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Sample records for absorption spectrum shift

  1. Absorption driven focus shift

    NASA Astrophysics Data System (ADS)

    Harrop, N.; Wolf, S.; Maerten, O.; Dudek, K.; Ballach, S.; Kramer, R.

    2016-03-01

    Modern high brilliance near infrared lasers have seen a tremendous growth in applications throughout the world. Increased productivity has been achieved by higher laser power and increased brilliance of lasers. Positive impacts on the performance and costs of parts are opposed to threats on process stability and quality, namely shift of focus position over time. A high initial process quality will be reduced by contamination of optics, eventually leading to a focus shift or even destruction of the optics. Focus analysis at full power of multi-kilowatt high brilliance lasers is a very demanding task because of high power densities in the spot and the high power load on optical elements. With the newly developed high power projection optics, the High-Power Micro-Spot Monitor High Brilliance (HP-MSM-HB) is able to measure focus diameter as low as 20 μm at power levels up to 10 kW at very low internal focus shift. A main driving factor behind thermally induced focus shift is the absorption level of the optical element. A newly developed measuring system is designed to determine the relative absorption level in reference to a gold standard. Test results presented show a direct correlation between absorption levels and focus shift. The ability to determine the absorption level of optical elements as well as their performance at full processing power before they are put to use, enables a high level of quality assurance for optics manufacturers and processing head manufacturers alike.

  2. Ultraviolet absorption spectrum of HOCl

    NASA Technical Reports Server (NTRS)

    Burkholder, James B.

    1993-01-01

    The room temperature UV absorption spectrum of HOCl was measured over the wavelength range 200 to 380 nm with a diode array spectrometer. The absorption spectrum was identified from UV absorption spectra recorded following UV photolysis of equilibrium mixtures of Cl2O/H2O/HOCl. The HOCl spectrum is continuous with a maximum at 242 nm and a secondary peak at 304 nm. The measured absorption cross section at 242 nm was (2.1 +/- 0.3) x 10 exp -19/sq cm (2 sigma error limits). These results are in excellent agreement with the work of Knauth et al. (1979) but in poor agreement with the more recent measurements of Mishalanie et al. (1986) and Permien et al. (1988). An HOCl nu2 infrared band intensity of 230 +/- 35/sq cm atm was determined based on this UV absorption cross section. The present results are compared with these previous measurements and the discrepancies are discussed.

  3. Visible absorption spectrum of liquid ethylene

    PubMed Central

    Nelson, Edward T.; Patel, C. Kumar N.

    1981-01-01

    The visible absorption spectrum of liquid ethylene at ≈ 108 K from 5500 Å to 7200 Å was measured by using a pulsed tunable dye laser, immersed-transducer, gated-detection opto-acoustic spectroscopy technique. The absorption features show the strongest band with an absorption coefficient of ≈2 × 10-2 cm-1 and the weakest band with an absorption coefficient of ≈1 × 10-4 cm-1. Proposed assignments of the observed absorption peaks involve combinations of overtones of local and normal modes of vibration of ethylene. PMID:16592978

  4. Quantum Entanglement Molecular Absorption Spectrum Simulator

    NASA Technical Reports Server (NTRS)

    Nguyen, Quang-Viet; Kojima, Jun

    2006-01-01

    Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating two photon molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixed-frequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QEMASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled photon spectroscopy for development and implementation of emerging quantum-spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad software package.

  5. Ultraviolet absorption spectrum of gaseous HOCl

    SciTech Connect

    Mishalanie, E.A; Rutkowski, C.J.; Hutte, R.S.; Birks, J.W.

    1986-10-23

    The UV absorption spectrum of gaseous HOCl was investigated in the wavelength region 240 to 390 nm by using a dynamic HOCl source. Substantial quantities of HOCl were produced compared to two species (Cl/sub 2/O, ClO/sub 2/) that are spectral interferences in the wavelength region of interest. Thirteen experimental absorption spectra were analyzed by the statistical method of factor analysis. This analysis revealed that two major components were contributing to the total absorbance in each spectrum and that these two components accounted for 99.97% of all variance in the data. Mass spectra were simultaneously recorded with the absorption spectra by a quadrupole mass spectrometer that was calibrated for HOCl, Cl/sub 2/, Cl/sub 2/O, ClO/sub 2/, and other species. The two components in the absorption spectra were identified as Cl/sub 2/ and HOCl containing trace levels of ClO/sub 2/. The isolated Cl/sub 2/ and HOCl/ClO/sub 2/ spectral curves were obtained from a spectral-isolation factor analysis and quantified by using the Cl/sub 2/ spectrum as an internal standard. Atmospheric photolysis constants averaged over 24 h were calculated as a function of altitude from these cross sections and those currently recommended for atmospheric modeling. The calculated j values from the cross sections generated in this work predict a shorter photolysis lifetime for HOCl above 28 km. This results in a 6 to 19% decrease in the predicted HOCl diurnal average concentration in the altitude region 28 to 34 km, respectively, compared to the concentrations predicted by the currently recommended cross sections.

  6. [The measurement and analysis of visible-absorption spectrum and fluorescence spectrum of lycopene].

    PubMed

    Yang, Xiao-zhan; Li, Ping; Dai, Song-hui; Wu, Da-cheng; Li, Rui-xia; Yang, Jian-hui; Xiao, Hai-bo

    2005-11-01

    Using ICCD spectral detection system, the absorbency of lycopene-carbon bisulfide solution with different concentration was measured, and the result shows that in a specified range the absorption rule of lycopene solution agrees with Lambert-Beer Law. Absorption spectral wavelength shifts were measured respectively when lycopene was dissolved in acetone, normal hexane, petroleum ether, benzene, ethyl acetate, and carbon bisulfide, and comparing to acetone, different red-shift appeared when lycopene was dissolved in benzene, ethyl acetate, and carbon bisulfide when water was added in lycopene-acetone solution, t he absorbency of lycopene dropped, the fine structure of absorption spectrum became indistinct, and a new absorption peak appeared in UV. The reason for these phenomena is that the solvent molecule had different effect on lycopene molecule when lycopene was dissolved in different solvent. Using fluorecence spectrophotometer, fluorescence spectra of lycopene in different concentrations were collected, and the results show that the fluorescence spectra of lycopene were mainly in 500-680 nm. When concentration was lower than 50 microg x mL(-1), the fluorescence intensity linearly increased with increasing concentration, and when concentration was higher than 60 microg x mL(-1), the fluorescence intensity dropped because of the interaction between lycopene molecules. PMID:16499057

  7. Ab initio calculation of the electronic absorption spectrum of liquid water

    NASA Astrophysics Data System (ADS)

    Martiniano, Hugo F. M. C.; Galamba, Nuno; Cabral, Benedito J. Costa

    2014-04-01

    The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O-H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase.

  8. Ab initio calculation of the electronic absorption spectrum of liquid water

    SciTech Connect

    Martiniano, Hugo F. M. C.; Galamba, Nuno; Cabral, Benedito J. Costa

    2014-04-28

    The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O–H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase.

  9. The Absorption Spectrum of Iodine Vapour

    ERIC Educational Resources Information Center

    Tetlow, K. S.

