15. Light absorption efficiencies of photosynthetic pigments: the dependence on spectral types of central stars

    NASA Astrophysics Data System (ADS)

    Komatsu, Yu; Umemura, Masayuki; Shoji, Mitsuo; Kayanuma, Megumi; Yabana, Kazuhiro; Shiraishi, Kenji

    2015-07-01

    For detecting life from reflection spectra on extrasolar planets, trace of photosynthesis is one of the indicators. However, it is not yet clear what kind of radiation environments is acceptable for photosynthesis. Light absorption in photosystems on the Earth occurs using limited photosynthetic pigments such as chlorophylls (Chls) and bacteriochlorophylls (BChls). Efficiencies of light absorption for the pigments were evaluated by calculating the specific molecular absorption spectra at the high accuracy-quantum mechanical level. We used realistic stellar radiation spectra such as F, G, K and M-type stars to investigate the efficiencies. We found that the efficiencies are increased with the temperature of stars, from M to F star. Photosynthetic pigments have two types of absorption bands, the Q y and Soret. In higher temperature stars like F star, contributions from the Soret region of the pigments are dominant for the efficiency. On the other hand, in lower temperature stars like M stars, the Q y band is crucial. Therefore, differences on the absorption intensity and the wavelength between the Q y and Soret band are the most important to characterize the photosynthetic pigments. Among photosynthetic pigments, Chls tend to be efficient in higher temperature stars, while BChls are efficient for M stars. Blueward of the 4000 Å break, the efficiencies of BChls are smaller than Chls in the higher temperature stars.

  16. Measurements of parallel electron velocity distributions using whistler wave absorption.

    PubMed

    Thuecks, D J; Skiff, F; Kletzing, C A

    2012-08-01

    We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense (ω(pe) > ω(ce)). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency ω(ce). As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation ω - k([parallel])v([parallel]) = ω(ce). The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.

  17. Measurements of parallel electron velocity distributions using whistler wave absorption

    SciTech Connect

    Thuecks, D. J.; Skiff, F.; Kletzing, C. A.

    2012-08-15

    We describe a diagnostic to measure the parallel electron velocity distribution in a magnetized plasma that is overdense ({omega}{sub pe} > {omega}{sub ce}). This technique utilizes resonant absorption of whistler waves by electrons with velocities parallel to a background magnetic field. The whistler waves were launched and received by a pair of dipole antennas immersed in a cylindrical discharge plasma at two positions along an axial background magnetic field. The whistler wave frequency was swept from somewhat below and up to the electron cyclotron frequency {omega}{sub ce}. As the frequency was swept, the wave was resonantly absorbed by the part of the electron phase space density which was Doppler shifted into resonance according to the relation {omega}-k{sub ||v||} = {omega}{sub ce}. The measured absorption is directly related to the reduced parallel electron distribution function integrated along the wave trajectory. The background theory and initial results from this diagnostic are presented here. Though this diagnostic is best suited to detect tail populations of the parallel electron distribution function, these first results show that this diagnostic is also rather successful in measuring the bulk plasma density and temperature both during the plasma discharge and into the afterglow.

  18. Tropospheric ozone distributions measured with an airborne laser absorption spectrometer

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1978-01-01

    Measurements of tropospheric ozone have been made in the southern and middle California regions and over the Pacific Ocean during two series of flights in February and May 1977. The data were obtained by using a laser absorption spectrometer, a nadir-viewing instrument which remotely measures the ozone column abundance between ground level and aircraft altitude by interacting with ozone at specific wavelengths near 9.5 microns. The measurements indicate significantly lower ozone abundances above the Mojave Desert region as compared with farm, forest, and urban areas. The average tropospheric column density was found to be 0.0027 atm cm/km over the California region and 0.0035 atm cm/km over the Pacific Ocean region 1000-2000 km west of the coast of Mexico.

  19. Estimation of background gas concentration from differential absorption lidar measurements

    NASA Astrophysics Data System (ADS)

    Harris, Peter; Smith, Nadia; Livina, Valerie; Gardiner, Tom; Robinson, Rod; Innocenti, Fabrizio

    2016-10-01

    Approaches are considered to estimate the background concentration level of a target species in the atmosphere from an analysis of the measured data provided by the National Physical Laboratory's differential absorption lidar (DIAL) system. The estimation of the background concentration level is necessary for an accurate quantification of the concentration level of the target species within a plume, which is the quantity of interest. The focus of the paper is on methodologies for estimating the background concentration level and, in particular, contrasting the assumptions about the functional and statistical models that underpin those methodologies. An approach is described to characterise the noise in the recorded signals, which is necessary for a reliable estimate of the background concentration level. Results for measured data provided by a field measurement are presented, and ideas for future work are discussed.

  20. Electron Bunch Shape Measurements Using Electro-optical Spectral Decoding

    NASA Astrophysics Data System (ADS)

    Borysenko, A.; Hiller, N.; Müller, A.-S.; Steffen, B.; Peier, P.; Ivanisenko, Y.; Ischebeck, R.; Schlott, V.

    Longitudinal diagnostics of the electron bunch shapes play a crucial role in the operation of linac-based light sources. Electro-optical techniques allow us to measure the longitudinal electron bunch profiles non-destructively on a shot-by-shot basis. Here we present results from measurements of electron bunches with a length of 200-900 fs rms at the Swiss FEL Injector Test Facility. All the measurements were done using an Yb-doped fibre laser system (with a central wavelength of a 1050 nm) and a GaP crystal. The technique of electro-optical spectral decoding (EOSD) was applied and showed great capabilities to measure bunch shapes down to around 370 fs rms. Measurements were performed for different electron energies to study the expected distortions of the measured bunch profile due to the energy-dependent widening of the electric field, which plays a role for low beam energies below and around 40 MeV. The studies provide valuable input for the design of the EOSD monitors for the compact linear accelerator FLUTE that is currently under commissioning at the Karslruhe Institute of Technology (KIT).

  1. Spectral Measurements of PMCs from SBUV/2 Instruments

    NASA Technical Reports Server (NTRS)

    DeLand, Matthew T.; Shettle, Eric P.; Thomas, Gary E.; Olivero, John J.

    2006-01-01

    The SBUV/2 (Solar Backscattered Ultraviolet, model 2) instrument is designed to monitor ozone stratospheric profile and total column ozone using measurements of the Earth's backscattered ultraviolet albedo. We have previously demonstrated that the normal radiance measurements from SBUV/2 instruments, which sample 12 discrete wavelengths between 252 and 340 nm during each scan, can be used to identify polar mesospheric clouds (PMCs). Some SBUV/2 instruments also periodically view the earth in continuous scan mode, covering the wavelength range 160-400 nm with 0.15 nm sampling. Analysis of these data show PMC occurrence rates similar to the normal discrete scan results, although the observation technique reduces the number of daily measurements by a factor of six. PMC observed by SBUV/2 instruments show a monotonic variation in the residual spectral albedo over the wavelength range 250 300 nm, with maximum enhancements of 10 15% at 250 nm. This result is consistent with microphysical model predictions from Jensen [1989. A numerical model of polar mesospheric cloud formation and evolution, Ph. D. Thesis, University of Colorado]. We find no evidence for a systematic localized increase in PMC residual albedo for wavelengths near 260 nm, in contrast to the recently reported results from the MSX UVISI instrument [Carbary J.F., et al., 2004. Evidence for bimodal particle distribution from the spectra of polar mesospheric clouds. Geophysics Research. Letters 31, L13108]. This result is observed for three different SBUV/2 instruments in both Northern and Southern Hemisphere data over a 13-year span. Our Mie scattering calculations show that the location and magnitude of the 260 nm hump feature is dependent upon the specific scattering angles appropriate to the MSX measurements. Although it explains the MSX spectrum, the bimodal size distribution proposed by Carbary et al. (2004), cannot explain the lack of scattering angle dependence of the SBUV/2 spectral shapes. The

  2. Spectral surface albedo derived from GOME-2/Metop measurements

    NASA Astrophysics Data System (ADS)

    Pflug, Bringfried; Loyola, Diego

    2009-09-01

    Spectral surface albedo is an important input for GOME-2 trace gas retrievals. An algorithm was developed for estimation of spectral surface albedo from top-of-atmosphere (TOA)-radiances measured by the Global Ozone Monitoring Experiment GOME-2 flying on-board MetOp-A. The climatologically version of this algorithm estimates Minimum Lambert-Equivalent Reflectivity (MLER) for a fixed time window and can use data of many years in contrast to the Near-real time version. Accuracy of surface albedo estimated by MLER-computation increases with the amount of available data. Unfortunately, most of the large GOME pixels are partly covered by clouds, which enhance the LER-data. A plot of LER-values over cloud fraction is used within this presentation to account for this influence of clouds. This "cloud fraction plot" can be applied over all surface types. Surface albedo obtained using the "cloud fraction plot" is compared with reference surface albedo spectra and with the FRESCO climatology. There is a general good agreement; however there are also large differences for some pixels.

  3. Red edge spectral measurements from sugar maple leaves

    NASA Technical Reports Server (NTRS)

    Vogelmann, J. E.; Rock, B. N.; Moss, D. M.

    1993-01-01

    Many sugar maple stands in the northeastern United States experienced extensive insect damage during the 1988 growing season. Chlorophyll data and high spectral resolution spectrometer laboratory reflectance data were acquired for multiple collections of single detached sugar maple leaves variously affected by the insect over the 1988 growing season. Reflectance data indicated consistent and diagnostic differences in the red edge portion (680-750 nm) of the spectrum among the various samples and populations of leaves. These included differences in the red edge inflection point (REIP), a ratio of reflectance at 740-720 nm (RE3/RE2), and a ratio of first derivative values at 715-705 nm (D715/D705). All three red edge parameters were highly correlated with variation in total chlorophyll content. Other spectral measures, including the Normalized Difference Vegetation Index (NDVI) and the Simple Vegetation Index Ratio (VI), also varied among populations and over the growing season, but did not correlate well with total chlorophyll content. Leaf stacking studies on light and dark backgrounds indicated REIP, RE3/RE2 and D715/D705 to be much less influenced by differences in green leaf biomass and background condition than either NDVI or VI.

  4. Neutron spectral measurements in the D0 collision hall

    SciTech Connect

    Yurista, P.M.; Elwyn, A.J.; Salsbury, W.C.

    1989-05-03

    The characterization of radiation fields is important to many applications. For example, in operational health physics, the choice of instrumentation for monitoring and of a personnel dosimeter for use by radiation workers depend on both the type and spectral characteristics of the radiation. Furthermore, the spectral distribution of the fluence affects radiation damage estimates for materials for new or replacement equipment within the radiation environment. At the same time, knowledge of the character of the radiation fields at a high-energy accelerator leads to a better theoretical understanding of its nature, and is important to the specification of civil construction requirements for future upgrades of the accelerator. At Fermilab as at many high-energy accelerators neutrons dominate the radiation fields outside of beam pipes within enclosures. In a continuing effort to characterize as completely as possible the fields at various locations around the site, we have measured the neutron spectrum within the DO collision hall. Both the fluence and dose-equivalent energy distributions are summarized in this note. 12 refs., 4 figs., 2 tabs.

  5. Gemstone spectral imaging for measuring adult bone mineral density

    PubMed Central

    Shao, Wei-Guang; Liu, Dian-Mei

    2016-01-01

    The present study aimed to detect the bone Ca2+ content of L3 vertebrae in adults by gemstone spectral computed tomography. In total, 235 patients were selected and divided into age groups of 10 years each. The scanning data were used to detect the water-based and Ca2+-based substance levels on the L3 vertebral cancellous bone images. The results indicated that there were significant differences in vertebral Ca2+-water and water-Ca2+ densities determined by gemstone spectral imaging (GSI) between males and females in subjects aged 50–59 years, 60–69 years, 70–79 years and ≥80 years (P<0.05). The ages of male and female participants were negatively correlated with vertebral Ca2+-water density (P<0.01) and water-Ca2+ density (P<0.01). In conclusion, GSI may be used as a novel method of measuring the vertebral adult bone mineral density. PMID:27703518

  6. Clinical measurements analysis of multi-spectral photoplethysmograph biosensors

    NASA Astrophysics Data System (ADS)

    Asare, Lasma; Kviesis-Kipge, Edgars; Spigulis, Janis

    2014-05-01

    The developed portable multi-spectral photoplethysmograph (MS-PPG) optical biosensor device, intended for analysis of peripheral blood volume pulsations at different vascular depths, has been clinically verified. Multi-spectral monitoring was performed by means of a four - wavelengths (454 nm, 519 nm, 632 nm and 888 nm) light emitted diodes and photodiode with multi-channel signal output processing. Two such sensors can be operated in parallel and imposed on the patient's skin. The clinical measurements confirmed ability to detect PPG signals at four wavelengths simultaneously and to record temporal differences in the signal shapes (corresponding to different penetration depths) in normal and pathological skin. This study analyzed wavelengths relations between systole and diastole peak difference at various tissue depths in normal and pathological skin. The difference between parameters of healthy and pathological skin at various skin depths could be explain by oxy- and deoxyhemoglobin dominance at different wavelengths operated in sensor. The proposed methodology and potential clinical applications in dermatology for skin assessment are discussed.

  7. X-ray absorption spectral studies of copper (II) mixed ligand complexes

    NASA Astrophysics Data System (ADS)

    Soni, B.; Dar, Davood Ah; Shrivastava, B. D.; Prasad, J.; Srivastava, K.

    2014-09-01

    X-ray absorption spectra at the K-edge of copper have been studied in two copper mixed ligand complexes, one having tetramethyethylenediamine (tmen) and the other having tetraethyethylenediamine (teen) as one of the ligands. The spectra have been recorded at BL-8 dispersive extended X-ray absorption fine structure (EXAFS) beamline at the 2.5 GeV INDUS- 2 synchrotron, RRCAT, Indore, India. The data obtained has been processed using the data analysis program Athena. The energy of the K-absorption edge, chemical shift, edge-width and shift of the principal absorption maximum in the complexes have been determined and discussed. The values of these parameters have been found to be approximately the same in both the complexes indicating that the two complexes possess similar chemical environment around the copper metal atom. The chemical shift has been utilized to estimate effective nuclear charge on the absorbing atom. The normalized EXAFS spectra have been Fourier transformed. The position of the first peak in the Fourier transform gives the value of first shell bond length, which is shorter than the actual bond length because of energy dependence of the phase factors in the sine function of the EXAFS equation. This distance is thus the phase- uncorrected bond length. Bond length has also been determined by Levy's, Lytle's and Lytle, Sayers and Stern's (LSS) methods. The results obtained from LSS and the Fourier transformation methods are comparable with each other, since both are phase uncorrected bond lengths.

  8. Measurement of solutes in dialysate using UV absorption

    NASA Astrophysics Data System (ADS)

    Fridolin, Ivo; Magnusson, Martin; Lindberg, Lars-Goeran

    2001-06-01

    The aim of this work was to describe a new method for optical monitoring of solutes in a spent dialysate. The method utilizes UV light absorption employing a commercially available spectrophotometer. Measurements were performed both on collected dialysate samples and on-line. The concentration of several removed solutes and electrolytes in the serum and in the dialysate was determined simultaneously using standard laboratory techniques. During on-line monitoring the spectrophotometer was connected to the fluid outlet of the dialysis machine. On-line measurements during a single hemodialysis session demonstrated a possibility to monitor deviations in the dialysator performance (e.g. dialysator in by-pass). The experimental results indicated a good correlation between UV absorption and several removed solutes (urea, creatinine) in the spent dialysate. The correlation coefficient for urea and creatinine concentrations in the dialysate was very high for every individual treatment. The UV absorbance correlates well to the concentrations of several solutes thought to be uremic toxins. The results indicate that the technique can be used as a continuous, on-line method for monitoring deviations in the dialysator performance and may estimate the removal of the overall toxins. In the future, the new method will be used to evaluate parameters describing delivery of the prescribed treatment dose such as KT/V and Urea Reduction Rate (URR).

  9. Measurements of the absorption coefficient of stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    Ogren, J. A.; Ahlquist, N. C.; Clarke, A. D.; Charlson, R. J.

    1981-01-01

    The absorption coefficients of stratospheric aerosols are measured using a variation on the integrating plate method. The technique is based on the decrease in the transparency of a substrate when an absorbing aerosol is deposited on it. A Lambert scatterer is placed behind the substrate to integrate forward scattered light and minimize the effect of scattering on the measurement. The low pressure in the stratosphere is used for the direct impaction of particles onto a narrow strip of opal glass. The eight samples collected had a median value of 4 x 10 to the -9th m with an uncertainty of + or - 5 x 10 to the -9th m. If this absorption is due to graphitic carbon, then its concentration is estimated at about 0.4 ng/cu m, or about 0.25% of the total aerosol mass concentration. Estimates of the aerosol scattering coefficients based on satellite extinction inversions result in an aerosol single-scattering albedo in the range of 0.96-1.0.

  10. Biogeochemical origins of particles obtained from the inversion of the volume scattering function and spectral absorption in coastal waters

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Huot, Y.; Gray, D. J.; Weidemann, A.; Rhea, W. J.

    2013-09-01

    In the aquatic environment, particles can be broadly separated into phytoplankton (PHY), non-algal particle (NAP) and dissolved (or very small particle, VSP) fractions. Typically, absorption spectra are inverted to quantify these fractions, but volume scattering functions (VSFs) can also be used. Both absorption spectra and VSFs were used to estimate particle fractions for an experiment in the Chesapeake Bay. A complete set of water inherent optical properties was measured using a suite of commercial instruments and a prototype Multispectral Volume Scattering Meter (MVSM); the chlorophyll concentration, [Chl] was determined using the HPLC method. The total scattering coefficient measured by an ac-s and the VSF at a few backward angles measured by a HydroScat-6 and an ECO-VSF agreed with the LISST and MVSM data within 5%, thus indicating inter-instrument consistency. The size distribution and scattering parameters for PHY, NAP and VSP were inverted from measured VSFs. For the absorption inversion, the "dissolved" absorption spectra were measured for filtrate passing through a 0.2 μm filter, whereas [Chl] and NAP absorption spectra were inverted from the particulate fraction. Even though the total scattering coefficient showed no correlation with [Chl], estimates of [Chl] from the VSF-inversion agreed well with the HPLC measurements (r = 0.68, mean relative errors = -20%). The scattering associated with NAP and VSP both correlated well with the NAP and "dissolved" absorption coefficients, respectively. While NAP dominated forward, and hence total, scattering, our results also suggest that the scattering by VSP was far from negligible and dominated backscattering. Since the sizes of VSP range from 0.02 to 0.2 μm, covering (a portion of) the operationally defined "dissolved" matter, the typical assumption that colored dissolved organic matter (i.e., CDOM) does not scatter may not hold, particularly in a coastal or estuarine environment.

  11. Error reduction in retrievals of atmospheric species from symmetrically measured lidar sounding absorption spectra.

    PubMed

    Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

    2014-10-20

    We report new methods for retrieving atmospheric constituents from symmetrically-measured lidar-sounding absorption spectra. The forward model accounts for laser line-center frequency noise and broadened line-shape, and is essentially linearized by linking estimated optical-depths to the mixing ratios. Errors from the spectral distortion and laser frequency drift are substantially reduced by averaging optical-depths at each pair of symmetric wavelength channels. Retrieval errors from measurement noise and model bias are analyzed parametrically and numerically for multiple atmospheric layers, to provide deeper insight. Errors from surface height and reflectance variations are reduced to tolerable levels by "averaging before log" with pulse-by-pulse ranging knowledge incorporated.

  12. Phase measurement of fast light pulse in electromagnetically induced absorption.

    PubMed

    Lee, Yoon-Seok; Lee, Hee Jung; Moon, Han Seb

    2013-09-23

    We report the phase measurement of a fast light pulse in electromagnetically induced absorption (EIA) of the 5S₁/₂ (F = 2)-5P₃/₂ (F' = 3) transition of ⁸⁷Rb atoms. Using a beat-note interferometer method, a stable measurement without phase dithering of the phase of the probe pulse before and after it has passed through the EIA medium was achieved. Comparing the phases of the light pulse in air and that of the fast light pulse though the EIA medium, the phase of the fast light pulse at EIA resonance was not shifted and maintained to be the same as that of the free-space light pulse. The classical fidelity of the fast light pulse according to the advancement of the group velocity by adjusting the atomic density was estimated to be more than 97%.

  13. Ultra sound absorption measurements in rock samples at low temperatures

    NASA Technical Reports Server (NTRS)

    Herminghaus, C.; Berckhemer, H.

    1974-01-01

    A new technique, comparable with the reverberation method in room acoustics, is described. It allows Q-measurements at rock samples of arbitrary shape in the frequency range of 50 to 600 kHz in vacuum (.1 mtorr) and at low temperatures (+20 to -180 C). The method was developed in particular to investigate rock samples under lunar conditions. Ultrasound absorption has been measured at volcanics, breccia, gabbros, feldspar and quartz of different grain size and texture yielding the following results: evacuation raises Q mainly through lowering the humidity in the rock. In a dry compact rock, the effect of evacuation is small. With decreasing temperature, Q generally increases. Between +20 and -30 C, Q does not change much. With further decrease of temperature in many cases distinct anomalies appear, where Q becomes frequency dependent.

  14. Ultraviolet absorption: Experiment MA-059. [measurement of atmospheric species concentrations

    NASA Technical Reports Server (NTRS)

    Donahue, T. M.; Hudson, R. D.; Rawlins, W. T.; Anderson, J.; Kaufman, F.; Mcelroy, M. B.

    1977-01-01

    A technique devised to permit the measurement of atmospheric species concentrations is described. This technique involves the application of atomic absorption spectroscopy and the quantitative observation of resonance fluorescence in which atomic or molecular species scatter resonance radiation from a light source into a detector. A beam of atomic oxygen and atomic nitrogen resonance radiation, strong unabsorbable oxygen and nitrogen radiation, and visual radiation was sent from Apollo to Soyuz. The density of atomic oxygen and atomic nitrogen between the two spacecraft was measured by observing the amount of resonance radiation absorbed when the line joining Apollo and Soyuz was perpendicular to their velocity with respect to the ambient atmosphere. Results of postflight analysis of the resonance fluorescence data are discussed.

  15. Spectral reflectance measurements of a virus host model

    NASA Technical Reports Server (NTRS)

    Toler, R. W.; Shankar, N. K.

    1972-01-01

    A technique has been developed to detect the characteristic spectral signatures of healthy and infected St. Augustine grass. It is possible to predict the coverage of the infected area provided ground truth coverage shows positive St. Augustine grass turf. Qualitative measurements from photographs of plants in the blue and red regions with polarization show that light reflected from healthy plants is more strongly polarized than that from diseased plants. Photographs taken through the blue Wratten 47 filter in conjuction with a polarizer show an excellent differentiation. A large photographic difference also appears in the red region. Much smaller differences were noted in the 540 to 550 nm region. Although the intensity in the near-IR region is much higher than the visible region of the spectrum, differences in the healthy and diseased plants' reflectance were quite small.

  16. Innovative Mobile Smart Photonic Dimensional, Color and Spectral Measurement Engineering

    NASA Astrophysics Data System (ADS)

    Hofmann, Dr Dietrich, Prof; Dittrich (B. Eng. , Paul-Gerald; Höfner (B. Eng. , Dieter; Kraus, Daniel

    2015-02-01

    Aim of the paper is the demonstration of a paradigm shift in dimensional, color and spectral measurements in industry, biology/medicine, farming/environmental protection and security, as well as in education and training: Measurement engineering and quality assurance become mobile, modular and smart. Smartpads, smartphones and smartwatches (smartcomps) in combination with innovative hardware apps (hwapps) and conventional software apps (swapps) are fundamental enablers for the transformation from conventional stationary working places towards innovative mobile working places with in-field measurements and point-of-care (POC) diagnostics. Furthermore mobile open online courses (MOOCs) are transforming the study habits. Practical examples for the application of innovative photonic micro dimensiometers, colorimeters and spectrometers will be given. The innovative approach opens so far untapped enormous markets for measurement science, engineering, applications, education and training. These innovative working conditions will be fast accepted due to their convenience, reliability and affordability. A highly visible advantage of smartcomps is the huge number of their real distribution, their worldwide connectivity via Internet and cloud services, the standardized interfaces like USB and HDMI and the experienced capabilities of their users for practical operations, obtained with their private smartcomps.

  17. Sub-millisecond Transient Absorption Frequency Comb Spectroscopy in the Mid-Infrared Spectral Region

    NASA Astrophysics Data System (ADS)

    Bjork, Bryce; Fleisher, Adam; Bui, Thinh; Cossel, Kevin; Okumura, Mitchio; Ye, Jun

    2013-05-01

    The study of highly-reactive transient reaction intermediates is fundamental to understanding chemical dynamics and is particularly relevant to applications such as atmospheric chemistry. Their study often poses a significant challenge for traditional spectrometers, which typically provide broad bandwidth or fast temporal resolution, but not both without long acquisition times. We introduce a cavity-enhanced frequency-comb solution that allows for high-resolution, sensitive spectra to be captured at millisecond intervals in the mid-infrared spectral region using a VIPA dispersive etalon. Once individual comb teeth are resolved, the spectral resolution of the system is limited by the comb linewidth (<40 kHz) while the temporal resolution is limited by the minimum integration time of the InSb detector array (10 μs). In this presentation, I will present the application of this real-time spectroscopic system to small molecule photodissociation.

  18. Evidence for cyclotron absorption from spectral features in gamma-ray bursts seen with Ginga

    NASA Technical Reports Server (NTRS)

    Murakami, T.; Fujii, M.; Hayashida, K.; Itoh, M.; Nishimura, J.

    1988-01-01

    New observations by the gamma-ray burst detector on board the Ginga satellite, which has two well-calibrated detectors covering a wide energy range of 1.5 to 375 keV, are reported. The spectral features obtained are consistent with first and second cyclotron harmonics. This finding is taken as strong evidence for the magnetized neutron star model of gamma-ray bursts.

  19. Laboratory Measurements of the 940, 1130, and 1370 nm Water Vapor Absorption Band Profiles

    NASA Technical Reports Server (NTRS)

    Giver, Lawrence P.; Gore, Warren J.; Pilewskie, P.; Freedman, R. S.; Chackerian, C., Jr.; Varanasi, P.

    2001-01-01

    We have used the solar spectral flux radiometer (SSFR) flight instrument with the Ames 25 meter base-path White cell to obtain about 20 moderate resolution (8 nm) pure water vapor spectra from 650 to 1650 nm, with absorbing paths from 806 to 1506 meters and pressures up to 14 torr. We also obtained a set at 806 meters with several different air-broadening pressures. Model simulations were made for the 940, 1130, and 1370 nm absorption bands for some of these laboratory conditions using the Rothman, et al HITRAN-2000 linelist. This new compilation of HITRAN includes new intensity measurements for the 940 nm region. We compared simulations for our spectra of this band using HITRAN-2000 with simulations using the prior HITRAN-1996. The simulations of the 1130 nm band show about 10% less absorption than we measured. There is some evidence that the total intensity of this band is about 38% stronger than the sum of the HITRAN line intensities in this region. In our laboratory conditions the absorption depends approximately on the square root of the intensity. Thus, our measurements agree that the band is stronger than tabulated in HITRAN, but by about 20%, substantially less than the published value. Significant differences have been shown between Doppler-limited resolution spectra of the 1370 nm band obtained at the Pacific Northwest National Laboratory and HITRAN simulations. Additional new intensity measurements in this region are continuing to be made. We expect the simulations of our SSFR lab data of this band will show the relative importance of improving the HITRAN line intensities of this band for atmospheric measurements.

  20. Laboratory absorption spectra of molecules at interstellar cloud temperatures - First measurements on CO at about 97 nm

    NASA Technical Reports Server (NTRS)

    Smith, P. L.; Yoshino, K.; Stark, G.; Ito, K.; Stevens, M. H.

    1991-01-01

    In the 91-100 nm spectral region, where absorption of photons by interstellar CO usually leads to dissociation, laboratory spectra obtained at 295 K show that most CO bands are both overlapped and perturbed. Reliable band oscillator strengths cannot be extracted from such spectra. As a consequence, synthetic extreme-ultraviolet absorption spectra for CO at the low temperatures that prevail in interstellar clouds are uncertain. A supersonic expansion technique has been used to cool CO to 30 K and three bands in the 97-nm region have been studied with high spectral resolution. The measured spectrum at 30 K is in reasonable agreement with some published modeled spectra, but the ratios of integrated cross sections are somewhat different from those determined from low resolution spectra obtained at 295 K, in which the bands are blended.

  1. Application of Video Spectral Comparator (absorption spectra) for establishing the chronological order of intersecting printed strokes and writing pen strokes.

    PubMed

    Kaur, Ridamjeet; Saini, Komal; Sood, N C

    2013-06-01

    The sequence of intersecting strokes of laser printers (black, blue, red and green) and typewriter ink (black) with the strokes of gel pen ink, ballpoint pen ink and fountain pen ink (black, blue, red and green) has been determined by studying their absorption spectra. The absorption spectra have been generated for each of the two pure inks (i.e. A and B) and points of their intersections (i.e. A over B and B over A) by using Video Spectral Comparator (VSC-2000-HR). The study was carried out with an assumption that the peak characteristics of spectra from the point of intersection should correspond to the peak characteristics of pure ink which was executed later. It was observed that the absorption spectrum of intersection corresponds with either the laser printer or the typewriter ink stroke, whether these strokes were executed earlier or later than the writing instrument strokes. As the results obtained from the study were negative, the FDEs are advised against the practice of this technique in the examination of the sequence of intersecting strokes for these specified inks. PMID:23601731

  2. Application of Video Spectral Comparator (absorption spectra) for establishing the chronological order of intersecting printed strokes and writing pen strokes.

    PubMed

    Kaur, Ridamjeet; Saini, Komal; Sood, N C

    2013-06-01

    The sequence of intersecting strokes of laser printers (black, blue, red and green) and typewriter ink (black) with the strokes of gel pen ink, ballpoint pen ink and fountain pen ink (black, blue, red and green) has been determined by studying their absorption spectra. The absorption spectra have been generated for each of the two pure inks (i.e. A and B) and points of their intersections (i.e. A over B and B over A) by using Video Spectral Comparator (VSC-2000-HR). The study was carried out with an assumption that the peak characteristics of spectra from the point of intersection should correspond to the peak characteristics of pure ink which was executed later. It was observed that the absorption spectrum of intersection corresponds with either the laser printer or the typewriter ink stroke, whether these strokes were executed earlier or later than the writing instrument strokes. As the results obtained from the study were negative, the FDEs are advised against the practice of this technique in the examination of the sequence of intersecting strokes for these specified inks.

  3. Broadband cavity enhanced spectroscopy in the ultraviolet spectral region for measurements of nitrogen dioxide and formaldehyde

    NASA Astrophysics Data System (ADS)

    Washenfelder, R. A.; Attwood, A. R.; Flores, J. M.; Rudich, Y.; Brown, S. S.

    2015-09-01

    measurements of aerosol extinction in ambient air, and this spectral region is important for characterizing the strong ultraviolet absorption by brown carbon aerosol.

  4. Preliminary measurements of leaf spectral reflectance in the 8-14 micrometer region.

    USGS Publications Warehouse

    Salisbury, J.W.

    1986-01-01

    Previous broad band measurements of the spectral reflectance of leaves indicate variations in spectral emissivity that, although small, might be detected with current airborne thermal infrared imaging systems. Preliminary high spectral resolution measurements of the spectral reflectance of leaves of four different species reported here show a different spectral response for each species. These data suggest that species discrimination using remote sensing data in the thermal infrared may be feasible, and raise the possibility that other factors that might affect leaf surface composition and spectral response, such as metal stress, might also be detected.-Author

  5. Spectral characterization of dielectric materials using terahertz measurement systems

    NASA Astrophysics Data System (ADS)

    Seligman, Jeffrey M.

    The performance of modern high frequency components and electronic systems are often limited by the properties of the materials from which they are made. Over the past decade, there has been an increased emphasis on the development of new, high performance dielectrics for use in high frequency systems. The development of these materials requires novel broadband characterization, instrumentation, and extraction techniques, from which models can be formulated. For this project several types of dielectric sheets were characterized at terahertz (THz) frequencies using quasi-optical (free-space) techniques. These measurement systems included a Fourier Transform Spectrometer (FTS, scalar), a Time Domain Spectrometer (TDS, vector), a Scalar Network Analyzer (SNA), and a THz Vector Network Analyzer (VNA). Using these instruments the THz spectral characteristics of dielectric samples were obtained. Polarization based anisotropy was observed in many of the materials measured using vector systems. The TDS was the most informative and flexible instrument for dielectric characterization at THz frequencies. To our knowledge, this is the first such comprehensive study to be performed. Anisotropy effects within materials that do not come into play at microwave frequencies (e.g. ~10 GHz) were found, in many cases, to increase measured losses at THz frequencies by up to an order of magnitude. The frequency dependent properties obtained during the course of this study included loss tangent, permittivity (index of refraction), and dielectric constant. The results were largely consistent between all the different systems and correlated closely to manufacturer specifications over a wide frequency range (325 GHz-1.5 THz). Anisotropic behavior was observed for some of the materials. Non-destructive evaluation and testing (NDE/NDT) techniques were used throughout. A precision test fixture was developed to accomplish these measurements. Time delay, insertion loss, and S-parameters were

  6. Measuring Microwaves via Absorption and Dispersion in Rydberg Atoms

    NASA Astrophysics Data System (ADS)

    Stack, Daniel; Kunz, Paul; Meyer, David; Solmeyer, Neal

    2016-05-01

    Weak microwave frequency electromagnetic fields can be difficult to detect and fully characterize with traditional methods. However it is possible to transduce the measurement of these fields from the microwave domain to the optical domain via resonant transitions between Rydberg levels in atomic vapors using electromagnetically-induced transparency and the Autler-Townes effect. This technique allows for sensitive measurements of the microwave field amplitude, polarization, and spatial waveform (via the position of the probe and coupling laser beams) as compared to measurements performed with dipole antennas. We are able to obtain these quantities by monitoring the properties of a probe laser beam as it passes through a rubidium vapor cell. Previous experiments using Rydberg spectroscopy have typically relied on measuring the absorption of the probe laser as it passed through the atomic system. We report on progress to use the polarization rotation of the probe as it passes through the atoms in a static magnetic field, which corresponds to the real part of the susceptibility of the atomic medium, for measuring the characteristics of a microwave frequency signal. This effect is known as Nonlinear Magneto Optical Rotation (NMOR) and has been used for sensitive magnetometry.

  7. Differential absorption lidar measurements of atmospheric water vapor using a pseudonoise code modulated AlGaAs laser. Thesis

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.

    1994-01-01

    Lidar measurements using pseudonoise code modulated AlGaAs lasers are reported. Horizontal path lidar measurements were made at night to terrestrial targets at ranges of 5 and 13 km with 35 mW of average power and integration times of one second. Cloud and aerosol lidar measurements were made to thin cirrus clouds at 13 km altitude with Rayleigh (molecular) backscatter evident up to 9 km. Average transmitter power was 35 mW and measurement integration time was 20 minutes. An AlGaAs laser was used to characterize spectral properties of water vapor absorption lines at 811.617, 816.024, and 815.769 nm in a multipass absorption cell using derivative spectroscopy techniques. Frequency locking of an AlGaAs laser to a water vapor absorption line was achieved with a laser center frequency stability measured to better than one-fifth of the water vapor Doppler linewidth over several minutes. Differential absorption lidar measurements of atmospheric water vapor were made in both integrated path and range-resolved modes using an externally modulated AlGaAs laser. Mean water vapor number density was estimated from both integrated path and range-resolved DIAL measurements and agreed with measured humidity values to within 6.5 percent and 20 percent, respectively. Error sources were identified and their effects on estimates of water vapor number density calculated.

  8. LDA measurements and turbulence spectral analysis in an agitated vessel

    NASA Astrophysics Data System (ADS)

    Kysela, Bohuš; Konfršt, Jiří; Chára, Zdeněk

    2013-04-01

    During the last years considerable improvement of the derivation of turbulence power spectrum from Laser Doppler Anemometry (LDA) has been achieved. The irregularly sampled LDA data is proposed to approximate by several methods e.g. Lomb-Scargle method, which estimates amplitude and phase of spectral lines from missing data, methods based on the reconstruction of the auto-correlation function (referred to as correlation slotting technique), methods based on the reconstruction of the time series using interpolation between the uneven sampling and subsequent resampling etc. These different methods were used on the LDA data measured in an agitated vessel and the results of the power spectrum calculations were compared. The measurements were performed in the mixing vessel with flat bottom. The vessel was equipped with four baffles and agitated with a six-blade pitched blade impeller. Three values of the impeller speed (Reynolds number) were tested. Long time series of the axial velocity component were measured in selected points. In each point the time series were analyzed and evaluated in a form of power spectrum.

  9. Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 2. Closure study.

    PubMed

    Müller, Thomas; Müller, Detlef; Dubois, René

    2006-04-01

    Spectral particle extinction coefficients of atmospheric aerosols were measured with, to the best of our knowledge, a newly designed differential optical absorption spectroscopy (DOAS) instrument. A closure study was carried out on the basis of optical and microphysical aerosol properties obtained from nephelometer, particle soot/absorption photometer, hygroscopic tandem differential mobility analyzer, twin differential mobility particle sizer, aerodynamic particle sizer, and Berner impactors. The data were collected at the urban site of Leipzig during a period of 10 days in March 2000. The performance test also includes a comparison of the optical properties measured with DOAS to particle optical properties calculated with a Mie-scattering code. The computations take into account dry and ambient particle conditions. Under dry particle conditions the linear regression and the correlation coefficient for particle extinction are 0.95 and 0.90, respectively. At ambient conditions these parameters are 0.89 and 0.97, respectively. An inversion algorithm was used to retrieve microphysical particle properties from the extinction coefficients measured with DOAS. We found excellent agreement within the retrieval uncertainties.

  10. Measurements of liquid film thickness, concentration, and temperature of aqueous urea solution by NIR absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Pan, R.; Jeffries, J. B.; Dreier, T.; Schulz, C.

    2016-01-01

    A multi-wavelength near-infrared (NIR) diode laser absorption sensor has been developed and demonstrated for real-time monitoring of the thickness, solute concentration, and temperature of thin films of urea-water solutions. The sensor monitors the transmittance of three near-infrared diode lasers through the thin liquid film. Film thickness, urea mass fraction, and liquid temperature were determined from measured transmittance ratios of suitable combinations of lasers. Available laser wavelengths were selected depending on the variation of the NIR absorption spectrum of the solution with temperature and solute concentration. The spectral database was measured by a Fourier transform infrared spectrometer in the range 5500-8000 cm-1 for urea solutions between 5 and 40 wt% and temperatures between 298 and 338 K. A prototype sensor was constructed, and the sensor concept was first validated with measurements using a calibration cell providing liquid layers of variable thickness (200-1500 µm), urea mass fraction (5-40 wt%) and temperature (298-318 K). Temporal variations of film thickness and urea concentration were captured during the constant-temperature evaporation of a liquid film deposited on an optically polished heated quartz flat.

  11. Particle extinction measured at ambient conditions with differential optical absorption spectroscopy. 2. Closure study.

    PubMed

    Müller, Thomas; Müller, Detlef; Dubois, René

    2006-04-01

    Spectral particle extinction coefficients of atmospheric aerosols were measured with, to the best of our knowledge, a newly designed differential optical absorption spectroscopy (DOAS) instrument. A closure study was carried out on the basis of optical and microphysical aerosol properties obtained from nephelometer, particle soot/absorption photometer, hygroscopic tandem differential mobility analyzer, twin differential mobility particle sizer, aerodynamic particle sizer, and Berner impactors. The data were collected at the urban site of Leipzig during a period of 10 days in March 2000. The performance test also includes a comparison of the optical properties measured with DOAS to particle optical properties calculated with a Mie-scattering code. The computations take into account dry and ambient particle conditions. Under dry particle conditions the linear regression and the correlation coefficient for particle extinction are 0.95 and 0.90, respectively. At ambient conditions these parameters are 0.89 and 0.97, respectively. An inversion algorithm was used to retrieve microphysical particle properties from the extinction coefficients measured with DOAS. We found excellent agreement within the retrieval uncertainties. PMID:16607998

  12. Calibration of AIS Data Using Ground-based Spectral Reflectance Measurements

    NASA Technical Reports Server (NTRS)

    Conel, J. E.

    1985-01-01

    Present methods of correcting airborne imaging spectrometer (AIS) data for instrumental and atmospheric effects include the flat- or curved-field correction and a deviation-from-the-average adjustment performed on a line-by-line basis throughout the image. Both methods eliminate the atmospheric absorptions, but remove the possibility of studying the atmosphere for its own sake, or of using the atmospheric information present as a possible basis for theoretical modeling. The method discussed here relies on use of ground-based measurements of the surface spectral reflectance in comparison with scanner data to fix in a least-squares sense parameters in a simplified model of the atmosphere on a wavelength-by-wavelength basis. The model parameters (for optically thin conditions) are interpretable in terms of optical depth and scattering phase function, and thus, in principle, provide an approximate description of the atmosphere as a homogeneous body intervening between the sensor and the ground.

  13. Atmospheric and Laser Spectral Influences on the Column CO2 Measurements at 1.57 μm

    NASA Astrophysics Data System (ADS)

    Refaat, T. F.; Ismail, S.; Kooi, S. A.; Lin, B.; Harrison, F. W.; Browell, E. V.

    2012-12-01

    The 2007 National Research Council Decadal Survey recommended implementation of the Active Sensing of CO2 Emission over Nights, Days, and Seasons (ASCENDS) mission to address uncertainties in the knowledge of the sources and sinks of atmospheric carbon dioxide. Consequently, ASCENDS has become a part of NASA plans to monitor atmospheric carbon dioxide form space using active remote sensing. One such technique under evaluation by NASA Langley Research Center is the integrated path differential absorption (IPDA) lidar operating near 1571 nm. High precision and accuracy, of about 0.1% each, are required for the carbon dioxide mixing ratio measurements in order to improve our understanding of the gas sources and sinks. Therefore, applying the IPDA technique requires an evaluation of the influence of systematic errors and biases resulting from uncertainties in various atmospheric conditions. These conditions include atmospheric temperature, pressure and relative humidity. Furthermore, the impacts of these conditions on the spectral characteristics of the carbon dioxide absorption, transmitted laser source and other interfering atmospheric species, such as absorbing molecules and scattering aerosols have to be investigated. In this paper systematic error sources are evaluated for measurements of atmospheric carbon dioxide using the IPDA technique. The study is focused on the carbon dioxide R24 line at 1571.111903 nm wavelength. This line has been selected for operation by the airborne Multi-functional Fiber Laser Lidar (MFLL) system that is a precursor to a space-based IPDA system. For modeling the systematic effects, 2008 HITRAN database was used, as well as most recent updates, to obtain the spectral lines parameters. The Voigt profile was applied to model the absorption spectra of carbon dioxide, as well as those of the interfering species consisting of water vapor, carbon monoxide, nitrous oxide, oxygen, ozone, acetylene and methane. For all species, absorption lines

  14. Contact sponge water absorption test implemented for in situ measures

    NASA Astrophysics Data System (ADS)

    Gaggero, Laura; Scrivano, Simona

    2016-04-01

    The contact sponge method is a non-destructive in-situ methodology used to estimate a water uptake coefficient. The procedure, unlike other in-situ measurement was proven to be directly comparable to the water uptake laboratory measurements, and was registered as UNI 11432:2011. The UNI Normal procedure requires to use a sponge with known density, soaked in water, weighed, placed on the material for 1 minute (UNI 11432, 2011; Pardini & Tiano, 2004), then weighed again. Difficulties arise in operating on test samples or on materials with porosity varied for decay. While carrying on the test, fluctuations in the bearing of the environmental parameters were negligible, but not the pressure applied to the surface, that induced the release of different water amounts towards the material. For this reason we designed a metal piece of the same diameter of the plate carrying the sponge, to be screwed at the tip of a pocket penetrometer. With this instrument the sponge was kept in contact with the surface for 1 minute applying two different loads, at first pushed with 0.3 kg/cm2 in order to press the sponge, but not its holder, against the surface. Then, a load of 1.1 kg/ cm2 was applied, still avoiding deviating the load to the sponge holder. We applied both the current and our implemented method to determine the water absorption by contact sponge on 5 fresh rock types (4 limestones: Fine - and Coarse grained Pietra di Vicenza, Rosso Verona, Breccia Aurora, and the silicoclastic Macigno sandstone). The results show that 1) the current methodology imply manual skill and experience to produce a coherent set of data; the variable involved are in fact not only the imposed pressure but also the compression mechanics. 2) The control on the applied pressure allowed reproducible measurements. Moreover, 3) the use of a thicker sponge enabled to apply the method even on rougher surfaces, as the device holding the sponge is not in contact with the tested object. Finally, 4) the

  15. An experimental study of the electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles and their electrosynthesized polymers.