    1972-01-01

    A laboratory experiment is described which presents some molecular parameters of iodine molecule by studying iodine spectrum. Points out this experiment can be conducted by sixth form students in high school laboratories. (PS)

  10. Spread-Spectrum Carrier Estimation With Unknown Doppler Shift

    NASA Technical Reports Server (NTRS)

    DeLeon, Phillip L.; Scaife, Bradley J.

    1998-01-01

    We present a method for the frequency estimation of a BPSK modulated, spread-spectrum carrier with unknown Doppler shift. The approach relies on a classic periodogram in conjunction with a spectral matched filter. Simulation results indicate accurate carrier estimation with processing gains near 40. A DSP-based prototype has been implemented for real-time carrier estimation for use in New Mexico State University's proposal for NASA's Demand Assignment Multiple Access service.

  11. Hearing sensitivity to shifts of rippled-spectrum patterns.

    PubMed

    Nechaev, Dmitry I; Supin, Alexander Ya

    2013-10-01

    The sensitivity of human hearing to shifts in rippled spectrum patterns of sound was investigated. The test signal was band-limited rippled noise with spectrum ripples of various frequency spacing and bandwidth; this type of sound may be considered as a quantitatively controlled imitation of complex natural sounds. The listener was required to detect a shift in the spectrum ripple phase while keeping the other parameters of the noise constant. For cosine-shaped ripples, the lowest threshold (1.1%) was found at a ripple frequency of 3.5 ripples per octave (rpo), which corresponds to a ripple spacing of 20% of the center frequency. The threshold increased for both lower and higher ripple densities. Qualitatively similar patterns of threshold dependence on ripple density were observed for center frequencies from 1 to 4 kHz. Making the ripples narrower than cosine decreased the thresholds to 0.7%-0.75% for ripple densities of 2-5 rpo. Keeping the ripple width constant at 3.5%-7.5% of the frequency resulted in a monotonic threshold dependence on ripple density: The threshold decreased with decreasing density (down to 0.7%). An excitation-pattern model explains qualitatively the observed dependence of the ripple-phase shift threshold on ripple pattern parameters. PMID:24116427

  12. On the bathochromic shift of the absorption by astaxanthin in crustacyanin: a quantum chemical study

    NASA Astrophysics Data System (ADS)

    Durbeej, Bo; Eriksson, Leif A.

    2003-06-01

    The structural origin of the bathochromic shift assumed by the electronic absorption spectrum of protein-bound astaxanthin, the carotenoid that upon binding to crustacyanin is responsible for the blue colouration of lobster shell, is investigated by means of quantum chemical methods. The calculations suggest that the bathochromic shift is largely due to one of the astaxanthin C4 keto groups being hydrogen-bonded to a histidine residue of the surrounding protein, and that the effect of this histidine is directly dependent on its protonation state. Out of the different methodologies (CIS, TD-DFT, and ZINDO/S) employed to calculate wavelengths of maximum absorption, the best agreement with experimental data is obtained using the semiempirical ZINDO/S method.

  13. New transient absorption observed in the spectrum of colloidal CdSe nanoparticles pumped with high-power femtosecond pulses

    SciTech Connect

    Burda, C.; Link, S.; Green, T.C.; El-Sayed, M.A.

    1999-12-09

    The power dependence of the transient absorption spectrum of CdSe nanoparticle colloids with size distribution of 4.0 {+-} 0.4 nm diameter is studied with femtosecond pump-probe techniques. At the lowest pump laser power, the absorption bleaching (negative spectrum) characteristic of the exciton spectrum is observed with maxima at 560 and 480 nm. As the pump laser power increases, two new transient absorptions at 510 and 590 nm with unresolved fast rise (<100 fs) and long decay times ({much{underscore}gt}150 ps) are observed. The energy of each of the positive absorption is red shifted from that of the bleach bands by {approximately}120 MeV. The origin of this shift is discussed in terms of the effect of the internal electric field of the many electron-hole pairs formed within the quantum dot at the high pump intensity, absorption from a metastable excited state or the formation of biexcitons.

  14. Extreme-ultraviolet absorption spectrum of Ga+

    NASA Astrophysics Data System (ADS)

    Dunne, P.; O'sullivan, G.; Ivanov, V. K.

    1993-12-01

    Time-resolved photoabsorption spectra of gallium plasmas have been photographed in the 50-450-Å region using the dual-laser-produced-plasma technique. The absorbing plasmas were produced by focusing the output of a Q-switched ruby laser onto slab targets while the background continuum was produced by focusing the output of a Nd:YAG oscillator-amplifier system (where Nd:YAG denotes neodymium-doped yttrium-aluminum-garnet) onto a samarium or hafnium target. At 130-ns delay between the two pulses the spectrum recorded was due almost exclusively to Ga+. We have observed transitions due to both 3d and 3p excitation. In the former case we identified 3d104s2-3d94s2nf and 3d94s2np series converging on the 2D3/2 and 2D5/2 limits of Ga2+. In the 3p case no strong transitions were observed because of line broadening by super-Coster-Kronig decay of the 3p hole. The identifications were made by comparison with the predictions of Hartree-Fock and Dirac-Fock atomic-structure codes. Many-body calculations were also performed which proved invaluable in estimating the effects of different decay processes. The theoretical predictions are compared with the experimental data.

  15. On the Absorption Spectrum of Noble Gases at the Arc Spectrum Limit

    PubMed Central

    Fano, Ugo; Pupillo, Guido; Zannoni, Alberto; Clark, Charles W.

    2005-01-01

    Rydberg spectral lines of an atom are sometimes superimposed on the continuous spectrum of a different configuration. Effects of interaction among different configurations in one of these cases are theoretically investigated, and a formula is obtained that describes the behavior of absorption spectrum intensity. This offers qualitative justification of some experimental results obtained by BEUTLER in studies of absorption arc spectra of noble gases and Ib spectra of some metal vapors. PMID:27308180

  16. Optical absorption spectrum of Cu 2+ in calcium tartrate tetrahydrate

    NASA Astrophysics Data System (ADS)

    Swamy, Y. K. R.; Reddy, P. P.; Reddy, Y. P.

    1980-02-01

    Copper doped single crystals of calcium tartrate tetrahydrate are grown from silica gel. The optical absorption spectrum is investigated with polarised and unpolarised beams of incident light. The spectrum is attributed to the Cu 2+ ion in C 4V symmetry associated with spin-orbit coupling. The following crystal field parameters are evaluated: Dq = 1000 cm -1; λ = -830 cm -1; Ds = 1540 cm -1; Dt = 470 cm -1.

  17. Absorption spectrum of DNA for wavelengths greater than 300 nm

    SciTech Connect

    Sutherland, J.C.; Griffin, K.P.

    1981-06-01

    Although DNA absorption at wavelengths greater than 300 nm is much weaker than that at shorter wavelengths, this absorption seems to be responsible for much of the biological damage caused by solar radiation of wavelengths less than 320 nm. Accurate measurement of the absorption spectrum of DNA above 300 nm is complicated by turbidity characteristic of concentrated solutions of DNA. We have measured the absorption spectra of DNA from calf thymus, Clostridium perfringens, Escherichia coli, Micrococcus luteus, salmon testis, and human placenta using procedures which separate optical density due to true absorption from that due to turbidity. Above 300 nm, the relative absorption of DNA increases as a function of guanine-cytosine content, presumably because the absorption of guanine is much greater than the absorption of adenine at these wavelengths. This result suggests that the photophysical processes which follow absorption of a long-wavelength photon may, on the average, differ from those induced by shorter-wavelength photons. It may also explain the lower quantum yield for the killing of cells by wavelengths above 300 nm compared to that by shorter wavelengths.