    PubMed

    Diaw, A K D; Gningue-Sall, D; Yassar, A; Brochon, J-C; Henry, E; Aaron, J-J

    2015-01-25

    Electronic absorption and fluorescence spectral properties of new p-substituted-N-phenylpyrroles (N-PhPys), including HOPhPy, MeOPhPy, ThPhPy, PhDPy, DPhDPy, PyPhThThPhPy, and their available, electrosynthesized polymers were investigated. Electronic absorption spectra, fluorescence excitation and emission spectra, fluorescence quantum yields (ΦF) and lifetimes (τF), and other photophysical parameters of these N-PhPy derivatives and their polymers were measured in DMF, DMSO diluted solutions and/or solid state at room temperature. The electronic absorption spectra of N-PhPy derivatives and their polymers included one to several bands, located in the 270-395 nm region, according to the p-phenyl substituent electron-donating effect and conjugated heteroaromatic system length. The fluorescence excitation spectra were characterized by one broad main peak, with, in most cases, one (or more) poorly resolved shoulder (s), appearing in the 270-405 nm region, and their emission spectra were generally constituted of several bands located in the 330-480 nm region. No significant shift of the absorption, fluorescence excitation and emission spectra wavelengths was found upon going from the monomers to the corresponding polymers. ΦF values were high, varying between 0.11 and 0.63, according to the nature of substituents(s) and to the conjugated system extension. Fluorescence decays were mono-exponential for the monomers and poly-exponential for PyPhThThPhPy and for polymers. τF values were relatively short (0.35-5.17 ns), and markedly decreased with the electron-donor character of the phenyl group p-substituent and the conjugated system extension.

  16. Multiphase flow measurement using multiple energy gamma ray absorption (MEGRA) composition measurement

    SciTech Connect

    Scheers, A.M.; Slijkerman, W.F.J.

    1996-12-31

    Some multiphase flowmeters use the principle of Dual Energy Gamma Ray Absorption (DEGRA) composition measurement to determine the individual water, oil and gas fractions. Under homogeneous flow conditions the ultimate uncertainty in phase fractions achievable with this technique depends strongly on the choice of hardware. The meter presented in this paper uses unique components that have been optimized for the water, oil and gas fraction measurement with theoretical uncertainties of 2% in the fractions over a 1 second measurement period. Generally, composition meters are sensitive to a change in production water salinity and this will cause significant systematic effort in the fraction and watercut measurements. A new measurement concept is presented that is not sensitive to salinity variations and based on Multiple Energy Gamma Ray Absorption (MEGRA) composition measurement. A multiphase flowmeter equipped with the MEGRA concept does not require field-calibration, a decisive advantage in subsea or marginal field developments.

  17. Spectral induced polarization (SIP) measurement of NAPL contaminated soils

    NASA Astrophysics Data System (ADS)

    Schwartz, N.; Huisman, J. A.; Furman, A.

    2010-12-01

    The potential applicability of spectral induce polarization (SIP) as a tool to map NAPLs (non aqueous phase liquids) contaminants at the subsurface lead researchers to investigate the electric signature of those contaminant on the spectral response. However, and despite the cumulative efforts, the effect of NAPL on the electrical properties of soil, and the mechanisms that control this effect are largely unknown. In this work a novel experiment is designed to further examine the effect of NAPL on the electrical properties of partially saturated soil. The measurement system that used is the ZEL-SIP04 impedance meter developed at the Forschungszentrum Julich, Germany. The system accurately (nominal phase precision of 0.1 mrad below 1 kHz) measures the phase and the amplitude of a material possessing a very low polarization (such as soil). The sample holder has a dimension of 60 cm long and 4.6 cm in diameter. Current and potential electrodes were made of brass, and while the current electrodes were inserted in full into the soil, the contact between the potential electrode and the soil was made through an Agarose bridge. Two types of soils were used: clean quartz sand, and a mixture of sand with clean Bentonite. Each soil (sandy or clayey) was mixed with water to get saturation degree of 30%. Following the mixture with water, NAPL was added and the composite were mixed again. Packing was done by adding and compressing small portions of the soil to the column. A triplicate of each mixture was made with a good reproducible bulk density. Both for the sandy and clayey soils, the results indicate that additions of NAPL decrease the real part of the complex resistivity. Additionally, for the sandy soil this process is time depended, and that a further decrease in resistivity develops over time. The results are analyzed considering geometrical factors: while the NAPL is electrically insulator, addition of NAPL to the soil is expected to increase the connectivity of the

  18. OBSERVATION AND SPECTRAL MEASUREMENTS OF THE CRAB NEBULA WITH MILAGRO

    SciTech Connect

    Abdo, A. A.; Allen, B. T.; Chen, C.; Atkins, R.; Aune, T.; Benbow, W.; Coyne, D. G.; Dorfan, D. E.; Berley, D.; Blaufuss, E.; Bussons, J.; Bonamente, E.; Galbraith-Frew, J.; Christopher, G. E.; Fleysher, L.; Fleysher, R.; DeYoung, T.; Falcone, A.; Dingus, B. L.; Ellsworth, R. W.; and others

    2012-05-01

    The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV-100 TeV gamma-ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula between {approx}1 and {approx}100 TeV. The TeV emission is believed to be caused by inverse-Compton upscattering of ambient photons by an energetic electron population. The location of a TeV steepening or cutoff in the energy spectrum reveals important details about the underlying electron population. We describe the experiment and the technique for distinguishing gamma-ray events from the much more-abundant hadronic events. We describe the calculation of the significance of the excess from the Crab and how the energy spectrum is fitted. The differential photon energy spectrum, including the statistical errors from the fit, obtained using a simple power-law hypothesis for data between 2005 September and 2008 March is (6.5 {+-} 0.4) Multiplication-Sign 10{sup -14}(E/10 TeV){sup -3.1{+-}0.1}(cm{sup 2} s TeV ){sup -1} between {approx}1 TeV and {approx}100 TeV. Allowing for a possible exponential cutoff, the photon energy spectrum is fitted as (2.5{sup +0.7}{sub -0.4}) Multiplication-Sign 10{sup -12}(E/3 TeV){sup -2.5{+-}0.4}exp (- E/32{sup +39}{sub -18} TeV) (cm{sup 2} s TeV){sup -1}. The results are subject to an {approx}30% systematic uncertainty in the overall flux and an {approx}0.1 systematic uncertainty in the power-law indices quoted. Uncertainty in the overall energy scale has been absorbed into these errors. Fixing the spectral index to values that have been measured below 1 TeV by IACT experiments (2.4-2.6), the fit to the Milagro data suggests that Crab exhibits a

  19. Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Several Surfaces and Ecosystem over Southern Africa

    NASA Astrophysics Data System (ADS)

    Gatebe, C. K.; King, M. D.; Tsay, S.; Arnold, G. T.; Li, J. Y.

    2001-12-01

    The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF measurements were obtained over different natural surfaces and ecosystem in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 oS, 31.5 oE) and Mongu tower, Zambia (15.4 oS, 23.3 oE). Additional sites are also considered and include, Maun tower, Botswana (20.0 oS, 23.5 oE), Sowa Pan, Botswana (20.6 oS, 26.2 oE) and Etosha Pan, Namibia (19.0 oS, 16.0 oE). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 μ m), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 μ m). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of ~20 o and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were

  20. Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Skukuza and Mongu Sites

    NASA Technical Reports Server (NTRS)

    Gatebe, C. K.; King, Michael D.; Arnold, G. T.; Li, J. Y.

    2001-01-01

    The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF (bidirectional reflection function) measurements were obtained over different natural surfaces and ecosystems in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS (Earth Observing System) satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 S, 31.5 E) and Mongu tower, Zambia (15.4 S, 23.3 E). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 microns), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 microns). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of approximately 20 degrees and fly in a circle about 3 km in diameter above the surface for roughly two minutes. Replicated observations (multiple circular orbits) were acquired over selected surfaces so that average BRF smooth out small-scale surface and

  1. Airborne spectral Measurements of Surface-Atmosphere Anisotropy for Several Surfaces and Ecosystem over Southern Africa

    NASA Technical Reports Server (NTRS)

    Gatebe, Charles K.; King, M. D.; Arnold, G. T.; Li, J. Y.; Lau, William K. M. (Technical Monitor)

    2001-01-01

    The Cloud Absorption Radiometer (CAR) was flown aboard the University of Washington Convair CV-580 research aircraft and took measurements on 23 flights between August 15 and September 16. On 12 of those flights, BRF measurements were obtained over different natural surfaces and ecosystem in southern Africa. The BRF measurements were done to characterize surface anisotropy in support of SAFARI 2000 science objectives principally to validate products from NASA's EOS satellites, and to parameterize and validate BRF models. In this paper we present results of BRFs taken over two EOS validation sites: Skukuza tower, South Africa (25.0 deg S, 31.5 deg E) and Mongu tower, Zambia (15.4 deg S, 23.3 deg E). Additional sites are also considered and include, Maun tower, Botswana (20.0 deg S, 23.5 deg E), Sowa Pan, Botswana (20.6 deg S, 26.2 deg E) and Etosha Pan, Namibia (19.0 deg S, 16.0 deg E). The CAR is capable of measuring scattered light in fourteen spectral bands. The scan mirror, rotating at 100 rpm, directs the light into a Dall-Kirkham telescope where the beam is split into nine paths. Eight light beams pass through beam splitters, dichroics, and lenses to individual detectors (0.34-1.27 micrometers), and finally are registered by eight data channels. They are sampled simultaneously and continuously. The ninth beam passes through a spinning filter wheel to an InSb detector cooled by a Stirling cycle cooler. Signals registered by the ninth data channel are selected from among six spectral channels (1.55-2.30 micrometers). The filter wheel can either cycle through all six spectral bands at a prescribed interval (usually changing filter every fifth scan line), or lock onto any one of the six spectral bands and sample it continuously. To measure the BRF of the surface-atmosphere system, the University of Washington CV-580 had to bank at a comfortable roll angle of approximately 20 degrees and fly in a circle about 3 km in diameter above the surface for roughly two

  2. Method for improving terahertz band absorption spectrum measurement accuracy using noncontact sample thickness measurement.

    PubMed

    Li, Zhi; Zhang, Zhaohui; Zhao, Xiaoyan; Su, Haixia; Yan, Fang; Zhang, Han

    2012-07-10

    The terahertz absorption spectrum has a complex nonlinear relationship with sample thickness, which is normally measured mechanically with limited accuracy. As a result, the terahertz absorption spectrum is usually determined incorrectly. In this paper, an iterative algorithm is proposed to accurately determine sample thickness. This algorithm is independent of the initial value used and results in convergent calculations. Precision in sample thickness can be improved up to 0.1 μm. A more precise absorption spectrum can then be extracted. By comparing the proposed method with the traditional method based on mechanical thickness measurements, quantitative analysis experiments on a three-component amino acid mixture shows that the global error decreased from 0.0338 to 0.0301.

  3. Combined High Spectral Resolution Lidar and Radar Measurement of Drizzle

    NASA Astrophysics Data System (ADS)

    Eloranta, Edwin

    2015-04-01

    Marine stratus clouds are an important feature of the global climate system. Cloud lifetime is sensitive to drizzle rates. Drizzle not only removes water from the cloud but it's evaporation cools the sub-cloud layer acting to suppress convection. Accurate measurements of drizzle rates will improve our understanding of cloud maintenance. Simultaneous lidar measurements of extinction and radar backscatter allow determination of drizzle droplet particle size, liquid water content, fall velocity and water flux. However, drizzle measurements with conventional lidar are hampered by: 1)changes in the transmission of the output window caused by water accumulation on the lidar output window, 2)the difficulty of correcting the backscatter signal for atmospheric extinction and, 3)the effects of multiple scattering. High spectral resolution lidar avoids problems with window transmission and atmospheric attenuation because the backscatter is referenced to the known molecular scattering cross section at each point in the profile. Although multiple scattering degrades the direct measurement of extinction with the HSRL, it has little effect the HSRL measurement of backscatter cross section. We have developed an iterative solution that begins by estimating the extinction cross in drizzle using an assumed lidar ratio and the backscatter measurement. This is combined with the radar backscatter to make a first estimate of the particle size distribution. Mie scattering theory is then used to compute an improved lidar ratio for this particle size distribution and the new lidar ratio provides an improved extinction cross section. The calculation assumes a modified gamma distribution of sizes. The mode diameter of the distribution is fixed by the lidar-radar cross section ratio, while the width of the distribution is determined by matching the computed fall velocity of the drizzle with the observed radar Doppler velocity. The strengths and limitations of the this approach are examined

  4. Spectral Moments of Collision-Induced Absorption of CO2 Pairs: The Role of the Intermolecular Potential

    NASA Technical Reports Server (NTRS)

    Gruszka, Marcin; Borysow, Aleksandra

    1994-01-01

    In this paper we examine the role of the anisotropy of the intermolecular potential in the rototranslational collision-induced absorption of the CO2 pairs. Using newly developed formulas that include the effects of anisotropy of the potential to all orders, we calculate the two lowest spectral moments gamma(prime), and alpha(prime), for four different classes of C02 pair potentials and compare the results with the experimental values. We assumed only multipolar induction in the process of forming the induced dipole, with the second-order contributions included. Using a site-site LJ and a site-site semi-ab initio intermolecular potentials we were able to reproduce the experimental values of gamma(prime), and alpha(prime) moments over entire temperature range from 230 to 330 K. Also, the role of an electrostatic interaction between two C02 molecules and its impact on the spectral moments is thoroughly investigated. An isotropic core with a point quadrupole centered at each molecule is shown to be an inadequate representation of the C02-CO2 potential. Additionally, we show the results obtained with the first- and second-order perturbation theory to be more than twice too small.

  5. [Correction method for infrared spectral emissivity measurement system based on integrating sphere reflectometer].

    PubMed

    Zhang, Yu-Feng; Dai, Jing-Min; Zhang, Yu; Pan, Wei-Dong; Zhang, Lei

    2013-08-01

    In view of the influence of non-ideal reference standard on spectral emissivity measurement, by analyzing the principle of infrared emissivity measurement system based on integrating sphere reflectometer, a calibration method suitable for measuring spectral emissivity system using the reflection measurement was proposed. By fitting a spectral reflectance curve of the reference standard sample to the given reflectance data, the correction coefficient of measurement system was computed. Then the output voltage curve of reference standard sample was corrected by this coefficient. The system error caused by the imperfection of reference standard was eliminated. The correction method was applied to the spectral emissivity measurement system based on integrating sphere reflectometer. The results measured by the corrected system and the results measured by energy comparison measurement were compared to verify the feasibility and effectivity of this correction method in improving the accuracy of spectral emissivity measurement.

  6. Urban ozone measurements using differential optical absorption spectroscopy.

    PubMed

    Morales, J A; Treacy, J; Coffey, S

    2004-05-01

    In order to improve the air quality in Europe the European Commission has issued a number of directives with regard to acceptable levels of a range of gaseous pollutants, which includes ozone. Therefore, monitoring of this compound is necessary to comply with EU legislation, to provide improved pollution warnings for those who are sensitive to air pollutants as well as providing valuable data for environmental planning. Open-path spectroscopic techniques, such as differential optical absorption spectroscopy (DOAS), are ideal for monitoring pollutants because of the advantages they offer over classical methods and point-source analysers. A DOAS system has been installed in Dublin city centre to monitor a range of criteria pollutants including ozone. Observations of urban background ozone concentrations are presented. The measurements are compared with those obtained using a UV point-source analyser and are presented in the context of the current EU directive. The influence of trans-boundary pollution from mainland Europe leading to ozone episodes is also discussed. Observations of high ozone during this measurement campaign coincided with the influx of photochemically polluted air masses which originated over continental Europe. For the analysed time interval, the data suggest that the ground ozone level in Dublin might be significantly influenced by long-range transport from the United Kingdom and continental Europe. PMID:14963627

  7. COMPENSATIONAL THREE-WAVELENGTH DIFFERENTIAL-ABSORPTION LIDAR TECHNIQUE FOR REDUCING THE INFLUENCE OF DIFFERENTIAL SCATTERING ON OZONE-CONCENTRATION MEASUREMENTS.

    EPA Science Inventory

    A three-wavelength differential-absorption lidar (DIAL) technique for the UV spectral region is presented that reduces the influence of aerosol differential scattering on measured O3-concentration profiles. The principal advantage of this approach is that, to a good first approxi...

  8. Real-time calibration of laser absorption spectrometer using spectral correlation performed with an in-line gas cell.

    PubMed

    Smith, Clinton J; Wang, Wen; Wysocki, Gerard

    2013-09-23

    A real-time drift correction and calibration method using spectral correlation based on a revolving in-line gas cell for laser-based spectroscopic trace-gas measurements has been developed and evaluated experimentally. This technique is relatively simple to implement in laser spectroscopy systems and assures long-term stability of trace-gas measurements by minimizing the effects of external sources of drift in real-time. Spectroscopic sensitivity sufficient for environmental monitoring and effective drift suppression has been achieved for long-term measurements of CO₂ with a quantum cascade laser based spectrometer.

  9. Design and measurements of the absorption section of an up-conversion device based on PbSe quantum-dots

    NASA Astrophysics Data System (ADS)

    Hechster, Elad; Sarusi, Gabby

    2015-12-01

    The absorption section of quantum dots (QD) based night vision devices consists of the OQ sensitizing layer which absorbs the Infrared radiation, the substrate on which the QD are placed, the electrode and, in several cases, a blocking layer that prevents the flow of charge carriers toward the inverse direction. The absorption section plays a dominant role in determining the absorption spectral ranges and the signal-to-noise ratios of the devices. In this work, we show the design of the absorption section of a short wavelength infrared (SWIR) to visible direct up-conversion device. The growth was 300 nm thick PbSe quantum dots (QD) separated by PbSe grain boundaries layer on intrinsic GaAs substrate. Photo-luminescence and absorption measurements suggested that the quantum dots spectral response is blue-shifted to the spectral range in which the up-conversion device is operated i.e., SWIR. We preformed sheet resistance measurements in dark and under illumination that showed that the device exhibits an improvement in the signal-to-noise ratio after annealing ion chloride atmosphere compare with annealing in oxygen atmosphere. These samples have great potential for the use as the absorption section of low-cost, compact, low power consumption, and cooler free up-conversion devices.

  10. Atmospheric extinction in solar tower plants: absorption and broadband correction for MOR measurements

    NASA Astrophysics Data System (ADS)

    Hanrieder, N.; Wilbert, S.; Pitz-Paal, R.; Emde, C.; Gasteiger, J.; Mayer, B.; Polo, J.

    2015-08-01

    Losses of reflected Direct Normal Irradiance due to atmospheric extinction in concentrated solar tower plants can vary significantly with site and time. The losses of the direct normal irradiance between the heliostat field and receiver in a solar tower plant are mainly caused by atmospheric scattering and absorption by aerosol and water vapor concentration in the atmospheric boundary layer. Due to a high aerosol particle number, radiation losses can be significantly larger in desert environments compared to the standard atmospheric conditions which are usually considered in ray-tracing or plant optimization tools. Information about on-site atmospheric extinction is only rarely available. To measure these radiation losses, two different commercially available instruments were tested, and more than 19 months of measurements were collected and compared at the Plataforma Solar de Almería. Both instruments are primarily used to determine the meteorological optical range (MOR). The Vaisala FS11 scatterometer is based on a monochromatic near-infrared light source emission and measures the strength of scattering processes in a small air volume mainly caused by aerosol particles. The Optec LPV4 long-path visibility transmissometer determines the monochromatic attenuation between a light-emitting diode (LED) light source at 532 nm and a receiver and therefore also accounts for absorption processes. As the broadband solar attenuation is of interest for solar resource assessment for concentrated solar power (CSP), a correction procedure for these two instruments is developed and tested. This procedure includes a spectral correction of both instruments from monochromatic to broadband attenuation. That means the attenuation is corrected for the time-dependent solar spectrum which is reflected by the collector. Further, an absorption correction for the Vaisala FS11 scatterometer is implemented. To optimize the absorption and broadband correction (ABC) procedure, additional

  11. Spectral emission measurement of igneous rocks using a spectroradiometer

    NASA Technical Reports Server (NTRS)

    Hunton, W. D.

    1970-01-01

    Spectroradiometer is used for either close or remote identification of rocks not heated to high temperatures. Instrument yields reproducible data spectra with excellent signal-to-noise ratios and readily identifiable spectral details, including differences in subclasses.

  12. Correlation of Coal Calorific Value and Sulphur Content with 57Fe Mössbauer Spectral Absorption

    NASA Astrophysics Data System (ADS)

    Wynter, C. I.; May, L.; Oliver, F. W.; Hall, J. A.; Hoffman, E. J.; Kumar, A.; Christopher, L.

    Coal is the most abundant, most economical and widely distributed fossil fuel in the world today. It is also the principal form of reductant in the iron and steel industry. This study was undertaken to not only add to the growing use of Mössbauer spectroscopy application in industry but also to increase the chemistry and physics knowledge base of coal. Coal is 40 to 80 percent carbon with small amounts of sulphur and iron as pyrite and ferrous sulphate. The environmental concern associated with mining and burning of coal has long been a subject of investigation with emphasis on the sulphur content. We examined five ranks of coal: anthracite, Eastern bituminous, bituminous, sub-bituminous, and lignite. Relationships were investigated between the Calorific Value (CV) of coal and inorganic sulphur content, 57Fe Mössbauer absorption, and ratio of pyrite (FeS2) to FeSO4. Twenty-eight samples of the five different types of coal had CVs ranging from 32,403 to 16,100 kJ/kg and sulphur concentrations ranging from 0.28 to 2.5 percent. CV appeared to be positively correlated with concentrations of sulphur and of iron-sulphur salts, although there appears to be little connection with the distribution of their oxidation states.