  18. Ultraviolet Absorption Spectrum of Malonaldehyde in Water Is Dominated by Solvent-Stabilized Conformations

    SciTech Connect

    Xu, Xuefei; Zheng, Jingjing; Truhlar, Donald G.

    2015-07-01

    Free energy calculations for eight enol isomers of malonaldehyde (MA) and simulation of the ultraviolet (UV) absorption spectrum in both the gas phase and water (pH = 3, where the molecule exists in neutral undeprotonated form) show that in water the two s-trans nonchelated enol conformers of MA become thermodynamically more stable than the internally hydrogen-bonded (“chelated enol”) conformer (CE). The pure CE conformer in water has a slightly red-shifted UV spectrum with respect to that in the gas phase, but the blue-shifted spectrum observed in water at pH 3 is dominated by solvent-stabilized conformations that have negligible populations in the gas phase. Density functional calculations with the solvation model based on density (SMD) and an ensemble-averaged vertical excitation model explain the experimental observations in detail.

  19. Tuning the Protein-Induced Absorption Shifts of Retinal in Engineered Rhodopsin Mimics.

    PubMed

    Suomivuori, Carl-Mikael; Lang, Lucas; Sundholm, Dage; Gamiz-Hernandez, Ana P; Kaila, Ville R I

    2016-06-01

    Rational design of light-capturing properties requires understanding the molecular and electronic structure of chromophores in their native chemical or biological environment. We employ here large-scale quantum chemical calculations to study the light-capturing properties of retinal in recently designed human cellular retinol binding protein II (hCRBPII) variants (Wang et al. Science, 2012, 338, 1340-1343). Our calculations show that these proteins absorb across a large part of the visible spectrum by combined polarization and electrostatic effects. These effects stabilize the ground or excited state energy levels of the retinal by perturbing the Schiff-base or β-ionone moieties of the chromophore, which in turn modulates the amount of charge transfer within the molecule. Based on the predicted tuning principles, we design putative in silico mutations that further shift the absorption properties of retinal in hCRBPII towards the ultraviolet and infrared regions of the spectrum. PMID:27120137

  20. ULTRAVIOLET ABSORPTION SPECTRUM OF NITROUS OXIDE AS FUNCTION OF TEMPERATURE AND ISOTOPIC SUBSTITUTION

    SciTech Connect

    Selwyn, G.S.; Johnston, H.S.

    1980-07-01

    The ultraviolet absorption spectra of nitrous oxide and its {sup 15}N isotopes over the wavelength range 197 to 172 nm and between 150 and 500 K show a weak continuous absorption and a pattern of diffuse banding that became pronounced at higher temperatures. The temperature dependence of the absorption spectrum results from the activation of the n{sub 2}{double_prime} bending mode. Deconvolution of the data shows that absorption by molecules in the (010) vibrational mode results in a spectrum of vibrational bands superimposed on a continuum. A weaker and nearly continuous spectrum results from the ultraviolet absorption by molecules in the (000) vibrational mode. Analysis of the structuring indicates n{sub 2}{double_prime} = (490 {+-} 10) cm{sup -1}. No rotational structure can be observed. Measurement of the n{sub 2}{double_prime} isotope shift is used to identify the quantum number of the upper state vibrational levels. Normal coordinate analysis of the excited state is used to determine a self-consistent set of molecular parameters: bond angle (115{sup o}), the values of n{sub 1}{prime} and n{sub 3}{prime} (1372 and 1761 cm{sup -1}, respectively), and the force constants of the upper state. It is suggested that the transitions observed are {sup 1}S{sup -}({sup 1}A{sup -}) {l_arrow} X- {sup 1}{sup +} and {sup 1}D {l_arrow} {tilde X} {sup 1}S{sup +}.

  1. Ultraviolet absorption spectrum of chlorine nitrite, ClONO

    NASA Technical Reports Server (NTRS)

    Molina, L. T.; Molina, M. J.

    1977-01-01

    The near-ultraviolet absorption spectrum of chlorine nitrite (ClONO) has been quantitatively investigated over the wavelength range 230-400 nm at 231 K. An absorption maximum was observed at 290 nm with a cross section of 1.5 by 10 to the -18th power sq cm. The calculated lifetime against photodissociation for ClONO in the atmosphere is 2 to 3 minutes. The large photolysis rate indicates that ClONO does not play a significant role in the stratosphere as a temporary holding tank for chlorine.

  2. The root economics spectrum: divergence of absorptive root strategies with root diameter

    NASA Astrophysics Data System (ADS)

    Kong, D.; Wang, J.; Kardol, P.; Wu, H.; Zeng, H.; Deng, X.; Deng, Y.

    2015-08-01

    Plant roots usually vary along a dominant ecological axis, the root economics spectrum (RES), depicting a tradeoff between resource acquisition and conservation. For absorptive roots, which are mainly responsible for resource acquisition, we hypothesized that root strategies as predicted from the RES shift with increasing root diameter. To test this hypothesis, we used seven contrasting plant species for which we separated absorptive roots into two categories: thin roots (< 247 μm diameter) and thick roots. For each category, we analyzed a~range of root traits closely related to resource acquisition and conservation, including root tissue density, carbon (C) and nitrogen (N) fractions as well as root anatomical traits. The results showed that trait relationships for thin absorptive roots followed the expectations from the RES while no clear trait relationships were found in support of the RES for thick absorptive roots. Our results suggest divergence of absorptive root strategies in relation to root diameter, which runs against a single economics spectrum for absorptive roots.

  3. Dynamic registration of D216O absorption spectrum in silica aerogel

    NASA Astrophysics Data System (ADS)

    Sinitsa, L.; Lavrentieva, N.; Lugovskoi, A.

    2014-09-01

    Absorption spectra of the gas phase and adsorbed D2О in the silica aerogel with nanoscale pores were investigated in 3700-5400 cm-1 range using dynamic registration with Fourier Transform spectrometer IFS-125M. Two types of sample with pores of 60 nm wide - the nitrogen gas-treated and untreated aerogels - were examined. The surface treatment of the sample changes noticeably the broadband absorption of adsorbed water. Spectrum of D2O in the pores differs from the spectrum of bulk water as for bandwidth so for band maximum. It was found that treatment of the pores by dry nitrogen leads to increasing hydrophilic properties of the material and to change water band contour. The D2О line widths in both the aerogels exceed those of free monomer in 1.1-3 times at the same pressure. Calculations of self-broadening coefficients of the D2O lines were performed using semi-empirical method based on the impact theory of broadening and includes the correction factors. The calculated results well agree with experimental data. Greater differences were found for the shift of the line centre. The D2O line shifts in the treated pores significantly exceed line shifts in the untreated pores. For some lines, these shifts have the opposite sign indicating complex nature of the molecule-wall interaction.

  4. The Absorption Spectrum of the η Car Ejecta

    NASA Astrophysics Data System (ADS)

    Nielsen, K. E.; Viera, G.; Gull, T. R.

    2005-09-01

    The ultraviolet spectrum of η Car and the very nearby ejecta is dominated by complex wind profiles of the extended atmosphere. Increasingly from the STIS NUV to FUV, absorption features from the ejecta and the interstellar medium are superimposed. The absorption from the foreground ejecta display a velocity dispersion between -650 > v > -100 km s-1, with two easily separated components at -146 and -513 km s-1. These two velocities components have earlier been determined to be formed at very different distances from the central source (Gull et al. 2004), and seem to be linked to Little Homunculus and the Homunculus, respectively.The -146 and -513 km s-1 components show different ionization structures. While the -146 km s-1 component shows a spectrum from almost exclusively singly ionized iron group elements, the fast -513 km s-1 has a lower excitation temperature and consequently shows lines from both neutral and singly ionized species. H2 has a huge impact on the spectrum between 1200 to 1650 Å{} and can for some regions completely describe the ejecta spectrum. The ejecta vary in absorption throughout the spectroscopic period. The -146 km s-1 component strengthens when the minimum approaches. The fast component is not significantly affected across the minimum, however, the molecular lines show a dramatic decrease in intensity likely caused by the drop of FUV radiation reaching the -513 km s-1 ejecta. In this spectral range interstellar features such as S II, C II, C IV, Si II and Si IV have a significant impact on the spectrum. We used an earlier study by Walborn et al. (2002) to estimate the ISM's influence on the η Car spectrum. Many of the interstellar lines show a large velocity dispersion (-388 to +127 km s-1). Within 0.1 arcsec of the central source, STIS resolves spatial features at the 0.25 arcsec scale. A number of strong emission lines are observable in the spectrum and associable with the Weigelt blobs B and C. During the minimum when the FUV and X

  5. Photoionization and absorption spectrum of formaldehyde in the vacuum ultraviolet.

    NASA Technical Reports Server (NTRS)

    Mentall, J. E.; Gentieu, E. P.; Krauss, M.; Neumann, D.

    1971-01-01

    The measurements have been conducted in the spectral range from 600 to 2000 A. Integrated oscillator strengths were determined for a number of strong Rydberg transitions above 1200 A. From the photoionization curve the first adiabatic ionization potential was found to be 10.87 plus or minus 0.01 eV. As an aid in interpreting the absorption spectrum, theoretical calculations were made using a single-configuration self-consistent field procedure for the Rydberg states and a model which included mixing between the Rydberg and valence states.

  6. Infrared absorption spectrum of the simplest deuterated Criegee intermediate CD2OO

    NASA Astrophysics Data System (ADS)

    Huang, Yu-Hsuan; Nishimura, Yoshifumi; Witek, Henryk A.; Lee, Yuan-Pern

    2016-07-01

    We report a transient infrared (IR) absorption spectrum of the simplest deuterated Criegee intermediate CD2OO recorded using a step-scan Fourier-transform spectrometer coupled with a multipass absorption cell. CD2OO was produced from photolysis of flowing mixtures of CD2I2, N2, and O2 (13 or 87 Torr) with laser light at 308 nm. The recorded spectrum shows close structural similarity with the spectrum of CH2OO reported previously [Y.-T. Su et al., Science 340, 174 (2013)]. The four bands observed at 852, 1017, 1054, and 1318 cm-1 are assigned to the OO stretching mode, two distinct in-plane OCD bending modes, and the CO stretching mode of CD2OO, respectively, according to vibrational wavenumbers, IR intensities, rotational contours, and deuterium-isotopic shifts predicted with extensive quantum-chemical calculations. The CO-stretching mode of CD2OO at 1318 cm-1 is blue shifted from the corresponding band of CH2OO at 1286 cm-1; this can be explained by a mechanism based on mode mixing and isotope substitution. A band near 936 cm-1, observed only at higher pressure (87 Torr), is tentatively assigned to the CD2 wagging mode of CD2IOO.

  7. Infrared absorption spectrum of the simplest deuterated Criegee intermediate CD2OO.

    PubMed

    Huang, Yu-Hsuan; Nishimura, Yoshifumi; Witek, Henryk A; Lee, Yuan-Pern

    2016-07-28

    We report a transient infrared (IR) absorption spectrum of the simplest deuterated Criegee intermediate CD2OO recorded using a step-scan Fourier-transform spectrometer coupled with a multipass absorption cell. CD2OO was produced from photolysis of flowing mixtures of CD2I2, N2, and O2 (13 or 87 Torr) with laser light at 308 nm. The recorded spectrum shows close structural similarity with the spectrum of CH2OO reported previously [Y.-T. Su et al., Science 340, 174 (2013)]. The four bands observed at 852, 1017, 1054, and 1318 cm(-1) are assigned to the OO stretching mode, two distinct in-plane OCD bending modes, and the CO stretching mode of CD2OO, respectively, according to vibrational wavenumbers, IR intensities, rotational contours, and deuterium-isotopic shifts predicted with extensive quantum-chemical calculations. The CO-stretching mode of CD2OO at 1318 cm(-1) is blue shifted from the corresponding band of CH2OO at 1286 cm(-1); this can be explained by a mechanism based on mode mixing and isotope substitution. A band near 936 cm(-1), observed only at higher pressure (87 Torr), is tentatively assigned to the CD2 wagging mode of CD2IOO. PMID:27475359

  8. Excitonic Effects and Optical Absorption Spectrum of Doped Graphene

    NASA Astrophysics Data System (ADS)

    Jornada, Felipe; Deslippe, Jack; Louie, Steven

    2012-02-01

    First-principles calculations based on the GW-Bethe-Salpeter Equation (GW-BSE) approach and subsequent experiments have shown large excitonic effects in the optical absorbance of graphene. Here we employ the GW-BSE formalism to probe the effects of charge carrier doping and of having an external electric field on the absorption spectrum of graphene. We show that the absorbance peak due to the resonant exciton exhibits systematic changes in both its position and profile when graphene is gate doped by carriers, in excellent agreement to very recent measurementsootnotetextTony F. Heinz, private communications.. We analyze the various contributions to these changes in the absorption spectrum, such as the effects of screening by carriers to the quasiparticle energies and electron-hole interactions. This work was supported by National Science Foundation Grant No. DMR10-1006184, the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, and the U.S. DOD - Office of Naval Research under RTC Grant No. N00014-09-1-1066. Computer time was provided by NERSC.

  9. Temperature dependence of the NO3 absorption spectrum

    NASA Technical Reports Server (NTRS)

    Sander, Stanley P.