  13. Organic Carbon: Correlating UV-Vis Absorption Spectral Patterns to Hygroscopicity

    NASA Astrophysics Data System (ADS)

    Kanu, A. M.; Bond, T. C.

    2005-12-01

    The complex composition of organic aerosols (OC) in the atmosphere results from an array of sources. Thousands of individual organic compounds within these aerosols are difficult to identify: however, studies suggest these mixtures affect the radiative balance of Earth's atmosphere. Therefore, it is at least as vital to study the absorption and scattering of incoming solar radiation by aerosols as it is to distinguish and quantify the myriad compounds. OC can represent significant fractions of atmospheric aerosol and can play a prominent role in atmospheric radiative forcing. My research focuses on identifying organic carbon with different hygroscopic and optical properties--both of which are affected by composition. We use gradient chromatographic elution with reverse-phase and ion-exchange chromatography columns. We examine aerosols from wood combustion generated within strict temperature regimes. Results demonstrate distinct clusters according to different water affinities. Furthermore, each cluster absorbs in staggered regimes of ultraviolet and visible light, depending on the combustion temperature at which the OC fraction is generated. The association between various absorbing features and hygroscopic properties may imply distinct climate forcing potentials for different fractions of the organic carbon.

  14. Spectral broadening measurements of the ionospheres of Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Woo, R.; Armstrong, J. W.

    1980-01-01

    Using data obtained from radio occultation experiments of Pioneer 10 and 11, the theory for spectral broadening is compared with the theory of weak intensity scintillation. This comparison is possible because Pioneer's observed spectral broadening occurred when the intensity scintillations were weak. Good agreement is found, and the inferred characteristics of the electron density irregularities for the ionospheres of both Jupiter and Saturn are presented.

  15. CO total column retrieval from SCIAMACHY and TROPOMI Earthshine measurements in the shortwave infrared spectral range

    NASA Astrophysics Data System (ADS)

    Borsdorff, Tobias; Landgraf, Jochen; Aben Aben, Ilse; Williams, Jason; de Laat, Jos

    2015-04-01

    ESA's Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) was operational from 2002 until April 2012 when the contact to its host ENVISAT was finally lost. In this period, an almost continuous long-term record of 10 years Shortwave Infrared (SWIR) measurements of the 2.3 μm spectral range from space has been recorded. Beginning of 2016, this dataset will be continued with the launch of ESA's Sentinel 5 Precursor (S5-P) mission with the Tropospheric Monitoring Instrument (TROPOMI) on board measuring also the 2.3 μm spectral range but with improved radiometric performance and spatial resolution. For the S5-P mission, the highly efficient Infrared CO Retrieval algorithm (SICOR) is developed as part of the operational data processor. Using a common retrieval approach for the two satellite instruments is desirable to ensure comparability and consistency of a long-term CO dataset. For this study, we processed the entire SCIAMACHY dataset with the SICOR algorithm and by that derived a new SCIAMACHY CO dataset for the entire ENVISAT mission, preliminary limited to land and cloud free scenes. For the SCIAMACHY dataset, it is necessary to account for the time dependent instrument degradation due to a growing ice layer on the detector array and a considerable loss of detector pixels due to radiation damage in the later years of the mission. For this purpose, we use cloud-free measurements over the Sahara region as a natural calibration target to identify the time dependence of detector male functions and the loss of radiometric accuracy. The 10-year CO dataset is validated with on-ground TCCON and NDACC measurements at 10 sites. To demonstrate the ability of the new SCIAMACHY CO dataset, we compare the spatial and temporal variation of SCIAMACHY CO fields over biomass burning areas with model fields of a global chemistry transport model (TM5).

  16. Statistical Estimation of the Atmospheric Aerosol Absorption Coefficient Based on the Data of Optical Measurements

    SciTech Connect

    Uzhegov, V.N.; Kozlov, V.S.; Panchenko, M.V.; Pkhalagov, Yu.A.; Pol'kin, V.V.; Terpugova, S.A.; Shmargunov, V.P.; Yausheva, E.P.

    2005-03-18

    The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis

  17. Improved self-absorption correction for extended x-ray absorption fine-structure measurements

    SciTech Connect

    Booth, C.H.; Bridges, F.

    2003-06-04

    Extended x-ray absorption fine-structure (EXAFS) data collected in the fluorescence mode are susceptible to an apparent amplitude reduction due to the self-absorption of the fluorescing photon by the sample before it reaches a detector. Previous treatments have made the simplifying assumption that the effect of the EXAFS on the correction term is negligible, and that the samples are in the thick limit. We present a nearly exact treatment that can be applied for any sample thickness or concentration, and retains the EXAFS oscillations in the correction term.

  18. Improved detection sensitivity of D-mannitol crystalline phase content using differential spectral phase shift terahertz spectroscopy measurements.

    PubMed

    Allard, Jean-François; Cornet, Alain; Debacq, Christophe; Meurens, Marc; Houde, Daniel; Morris, Denis

    2011-02-28

    We report quantitative measurement of the relative proportion of δ- and β-D-mannitol crystalline phases inserted into polyethylene powder pellets, obtained by time-domain terahertz spectroscopy. Nine absorption bands have been identified from 0.2 THz to 2.2 THz. The best quantification of the δ-phase proportion is made using the 1.01 THz absorption band. Coherent detection allows using the spectral phase shift of the transmitted THz waveform to improve the detection sensitivity of the relative δ-phase proportion. We argue that differential phase shift measurements are less sensitive to samples' defects. Using a linear phase shift compensation for pellets of slightly different thicknesses, we were able to distinguish a 0.5% variation in δ-phase proportion.

  19. A procedure for estimation of sea-surface temperature from remote measurements in the 10 - 13 micrometers spectral region

    NASA Technical Reports Server (NTRS)

    Anding, D. C.

    1975-01-01

    The feasibility is demonstrated of a procedure for the remote measurement of sea-surface temperature which inherently corrects for the effect of the intervening atmosphere without recourse to climatological data. The procedure relies upon the near-linear differential absorption properties of the infrared window region between 10 and 13 micrometers and requires radiometric measurements in a minimum of two spectral intervals within the infrared window which have a significant difference in absorption coefficient. The procedure was applied to Nimbus 4 infrared interferometer spectrometer (IRIS) data and to Skylab EREP S191 spectrometer data, and it is demonstrated that atmospheric effects on the observed brightness temperature can be reduced to less than 1.0 Kelvin.

  20. Enhanced joint spectral and time domain optical coherence tomography for quantitative flow velocity measurement

    NASA Astrophysics Data System (ADS)

    Walther, Julia; Koch, Edmund

    2011-06-01

    Recently, a new method called joint spectral and time domain optical coherence tomography (STdOCT) for flow velocity measurement in spectral domain OCT (SD OCT) was presented. This method analyzes the detected timeresolved interference fringe spectra by using a two-dimensional fast Fourier transformation (2D FFT) to determine directly the Doppler frequency shift instead of calculating the phase difference at each depth position of adjacent A-scans. There, it was found that STdOCT is more robust for measurements with low signal to noise ratio than the classic phase-resolved Doppler OCT (DOCT) making it attractive first for imaging fast flow velocities at which a strong Doppler angle dependent signal damping occurs due to interference fringe washout and second for investigating large blood vessels with a big diameter and a highly damped signal of blood with increasing depth due to strong scattering and absorption in the near-infrared wavelength range. In the present study, we would like to introduce an enhanced algorithm for STdOCT permitting a more precise flow velocity measurement in comparison to the conventional STdOCT. The new method determines the amplitude of the broadened Doppler frequency shift by calculating the center of gravity via the complex analytical signal as a result of the second FFT instead of detecting the maximum intensity signal. Furthermore, the comparison with phase-resolved DOCT was done experimentally by using a flow phantom consisting of a 1% Intralipid emulsion and a 320 μm glass capillary. As a result, the enhanced STdOCT and DOCT processed data are completely equivalent.

  1. Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand.

    PubMed

    Nolet, Corjan; Poortinga, Ate; Roosjen, Peter; Bartholomeus, Harm; Ruessink, Gerben

    2014-01-01

    Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure surface moisture at a high spatio-temporal resolution. It is based on the principle that wet sand appears darker than dry sand: it is less reflective. The goals of this study are (1) to measure and model reflectance under controlled laboratory conditions as function of wavelength (λ) and surface moisture (θ) over the optical domain of 350-2500 nm, and (2) to explore the implications of our laboratory findings for accurately mapping the distribution of surface moisture under natural conditions. A laboratory spectroscopy experiment was conducted to measure spectral reflectance (1 nm interval) under different surface moisture conditions using beach sand. A non-linear increase of reflectance upon drying was observed over the full range of wavelengths. Two models were developed and tested. The first model is grounded in optics and describes the proportional contribution of scattering and absorption of light by pore water in an unsaturated sand matrix. The second model is grounded in soil physics and links the hydraulic behaviour of pore water in an unsaturated sand matrix to its optical properties. The optical model performed well for volumetric moisture content θ < 24% (R2 > 0.97), but underestimated reflectance for θ between 24-30% (R2 > 0.92), most notable around the 1940 nm water absorption peak. The soil-physical model performed very well (R2 > 0.99) but is limited to 4% > θ < 24%. Results from a field experiment show that a short-wave infrared terrestrial laser scanner (λ = 1550 nm) can accurately relate surface moisture to reflectance (standard error 2.6%), demonstrating its potential to derive spatially extensive surface moisture maps of a natural coastal beach.

  2. Measuring and modeling the effect of surface moisture on the spectral reflectance of coastal beach sand.

    PubMed

    Nolet, Corjan; Poortinga, Ate; Roosjen, Peter; Bartholomeus, Harm; Ruessink, Gerben

    2014-01-01

    Surface moisture is an important supply limiting factor for aeolian sand transport, which is the primary driver of coastal dune development. As such, it is critical to account for the control of surface moisture on available sand for dune building. Optical remote sensing has the potential to measure surface moisture at a high spatio-temporal resolution. It is based on the principle that wet sand appears darker than dry sand: it is less reflective. The goals of this study are (1) to measure and model reflectance under controlled laboratory conditions as function of wavelength (λ) and surface moisture (θ) over the optical domain of 350-2500 nm, and (2) to explore the implications of our laboratory findings for accurately mapping the distribution of surface moisture under natural conditions. A laboratory spectroscopy experiment was conducted to measure spectral reflectance (1 nm interval) under different surface moisture conditions using beach sand. A non-linear increase of reflectance upon drying was observed over the full range of wavelengths. Two models were developed and tested. The first model is grounded in optics and describes the proportional contribution of scattering and absorption of light by pore water in an unsaturated sand matrix. The second model is grounded in soil physics and links the hydraulic behaviour of pore water in an unsaturated sand matrix to its optical properties. The optical model performed well for volumetric moisture content θ < 24% (R2 > 0.97), but underestimated reflectance for θ between 24-30% (R2 > 0.92), most notable around the 1940 nm water absorption peak. The soil-physical model performed very well (R2 > 0.99) but is limited to 4% > θ < 24%. Results from a field experiment show that a short-wave infrared terrestrial laser scanner (λ = 1550 nm) can accurately relate surface moisture to reflectance (standard error 2.6%), demonstrating its potential to derive spatially extensive surface moisture maps of a natural coastal beach

  3. Measurement and Shaping of Biphoton Spectral Wave Functions.

    PubMed

    Tischler, N; Büse, A; Helt, L G; Juan, M L; Piro, N; Ghosh, J; Steel, M J; Molina-Terriza, G

    2015-11-01

    In this work we present a simple method to reconstruct the complex spectral wave function of a biphoton, and hence gain complete information about the spectral and temporal properties of a photon pair. The technique, which relies on quantum interference, is applicable to biphoton states produced with a monochromatic pump when a shift of the pump frequency produces a shift in the relative frequencies contributing to the biphoton. We demonstrate an example of such a situation in type-II parametric down conversion allowing arbitrary paraxial spatial pump and detection modes. Moreover, our test cases demonstrate the possibility to shape the spectral wave function. This is achieved by choosing the spatial mode of the pump and of the detection modes, and takes advantage of spatiotemporal correlations.

  4. The Zugspitze radiative closure experiment for quantifying water vapor absorption over the terrestrial and solar infrared - Part 3: Quantification of the mid- and near-infrared water vapor continuum in the 2500 to 7800 cm-1 spectral range under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Reichert, Andreas; Sussmann, Ralf

    2016-09-01

    We present a first quantification of the near-infrared (NIR) water vapor continuum absorption from an atmospheric radiative closure experiment carried out at the Zugspitze (47.42° N, 10.98° E; 2964 m a.s.l.). Continuum quantification is achieved via radiative closure using radiometrically calibrated solar Fourier transform infrared (FTIR) absorption spectra covering the 2500 to 7800 cm-1 spectral range. The dry atmospheric conditions at the Zugspitze site (IWV 1.4 to 3.3 mm) enable continuum quantification even within water vapor absorption bands, while upper limits for continuum absorption can be provided in the centers of window regions. Throughout 75 % of the 2500 to 7800 cm-1 spectral range, the Zugspitze results agree within our estimated uncertainty with the widely used MT_CKD 2.5.2 model (Mlawer et al., 2012). In the wings of water vapor absorption bands, our measurements indicate about 2-5 times stronger continuum absorption than MT_CKD, namely in the 2800 to 3000 cm-1 and 4100 to 4200 cm-1 spectral ranges. The measurements are consistent with the laboratory measurements of Mondelain et al. (2015), which rely on cavity ring-down spectroscopy (CDRS), and the calorimetric-interferometric measurements of Bicknell et al. (2006). Compared to the recent FTIR laboratory studies of Ptashnik et al. (2012, 2013), our measurements are consistent within the estimated errors throughout most of the spectral range. However, in the wings of water vapor absorption bands our measurements indicate typically 2-3 times weaker continuum absorption under atmospheric conditions, namely in the 3200 to 3400, 4050 to 4200, and 6950 to 7050 cm-1 spectral regions.

  5. Sensor for headspace pressure and H2O concentration measurements in closed vials by tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Cai, Tingdong; Wang, Guishi; Cao, Zhensong; Zhang, Weijun; Gao, Xiaoming

    2014-07-01

    The concentration of H2O and the pressure in the headspace of vials are simultaneously measured by a tunable diode laser sensor based on absorption spectroscopy techniques. The 7168.437 cm-1 spectral line of H2O is chosen as the sensing transition for its strong absorption strength and being reasonably far away from its neighboring molecular transitions. In order to prevent interference absorption by ambient water vapor in the room air, a difference between the measured signal and the referenced signal is used to calculate the pressure and H2O concentration in the headspace of vials, eliminating the need for inert gas purges and calibration with known gas. The validation of the sensor is conducted in a static vial, yielding an accuracy of 1.23% for pressure and 3.81% for H2O concentration. The sensitivity of the sensor is estimated to be about 2.5 Torr for pressure and 400 ppm for H2O concentration over a 3 cm absorption path length respectively. Accurate measurements for commercial freeze-dried products demonstrate the in-line applications of the sensor for the pharmaceutical industry.

  6. The spectral variability of the GHZ-Peaked spectrum radio source PKS 1718-649 and a comparison of absorption models

    SciTech Connect

    Tingay, S. J.; Macquart, J.-P.; Wayth, R. B.; Trott, C. M.; Emrich, D.; Collier, J. D.; Wong, G. F.; Rees, G.; Stevens, J.; Carretti, E.; Callingham, J. R.; Gaensler, B. M.; McKinley, B.; Briggs, F.; Bernardi, G.; Bowman, J. D.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Goeke, R.; and others

    2015-02-01

    Using the new wideband capabilities of the ATCA, we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked spectrum radio source. The observations, between approximately 1 and 10 GHz over 3 epochs spanning approximately 21 months, reveal variability both above the spectral peak at ∼3 GHz and below the peak. The combination of the low- and high-frequency variability cannot be easily explained using a single absorption mechanism, such as free–free absorption or synchrotron self-absorption. We find that the PKS 1718-649 spectrum and its variability are best explained by variations in the free–free optical depth on our line of sight to the radio source at low frequencies (below the spectral peak) and the adiabatic expansion of the radio source itself at high frequencies (above the spectral peak). The optical depth variations are found to be plausible when X-ray continuum absorption variability seen in samples of active galactic nuclei is considered. We find that the cause of the peaked spectrum in PKS 1718-649 is most likely due to free–free absorption. In agreement with previous studies, we find that the spectrum at each epoch of observation is best fit by a free–free absorption model characterized by a power-law distribution of free–free absorbing clouds. This agreement is extended to frequencies below the 1 GHz lower limit of the ATCA by considering new observations with Parkes at 725 MHz and 199 MHz observations with the newly operational Murchison Widefield Array. These lower frequency observations argue against families of absorption models (both free–free and synchrotron self-absorption) that are based on simple homogenous structures.

  7. Broadband spectroscopy with external cavity quantum cascade lasers beyond conventional absorption measurements.

    PubMed

    Lambrecht, Armin; Pfeifer, Marcel; Konz, Werner; Herbst, Johannes; Axtmann, Felix

    2014-05-01

    Laser spectroscopy is a powerful tool for analyzing small molecules, i.e. in the gas phase. In the mid-infrared spectral region quantum cascade lasers (QCLs) have been established as the most frequently used laser radiation source. Spectroscopy of larger molecules in the gas phase, of complex mixtures, and analysis in the liquid phase requires a broader tuning range and is thus still the domain of Fourier transform infrared (FTIR) spectroscopy. However, the development of tunable external cavity (EC) QCLs is starting to change this situation. The main advantage of QCLs is their high spectral emission power that is enhanced by a factor of 10(4) compared with thermal light sources. Obviously, transmission measurements with EC-QCLs in strongly absorbing samples are feasible, which can hardly be measured by FTIR due to detector noise limitations. We show that the high power of EC-QCLs facilitates spectroscopy beyond simple absorption measurements. Starting from QCL experiments with liquid samples, we show results of fiber evanescent field analysis (FEFA) to detect pesticides in drinking water. FEFA is a special case of attenuated total reflection spectroscopy. Furthermore, powerful CW EC-QCLs enable fast vibrational circular dichroism (VCD) spectroscopy of chiral molecules in the liquid phase - a technique which is very time consuming with standard FTIR equipment. We present results obtained for the chiral compound 1,1'-bi-2-naphthol (BINOL). Finally, powerful CW EC-QCLs enable the application of laser photothermal emission spectroscopy (LPTES). We demonstrate this for a narrowband and broadband absorber in the gas phase. All three techniques have great potential for MIR process analytical applications.

  8. Nocturnal Measurements of HONO by Differential Optical Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wojtal, P.; McLaren, R.

    2011-12-01

    Differential optical absorption spectroscopy (DOAS) was used to quantify the concentration of HONO, NO2 and SO2 in the nocturnal urban atmosphere at York University over a period of one year. These measurements form a comprehensive HONO data set, including a large range of temperatures, relative humidity, surface conditions (snow, water, dry, etc.) and NO2 concentrations. Laboratory studies and observations within the nocturnal boundary layer reported in the literature suggest heterogeneous conversion of NO2 on surface adsorbed water as the major nighttime source of HONO. HONO formation and photolysis is believed to represent a major source term in the hydroxyl radical budget in polluted continental regions. Currently, most air quality models tend to significantly underpredict HONO, caused by the lack of understanding of HONO formation processes and the parameters that affect its concentration. Recently, we reported nocturnal pseudo steady states (PSS) of HONO in an aqueous marine environment and a conceptual model for HONO formation on aqueous surfaces was proposed. The data set collected at York University is being analyzed with a view towards further understanding the nighttime HONO formation mechanism and testing several hypotheses: 1) A HONO PSS can exist during certain times at night in an urban area in which the HONO concentration is independent of NO2, given the surface contains sufficient water coverage and is saturated with nitrogen containing precursors; 2) The concentration of HONO is positively correlated with temperature during periods where a PSS exists; 3) Different conversion efficiencies of NO2 to HONO exist on dry, wet and snow surfaces; 4) HONO formation has a NO2 order dependence between 0 and 2nd order, dependant on NO2 concentration, relative humidity, etc. The data set will be presented along with statistical analysis that sheds new light on the source of HONO in urban areas at night.

  9. Spectrally Consistent Scattering, Absorption, and Polarization Properties of Atmospheric Ice Crystals at Wavelengths from 0.2 to 100 um

    NASA Technical Reports Server (NTRS)

    Yang, Ping; Bi, Lei; Baum, Bryan A.; Liou, Kuo-Nan; Kattawar, George W.; Mishchenko, Michael I.; Cole, Benjamin

    2013-01-01

    A data library is developed containing the scattering, absorption, and polarization properties of ice particles in the spectral range from 0.2 to 100 microns. The properties are computed based on a combination of the Amsterdam discrete dipole approximation (ADDA), the T-matrix method, and the improved geometric optics method (IGOM). The electromagnetic edge effect is incorporated into the extinction and absorption efficiencies computed from the IGOM. A full set of single-scattering properties is provided by considering three-dimensional random orientations for 11 ice crystal habits: droxtals, prolate spheroids, oblate spheroids, solid and hollow columns, compact aggregates composed of eight solid columns, hexagonal plates, small spatial aggregates composed of 5 plates, large spatial aggregates composed of 10 plates, and solid and hollow bullet rosettes. The maximum dimension of each habit ranges from 2 to 10,000 microns in 189 discrete sizes. For each ice crystal habit, three surface roughness conditions (i.e., smooth, moderately roughened, and severely roughened) are considered to account for the surface texture of large particles in the IGOM applicable domain. The data library contains the extinction efficiency, single-scattering albedo, asymmetry parameter, six independent nonzero elements of the phase matrix (P11, P12, P22, P33, P43, and P44), particle projected area, and particle volume to provide the basic single-scattering properties for remote sensing applications and radiative transfer simulations involving ice clouds. Furthermore, a comparison of satellite observations and theoretical simulations for the polarization characteristics of ice clouds demonstrates that ice cloud optical models assuming severely roughened ice crystals significantly outperform their counterparts assuming smooth ice crystals.