    1986-01-01

    The absorption spectrum of the gas-phase NO3 radical has been studied between 220 and 700 nm by using both flash photolysis and discharge flow reactors for the production of NO3. In the flash photolysis method, cross sections at the peak of the (0,0) band at 661.9 nm were measured relative to the cross section of ClONO2 at several different wavelengths. From the best current measurements of the ClONO2 spectrum, the NO3 cross section at 661.9 nm was determined to be (2.28 + or 0.34) x 10 to the -17th sq cm/molecule at 298 K. Measurements at 230 K indicated that the cross section increases by a factor of 1.18 at the peak of the (0,0) band. The discharge flow method was used both to obtain absolute cross sections at 661.9 nm and to obtain relative absorption spectra between 300 and 700 nm at 298 and 230 K. A value of (1.83 + or - 0.27) x 10 to the -17th sq cm/molecule was obtained for sigma NO3 at 661.9 nm at 298 K. Upper limits to the NO3 cross sections were also measured between 220 and 260 nm with the discharge flow method.

  10. Cause of absorption band shift of disperse red-13 attached on silica spheres

    NASA Astrophysics Data System (ADS)

    Kim, Byoung-Ju; Kim, Hyung-Deok; Kim, Na-Rae; Bang, Byeong-Gyu; Park, Eun-Hye; Kang, Kwang-Sun

    2015-08-01

    A reversible color change and large absorption band shift have been observed for the disperse red-13 (DR-13) attached on the surface of the monodisperse silica spheres. Two step synthetic processes including urethane bond formation and hydrolysis-condensation reactions were used to attach the DR-13 on the surface of the silica spheres. After the reaction, the characteristic absorption peak at 2270 cm-1 representing the -N=C=O asymmetric stretching vibration disappeared, and the a new absorption peak at 1700 cm-1 corresponding the C=O stretching vibration appeared. A visual and reversible color change was observed before and after wetting in alcohol. Although the absorption peak of DR-13 in alcohol is at 510 nm, the absorption peak shifts to 788 nm when it is dried. The absorption peak shifts to 718 nm when it is wetted in alcohol. This result can be explained by the formation of intramolecular charge transfer band.

  11. The energy spectrum and the optical absorption spectrum of C{sub 60} fullerene within the Hubbard model

    SciTech Connect

    Silant’ev, A. V.

    2015-10-15

    Anticommutator Green’s functions and the energy spectrum of C{sub 60} fullerene are calculated in the approximation of static fluctuations within the Hubbard model. On the basis of this spectrum, an interpretation is proposed for the experimentally observed optical absorption bands of C{sub 60} fullerene. The parameters of C{sub 60} fullerene that characterize it within the Hubbard model are calculated by the optical absorption spectrum.

  12. Vertical transition energies vs. absorption maxima: illustration with the UV absorption spectrum of ethylene.

    PubMed

    Lasorne, Benjamin; Jornet-Somoza, Joaquim; Meyer, Hans-Dieter; Lauvergnat, David; Robb, Michael A; Gatti, Fabien

    2014-02-01

    We revisit the validity of making a direct comparison between measured absorption maxima and computed vertical transition energies within 0.1 eV to calibrate an excited-state level of theory. This is illustrated on the UV absorption spectrum of ethylene for which the usual experimental values of 7.66 eV (V←N) and 7.11 eV (R(3s)←N) cannot be compared directly to the results of electronic structure calculations for two very different reasons. After validation of our level of theory against experimental data, a new experimental reference of 7.28 eV is suggested for benchmarking the Rydberg state, and the often-cited average transition energy (7.80 eV) is confirmed as a safer estimate for the valence state. PMID:23711543

  13. UV absorption spectrum of the C2 Criegee intermediate CH{sub 3}CHOO

    SciTech Connect

    Smith, Mica C.; Ting, Wei-Lun; Chang, Chun-Hung; Takahashi, Kaito; Boering, Kristie A.; Lin, Jim Jr-Min

    2014-08-21

    The UV spectrum of CH{sub 3}CHOO was measured by transient absorption in a flow cell at 295 K. The absolute absorption cross sections of CH{sub 3}CHOO were measured by laser depletion in a molecular beam to be (1.06 ± 0.09) × 10{sup −17} cm{sup 2} molecule{sup −1} at 308 nm and (9.7 ± 0.6) × 10{sup −18} cm{sup 2} molecule{sup −1} at 352 nm. After scaling the UV spectrum of CH{sub 3}CHOO to the absolute cross section at 308 nm, the peak UV cross section is (1.27 ± 0.11) × 10{sup −17} cm{sup 2} molecule{sup −1} at 328 nm. Compared to the simplest Criegee intermediate CH{sub 2}OO, the UV absorption band of CH{sub 3}CHOO is similar in intensity but blue shifted by 14 nm, resulting in a 20% slower photolysis rate estimated for CH{sub 3}CHOO in the atmosphere.

  14. UV absorption spectrum of the C2 Criegee intermediate CH3CHOO.

    PubMed

    Smith, Mica C; Ting, Wei-Lun; Chang, Chun-Hung; Takahashi, Kaito; Boering, Kristie A; Lin, Jim Jr-Min

    2014-08-21

    The UV spectrum of CH3CHOO was measured by transient absorption in a flow cell at 295 K. The absolute absorption cross sections of CH3CHOO were measured by laser depletion in a molecular beam to be (1.06 ± 0.09) × 10(-17) cm(2) molecule(-1) at 308 nm and (9.7 ± 0.6) × 10(-18) cm(2) molecule(-1) at 352 nm. After scaling the UV spectrum of CH3CHOO to the absolute cross section at 308 nm, the peak UV cross section is (1.27 ± 0.11) × 10(-17) cm(2) molecule(-1) at 328 nm. Compared to the simplest Criegee intermediate CH2OO, the UV absorption band of CH3CHOO is similar in intensity but blue shifted by 14 nm, resulting in a 20% slower photolysis rate estimated for CH3CHOO in the atmosphere. PMID:25149781

  15. Attentional Shifts between Audition and Vision in Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Occelli, Valeria; Esposito, Gianluca; Venuti, Paola; Arduino, Giuseppe Maurizio; Zampini, Massimiliano

    2013-01-01

    Previous evidence on neurotypical adults shows that the presentation of a stimulus allocates the attention to its modality, resulting in faster responses to a subsequent target presented in the same (vs. different) modality. People with Autism Spectrum Disorders (ASDs) often fail to detect a (visual or auditory) target in a stream of stimuli after…

  16. Modified shifted angular spectrum method for numerical propagation at reduced spatial sampling rates.

    PubMed

    Ritter, André

    2014-10-20

    The shifted angular spectrum method allows a reduction of the number of samples required for numerical off-axis propagation of scalar wave fields. In this work, a modification of the shifted angular spectrum method is presented. It allows a further reduction of the spatial sampling rate for certain wave fields. We calculate the benefit of this method for spherical waves. Additionally, a working implementation is presented showing the example of a spherical wave propagating through a circular aperture. PMID:25401659

  17. Temperature dependence of the far-infrared absorption spectrum of gaseous methane.

    NASA Astrophysics Data System (ADS)

    Codastefano, P.; Dore, P.; Nencini, L.

    The rototranslational absorption spectrum of gaseous methane has been measured at seven different temperatures from 296 to 140 K. The authors have analyzed both the spectral moments and the experimental absorption shapes, assuming that only octupolar and hexadecapolar induction mechanisms contribute to the absorption. This assumption allows to parameterize the temperature dependence of both the intensity and the shape of the absorption band. The results obtained indicate that other contributions to absorption are not negligible.