  10. Application of independent component analysis method in real-time spectral analysis of gaseous mixtures for acousto-optical spectrometers based on differential optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Fadeyev, A. V.; Pozhar, V. E.

    2012-10-01

    It is discussed the reliability problem of time-optimized method for remote optical spectral analysis of gas-polluted ambient air. The method based on differential optical absorption spectroscopy (DOAS) enables fragmentary spectrum registration (FSR) and is suitable for random-spectral-access (RSA) optical spectrometers like acousto-optical (AO) ones. Here, it is proposed the algorithm based on statistical method of independent component analysis (ICA) for estimation of a correctness of absorption spectral lines selection for FSR-method. Implementations of ICA method for RSA-based real-time adaptive systems are considered. Numerical simulations are presented with use of real spectra detected by the trace gas monitoring system GAOS based on AO spectrometer.

  11. Experimental recovery of intrinsic fluorescence and fluorophore concentration in the presence of hemoglobin: spectral effect of scattering and absorption on fluorescence

    NASA Astrophysics Data System (ADS)

    Du Le, Vinh Nguyen; Patterson, Michael S.; Farrell, Thomas J.; Hayward, Joseph E.; Fang, Qiyin

    2015-12-01

    The ability to recover the intrinsic fluorescence of biological fluorophores is crucial to accurately identify the fluorophores and quantify their concentrations in the media. Although some studies have successfully retrieved the fluorescence spectral shape of known fluorophores, the techniques usually came with heavy computation costs and did not apply for strongly absorptive media, and the intrinsic fluorescence intensity and fluorophore concentration were not recovered. In this communication, an experimental approach was presented to recover intrinsic fluorescence and concentration of fluorescein in the presence of hemoglobin (Hb). The results indicated that the method was efficient in recovering the intrinsic fluorescence peak and fluorophore concentration with an error of 3% and 10%, respectively. The results also suggested that chromophores with irregular absorption spectra (e.g., Hb) have more profound effects on fluorescence spectral shape than chromophores with monotonic absorption and scattering spectra (e.g., black India ink and polystyrene microspheres).

  12. Theoretical computation of trace gases retrieval random error from measurements of high spectral resolution infrared sounder

    NASA Technical Reports Server (NTRS)

    Huang, Hung-Lung; Smith, William L.; Woolf, Harold M.; Theriault, J. M.

    1991-01-01

    The purpose of this paper is to demonstrate the trace gas profiling capabilities of future passive high spectral resolution (1 cm(exp -1) or better) infrared (600 to 2700 cm(exp -1)) satellite tropospheric sounders. These sounders, such as the grating spectrometer, Atmospheric InfRared Sounders (AIRS) (Chahine et al., 1990) and the interferometer, GOES High Resolution Interferometer Sounder (GHIS), (Smith et al., 1991) can provide these unique infrared spectra which enable us to conduct this analysis. In this calculation only the total random retrieval error component is presented. The systematic error components contributed by the forward and inverse model error are not considered (subject of further studies). The total random errors, which are composed of null space error (vertical resolution component error) and measurement error (instrument noise component error), are computed by assuming one wavenumber spectral resolution with wavenumber span from 1100 cm(exp -1) to 2300 cm(exp -1) (the band 600 cm(exp -1) to 1100 cm(exp -1) is not used since there is no major absorption of our three gases here) and measurement noise of 0.25 degree at reference temperature of 260 degree K. Temperature, water vapor, ozone and mixing ratio profiles of nitrous oxide, carbon monoxide and methane are taken from 1976 US Standard Atmosphere conditions (a FASCODE model). Covariance matrices of the gases are 'subjectively' generated by assuming 50 percent standard deviation of gaussian perturbation with respect to their US Standard model profiles. Minimum information and maximum likelihood retrieval solutions are used.

  13. Acousto-optic differential optical absorption spectroscopy for atmospheric measurement of nitrogen dioxide in Hong Kong.

    PubMed

    Cheng, Andrew Y S; Chan, M H

    2004-12-01

    Measurement of the atmospheric concentration of nitrogen dioxide (NO(2)) pollutant was demonstrated by differential optical absorption spectroscopy (DOAS) using a visible acousto-optic tunable filter. In a traditional spectral scanning DOAS system for atmospheric concentration monitoring, a highly stable light source is required. When the light intensity fluctuates during scanning, the concentration retrieval will be inaccurate. In order to reduce the error due to intensity fluctuations, a modified DOAS system has been developed by introducing a broadband light intensity monitoring channel. Using the measured intensity of the broadband channel as the intensity of the light source, the spectrum can be de-biased and the residual intensity variation will primarily result from atmospheric extinction. In addition, by employing the lock-in detection technique, the background light interference is also removed in the modified DOAS system. The atmospheric NO(2) concentration measurement was performed at the campus of City University of Hong Kong, and the results were compared with the concentration reported from a nearby monitoring station in Sham Shui Po, operated by the Hong Kong Environmental Protection Department.

  14. Lanthanides and other spectral oddities in a Centauri. Ce III, Nd III, Kr II, and broad absorption features

    NASA Astrophysics Data System (ADS)

    Cowley, C. R.; Hubrig, S.; González, J. F.

    2010-11-01

    Context. There is considerable interest in the helium variable a Cen as a bridge between helium-weak and helium-strong CP stars. Aims: We investigate Ce iii and other possible lanthanides in the spectrum the of hottest chemically peculiar (CP) star in which these elements have been found. A Kr ii line appears within a broad absorption which we suggest may be due to a high-level transition in C ii. Methods: Wavelengths and equivalent widths are measured on high-resolution UVES spectra, analyzed, and their phase-variations investigated. Results: New, robust identifications of Ce iii and Kr ii are demonstrated. Nd iii is likely present. A broad absorption near λ4619 is present at all phases of a Cen, and in some other early B stars. Conclusions: The presence of lanthanides in a Cen strengthens the view that this star is a significant link between the cooler CP stars and the hotter helium-peculiar stars. Broad absorptions in a Cen are not well explained. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO programmes 65.L-0316(A), 073.D-0504(A), and 076.B-0055(A)).

  15. Nanodisplacement measurement using spectral shifts in a white-light interferometer.

    PubMed

    Brundavanam, Maruthi M; Viswanathan, Nirmal K; Rao, D Narayana

    2008-12-01

    We report a novel experimental method to measure nanometer displacements using wavelength shifts of spectral peaks around spectral switch or singular phase points in the interference spectra due to temporal correlation in a Michelson interferometer illuminated by a broadband white-light source. Dramatic changes in the spectral characteristics are recorded as a function of path difference between the interfering beams around the spectral switch position. These are then compared with measurements far from it in order to demonstrate the higher sensitivities involved in the proposed method.

  16. Airborne spectral measurements of surface-atmosphere anisotropy during the SCAR-A, Kuwait oil fire, and TARFOX experiments

    NASA Astrophysics Data System (ADS)

    Soulen, Peter F.; King, Michael D.; Tsay, Si-Chee; Arnold, G. Thomas; Li, Jason Y.

    2000-04-01

    During the SCAR-A, Kuwait Oil Fire Smoke Experiment, and TARFOX deployments, angular distributions of spectral reflectance for various surfaces were measured using the scanning Cloud Absorption Radiometer (CAR) mounted on the nose of the University of Washington C-131A research aircraft. The CAR contains 13 narrowband spectral channels between 0.47 and 2.3 μm with a 190° scan aperture (5° before zenith to 5° past nadir) and 1° instantaneous field of view. The bidirectional reflectance is obtained by flying a clockwise circular orbit above the surface, resulting in a ground track approximately 3 km in diameter within about 2 min. Spectral bidirectional reflectances of four surfaces are presented: the Great Dismal Swamp in Virginia with overlying haze layer, the Saudi Arabian Desert and the Persian Gulf in the Middle East, and the Atlantic Ocean measured east of Richmond, Virginia. Although the CAR measurements are contaminated by atmospheric effects, results show distinct spectral characteristics for various types of surface-atmosphere systems, including hot spots, limb brightening and darkening, and Sun glint. In addition, the hemispherical albedo of each surface-atmosphere system is calculated directly by integrating over all high angular-resolution CAR measurements for each spectral channel. Comparing the nadir reflectance with the overall hemispherical albedo of each surface, we find that using nadir reflectances as a surrogate for hemispherical albedo can cause albedos to be underestimated by as much as 95% and overestimated by up to 160%, depending on the type of surface and solar zenith angle.

  17. Measurements of the Absorption by Auditorium SEATING—A Model Study

    NASA Astrophysics Data System (ADS)

    BARRON, M.; COLEMAN, S.

    2001-01-01

    One of several problems with seat absorption is that only small numbers of seats can be tested in standard reverberation chambers. One method proposed for reverberation chamber measurements involves extrapolation when the absorption coefficient results are applied to actual auditoria. Model seat measurements in an effectively large model reverberation chamber have allowed the validity of this extrapolation to be checked. The alternative barrier method for reverberation chamber measurements was also tested and the two methods were compared. The effect on the absorption of row-row spacing as well as absorption by small numbers of seating rows was also investigated with model seats.

  18. On the errors in measuring the particle density by the light absorption method

    SciTech Connect

    Ochkin, V. N.

    2015-04-15

    The accuracy of absorption measurements of the density of particles in a given quantum state as a function of the light absorption coefficient is analyzed. Errors caused by the finite accuracy in measuring the intensity of the light passing through a medium in the presence of different types of noise in the recorded signal are considered. Optimal values of the absorption coefficient and the factors capable of multiplying errors when deviating from these values are determined.

  19. Technical progress report: Completion of spectral rotating shadowband radiometers and analysis of atmospheric radiation measurement spectral shortwave data

    SciTech Connect

    Michalsky, J.; Harrison, L.

    1996-04-01

    Our goal in the Atmospheric Radiation Measurement (ARM) Program is the improvement of radiation models used in general circulation models (GCMs), especially in the shortwave, (1) by providing improved shortwave radiometric measurements for the testing of models and (2) by developing methods for retrieving climatologically sensitive parameters that serve as input to shortwave and longwave models. At the Atmospheric Sciences Research Center (ASRC) in Albany, New York, we are acquiring downwelling direct and diffuse spectral irradiance, at six wavelengths, plus downwelling broadband longwave, and upwelling and downwelling broadband shortwave irradiances that we combine with National Weather Service surface and upper air data from the Albany airport as a test data set for ARM modelers. We have also developed algorithms to improve shortwave measurements made at the Southern Great Plains (SGP) ARM site by standard thermopile instruments and by the multifilter rotating shadowband radiometer (MFRSR) based on these Albany data sets. Much time has been spent developing techniques to retrieve column aerosol, water vapor, and ozone from the direct beam spectral measurements of the MFRSR. Additionally, we have had success in calculating shortwave surface albedo and aerosol optical depth from the ratio of direct to diffuse spectral reflectance.

  20. Measurements of the absorption cross section of (13)CHO(13)CHO at visible wavelengths and application to DOAS retrievals.

    PubMed

    Goss, Natasha R; Waxman, Eleanor M; Coburn, Sean C; Koenig, Theodore K; Thalman, Ryan; Dommen, Josef; Hannigan, James W; Tyndall, Geoffrey S; Volkamer, Rainer

    2015-05-14

    The trace gas glyoxal (CHOCHO) forms from the atmospheric oxidation of hydrocarbons and is a precursor to secondary organic aerosol. We have measured the absorption cross section of disubstituted (13)CHO(13)CHO ((13)C glyoxal) at moderately high (1 cm(-1)) optical resolution between 21 280 and 23 260 cm(-1) (430-470 nm). The isotopic shifts in the position of absorption features were found to be largest near 455 nm (Δν = 14 cm(-1); Δλ = 0.29 nm), whereas no significant shifts were observed near 440 nm (Δν < 0.5 cm(-1); Δλ < 0.01 nm). These shifts are used to investigate the selective detection of (12)C glyoxal (natural isotope abundance) and (13)C glyoxal by in situ cavity enhanced differential optical absorption spectroscopy (CE-DOAS) in a series of sensitivity tests using synthetic spectra, and laboratory measurements of mixtures containing (12)C and (13)C glyoxal, nitrogen dioxide, and other interfering absorbers. We find the changes in apparent spectral band shapes remain significant at the moderately high optical resolution typical of CE-DOAS (0.55 nm fwhm). CE-DOAS allows for the selective online detection of both isotopes with detection limits of ∼200 pptv (1 pptv = 10(-12) volume mixing ratio), and sensitivity toward total glyoxal of few pptv. The (13)C absorption cross section is available for download from the Supporting Information. PMID:25551419

  1. Fiber laser based high-spectral resolution lidar for earth science measurements

    NASA Astrophysics Data System (ADS)

    Chen, Youming; Berkoff, Timothy; Kimpel, Frank; Storm, Mark; Hoff, Raymond; Gupta, Shantanu

    2013-03-01

    We present a special high spectral resolution lidar (HSRL) by using a novel tunable fiber based transmitter. The transmitter can produce 50μJ pulse energy at 1064nm and >25μJ pulse energy at 532nm with 10 kHz repetition rate, 5ns pulse width, respectively. A key advantage of the transmitter is the frequency-tunability. The laser can be tuned over the Iodine absorption lines from 1111 to 1104. The laser has a ~130MHz linewidth at 1064nm close to the transform limit linewidth ~ 88MHz for a pulse width of 5ns. Even though it was not frequency locked, the laser has very good frequency stability, which is on the order of ~200MHz over minutes. The beam quality M2 is less than 1.5. All the preliminary transmitter parameters meet the basic requirements of a HSRL. The transmitter was implemented in UMBC's lidar lab that includes a ceiling hatch to enable vertical propagation and viewing of transmitted laser beams into the atmosphere. The atmospheric measurement demonstrates good agreement of the signal to the model Rayleigh decay over the profile range with no significant deviations. Most importantly, these results show that the measurement successfully suppresses the Mie scattering from clouds while recovering the full molecular signal as expected.

  2. Evaluation of bio-optical inversion of spectral irradiance measured from an autonomous underwater vehicle

    NASA Astrophysics Data System (ADS)

    Moline, Mark A.; Robbins, Ian; Zelenke, Brian; Pegau, W. Scott; Wijesekera, Hemantha

    2012-07-01

    Autonomous underwater vehicles (AUVs) can map water conditions at high spatial (horizontal and vertical) and temporal resolution, including under cloudy conditions when satellite and airborne remote sensing are not feasible. As part of the RADYO program, we deployed a passive radiometer on an AUV in the Santa Barbara Channel and off the coast of Hawaii to apply existing bio-optical algorithms for characterizing the optical constituents of coastal seawater (i.e., dissolved organic material, algal biomass, and other particles). The spectral differences between attenuation coefficients were computed from ratios of downwelling irradiance measured at depth and used to provide estimates of the in-water optical constituents. There was generally good agreement between derived values of absorption and concurrent measurements of this inherent optical property in Santa Barbara Channel. Wave focusing, cloud cover, and low attenuation coefficients influenced results off the coast of Hawaii and are used to evaluate the larger-scale application of these methods in the near surface coastal oceans.

  3. Recent advances in measurement of the water vapour continuum in the far-infrared spectral region.

    PubMed

    Green, Paul D; Newman, Stuart M; Beeby, Ralph J; Murray, Jonathan E; Pickering, Juliet C; Harries, John E

    2012-06-13

    We present a new derivation of the foreign-broadened water vapour continuum in the far-infrared (far-IR) pure rotation band between 24 μm and 120 μm (85-420 cm(-1)) from field data collected in flight campaigns of the Continuum Absorption by Visible and IR radiation and Atmospheric Relevance (CAVIAR) project with Imperial College's Tropospheric Airborne Fourier Transform Spectrometer (TAFTS) far-IR spectro-radiometer instrument onboard the Facility for Airborne Atmospheric Measurement (FAAM) BAe-146 research aircraft; and compare this new derivation with those recently published in the literature in this spectral band. This new dataset validates the current Mlawer-Tobin-Clough-Kneizys-Davies (MT-CKD) 2.5 model parametrization above 300 cm(-1), but indicates the need to strengthen the parametrization below 300 cm(-1), by up to 50 per cent at 100 cm(-1). Data recorded at a number of flight altitudes have allowed measurements within a wide range of column water vapour environments, greatly increasing the sensitivity of this analysis to the continuum strength.

  4. Spectral-Domain Measurements of Birefringence and Sensing Characteristics of a Side-Hole Microstructured Fiber

    PubMed Central

    Hlubina, Petr; Martynkien, Tadeusz; Olszewski, Jacek; Mergo, Pawel; Makara, Mariusz; Poturaj, Krzysztof; Urbańczyk, Waclaw

    2013-01-01

    We experimentally characterized a birefringent side-hole microstructured fiber in the visible wavelength region. The spectral dependence of the group and phase modal birefringence was measured using the methods of spectral interferometry. The phase modal birefringence of the investigated fiber increases with wavelength, but its positive sign is opposite to the sign of the group modal birefringence. We also measured the sensing characteristics of the fiber using a method of tandem spectral interferometry. Spectral interferograms corresponding to different values of a physical parameter were processed to retrieve the spectral phase functions and to determine the spectral dependence of polarimetric sensitivity to strain, temperature and hydrostatic pressure. A negative sign of the polarimetric sensitivity was deduced from the simulation results utilizing the known modal birefringence dispersion of the fiber. Our experimental results show that the investigated fiber has a very high polarimetric sensitivity to hydrostatic pressure, reaching −200 rad × MPa−1× m−1 at 750 nm. PMID:23989824

  5. Versatile chromatic dispersion measurement of a single mode fiber using spectral white light interferometry.

    PubMed

    Lee, Ji Yong; Kim, Dug Young

    2006-11-27

    We present a versatile and accurate chromatic dispersion measurement method for single mode optical fibers over a wide spectral range (200 nm) using a spectral domain white light interferometer. This technique is based on spectral interferometry with a Mach-Zehnder interferometer setup and a broad band light source. It takes less than a second to obtain a spectral interferogram for a few tens of centimeter length fiber sample. We have demonstrated that the relative group velocity, the chromatic dispersion and the dispersion slope of a sample fiber can be obtained very accurately regardless of the zero-dispersion wavelength (ZDW) of a sample after frequency dependent optical phase was directly retrieved from a spectral interferogram. The measured results with our proposed method were compared with those obtained with a conventional time-domain dispersion measurement method. A good agreement between those results indicates that our proposed method can measure the chromatic dispersion of a short length optical fiber with very high accuracy.

  6. Study on the key technology of spectral reflectance reconstruction based on the weighted measurement matrix

    NASA Astrophysics Data System (ADS)

    Leihong, Zhang; Bei, Li; Dong, Liang; Xiuhua, Ma

    2016-07-01

    In order to reconstruct the spectral reflectance accurately, a new method of spectral reflectance reconstruction based on the weighted measurement matrix is proposed in this paper. By optimizing the measurement matrix between spectral reflectance and the response of a camera, the method can improve the reconstruction accuracy. The new method is a combination of three kinds of common reflectance reconstruction methods, which are the pseudo inverse method, the Wiener estimation method and the principal component analysis method. The new measurement matrix can be achieved after weighting the measurement matrices of these three methods to reconstruct the spectral reflectance. What is more, the weights of the three methods can be obtained by minimizing the color difference. Results show that the CIE1976 color difference and RMSE value of the weighted reconstructed spectra are less than that of three common reconstruction methods. The spectral matching accuracy GFC of the method is higher than 0.99 and its reconstruction accuracy is high.

  7. Airborne Laser Absorption Spectrometer Measurements of CO2 Column Mixing Ratios: Source and Sink Detection in the Atmospheric Environment

    NASA Astrophysics Data System (ADS)

    Menzies, Robert T.; Spiers, Gary D.; Jacob, Joseph C.

    2016-06-01

    The JPL airborne Laser Absorption Spectrometer instrument has been flown several times in the 2007-2011 time frame for the purpose of measuring CO2 mixing ratios in the lower atmosphere. The four most recent flight campaigns were on the NASA DC-8 research aircraft, in support of the NASA ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons) mission formulation studies. This instrument operates in the 2.05-μm spectral region. The Integrated Path Differential Absorption (IPDA) method is used to retrieve weighted CO2 column mixing ratios. We present key features of the CO2LAS signal processing, data analysis, and the calibration/validation methodology. Results from flights in various U.S. locations during the past three years include observed mid-day CO2 drawdown in the Midwest, also cases of point-source and regional plume detection that enable the calculation of emission rates.

  8. New High-Resolution Absorption Cross-Section Measurements of HCFC-142B in the Mid-Ir

    NASA Astrophysics Data System (ADS)

    Le Bris, Karine; Strong, Kimberly; Melo, Stella

    2009-06-01

    HCFC-142b (1-chloro-1,1-difluoroethane) is a temporary substitute for ozone-depleting chlorofluorocarbons (CFCs). However, due to its high absorption cross-sections in the mid-IR, HCFC-142b is also a highly potent greenhouse gas, now detectable from space by satellite missions. So far, the accuracy of the retrieval has been limited by the lack of reference data in a range of temperatures compatible with atmospheric observations. We present new absorption cross section measurements of HCFC-142b at high-resolution (0.02 cm^{-1}) from 223 K to 283 K in the 600 cm^{-1}- 4000 cm^{-1} spectral window. The composite spectra are calculated for each temperature from a set of acquisitions at different pressures by Fourier transform spectroscopy.

  9. Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

    2014-06-01

    The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm-1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.

  10. Measuring the Spectral Expression of Carbon Dioxide in the Solar Reflected Spectrum with AVIRIS

    NASA Technical Reports Server (NTRS)

    Green, Robert O.

    2001-01-01

    Carbon dioxide is a low-concentration, but important, component of the Earth's atmosphere. This gas absorbs electromagnetic radiation (EMR) in several regions of the spectrum. Absorption of energy by carbon dioxide adds heat to the atmosphere. In the world today, the burning of fossil fuels and other anthropogenic processes adds carbon dioxide to the atmosphere. Other natural processes in the Earth's system both add and remove carbon dioxide. Overall, measurements of atmospheric carbon dioxide at selected sites around the globe show an increased carbon dioxide concentration in the atmosphere. A figure shows the measured carbon dioxide from Mauna Loa, Hawaii, from 1958 to 2000. Overall, the concentration has increased from 315 to 365 ppm at this site over this period. (There is also a yearly cycle to the concentration that is timed with and hypothesized to be related to the vegetation growing season in the Northern Hemisphere.) The overall expected effect of this increase of atmospheric carbon dioxide is trapping of heat in the atmosphere and global warming. While this overall relationship between carbon dioxide and global warming seems straightforward, many of the specific details relating to regional and local sources and sinks and gradients of carbon dioxide are not well understood. A remote sensing capability to measure carbon dioxide could provide important inputs for scientific research to better understand the distribution and change in atmospheric carbon dioxide at detailed spatial and temporal levels. In pursuit of this remote sensing of carbon dioxide objective, this paper analyzes the expression of carbon dioxide in the spectral range measured by the Airborne Visible/Infrared Imagery Spectrometer (AVIRIS). Based on these analyses, a spectral-fitting algorithm that uses AVIRIS measured spectra and MODTRAN radiative-transfer code modeled spectra to derive total column carbon dioxide abundance has been developed. This algorithm has been applied to an AVIRIS

  11. Airborne Measurements of CO2 Column Absorption and Range Using a Pulsed Direct-Detection Integrated Path Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Weaver, Clark J.; Mao, Jianping; Allan, Graham R.; Hasselbrack, William E.; Browell, Edward V.

    2013-01-01

    We report on airborne CO2 column absorption measurements made in 2009 with a pulsed direct-detection lidar operating at 1572.33 nm and utilizing the integrated path differential absorption technique. We demonstrated these at different altitudes from an aircraft in July and August in flights over four locations in the central and eastern United States. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The lidar measurement statistics were also calculated for each flight as a function of altitude. The optical depth varied nearly linearly with altitude, consistent with calculations based on atmospheric models. The scatter in the optical depth measurements varied with aircraft altitude as expected, and the median measurement precisions for the column varied from 0.9 to 1.2 ppm. The altitude range with the lowest scatter was 810 km, and the majority of measurements for the column within it had precisions between 0.2 and 0.9 ppm.

  12. Spectral emissivity measurements of land-surface materials and related radiative transfer simulations

    NASA Technical Reports Server (NTRS)

    Wan, Z.; Ng, D.; Dozier, J.

    1994-01-01

    Spectral radiance measurements have been made in the laboratory and in the field for deriving spectral emissivities of some land cover samples with a spectroradiometer and an auxiliary radiation source in the wavelength range 2.5-14.5 micrometers. A easy and quick four-step method (four steps to measure the sample and a diffuse reflecting plate surface under sunshine and shadowing conditions, respectively) has been used for simultaneous determination of surface temperature and emissivity. We emphasized in-situ measurements in combination with radiative transfer simulations, and an error analysis for basic assumptions in deriving spectral emissivity of land-surface samples from thermal infrared measurements.

  13. Autocorrelation measurement of femtosecond laser pulses based on two-photon absorption in GaP photodiode

    SciTech Connect

    Chong, E. Z.; Watson, T. F.; Festy, F.

    2014-08-11

    Semiconductor materials which exhibit two-photon absorption characteristic within a spectral region of interest can be useful in building an ultra-compact interferometric autocorrelator. In this paper, we report on the evidence of a nonlinear absorption process in GaP photodiodes which was exploited to measure the temporal profile of femtosecond Ti:sapphire laser pulses with a tunable peak wavelength above 680 nm. The two-photon mediated conductivity measurements were performed at an average laser power of less than a few tenths of milliwatts. Its suitability as a single detector in a broadband autocorrelator setup was assessed by investigating the nonlinear spectral sensitivity bandwidth of a GaP photodiode. The highly favourable nonlinear response was found to cover the entire tuning range of our Ti:sapphire laser and can potentially be extended to wavelengths below 680 nm. We also demonstrated the flexibility of GaP in determining the optimum compensation value of the group delay dispersion required to restore the positively chirped pulses inherent in our experimental optical system to the shortest pulse width possible. With the rise in the popularity of nonlinear microscopy, the broad two-photon response of GaP and the simplicity of this technique can provide an alternative way of measuring the excitation laser pulse duration at the focal point of any microscopy systems.

  14. Biomass Burning Aerosol Absorption Measurements with MODIS Using the Critical Reflectance Method

    NASA Technical Reports Server (NTRS)

    Zhu, Li; Martins, Vanderlei J.; Remer, Lorraine A.

    2010-01-01

    This research uses the critical reflectance technique, a space-based remote sensing method, to measure the spatial distribution of aerosol absorption properties over land. Choosing two regions dominated by biomass burning aerosols, a series of sensitivity studies were undertaken to analyze the potential limitations of this method for the type of aerosol to be encountered in the selected study areas, and to show that the retrieved results are relatively insensitive to uncertainties in the assumptions used in the retrieval of smoke aerosol. The critical reflectance technique is then applied to Moderate Resolution Imaging Spectrometer (MODIS) data to retrieve the spectral aerosol single scattering albedo (SSA) in South African and South American 35 biomass burning events. The retrieved results were validated with collocated Aerosol Robotic Network (AERONET) retrievals. One standard deviation of mean MODIS retrievals match AERONET products to within 0.03, the magnitude of the AERONET uncertainty. The overlap of the two retrievals increases to 88%, allowing for measurement variance in the MODIS retrievals as well. The ensemble average of MODIS-derived SSA for the Amazon forest station is 0.92 at 670 nm, and 0.84-0.89 for the southern African savanna stations. The critical reflectance technique allows evaluation of the spatial variability of SSA, and shows that SSA in South America exhibits higher spatial variation than in South Africa. The accuracy of the retrieved aerosol SSA from MODIS data indicates that this product can help to better understand 44 how aerosols affect the regional and global climate.

  15. Measurement of the absorption coefficient of acoustical materials using the sound intensity method

    NASA Technical Reports Server (NTRS)

    Atwal, Mahabir S.; Crocker, Malcolm J.

    1987-01-01

    In this study the possibility of using the two-microphone sound intensity technique to measure the normal incidence and the random incidence sound absorption coefficient was investigated. The normal incidence absorption coefficient was determined by measuring the intensity incidence on the sample and the intensity reflected by the sample placed in an anechoic chamber. The random incidence absorption coefficient was determined by measuring the intensity incident on the sample and the intensity reflected by the sample placed in a reverberation chamber. Absorption coefficient results obtained by the sound intensity technique were compared with standard techniques, namely the reverberation chamber and the standing wave tube. The major advantages of using the sound intensity technique are that it permits 'in situ' measurements and the absorption coefficient for a large range of frequencies can be obtained from a single measurement.

  16. Characterization of structure and properties of bone by spectral measure method.

    PubMed

    Cherkaev, Elena; Bonifasi-Lista, Carlos

    2011-01-11

    Novel mathematical method called spectral measure method (SMM) is developed for characterization of bone structure and indirect estimation of bone properties. The spectral measure method is based on an inverse homogenization technique which allows to derive information about the structure of composite material from measured effective electric or viscoelastic properties. The mechanical properties and ability to withstand fracture depend on the structural organization of bone as a hierarchical composite. Information about the bone structural parameters is contained in the spectral measure in the Stieltjes integral representation of the effective properties. The method is based on constructing the spectral measure either by calculating it directly from micro-CT images or using measurements of electric or viscoelastic properties over a frequency range. In the present paper, we generalize the Stieltjes representation to the viscoelastic case and show how bone microstructure, in particular, bone volume or porosity, can be characterized by the spectral function calculated using measurements of complex permittivity or viscoelastic modulus. For validation purposes, we numerically simulated measured data using micro-CT images of cancellous bone. Recovered values of bone porosity are in excellent agreement with true porosity estimated from the micro-CT images. We also discuss another application of this method, which allows to estimate properties difficult to measure directly. The spectral measure method based on the derived Stieltjes representation for viscoelastic composites, has a potential for non-invasive characterization of bone structure using electric or mechanical measurements. The method is applicable to sea ice, porous rock, and other composite materials.

  17. Potential of optical spectral transmission measurements for joint inflammation measurements in rheumatoid arthritis patients

    NASA Astrophysics Data System (ADS)

    Meier, A. J. Louise; Rensen, Wouter H. J.; de Bokx, Pieter K.; de Nijs, Ron N. J.

    2012-08-01

    Frequent monitoring of rheumatoid arthritis (RA) patients enables timely treatment adjustments and improved outcomes. Currently this is not feasible due to a shortage of rheumatologists. An optical spectral transmission device is presented for objective assessment of joint inflammation in RA patients, while improving diagnostic accuracy and clinical workflow. A cross-sectional, nonrandomized observational study was performed with this device. In the study, 77 proximal interphalangeal (PIP) joints in 67 patients have been analyzed. Inflammation of these PIP joints was also assessed by a rheumatologist with a score varying from 1 (not inflamed) to 5 (severely inflamed). Out of 77 measurements, 27 were performed in moderate to strongly inflamed PIP joints. Comparison between the clinical assessment and an optical measurement showed a correlation coefficient r=0.63, p<0.001, 95% CI [0.47, 0.75], and a ROC curve (AUC=0.88) that shows a relative good specificity and sensitivity. Optical spectral transmission measurements in a single joint correlate with clinical assessment of joint inflammation, and therefore might be useful in monitoring joint inflammation in RA patients.

  18. Chirp measurement of large-bandwidth femtosecond optical pulses using two-photon absorption

    NASA Astrophysics Data System (ADS)

    Albrecht, T. F.; Seibert, K.; Kurz, H.

    1991-08-01

    We describe a novel method for accurate chirp measurement of broadband femtosecond pulses over their entire bandwidth based on two-photon absorption. These chirp measurements are applied for the optimization of a fiber-grating-prism pulse compressor.

  19. Spectral Measurement of Watershed Coefficients in the Southern Great Plains

    NASA Technical Reports Server (NTRS)

    Blanchard, B. J. (Principal Investigator); Bausch, W.

    1978-01-01

    The author has identified the following significant results. It was apparent that the spectra calibration of runoff curve numbers cannot be achieved on watersheds where significant areas of timber were within the drainage area. The absorption of light by wet soil conditions restricts differentiation of watersheds with regard to watershed runoff curve numbers. It appeared that the predominant factor influencing the classification of watershed runoff curve numbers was the difference in soil color and its associated reflectance when dry. In regions where vegetation grown throughout the year, where wet surface conditions prevail or where watersheds are timbered, there is little hope of classifying runoff potential with visible light alone.

  20. Measurements of the infrared absorption cross-sections of HCFC-141b (CH3CFCl2)

    NASA Astrophysics Data System (ADS)

    Le Bris, Karine; McDowell, James; Strong, Kimberly

    2012-10-01

    Detection of atmospheric trace gases by optical remote sensing techniques relies on the availability of molecular absorption spectra over a range of relevant temperatures. Absorption cross-sections of a pure vapour of the hydrochlorofluorocarbon HCFC-141b are reported at a resolution of 0.02 cm-1 for a range of temperatures between 223 and 283 K and a spectral range of 570-3100 cm-1. The integrated intensities of the nine main harmonic bands compare well with the data available from previous experimental studies and with theoretical calculations by ab initio and density functional theories.

  1. Preliminary measurements of spectral signatures of tropical and temperate plants in the thermal infrared

    NASA Technical Reports Server (NTRS)

    Salisbury, John W.; Milton, N. M.

    1987-01-01

    Spectral reflectance measurements of seven tropical species and six deciduous species were carried out in thermal infrared to establish the species-dependent spectral characteristics and to investigate the effect on spectral signatures of environmental variables, such as leaf maturity, drought, and metal stress. Seasonal variations of spectral signatures occurred between spring and summer leaves, but such variations were minimal during summer and early fall. Overall reflectance of senescent leaves was higher than that of young leaves, as was the reflectance of leaves from trees growing in metal-enriched soils, as compared with leaves from the control area. However, the characteristic spectral features were not changed in either case. It was also found that water stress did not have any effect on the infrared signatures: trees grown during a drought season maintained their characteristic spectral signatures.

  2. Confocal absorption spectral imaging of MoS2: optical transitions depending on the atomic thickness of intrinsic and chemically doped MoS2.

    PubMed

    Dhakal, Krishna P; Duong, Dinh Loc; Lee, Jubok; Nam, Honggi; Kim, Minsu; Kan, Min; Lee, Young Hee; Kim, Jeongyong

    2014-11-01

    We performed a nanoscale confocal absorption spectral imaging to obtain the full absorption spectra (over the range 1.5-3.2 eV) within regions having different numbers of layers and studied the variation of optical transition depending on the atomic thickness of the MoS2 film. Three distinct absorption bands corresponding to A and B excitons and a high-energy background (BG) peak at 2.84 eV displayed a gradual redshift as the MoS2 film thickness increased from the monolayer, to the bilayer, to the bulk MoS2 and this shift was attributed to the reduction of the gap energy in the Brillouin zone at the K-point as the atomic thickness increased. We also performed n-type chemical doping of MoS2 films using reduced benzyl viologen (BV) and the confocal absorption spectra modified by the doping showed a strong dependence on the atomic thickness: A and B exciton peaks were greatly quenched in the monolayer MoS2 while much less effect was shown in larger thickness and the BG peak either showed very small quenching for 1 L MoS2 or remained constant for larger thicknesses. Our results indicate that confocal absorption spectral imaging can provide comprehensive information on optical transitions of microscopic size intrinsic and doped two-dimensional layered materials.

  3. Black carbon and wavelength-dependent aerosol absorption in the North China Plain based on two-year aethalometer measurements

    NASA Astrophysics Data System (ADS)

    Ran, L.; Deng, Z. Z.; Wang, P. C.; Xia, X. A.

    2016-10-01

    Light-absorbing components of atmospheric aerosols have gained particular attention in recent years due to their climatic and environmental effects. Based on two-year measurements of aerosol absorption at seven wavelengths, aerosol absorption properties and black carbon (BC) were investigated in the North China Plain (NCP), one of the most densely populated and polluted regions in the world. Aerosol absorption was stronger in fall and the heating season (from November to March) than in spring and summer at all seven wavelengths. Similar spectral dependence of aerosol absorption was observed in non-heating seasons despite substantially strong absorption in fall. With an average absorption Angström exponent (α) of 1.36 in non-heating seasons, freshly emitted BC from local fossil fuel burning was thought to be the major component of light-absorbing aerosols. In the heating season, strong ultraviolet absorption led to an average α of 1.81, clearly indicating the importance of non-BC light-absorbing components, which were possibly from coal burning for domestic heating and aging processes on a regional scale. Diurnally, the variation of BC mass concentrations experienced a double-peak pattern with a higher level at night throughout the year. However, the diurnal cycle of α in the heating season was distinctly different from that in non-heating seasons. α peaked in the late afternoon in non-heating seasons with concomitantly observed low valley in BC mass concentrations. In contrast, α peaked around the midnight in the heating season and lowered down during the daytime. The relationship of aerosol absorption and winds in non-heating seasons also differed from that in the heating season. BC mass concentrations declined while α increased with increasing wind speed in non-heating seasons, which suggested elevated non-BC light absorbers in transported aged aerosols. No apparent dependence of α on wind speed was found in the heating season, probably due to well mixed

  4. Measurement of the absorption coefficient using the sound-intensity technique

    NASA Technical Reports Server (NTRS)

    Atwal, M.; Bernhard, R.

    1984-01-01

    The possibility of using the sound intensity technique to measure the absorption coefficient of a material is investigated. This technique measures the absorption coefficient by measuring the intensity incident on the sample and the net intensity reflected by the sample. Results obtained by this technique are compared with the standard techniques of measuring the change in the reverberation time and the standing wave ratio in a tube, thereby, calculating the random incident and the normal incident adsorption coefficient.

  5. Long term spectral irradiance measurements of a 1000-watt xenon arc lamp

    NASA Technical Reports Server (NTRS)

    Schneider, W. E.

    1974-01-01

    Spectral irradiance measurements over the range of 200 to 1060 nm were made on a 1000-watt xenon arc lamp over a period of 1500 hours. Four sets of measurements were made after periods of 70, 525, 1000, and 1500 hours of operation. The lamp (Hanovia Compact Xenon Arc Lamp) was mounted in the NASA Solar Irradiation System. When used in the System, the lamp is used as the radiating source for six test stations. Measurements were made of both the longterm stability (or variation of spectral irradiance as a function of time) and the actual spectral irradiance incident on the test specimen.

  6. Development of Fourier transform spectrometry for UV-visible differential optical absorption spectroscopy measurements of tropospheric minor constituents.

    PubMed

    Vandaele, A C; Carleer, M

    1999-04-20

    Concentration measurements of trace gases in the atmosphere require the use of highly sensitive and precise techniques. The UV-visible differential optical absorption spectroscopy technique is one that is heavily used for tropospheric measurements. To assess the advantages and drawbacks of using a Fourier transform spectrometer, we built a differential optical absorption spectroscopy optical setup based on a Bruker IFS 120M spectrometer. The characteristics and the capabilities of this setup have been studied and compared with those of the more conventional grating-based instruments. Two of the main advantages of the Fourier transform spectrometer are (1) the existence of a reproducible and precise wave-number scale, which greatly simplifies the algorithms used to analyze the atmospheric spectra, and (2) the possibility of recording large spectral regions at relatively high resolution, enabling the simultaneous detection of numerous chemical species with better discriminating properties. The main drawback, on the other hand, is due to the fact that a Fourier transform spectrometer is a scanning device for which the scanning time is small compared with the total measurement time. It does not have the signal integration capabilities of the CCD or photodiode array-based grating spectrographs. The Fourier transform spectrometer therefore needs fairly large amounts of light and is limited to short to medium absorption path lengths when working in the UV.

  7. Spectral Measures Associated to Rank two Lie Groups and Finite Subgroups of {GL(2,{Z})}

    NASA Astrophysics Data System (ADS)

    Evans, David E.; Pugh, Mathew

    2016-05-01

    Spectral measures for fundamental representations of the rank two Lie groups SU(3), Sp(2) and G 2 have been studied. Since these groups have rank two, these spectral measures can be defined as measures over their maximal torus {{T}^2} and are invariant under an action of the corresponding Weyl group, which is a subgroup of {GL(2,{Z})}. Here we consider spectral measures invariant under an action of the other finite subgroups of {GL(2,{Z})}. These spectral measures are all associated with fundamental representations of other rank two Lie groups, namely {{T}^2=U(1) × U(1)}, {U(1) × SU(2)}, U(2), {SU(2) × SU(2)}, SO(4) and PSU(3).

  8. Hyper-spectral measurements of Howardites with the SPIM facility

    NASA Astrophysics Data System (ADS)

    De Angelis, S.; Manzari, P.; De Sanctis, M. C.; Ammannito, E.; Di Iorio, T.; Mittlefehldt, D. W.

    2014-04-01

    We report visible and infrared measurements on powdered samples (<75μm) of three howardite meteorites. These preliminary measurements are part of a set of spectroscopic measurements performed on 33 HED samples with different laboratory setups in use at INAF-IAPS. Here we describe reflectance spectra measured with the SPIM facility on three meteorites: CRE-01400, EET-87509 and EET-87513.

  9. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    SciTech Connect

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  10. Interference enhancement in spectral domain interferometric measurements on transparent plate.

    PubMed

    Zhang, Ke; Tao, Li; Cheng, Wenkai; Liu, Jianhua; Chen, Zhongping

    2014-09-10

    In spectral domain interferometry, the interference signal generated by directly reflected waves from the two surfaces of a sample plate under test is greatly enhanced by the blockage of those light waves reflected by the two arm mirrors in the Michelson interferometer. This sample surface-reflected interference signal, being the optical path length of the plate, is therefore identifiable directly from the Fourier-transformed interference spectrum. Consequently, the group refractive index and physical thickness of the plate can be obtained simultaneously without any prior information of them. Moreover, subsequent in situ angular scanning on the interference spectra helps to retrieve the wavelength-dependent phase refractive index and first-order dispersion. The order of magnitude of the relative error for the group refractive index is 10(-4), while that for the phase refractive index and the physical thickness is 10(-3).

  11. Retrieving the availability of light in the ocean utilising spectral signatures of vibrational Raman scattering in hyper-spectral satellite measurements

    NASA Astrophysics Data System (ADS)

    Dinter, T.; Rozanov, V. V.; Burrows, J. P.; Bracher, A.

    2015-05-01

    The availability of light in the ocean is an important parameter for the determination of phytoplankton photosynthesis processes and primary production from satellite data. It is also a useful parameter for other applications, e.g. the determination of heat fluxes. In this study, a method was developed utilising the vibrational Raman scattering (VRS) effect of water molecules to determine the number of photons available in the ocean water, which is expressed by the depth integrated scalar irradiance E0. Radiative transfer simulations with the SCIATRAN fully coupled ocean-atmosphere radiative transfer model (RTM) show clearly the relationship of E0 with the strength of the VRS signal measured at the top of the atmosphere (TOA). Taking advantage of VRS structures in hyper-spectral satellite measurements, a retrieval technique to derive E0 in the wavelength region from 390 to 444.5 nm was developed. This approach uses the weighting function differential optical absorption spectroscopy (WF-DOAS) technique, applied to TOA radiances, measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). Based on the approach of Vountas et al. (2007), where the DOAS method was used to fit modelled spectra of VRS, the method was improved by using the weighting function of VRS (VRS-WF) in the DOAS fit. This was combined with a look-up table (LUT) technique, where the E0 value was obtained for each VRS satellite fit directly. The VRS-WF and the LUT were derived from calculations with the SCIATRAN RTM (Rozanov et al., 2014). RTM simulations for different chlorophyll a concentrations and illumination conditions clearly show that low fit factors of VRS retrieval results correspond to low amounts of light in the water column and vice versa. Exemplarily, 1 month of SCIAMACHY data were processed and a global map of the depth integrated scalar irradiance E0 was retrieved. Spectral structures of VRS were clearly identified in the radiance measurements of

  12. Retrieving the availability of light in the ocean utilising spectral signatures of Vibrational Raman Scattering in hyper-spectral satellite measurements

    NASA Astrophysics Data System (ADS)

    Dinter, T.; Rozanov, V. V.; Burrows, J. P.; Bracher, A.