  18. Development of nanostructured luminophor coating for broadening of solar cell absorption spectrum

    NASA Astrophysics Data System (ADS)

    Kryuchyn, A. A.; Beliak, Ie. V.

    2014-10-01

    One of the major concerns in the area of high efficient solar cell production is a substantial shift between the solar radiation spectra and optical absorption spectra of a photoelectric transducer that significantly reduces solar cell efficiency. We propose a concept which based on coating of conventional and cheap photoelectric transducer with a luminophor that transmits longer wavelengths of the sunlight, absorbs shorter wavelengths and converts them into longer ones by the value of the Stocks shift. While photoluminescent light is not collimated and thus losses may reach up to 50% of converted light, it was also proposed to make micropattern formation at photoelectric transducer surface. We propose synthesizing of specific materials based on composite pyrazoline dyes with addition of polymethylmethacrylate, polystyrene and UV-laquers. It was revealed that synthesized luminophor coating are characterized by sufficiently enough Stocks shift (200-400 nm), high quantum yield (near 80%) and stability under circumstances of long term radiation. Further research demonstrated potential of the significant characteristic's improvement by introducing of organic dye molecules in the white zeolite matrix with additional laser annealing at low intensity. Experimental results have shown that photoluminescent spectrum of pyrazoline dye didn't change shape, bandwidth and amplitude for last 10 years. It was decided that obtained stability is being caused by porous matrix of white zeolite. Simulation of the solar cell functioning helped to understand physics of the process and simplify problem of microrelief and luminophor optimal parameters search.

  19. Red-shift law of intense laser-induced electro-absorption in solids

    NASA Astrophysics Data System (ADS)

    Deng, Hong-Xiang; Zu, Hao-Yue; Wu, Shao-Yi; Sun, Kai; Zu, Xiao-Tao

    2014-02-01

    A theoretical study on the red-shift of laser-induced electro-absorption is presented. It is found that laser-induced red-shift scales with the cube root of the pump laser intensity in the optical tunneling regime and has an obvious deviation from this scale in the multi-photon regime. Our results show that in the optical tunneling regime, the laser-induced red shift has the same law as that in the direct current (DC) approximation. Though the scales are the same in the optical tunneling regime, the physical pictures in the two cases are quite different. The electro-absorption in the DC case is a tunneling-assisted transition process, while the laser-induced electro-absorption is a mixed multi-photon process.

  20. [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

  1. Thermal frequency shift and tunable microwave absorption in BiFeO3 family

    NASA Astrophysics Data System (ADS)

    Li, Yong; Fang, Xiaoyong; Cao, Maosheng

    2016-04-01

    Tunable frequency is highly sought-after task of researcher, because of the potential for applications in selecting frequency, absorber, imaging and biomedical diagnosis. Here, we report the original observation of thermal frequency shift of dielectric relaxation in La/Nd doped BiFeO3 (BFO) in X-band from 300 to 673 K. It exhibits an unexpected result: the relaxation shifts to lower frequency with increasing temperature. The relaxation maximally shifts about a quarter of X-band. The nonlinear term of lattice vibration plays an important role in the frequency shift. The frequency shift leads to tuning microwave absorption, which almost covers the whole X-band by changing temperature. Meanwhile, the great increase of dielectric loss of La/Nd doped BFO due to thermal excited electron hopping enhances microwave absorption above ~460 and ~480 K, respectively. The microwave absorption of La/Nd doped BFO surpasses ‑20 dB at 673 K, and the minimum reflection loss of La doped BFO reaches ‑39 dB. These results open a new pathway to develop BFO-based materials in electromagnetic functional materials and devices for tunable frequency, stealth and thermal imaging at long wavelength.

  2. Thermal frequency shift and tunable microwave absorption in BiFeO3 family.

    PubMed

    Li, Yong; Fang, Xiaoyong; Cao, Maosheng

    2016-01-01

    Tunable frequency is highly sought-after task of researcher, because of the potential for applications in selecting frequency, absorber, imaging and biomedical diagnosis. Here, we report the original observation of thermal frequency shift of dielectric relaxation in La/Nd doped BiFeO3 (BFO) in X-band from 300 to 673 K. It exhibits an unexpected result: the relaxation shifts to lower frequency with increasing temperature. The relaxation maximally shifts about a quarter of X-band. The nonlinear term of lattice vibration plays an important role in the frequency shift. The frequency shift leads to tuning microwave absorption, which almost covers the whole X-band by changing temperature. Meanwhile, the great increase of dielectric loss of La/Nd doped BFO due to thermal excited electron hopping enhances microwave absorption above ~460 and ~480 K, respectively. The microwave absorption of La/Nd doped BFO surpasses -20 dB at 673 K, and the minimum reflection loss of La doped BFO reaches -39 dB. These results open a new pathway to develop BFO-based materials in electromagnetic functional materials and devices for tunable frequency, stealth and thermal imaging at long wavelength. PMID:27093897

  3. Thermal frequency shift and tunable microwave absorption in BiFeO3 family

    PubMed Central

    Li, Yong; Fang, Xiaoyong; Cao, Maosheng

    2016-01-01

    Tunable frequency is highly sought-after task of researcher, because of the potential for applications in selecting frequency, absorber, imaging and biomedical diagnosis. Here, we report the original observation of thermal frequency shift of dielectric relaxation in La/Nd doped BiFeO3 (BFO) in X-band from 300 to 673 K. It exhibits an unexpected result: the relaxation shifts to lower frequency with increasing temperature. The relaxation maximally shifts about a quarter of X-band. The nonlinear term of lattice vibration plays an important role in the frequency shift. The frequency shift leads to tuning microwave absorption, which almost covers the whole X-band by changing temperature. Meanwhile, the great increase of dielectric loss of La/Nd doped BFO due to thermal excited electron hopping enhances microwave absorption above ~460 and ~480 K, respectively. The microwave absorption of La/Nd doped BFO surpasses −20 dB at 673 K, and the minimum reflection loss of La doped BFO reaches −39 dB. These results open a new pathway to develop BFO-based materials in electromagnetic functional materials and devices for tunable frequency, stealth and thermal imaging at long wavelength. PMID:27093897

  4. Ultraviolet absorption spectrum of hydrogen peroxide vapor. [for atmospheric abundances

    NASA Technical Reports Server (NTRS)

    Molina, L. T.; Schinke, S. D.; Molina, M. J.

    1977-01-01

    The ultraviolet absorption cross sections of hydrogen peroxide vapor have been determined over the wavelength range 210 to 350 nm at 296 K. At the longer wavelengths, the gas phase absorptivities are significantly larger than the corresponding values in condensed phase. The atmospheric H2O2 photodissociation rate for overhead sun at the earth's surface is estimated to be about 1.3 x 10 to the -5th/sec.

  5. Methane absorption variations in the spectrum of Pluto

    SciTech Connect

    Buie, M.W.; Fink, U.

    1987-06-01

    The lightcurve phases of 0.18, 0.35, 0.49, and 0.98 covered by 5600-10,500 A absolute spectrophotometry of Pluto during four nights include minimum (0.98) light and one near-maximum (0.49) light. The spectra are noted to exhibit significant methane band absorption depth variations at 6200, 7200, 7900, 8400, 8600, 8900, and 10,000 A, with the minimum absorption occurring at minimum light and thereby indicating a 30-percent change in the methane column abundance in the course of three days. An attempt is made to model this absorption strength variation with rotational phase terms of an isotropic surface distribution of methane frost and a clear layer of CH4 gas. 34 references.