    2015-01-01

    The availability of light in the ocean is an important parameter for the determination of phytoplankton photosynthesis processes and primary production from satellite data. It is also a useful parameter for other applications, e.g. the determination of heat fluxes. In this study, a method was developed utilising the vibrational Raman scattering (VRS) effect of water molecules to determine the amount of photons available in the ocean water, which is expressed by the depth integrated scalar irradiance E0. Radiative transfer simulations with the fully coupled ocean-atmosphere Radiative Transfer Model (RTM) SCIATRAN show clearly the relationship of E0 to the strength of the VRS signal measured at the top of the atmosphere (TOA). Taking advantage of VRS structures in hyper-spectral satellite measurements a retrieval technique to derive E0 in the wavelength region from 390 to 444.5 nm was developed. This approach uses the Weighting Function Differential Optical Absorption Spectroscopy (WF-DOAS) technique, applied to TOA radiances, measured by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). Based on the approach of Vountas et al. (2007), where the DOAS method was used to fit modelled spectra of VRS, the method was improved by using the weighting function of VRS (VRS-WF) in the DOAS fit. This was combined with a look-up table (LUT) technique, where the E0 value was obtained for each VRS satellite fit directly. The VRS-WF and the LUT were derived from calculations with the RTM SCIATRAN (Rozanov et al., 2014). RTM simulations for different chlorophyll a concentrations and illumination conditions clearly show, that low fit factors of VRS retrieval results correspond to low amounts of light in the water column and vice versa. Exemplary, one month of SCIAMACHY data were processed and

  13. Spectral correlation measurements at the Hong-Ou-Mandel interference dip

    NASA Astrophysics Data System (ADS)

    Gerrits, T.; Marsili, F.; Verma, V. B.; Shalm, L. K.; Shaw, M.; Mirin, R. P.; Nam, S. W.

    2015-01-01

    We present an efficient tool capable of measuring the spectral correlations between photons emerging from a Hong-Ou-Mandel interferometer. We show that for our spectrally factorizable spontaneous down-conversion source, the Hong-Ou-Mandel interference visibility decreases as the photons' frequency spread is increased to a maximum of 165 nm. Unfiltered, we obtained a visibility of 92.0 %±0.2 %. The maximum visibility was 97 %±0.2 % after applying filtering. We show that the tool can be useful for the study of spectral correlations that impair high-visibility and high-fidelity multisource interference applications. The nature of this tool also allows for arbitrary post-selective spectral filtering and high-rate multiphoton spectral correlation measurements.

  14. Preparation and Absorption Spectral Property of a Multifunctional Water-Soluble Azo Compound with D-π-A Structure, 4-(4- Hydroxy-1-Naphthylazo)Benzoic Acid

    NASA Astrophysics Data System (ADS)

    Hu, L.; Lv, H.; Xie, C. G.; Chang, W. G.; Yan, Z. Q.

    2015-07-01

    A multifunctional water-soluble azo dye with the D-π-A conjugated structure, 4-(4-hydroxy-1-naphthylazo) benzoic acid ( HNBA), was designed and synthesized using 1-naphanol as the electron donator, benzoic acid as the electron acceptor, and -N=N- as the bridging group. After its structure was characterized by FTIR, 1H NMR, and element analysis, the UV-Vis absorption spectral performance of the target dye was studied in detail. The results showed that the dye, combining hydroxyl group, azo group, and carboxyl group, possessed excellent absorption spectral properties (ɛ = 1.2·104 l·mol-1·cm-1) changing with pH and solvents. In particular, in polar and protonic water, it had excellent optical response to some metal ions, i.e., Fe3+ and Pb2+, which might make it a latent colorimetric sensor for detecting heavy metal ions.

  15. Photoacoustic technique for simultaneous measurements of thermal effusivity and absorptivity of pigments in liquid solution.

    PubMed

    Balderas-López, J A; Díaz-Reyes, J; Zelaya-Angel, O

    2011-12-01

    A photoacoustic (PA) methodology, in the transmission configuration, for simultaneous measurements of thermal effusivity and molar absorption coefficient (absorptivity) for pigments in liquid solution is introduced. The analytical treatment involves a self-normalization procedure for the PA signal, as a function of the modulation frequency, for a strong absorbing material in the thermally thin regime, when the light travels across the sample under study. Two fitted parameters are obtained from the analysis of the self-normalized PA amplitude and phase, one of them proportional to the sample's optical absorption coefficient and from which, taking it for a series of samples at different concentrations, the pigment's absorptivity in liquid solution can be measured, the other one yields the sample's thermal effusivity. Methylene blue's absorptivity in distilled water was measured with this methodology at 658 nm, finding good agreement with the corresponding one reported in the literature.

  16. Spectral properties of agricultural crops and soils measured from space, aerial, field, and laboratory sensors

    NASA Technical Reports Server (NTRS)

    Bauer, M. E. (Principal Investigator); Vanderbilt, V. C.; Robinson, B. F.; Daughtry, C. S. T.

    1981-01-01

    Investigations of the multispectral reflectance characteristics of crops and soils as measured from laboratory, field, aerial, and satellite sensor systems are reviewed. The relationships of important biological and physical characteristics to the spectral properties of crops and soils are addressed.

  17. Direct measurements of nonlinear absorption and refraction in solutions of phthalocyanines

    NASA Technical Reports Server (NTRS)

    Wei, T. H.; Hagan, D. J.; Sence, M. J.; Van Stryland, E. W.; Perry, J. W.; Coulter, D. R.

    1992-01-01

    Direct measurements are reported of the excited singlet-state absorption cross section and the associated nonlinear refractive cross section using picosecond pulses at 532 nm in solutions of phthalocyanine and naphthalocyanine dyes. By monitoring the transmittance and far-field spatial beam distortion for different pulsewidths in the picosecond regime, it is shown that both the nonlinear absorption and refraction are fluence (energy-per-unit-area) rather than irradiance dependent. Thus, excited-state absorption is the dominant nonlinear absorption process, and the observed nonlinear refraction is also due to real population excitation.

  18. VizieR Online Data Catalog: AGN data and absorption-line measurements (Richter+, 2016)

    NASA Astrophysics Data System (ADS)

    Richter, P.; Wakker, B. P.; Fechner, C.; Herenz, P.; Tepper-Garcia, T.; Fox, A. J.

    2016-03-01

    Names, positions and emission redshifts for 303 QSOs are provided in Table A.1. Table A.2 summarizes the absorption-line measurements for 59 intervening SiIII absorbers including absorption redshifts, equivalent-widths, and column densities for various different ions. (2 data files).

  19. FTIR spectrometer with 30 m optical cell and its applications to the sensitive measurements of selective and nonselective absorption spectra

    NASA Astrophysics Data System (ADS)

    Ponomarev, Yu. N.; Solodov, A. A.; Solodov, A. M.; Petrova, T. M.; Naumenko, O. V.

    2016-07-01

    A description of the spectroscopic complex at V.E. Zuev Institute of Atmospheric Optics, SB RAS, operating in a wide spectral range with high threshold sensitivity to the absorption coefficient is presented. Measurements of weak lines and nonselective spectra of CO2 and H2O were performed based on the built setup. As new application of this setup, positions and intensities of 152 weak lines of H2O were measured between 2400 and 2560 cm-1 with threshold sensitivity of 8.6×10-10 cm-1, and compared with available calculated and experimental data. Essential deviations between the new intensity measurements and calculated data accepted in HITRAN 2012 and GEISA 2015 forthcoming release are found.

  20. Wavelength encoded polarization measurements for simultaneous spectral and polarimetric characterization in near field

    NASA Astrophysics Data System (ADS)

    Patel, H. S.; Swami, M. K.; Kushwaha, P. K.; Uppal, A.; Gupta, P. K.

    2016-08-01

    We report a scheme for polarization sensitive near field imaging of nanostructured samples by making use of broadband polarized near field illumination and detection of polarization states of scattered light by a spectrally encoded analyzer. The analyzer comprising a combination of polarizer, a multi-order waveplate and a broadband quarter waveplate allows analysis of the spectrally encoded polarization states of scattered light for characterization of the polarization properties of nano structures from a single image scan. The scheme was validated by measuring the near field polarization parameters of silver nanowires. The approach allows simultaneous measurement of polarization characteristics as well as spectral features of the nano materials.

  1. UV-VIS-IR Spectral Responsivity Measurement System for Solar Cells

    SciTech Connect

    Field, H.

    1998-11-12

    NREL's PV Cell and Module Performance Characterization group has built a new spectral responsivity measurement system for solar cells. It uses a xenon arc lamp source, a single, grating monochrometer, and a fiber-optic bundle to couple the monochromatic light to the test device. The system has a spectral bandwidth of 2 nm, minimum spot diameter of 1.6 mm, a spectral range of 280-1330 nm, and uncertainty better than {+-}3% over most of this range. It is capable of incorporating light bias with intensities exceeding one sun. This paper discusses the system's features, capabilities, calibration, and measurement uncertainties.

  2. Sound absorption by suspensions of nonspherical particles: measurements compared with predictions using various particle sizing techniques.

    PubMed

    Richards, Simon D; Leighton, Timothy G; Brown, Niven R

    2003-10-01

    Knowledge of the particle size distribution is required in order to predict ultrasonic absorption in polydisperse particulate suspensions. This paper shows that the method used to measure the particle size distribution can lead to important differences in the predicted absorption. A reverberation technique developed for measuring ultrasonic absorption by suspended particles is used to measure the absorption in suspensions of nonspherical particles. Two types of particulates are studied: (i) kaolin (china clay) particles which are platelike in form; and (ii) calcium carbonate particles which are more granular. Results are compared to theoretical predictions of visco-inertial absorption by suspensions of spherical particles. The particle size distributions, which are required for these predictions, are measured by laser diffraction, gravitational sedimentation and centrifugal sedimentation, all of which assume spherical particles. For a given sample, each sizing technique yields a different size distribution, leading to differences in the predicted absorption. The particle size distributions obtained by gravitational and centrifugal sedimentation are reinterpreted to yield a representative size distribution of oblate spheroids, and predictions for absorption by these spheroids are compared with the measurements. Good agreement between theory and measurement for the flat kaolin particles is obtained, demonstrating that these particles can be adequately represented by oblate spheroids. PMID:14587585

  3. Optical properties of Mg-doped VO2: Absorption measurements and hybrid functional calculations

    NASA Astrophysics Data System (ADS)

    Hu, Shuanglin; Li, S.-Y.; Ahuja, R.; Granqvist, C. G.; Hermansson, K.; Niklasson, G. A.; Scheicher, R. H.

    2012-11-01

    Mg-doped VO2 thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < ħω < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.

  4. Optical properties of Mg-doped VO{sub 2}: Absorption measurements and hybrid functional calculations

    SciTech Connect

    Hu Shuanglin; Li, S.-Y.; Granqvist, C. G.; Niklasson, G. A.; Ahuja, R.; Scheicher, R. H.; Hermansson, K.

    2012-11-12

    Mg-doped VO{sub 2} thin films with thermochromic properties were made by reactive DC magnetron co-sputtering onto heated substrates, and spectral absorption was recorded at room temperature in the 0.5 < h{omega} < 3.5 eV energy range. Clear evidence was found for a widening of the main band gap from 1.67 to 2.32 eV as the Mg/(V + Mg) atomic ratio went from zero to 0.19, thereby significantly lowering the luminous absorption. This technologically important effect could be reconciled with spin-polarized density functional theory calculations using the Heyd-Scuseria-Ernzerhof [Heyd et al., J. Chem. Phys. 118, 8207 (2003); ibid. 124, 219906 (2006)] hybrid functional. Specifically, the calculated luminous absorptance decreased when the Mg/(V + Mg) ratio was increased from 0.125 to 0.250.

  5. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    SciTech Connect

    Brauer, Carolyn S.; Blake, Thomas A.; Guenther, Alex B.; Sharpe, Steven W.; Sams, Robert L.; Johnson, Timothy J.

    2014-11-19

    The OH- and O3- initiated oxidations of isoprene, which is one of the primary volatile organic compounds produced by vegetation, are a major source of atmospheric formaldehyde and other oxygenated organics, yet little quantitative IR data exists for isoprene. We thus report absorption coefficients and integrated band intensities for isoprene in the 600 - 6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298 and 323 K in a 19.96 cm path length cell at 0.112 cm-1 resolution, using a Bruker 66V FTIR. Composite spectra are derived from a minimum of seven pressures at each temperature.

  6. SBUV/2 Long-Term Measurements of Solar Spectral Variability

    NASA Technical Reports Server (NTRS)

    DeLand, Matthew T.; Cebula, Richard P.

    1997-01-01

    The NOAA-11 SBUV/2 spectral solar data have been corrected for long-term instrument changes to produce a 5.5 year data record during solar cycle 22 (December 1988 - October 1994). Residual drifts in the data at long wavelengths are +/- 1% or less. At 200-205 nm, where solar variations drive stratospheric photochemistry, these data indicate long-term solar changes of 5-7% from the maximum of Cycle 22 in April 1991 through the end of the NOAA-11 data record. Comparisons of NOAA-11 data with UARS SUSIM and SOLSTICE for the period October 1991 - October 1994, when all 3 instruments were operating simultaneously, show that the observed long-term variations in 200-205 nm irradiance agree to within 2%. This result is consistent with predictions from the Mg-2 proxy index. The SBUV/2 instruments represent a valuable resource for long-term solar UV activity studies because of their overlapping data records. In addition to the NOAA-11 data presented here, the NOAA-9 SBUV/2 instrument began taking data in March 1985 and is still operating, providing a complete record of Cycle 22 behavior from a single instrument. Three additional SBUV/2 instruments are scheduled to be launched between 1997 and 2003, which should permit full coverage of solar cycle 23.

  7. Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements

    SciTech Connect

    Liu, Feilong; Kelley, Megan R.; Crooker, Scott A.; Nie, Wanyi; Mohite, Aditya D.; Ruden, P. Paul; Smith, Darryl L.

    2014-12-22

    The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the electron/hole polarons and the hydrogen nuclei of the host molecules. In this paper, we present an analytical theory of magnetoelectroluminescence for organic semiconductors. To be specific, we focus on bilayer heterostructure devices. In the case we are considering, light generation at the interface of the donor and acceptor layers results from the formation and recombination of exciplexes. The spin physics is described by a stochastic Liouville equation for the electron/hole spin density matrix. By finding the steady-state analytical solution using Bloch-Wangsness-Redfield theory, we explore how the singlet/triplet exciplex ratio is affected by the hyperfine interaction strength and by the external magnetic field. In order to validate the theory, spectrally resolved electroluminescence experiments on BPhen/m-MTDATA devices are analyzed. With increasing emission wavelength, the width of the magnetic field modulation curve of the electroluminescence increases while its depth decreases. Furthermore, these observations are consistent with the model.

  8. Magnetoelectroluminescence of organic heterostructures: Analytical theory and spectrally resolved measurements

    DOE PAGES

    Liu, Feilong; Kelley, Megan R.; Crooker, Scott A.; Nie, Wanyi; Mohite, Aditya D.; Ruden, P. Paul; Los Alamos National Lab.; Smith, Darryl L.; Los Alamos National Lab.

    2014-12-22

    The effect of a magnetic field on the electroluminescence of organic light emitting devices originates from the hyperfine interaction between the electron/hole polarons and the hydrogen nuclei of the host molecules. In this paper, we present an analytical theory of magnetoelectroluminescence for organic semiconductors. To be specific, we focus on bilayer heterostructure devices. In the case we are considering, light generation at the interface of the donor and acceptor layers results from the formation and recombination of exciplexes. The spin physics is described by a stochastic Liouville equation for the electron/hole spin density matrix. By finding the steady-state analytical solutionmore » using Bloch-Wangsness-Redfield theory, we explore how the singlet/triplet exciplex ratio is affected by the hyperfine interaction strength and by the external magnetic field. In order to validate the theory, spectrally resolved electroluminescence experiments on BPhen/m-MTDATA devices are analyzed. With increasing emission wavelength, the width of the magnetic field modulation curve of the electroluminescence increases while its depth decreases. Furthermore, these observations are consistent with the model.« less

  9. Spectral Sensitivity Measured with Electroretinogram Using a Constant Response Method

    PubMed Central

    Rocha, Fernando Allan de Farias; Gomes, Bruno Duarte; Silveira, Luiz Carlos de Lima; Martins, Sonia Limara; Aguiar, Renata Genaro; de Souza, John Manuel; Ventura, Dora Fix

    2016-01-01

    A new method is presented to determine the retinal spectral sensitivity function S(λ) using the electroretinogram (ERG). S(λ)s were assessed in three different species of myomorph rodents, Gerbils (Meriones unguiculatus), Wistar rats (Ratus norvegicus), and mice (Mus musculus). The method, called AC Constant Method, is based on a computerized automatic feedback system that adjusts light intensity to maintain a constant-response amplitude to a flickering stimulus throughout the spectrum, as it is scanned from 300 to 700 nm, and back. The results are presented as the reciprocal of the intensity at each wavelength required to maintain a constant peak to peak response amplitude. The resulting S(λ) had two peaks in all three rodent species, corresponding to ultraviolet and M cones, respectively: 359 nm and 511 nm for mice, 362 nm and 493 nm for gerbils, and 362 nm and 502 nm for rats. Results for mouse and gerbil were similar to literature reports of S(λ) functions obtained with other methods, confirming that the ERG associated to the AC Constant-Response Method was effective to obtain reliable S(λ) functions. In addition, due to its fast data collection time, the AC Constant Response Method has the advantage of keeping the eye in a constant light adapted state. PMID:26800521

  10. Spectral response of the intrinsic region of a GaAs-InAs quantum dot solar cell considering the absorption spectra of ideal cubic dots

    NASA Astrophysics Data System (ADS)

    Biswas, Sayantan; Chatterjee, Avigyan; Biswas, Ashim Kumar; Sinha, Amitabha

    2016-10-01

    Recently, attempts have been made by some researchers to improve the efficiency of quantum dot solar cells by incorporating different types of quantum dots. In this paper, the photocurrent density has been obtained considering the absorption spectra of ideal cubic dots. The effects of quantum dot size dispersion on the spectral response of the intrinsic region of a GaAs-InAs quantum dot solar cell have been studied. The dependence of the spectral response of this region on the size of quantum dots of such solar cell has also been investigated. The investigation shows that for smaller quantum dot size dispersion, the spectral response of the intrinsic region of the cell increases significantly. It is further observed that by enlarging the quantum dot size it is possible to enhance the spectral response of such solar cells as it causes better match between absorption spectra of the quantum dots and the solar spectrum. These facts indicate the significant role of quantum dot size and size dispersion on the performance of such devices. Also, the power conversion efficiency of such solar cell has been studied under 1 sun, AM 1.5 condition.

  11. Near-IR absorption in high-purity photothermorefractive glass and holographic optical elements: measurement and application for high-energy lasers

    SciTech Connect

    Lumeau, Julien; Glebova, Larissa; Glebov, Leonid B.

    2011-10-20

    Volume Bragg gratings (VBGs) in photothermorefractive (PTR) glass are widely used for laser beam control including high-power laser systems. Among them, spectral beam combining based on VBGs is one of the most promising. Achieving 100+ kW of combined laser beams requires the development of PTR glass and VBGs with an extremely low absorption coefficient and therefore methods of its measurement. This paper describes the calorimetric method that was developed for measuring a low absorption coefficient in PTR glass and VBGs. It is based on transmission monitoring of the intrinsic Fabry-Perot interferometer produced by the plane-parallel surfaces of the measured optical elements when heated by high-power laser radiation. An absorption coefficient at 1085 nm as low as 5x10{sup -5} cm{sup -1} is demonstrated in pristine PTR glass while an absorption coefficient as low as 1x10{sup -4} cm{sup -1} is measured in high-efficiency reflecting Bragg gratings with highest purity. The actual level of absorption in PTR glass allows laser beam control at the 10 kW level, while the 100 kW level would require active cooling and/or decreasing the absorption in PTR Bragg gratings to a value similar to that in virgin PTR glass.

  12. The measurement of solar spectral irradiances at wavelengths between 40 and 4000 A

    NASA Technical Reports Server (NTRS)

    Timothy, J. G.

    1983-01-01

    Two 1/8-meter Ebert-Fastie spectrometers were refurbished and upgraded in order to measure the solar spectral irradiances between 1160 A and 3100 A. An evacuated 1/4-meter normal-incidence spectrometer was also fabricated for spectral irradiance measurements over the wavelength range from 1250 A to 250 A. Procedures were developed for the calibration of all three instruments utilizing standards at the National Bureau of Standards. The two 1/8-meter spectrometers were flown to measure the solar spectral irradiances near solar maximum on two different dates. Data from these flights were analyzed. The performance of the spectrometers, and the results of an analysis of the variabilities of the solar spectral irradiances over the solar cycles 20 and 21 are discussed.

  13. The analytical design of spectral measurements for multispectral remote sensor systems

    NASA Technical Reports Server (NTRS)

    Wiersma, D. J.; Landgrebe, D. A. (Principal Investigator)

    1979-01-01

    The author has identified the following significant results. In order to choose a design which will be optimal for the largest class of remote sensing problems, a method was developed which attempted to represent the spectral response function from a scene as accurately as possible. The performance of the overall recognition system was studied relative to the accuracy of the spectral representation. The spectral representation was only one of a set of five interrelated parameter categories which also included the spatial representation parameter, the signal to noise ratio, ancillary data, and information classes. The spectral response functions observed from a stratum were modeled as a stochastic process with a Gaussian probability measure. The criterion for spectral representation was defined by the minimum expected mean-square error.

  14. Using broadband absorption spectroscopy to measure concentration of sulfur dioxide

    NASA Astrophysics Data System (ADS)

    Wang, H. S.; Zhang, Y. G.; Wu, S. H.; Lou, X. T.; Zhang, Z. G.; Qin, Y. K.

    2010-09-01

    A linear relationship between concentration of sulfur dioxide (SO2) and optical parameter (OP) is established using the Beer-Lambert law. The SO2 measuring system is set up to measure the concentration of sulfur dioxide in the wavelength range 275-315 nm. Experimental results indicate that the detection limit of the sulfur dioxide measuring system is below 0.2 ppm per meter of path length, and the measurement precision is better than ±1%. The proposed SO2 measuring method features limited interference from other gases and dust, and high stability and short response time.