  6. Cognitive Set Shifting Deficits and Their Relationship to Repetitive Behaviors in Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Miller, Haylie L.; Ragozzino, Michael E.; Cook, Edwin H.; Sweeney, John A.; Mosconi, Matthew W.

    2015-01-01

    The neurocognitive impairments associated with restricted and repetitive behaviors (RRBs) in autism spectrum disorder (ASD) are not yet clear. Prior studies indicate that individuals with ASD show reduced cognitive flexibility, which could reflect difficulty shifting from a previously learned response pattern or a failure to maintain a new…

  7. Optical absorption components of light-modulated absorption spectrum of CdS

    NASA Technical Reports Server (NTRS)

    Conway, E. J.; Long, E. R.

    1975-01-01

    The amplitude and decay coefficient of light-induced modulation of absorption (LIMA) was measured as a function of wavelength from 535 to 850 nm for single-crystal CdS. The decay coefficient exhibited a discontinuous resonance at 710 nm which was due to the overlap and cancellation of two opposing absorption changes. A method was developed to separate these opposing absorption changes using the measured decay coefficients. The discrete-level-to-band energy for one absorption change was found to be 1.64 eV. An improved model was developed which contains two associated levels in the band gap separated by 0.32 eV.

  8. The interstellar absorption-line spectrum of Mu Ophiuchi

    NASA Technical Reports Server (NTRS)

    Cardelli, J.; Boehm-Vitense, E.

    1982-01-01

    UV interstellar lines have been measured on high-resolution, long- and short-wavelength IUE spectra of the B8 V star Mu Oph. Column densities for the observed atoms and ions have been determined as well as turbulent velocities. The interstellar spectrum of Mu Oph is similar to the ones for Rho Oph and Zeta Oph. The ionization equilibria of several elements give consistent limits for the electron density. The C I line arising from different fine-structure levels are studied to yield estimates on the physical conditions in the cloud. Relative depletion of elements in the cloud seen in the interstellar spectrum of Mu Oph follows the same pattern as seen in the interstellar spectra of Zeta Oph and six other stars in the Rho Oph cloud complex.

  9. Influence of nanorod absorption spectrum width on superluminality effect for laser pulse propagation

    NASA Astrophysics Data System (ADS)

    Trofimov, Vyacheslav A.; Lysak, Tatiana M.

    2016-03-01

    We investigate the influence of the finite absorption spectrum width on the soliton formation and superluminality phenomenon at a femtosecond pulse propagation in a medium with noble nanoparticles. These effects take place if a positive phase-amplitude grating is induced by laser radiation. We take into account the two-photon absorption (TPA) of laser radiation by nanorods, and time-dependent nanorod aspect ratio changing due to their melting or reshaping because of laser energy absorption, and the nanorod absorption spectrum width. On the basis of computer simulation we demonstrate these effects in a medium with positive phase-amplitude grating, induced by laser radiation, if a weak laser energy absorption takes place on the laser pulse dispersion length.

  10. On the Theory of the Shift Linear Photovoltaic Effect in Semiconductors of Tetrahedral Symmetry Under Two-Photon Absorption

    NASA Astrophysics Data System (ADS)

    Rasulov, R. Ya.; Rasulov, V. R.; Eshboltaev, I.

    2016-05-01

    An occurrence of the current of the shift linear photovoltaic effect under two-photon absorption of light in semiconductors without a center of symmetry with a complex band structure is theoretically analyzed. The contributions both from the simultaneous absorption of two photons and successive absorption of two single photons to the photocurrent are taken into account.

  11. Application of spectrum shifting methodology to restore NaI(Tl)-recorded gamma spectra, shifted due to temperature variations in the environment.

    PubMed

    Mitra, Pratip; Roy, Arup Singha; Verma, Amit K; Pant, Amar D; Prakasha, M S; Anilkumar, S; Kumar, A Vinod

    2016-01-01

    A method has been standardized for restoring a shifted differential pulse height spectrum from a scintillator based gamma ray spectrometer recorded at measurement temperature, to the position of a desired spectrum, recorded at a reference temperature. The method is based on the assumption that the spectrum obtained at measurement temperature represents the same statistical distribution as that at reference temperature but with different energy scales. A computer program has been developed for calculation of the transformation between the energy scales and for the restoration of the shifted spectrum. The method developed has been successfully applied for the restoration of gamma spectra measured at different temperatures. PMID:26492324

  12. Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

    NASA Technical Reports Server (NTRS)

    Gibson, J. S.; Rosen, I. G.

    1985-01-01

    In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

  13. Shifting the closed-loop spectrum in the optimal linear quadratic regulator problem for hereditary systems

    NASA Technical Reports Server (NTRS)

    Gibson, J. S.; Rosen, I. G.

    1987-01-01

    In the optimal linear quadratic regulator problem for finite dimensional systems, the method known as an alpha-shift can be used to produce a closed-loop system whose spectrum lies to the left of some specified vertical line; that is, a closed-loop system with a prescribed degree of stability. This paper treats the extension of the alpha-shift to hereditary systems. As infinite dimensions, the shift can be accomplished by adding alpha times the identity to the open-loop semigroup generator and then solving an optimal regulator problem. However, this approach does not work with a new approximation scheme for hereditary control problems recently developed by Kappel and Salamon. Since this scheme is among the best to date for the numerical solution of the linear regulator problem for hereditary systems, an alternative method for shifting the closed-loop spectrum is needed. An alpha-shift technique that can be used with the Kappel-Salamon approximation scheme is developed. Both the continuous-time and discrete-time problems are considered. A numerical example which demonstrates the feasibility of the method is included.

  14. Origin of the red shifts in the optical absorption bands of nonplanar tetraalkylporphyrins.

    PubMed

    Haddad, Raid E; Gazeau, Stéphanie; Pécaut, Jacques; Marchon, Jean-Claude; Medforth, Craig J; Shelnutt, John A

    2003-02-01

    The view that the large red shifts seen in the UV-visible absorption bands of peripherally crowded nonplanar porphyrins are the result of nonplanar deformations of the macrocycle has recently been challenged by the suggestion that the red shifts arise from substituent-induced changes in the macrocycle bond lengths and bond angles, termed in-plane nuclear reorganization (IPNR). We have analyzed the contributions to the UV-visible band shifts in a series of nickel or zinc meso-tetraalkylporphyrins to establish the origins of the red shifts in these ruffled porphyrins. Structures were obtained using a molecular mechanics force field optimized for porphyrins, and the nonplanar deformations were quantified by using normal-coordinate structural decomposition (NSD). Transition energies were calculated by the INDO/S semiempirical method. These computational studies demonstrate conclusively that the large Soret band red shifts ( approximately 40 nm) seen for very nonplanar meso-tetra(tert-butyl)porphyrin compared to meso-tetra(methyl)porphyrin are primarily the result of nonplanar deformations and not IPNR. Strikingly, nonplanar deformations along the high-frequency 2B(1u) and 3B(1u) normal coordinates of the macrocycle are shown to contribute significantly to the observed red shifts, even though these deformations are an order of magnitude smaller than the observed ruffling (1B(1u)) deformation. Other structural and electronic influences on the UV-visible band shifts are discussed and problems with the recent studies are examined (e.g., the systematic underestimation of the 2B(1u) and 3B(1u) modes in artificially constrained porphyrin structures that leads to a mistaken attribution of the red shift to IPNR). The effect of nonplanar deformations on the UV-visible absorption bands is then probed experimentally with a series of novel bridled nickel chiroporphyrins. In these compounds, the substituent effect is essentially invariant and the amount of nonplanar deformation