  15. Compressive spectral imaging using multiple snapshot colored-mosaic detector measurements

    NASA Astrophysics Data System (ADS)

    Hinojosa, Carlos A.; Correa, Claudia V.; Arguello, Henry; Arce, Gonzalo R.

    2016-05-01

    Compressive spectral imaging (CSI) captures coded and dispersed projections of the spatio-spectral source rather than direct measurements of the voxels. Using the coded projections, an l1 minimization reconstruction algorithm is then used to reconstruct the underlying scene. An architecture known as the snapshot colored compressive spectral imager (SCCSI) exploits the compression capabilities of CSI techniques and efficiently senses a spectral image using a single snapshot by means of a colored mosaic FPA detector and a dispersive element. In CSI, different coding patterns are used to acquire multiple snapshots, yielding improved reconstructions of spatially detailed and spectrally rich scenes. SCCSI however, does not admit multiple coding patterns since the pixelated tiling of optical filters is directly attached to the detector. This paper extends the concept of SCCSI to a system admitting multiple measurement shots by rotating the dispersive element such that the dispersed spatio-spectral source is coded and integrated at different detector pixels in each rotation. This approach allows the acquisition of a different set of coded projections on each measurement shot. Simulations show that increasing the number of measurement snapshots results on improved reconstructions. More specifically, a gain up to 7 dB is obtained when results from four measurement shots are compared to the reconstruction from a single SCCSI snapshot.

  16. Spectral emission measurements of lithium on the lithium tokamak experiment.

    PubMed

    Gray, T K; Biewer, T M; Boyle, D P; Granstedt, E M; Kaita, R; Maingi, R; Majeski, R P

    2012-10-01

    There has been a long-standing collaboration between ORNL and PPPL on edge and boundary layer physics. As part of this collaboration, ORNL has a large role in the instrumentation and interpretation of edge physics in the lithium tokamak experiment (LTX). In particular, a charge exchange recombination spectroscopy (CHERS) diagnostic is being designed and undergoing staged testing on LTX. Here we present results of passively measured lithium emission at 5166.89 A in LTX in anticipation of active spectroscopy measurements, which will be enabled by the installation of a neutral beam in 2013. Preliminary measurements are made in transient LTX plasmas with plasma current, I(p) < 70 kA, ohmic heating power, P(oh) ∼ 0.3 MW and discharge lifetimes of 10-15 ms. Measurements are made with a short focal length spectrometer and optics similar to the CHERS diagnostics on NSTX [R. E. Bell, Rev. Sci. Instrum. 68(2), 1273-1280 (1997)]. These preliminary measurements suggest that even without the neutral beam for active spectroscopy, there is sufficient passive lithium emission to allow for line-of-sight profile measurements of ion temperature, T(i); toroidal velocity and v(t). Results show peak T(i) = 70 eV and peak v(t) = 45 km/s were reached 10 ms into the discharge.

  17. Spectral emission measurements of lithium on the lithium tokamak experiment

    SciTech Connect

    Gray, T. K.; Biewer, T. M.; Maingi, R.; Boyle, D. P.; Granstedt, E. M.; Kaita, R.; Majeski, R. P.

    2012-10-15

    There has been a long-standing collaboration between ORNL and PPPL on edge and boundary layer physics. As part of this collaboration, ORNL has a large role in the instrumentation and interpretation of edge physics in the lithium tokamak experiment (LTX). In particular, a charge exchange recombination spectroscopy (CHERS) diagnostic is being designed and undergoing staged testing on LTX. Here we present results of passively measured lithium emission at 5166.89 A in LTX in anticipation of active spectroscopy measurements, which will be enabled by the installation of a neutral beam in 2013. Preliminary measurements are made in transient LTX plasmas with plasma current, I{sub p} < 70 kA, ohmic heating power, P{sub oh}{approx} 0.3 MW and discharge lifetimes of 10-15 ms. Measurements are made with a short focal length spectrometer and optics similar to the CHERS diagnostics on NSTX [R. E. Bell, Rev. Sci. Instrum. 68(2), 1273-1280 (1997)]. These preliminary measurements suggest that even without the neutral beam for active spectroscopy, there is sufficient passive lithium emission to allow for line-of-sight profile measurements of ion temperature, T{sub i}; toroidal velocity and v{sub t}. Results show peak T{sub i} = 70 eV and peak v{sub t} = 45 km/s were reached 10 ms into the discharge.

  18. Spectral emission measurements of lithium on the lithium tokamak experimenta)

    NASA Astrophysics Data System (ADS)

    Gray, T. K.; Biewer, T. M.; Boyle, D. P.; Granstedt, E. M.; Kaita, R.; Maingi, R.; Majeski, R. P.

    2012-10-01

    There has been a long-standing collaboration between ORNL and PPPL on edge and boundary layer physics. As part of this collaboration, ORNL has a large role in the instrumentation and interpretation of edge physics in the lithium tokamak experiment (LTX). In particular, a charge exchange recombination spectroscopy (CHERS) diagnostic is being designed and undergoing staged testing on LTX. Here we present results of passively measured lithium emission at 5166.89 Å in LTX in anticipation of active spectroscopy measurements, which will be enabled by the installation of a neutral beam in 2013. Preliminary measurements are made in transient LTX plasmas with plasma current, Ip < 70 kA, ohmic heating power, Poh ˜ 0.3 MW and discharge lifetimes of 10-15 ms. Measurements are made with a short focal length spectrometer and optics similar to the CHERS diagnostics on NSTX [R. E. Bell, Rev. Sci. Instrum. 68(2), 1273-1280 (1997), 10.1063/1.1147885]. These preliminary measurements suggest that even without the neutral beam for active spectroscopy, there is sufficient passive lithium emission to allow for line-of-sight profile measurements of ion temperature, Ti; toroidal velocity and vt. Results show peak Ti = 70 eV and peak vt = 45 km/s were reached 10 ms into the discharge.

  19. Spectroscopic Character and Spatial Distribution of Hydroxyl and Water Absorption Features Measured on the Lunar Surface by the Moon Mineralogy Mapper Imaging Spectrometer on Chandrayaan-1

    NASA Astrophysics Data System (ADS)

    Green, R. O.; Pieters, C. M.; Goswami, J.; Clark, R. N.; Annadurai, M.; Boardman, J. W.; Buratti, B. J.; Combe, J.; Dyar, M. D.; Head, J. W.; Hibbitts, C.; Hicks, M.; Isaacson, P.; Klima, R. L.; Kramer, G. Y.; Kumar, S.; Livo, K. E.; Lundeen, S.; Malaret, E.; McCord, T. B.; Mustard, J. F.; Nettles, J. W.; Petro, N. E.; Runyon, C. J.; Staid, M.; Sunshine, J. M.; Taylor, L. A.; Tompkins, S.; Varanasi, P.

    2009-12-01

    The Moon Mineralogy Mapper imaging spectrometer on Chandrayaan-1 has a broad spectral range from 430 to 3000 nm. By design, the range was specified to extend to 3000 nm to allow for possible detection of trace volatile compounds that possess absorption bands near 3000 nm. Soon after acquisition and calibration of a large fraction of the lunar surface in early February 2009, absorption features in the 2700 to 3000 nm region were detected over unexpectedly large regional areas. This extraordinary discovery has withstood extensive re-analysis and falsification efforts. We have concluded these absorption features are fundamentally present in the M3 measurements and are indicators of extensive hydroxyl and water-bearing materials occurring on the surface of the Moon. Based on current analyses, these absorption features appear strongest at high latitudes, but also occur in association with several fresh feldspathic craters. Interestingly, the distribution of these absorption features are not directly correlated with existing neutron spectrometer hydrogen abundance data for the sunlight surface. This may indicate that the formation and retention of hydroxyl and water is an active process largely restricted to the upper most surface. We present the detailed spectroscopic character of these absorption features in the 2700 to 3000 nm spectral region, including selected examples through all levels of measurement processing from raw data to calibrated apparent surface reflectance. In summary we show the measured strength and latitudinal distribution of the absorptions as well as selected localized occurrences in association with fresh feldspathic craters. The presence of hydroxyl and water bearing material over extensive regions of the lunar surface provides a new and unexpected source of volatiles. Options for harvesting these elements directly from the regolith may provide an alternate supply of volatiles for long term human exploration objectives.

  20. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    DOE PAGES

    Brauer, C. S.; Blake, T. A.; Guenther, A. B.; Sharpe, S. W.; Sams, R. L.; Johnson, T. J.

    2014-11-19

    Isoprene (C5H8, 2-methyl-1,3-butadiene) is a volatile organic compound (VOC) and is one of the primary contributors to annual global VOC emissions. Isoprene is produced primarily by vegetation as well as anthropogenic sources, and its OH- and O3-initiated oxidations are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, limiting the ability to quantify isoprene emissions via remote or in situ infrared detection. We thus report absorption cross sections and integrated band intensities for isoprene in the 600–6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298, and 323 Kmore » in a 19.94 cm path-length cell at 0.112 cm-1 resolution, using a Bruker IFS 66v/S Fourier transform infrared (FTIR) spectrometer. Composite spectra are derived from a minimum of seven isoprene sample pressures, each at one of three temperatures, and the number densities are normalized to 296 K and 1 atm.« less

  1. Direct Measurements of Brown Carbon Absorption in A Wide Range of Biomass Burning Plumes

    NASA Astrophysics Data System (ADS)

    Murphy, S. M.; Pokhrel, R. P.; Beamesderfer, E.; Lack, D.; Langridge, J.; Wagner, N. L.

    2014-12-01

    Biomass burning represents one of the largest global sources of absorbing aerosol. Despite the importance of biomass burning emissions on the Earth's radiative balance, there remains significant uncertainty about the optical properties of emitted particles. Of particular interest is the impact of lensing on black carbon absorption and the impact of brown carbon. This presentation describes results from the Fire Lab at Missoula Experiment-4 (FLAME-4), which occurred in October 2012. Multi-channel photoacoustic (PAS) and Cavity Ringdown (CRDS) spectrometers were used to measure absorption, extinction, and absorption enhancement of aerosol particles produced from a wide range of globally relevant biomass fuels. Measurements were made at 405, 532, and 660 nm with duplicate channels at 405 and 660 measuring denuded particles, allowing for direct observation of the enhancement of absorption by black carbon particles caused by clear and brown organic coatings. Fuels were chosen based on their contribution to global wildfire emissions and a wide range of fuels will be discussed including some of the first optical measurements of Indonesian peat. The SSA and absorption angstrom exponent (AAE) of different biomass fuels will be explored and the relative importance of black and brown carbon emitted from different biomass fuels will be assessed, demonstrating that for certain fuels absorption from brown carbon is as important, or even more important than absorption from black carbon.

  2. Absorption Measurements of Periodically Poled Potassium Titanyl Phosphate (PPKTP) at 775 nm and 1550 nm

    PubMed Central

    Steinlechner, Jessica; Ast, Stefan; Krüger, Christoph; Singh, Amrit Pal; Eberle, Tobias; Händchen, Vitus; Schnabel, Roman

    2013-01-01

    The efficient generation of second-harmonic light and squeezed light requires non-linear crystals that have low absorption at the fundamental and harmonic wavelengths. In this work the photo-thermal self-phase modulation technique is exploited to measure the absorption coefficient of periodically poled potassium titanyl phosphate (PPKTP) at 1,550 nm and 775 nm. The measurement results are (84±40) ppm/cm and (127±24) ppm/cm, respectively. We conclude that the performance of state-of-the-art frequency doubling and squeezed light generation in PPKTP is not limited by absorption. PMID:23291574

  3. Absorption measurement of thin films by using photothermal techniques: The influence of thermal properties

    SciTech Connect

    Wu, Z.L.; Kuo, P.K.; Thomas, R.L.; Fan, Z.X.

    1995-12-31

    Photothermal techniques are widely used for measuring optical absorption of thin film coatings. In these applications the calibration of photothermal signal is typically based on the assumption that the thermal properties of the thin film make very little contribution. In this paper we take mirage technique as an example and present a detailed analysis of the influence of thin film thermal properties on absorption measurements. The results show that the traditional calibration method is not valid on surprisingly many situations.

  4. Measurements of the mass absorption cross section of atmospheric soot particles using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Nordmann, S.; Birmili, W.; Weinhold, K.; Müller, K.; Spindler, G.; Wiedensohler, A.

    2013-11-01

    Soot particles are a major absorber of shortwave radiation in the atmosphere. The mass absorption cross section is an essential quantity to describe this light absorption process. This work presents new experimental data on the mass absorption cross section of soot particles in the troposphere over Central Europe. Mass absorption cross sections were derived as the ratio between the light absorption coefficient determined by multiangle absorption photometry (MAAP) and the soot mass concentration determined by Raman spectroscopy. The Raman method is sensitive to graphitic structures present in the particle samples and was calibrated in the laboratory using Printex®90 model particles. Mass absorption cross sections were determined for a number of seven observation sites, ranging between 3.9 and 7.4 m2 g-1depending on measurement site and observational period. The highest values were found in a continentally aged air mass in winter, where soot particles were assumed to be mainly internally mixed. Our values are in the lower range of previously reported values, possibly due to instrumental differences to the former photometer and mass measurements. Overall, a value of 5.3m2 g-1from orthogonal regression over all samples is considered to be representative for the soot mass absorption cross section in the troposphere over Central Europe.

  5. [Measurement of atmospheric NO3 radical with long path differential optical absorption spectroscopy based on red light emitting diodes].

    PubMed

    Li, Su-Wen; Liu, Wen-Qing; Wang, Jiang-Tao; Xie, Pin-Hua; Wang, Xu-De

    2013-02-01

    Nitrate radical (NO3) is the most important oxidant in the tropospheric nighttime chemistry. Due to its high reactivity and low atmospheric concentrations, modern red light emitting diodes (LEDs) was proposed as light source in long path differential optical absorption spectroscopy (LP-DOAS) to measure NO3 radical in the atmosphere. The spectral properties of Luxeon LXHL-MD1D LEDs were analyzed in the present paper. The principle of LEDs-DOAS system to measure nitrate radical was studied in this paper. The experimental setup and retrieval method of NO3 radical were discussed in this paper. The retrieved example of NO3 was given and the time series of NO3 concentrations was performed for a week. The results showed that the detection limits of LEDs-DOAS system were 12 ppt for atmospheric NO3 radical when the optical path of LEDs-DOAS system was 2.8 km. PMID:23697129

  6. Spectral infrared hemispherical reflectance measurements for LDEF tray clamps

    NASA Technical Reports Server (NTRS)

    Cromwell, B. K.; Shepherd, S. D.; Pender, C. W.; Wood, B. E.

    1993-01-01

    Infrared hemispherical reflectance measurements that were made on 58 chromic acid anodized tray clamps from LDEF are described. The measurements were made using a hemiellipsoidal mirror reflectometer with interferometer for wavelengths between 2-15 microns. The tray clamps investigated were from locations about the entire spacecraft and provided the opportunity for comparing the effects of atomic oxygen at each location. Results indicate there was essentially no dependence on atomic oxygen fluence for the surfaces studied, but there did appear to be a slight dependence on solar radiation exposure. The reflectances of the front sides of the tray clamps consistently were slightly higher than for the protected rear tray clamp surfaces.

  7. Mass specific optical absorption coefficients of mineral dust components measured by a multi wavelength photoacoustic spectrometer

    NASA Astrophysics Data System (ADS)

    Utry, N.; Ajtai, T.; Pintér, M.; Tombácz, E.; Illés, E.; Bozóki, Z.; Szabó, G.

    2014-09-01

    Mass specific optical absorption coefficients of various mineral dust components including silicate clays (illite, kaolin and bentonite), oxides (quartz, hematite and rutile), and carbonate (limestone) were determined at wavelengths of 1064, 532, 355 and 266 nm. These values were calculated from aerosol optical absorption coefficients measured by a multi-wavelength photoacoustic (PA) instrument, the mass concentration and the number size distribution of the generated aerosol samples as well as the size transfer functions of the measuring instruments. These results are expected to have considerable importance in global radiative forcing calculations. They can also serve as reference for validating calculated wavelength dependent imaginary parts (κ) of complex refractive indices which up to now have been typically deduced from bulk phase measurements by using indirect measurement methods. Accordingly, the presented comparison of the measured and calculated aerosol optical absorption spectra revealed the strong need for standardized sample preparation and measurement methodology in case of bulk phase measurements.

  8. Errors in short circuit measurements due to spectral mismatch between sunlight and solar simulators

    NASA Technical Reports Server (NTRS)

    Curtis, H. B.

    1976-01-01

    Errors in short circuit current measurement were calculated for a variety of spectral mismatch conditions. The differences in spectral irradiance between terrestrial sunlight and three types of solar simulator were studied, as well as the differences in spectral response between three types of reference solar cells and various test cells. The simulators considered were a short arc xenon lamp AMO sunlight simulator, an ordinary quartz halogen lamp, and an ELH-type quartz halogen lamp. Three types of solar cells studied were a silicon cell, a cadmium sulfide cell and a gallium arsenide cell.

  9. Potential of remote visible and near-infrared spectral reflectance measurements for mapping thermal maturity variations

    SciTech Connect

    Rowan, L.C.; Pawlewicz, M.J.; Jones, O.D. )

    1989-09-01

    The visible and near-infrared (VNIR) spectral reflectance of rocks containing organic matter is related to thermal maturity because thermal alteration liberates hydrogen and forms highly absorbing carbon-rich polycondensed structures. To evaluate the usefulness of remote spectral reflectance measurements for mapping thermal maturity differences, Landsat Thematic Mapper (TM) images of the Eureka, Nevada, area were processed to produce a digital classification image maps that shows maturity in well-exposed, sparsely vegetated areas consisting of Chainman Shale. The relationship between spectral reflectance in TM bands and band ratios and maturity was confirmed through analysis of laboratory VNIR spectral reflectance and mean vitrinite reflectance (R{sub m}) measurements of 20 samples.

  10. Portable Instrument to Measure CDOM Light Absorption in Aquatic Systems: WPI Success Story

    NASA Technical Reports Server (NTRS)

    2001-01-01

    World Precision Instruments, Inc. (WPI), of Sarasota, FL, in collaboration with NASA's John C. Stennis Space Center, has developed an innovative instrument to accurately measure Colored Dissolved Organic Matter (CDOM) absorption in the field. This successful collaboration has culminated in an exciting new device, called the UltraPath, now commercially available through WPI. Traditional methods of measuring absorption of dissolved materials require special handling and storage prior to measurement. Use of laboratory spectrophotometers as the measuring devices have proven time consuming, cumbersome, and delicate to handle. The UltraPath provides a low-cost, highly sensitive, rugged, portable system that is capable of high sensitivity measurements in widely divergent waters.

  11. Ground-based Photon Path Measurements from Solar Absorption Spectra of the O2 A-band

    NASA Technical Reports Server (NTRS)

    Yang, Z.; Wennberg, P. O.; Cageao, R. P.; Pongetti, T. J.; Toon, G. C.; Sander, S. P.

    2005-01-01

    High-resolution solar absorption spectra obtained from Table Mountain Facility (TMF, 34.38degN, 117.68degW, 2286 m elevation) have been analyzed in the region of the O2 A-band. The photon paths of direct sunlight in clear sky cases are retrieved from the O2 absorption lines and compared with ray-tracing calculations based on the solar zenith angle and surface pressure. At a given zenith angle, the ratios of retrieved to geometrically derived photon paths are highly precise (approx.0.2%), but they vary as the zenith angle changes. This is because current models of the spectral lineshape in this band do not properly account for the significant absorption that exists far from the centers of saturated lines. For example, use of a Voigt function with Lorentzian far wings results in an error in the retrieved photon path of as much as 5%, highly correlated with solar zenith angle. Adopting a super-Lorentz function reduces, but does not completely eliminate this problem. New lab measurements of the lineshape are required to make further progress.

  12. A Two-Line Absorption Instrument for Scramjet Temperature and Water Vapor Concentration Measurement in HYPULSE

    NASA Technical Reports Server (NTRS)

    Tsai, C. Y.

    1998-01-01

    A three beam water vapor sensor system has been modified to provide for near simultaneous temperature measurement. The system employs a tunable diode laser to scan spectral line of water vapor. The application to measurements in a scramjet combustor environment of a shock tunnel facility is discussed. This report presents and discusses die initial calibration of the measurement system.

  13. Measurement of the absorption coefficient of scattering liquid media by the calorimetric method

    NASA Astrophysics Data System (ADS)

    Butenin, A. V.; Kogan, B. Ya.

    2012-02-01

    Using the example of a number of hydrosols (gold nanorods and nanoshells, silver nanoshells, zinc phthalocyanine nanoparticles), we show that the absorption coefficient of a scattering liquid medium can be measured from its heating by a short-time laser irradiation. The degree of heating was determined from expansion of the liquid in an ampoule with a capillary (the principle of liquid thermometer). Irradiation was performed at a wavelength of 671 or 1069 nm. From the transmission of samples of hydrosols at these wave-lengths, the sum of the absorption and scattering coefficients has been determined. To measure the absorption spectra of scattering liquids by this method, a laser with a tunable radiation wavelength is required. In the case of monodisperse colloidal solutions, the method ensures the measurement of the absorption and scattering cross-section ratio of particles.

  14. Measurement of Two-Photon Absorption Cross Section of Metal Ions by a Mass Sedimentation Approach

    PubMed Central

    Ma, Zhuo-Chen; Chen, Qi-Dai; Han, Bing; Liu, Xue-Qing; Song, Jun-Feng; Sun, Hong-Bo

    2015-01-01

    The photo-reduction of metal ions in solution induced by femtosecond laser is an important and novel method for fabricating three-dimensional metal microstructures. However, the nonlinear absorption cross section of metal ions remains unknown because its measurement is difficult. In the present study, a method based on Two-Photon Excited Sedimentation (TPES) is proposed to measure the two-photon absorption cross section (TPACS) of metal ions in solution. The power-squared dependence of the amount of sediment on the excitation intensity was confirmed, revealing that 800 nm femtosecond laser induced reduction of metal ions was a two photon absorption process. We believe that the proposed method may be applied to measure the TPACS of several metal ions, thereby opening a new avenue towards future analysis of two-photon absorption materials. PMID:26657990

  15. Thermooptic-based differential measurements of weak solute absorptions with an int