  15. Shift-invariant, DWT-based "projection" method for estimation of ultrasound pulse power spectrum.

    PubMed

    Michailovich, Oleg; Adam, Dan

    2002-08-01

    An approach to computing estimates of the ultrasound pulse spectrum from echo-ultrasound RF sequences, measured from biological tissues, is proposed. It is computed by a "projection" algorithm based on the Discrete Wavelet Transform (DWT) using averaging over a range of linear shifts. It is shown that the robust, shift invariant estimate of the ultrasound pulse power spectrum can be obtained by the projection of RF line log spectrum on an appropriately chosen subspace of L2(R) (i.e., the space of square-integrable functions) that is spanned by a redundant collection of compactly supported, scaling functions. This redundant set is formed from the traditional (in Wavelet analysis) orthogonal set of scaling functions and also by all its linear (discrete) shifts. A proof is given that the estimate, so obtained, could be viewed as the average of the orthogonal projections of the RF line log spectrum, computed for all significant linear shifts of the RF line log spectrum in frequency domain. It implies that the estimate is shift-invariant. A computationally efficient scheme is presented for calculating the estimate. Proof is given that the averaged, shift-invariant estimate can be obtained simply by a convolution with a kernel, which can be viewed as the discretized auto-correlation function of the scaling function, appropriate to the particular subspace being considered. It implies that the computational burden is at most O(n log2 n), where n is the problem size, making the estimate quite suitable for real-time processing. Because of the property of the wavelet transform to suppress polynomials of orders lower than the number of the vanishing moments of the wavelet used, the presented approach can be considered as a local polynomial fitting. This locality plays a crucial role in the performance of the algorithm, improving the robustness of the estimation. Moreover, it is shown that the "averaging" nature of the proposed estimation allows using (relatively) poorly

  16. Pressure-induced shifts of the fluorescence spectrum of rhodamine 6G in solution

    SciTech Connect

    Zhang, B.; Chandrasekhar, M.; Chandrasekhar, H.R.

    1985-09-01

    The effect of hydrostatic pressure on the fluorescence spectrum of rhodamine 6G dye in two different solutions is studied. The peak shifts to longer wavelengths with increasing pressure with a pressure coefficient of -29 and -19 cm/sup -1//kbar for ethanol and 4:1 methanol-ethanol solvents, respectively. Possible applications of increasing the tunability of dye lasers by pressure are discussed.

  17. Predicting flaw-induced resonance spectrum shift with theoretical perturbation analysis

    NASA Astrophysics Data System (ADS)

    Lai, C.; Sun, X.

    2013-10-01

    Resonance inspection is an emerging non-destructive evaluation (NDE) technique used by the automotive casting industry which uses the resonance spectra differences between the good part population and the flawed parts to identify anomalous parts. It was previously established that finite-element (FE)-based modal analysis can be used to predict the resonance spectrum for an engineering scale part with relatively good accuracy. However, FE-based simulations can be time consuming in examining the spectrum shifts induced by all possible structural flaws. This paper aims at developing a computationally efficient perturbation technique to quantify the frequency shifts induced by small structural flaws, based on the FE simulated resonance spectrum for the perfect part. A generic automotive connecting rod is used as the example part for our study. The results demonstrate that the linear perturbation theory provides a very promising way in predicting frequency changes induced by small structural flaws. As the flaw size increases, the discrepancy between the perturbation analysis and the actual FE simulation results increases due to nonlinearity, yet the perturbation analysis is still able to predict the right trend in frequency shift.

  18. Predicting Flaw-Induced Resonance Spectrum Shift with Theoretical Perturbation Analysis

    SciTech Connect

    Lai, Canhai; Sun, Xin

    2013-10-28

    Resonance inspection is an emerging non-destructive evaluation (NDE) technique which uses the resonance spectra differences between the good part population and the flawed parts to identify anomalous parts. It was previously established that finite-element (FE)-based modal analysis can be used to predict the resonance spectrum for an engineering scale part with relatively good accuracy. However, FE-based simulations can be time consuming in examining the spectrum shifts induced by all possible structural flaws. This paper aims at developing a computationally efficient perturbation technique to quantify the frequency shifts induced by small structural flaws, based on the FE simulated resonance spectrum for the perfect part. A generic automotive connecting rod is used as the example part for our study. The results demonstrate that the linear perturbation theory provides a very promising way in predicting frequency changes induced by small structural flaws. As the flaw size increases, the discrepancy between the perturbation analysis and the actual FE simulation results increases due to nonlinearity, yet the perturbation analysis is still able to predict the right trend in frequency shift.

  19. Complex Resonance Absorption Structure in the X-Ray Spectrum of IRAS 13349+2438

    NASA Technical Reports Server (NTRS)

    Sako, M.; Kahn, S. M.; Behar, E.; Kaastra, J. S.; Brinkman, A. C.; Boller, Th.; Puchnarewicz, E. M.; Starling, R.; Liedahl, D. A.; Clavel, J.

    2000-01-01

    The luminous infrared-loud quasar IRAS 13349+2438 was observed with the XMM - Newton Observatory as part of the Performance Verification program. The spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad (FWHM - 1400 km/s) absorption lines from highly ionized elements including hydrogen- and helium-like carbon, nitrogen, oxygen, and neon, and several iron L - shell ions (Fe XVII - XX). Also shown in the spectrum is the first astrophysical detection of a broad absorption feature around lambda = 16 - 17 A identified as an unresolved transition array (UTA) of 2p - 3d inner-shell absorption by iron M-shell ions in a much cooler medium; a feature that might be misidentified as an O VII edge when observed with moderate resolution spectrometers. No absorption edges are clearly detected in the spectrum. We demonstrate that the RGS spectrum of IRAS 13349+2438 exhibits absorption lines from two distinct regions, one of which is tentatively associated with the medium that produces the optical/UV reddening.

  20. The UV/Vis absorption spectrum of matrix-isolated dichlorine peroxide, ClOOCl.

    PubMed

    von Hobe, Marc; Stroh, Fred; Beckers, Helmut; Benter, Thorsten; Willner, Helge

    2009-03-14

    UV/Vis absorption spectra of ClOOCl isolated in neon matrices were measured in the wavelength range 220-400 nm. The purity of the trapped samples was checked by infrared and UV/Vis matrix spectroscopy as well as low-temperature Raman spectroscopy. At wavelengths below 290 nm, the results agree with the UV spectrum recently published by Pope et al. [J. Phys. Chem. A, 2007, 111, 4322-4332]. However, the observed absorption in the long wavelength tail of the spectrum-relevant for polar stratospheric ozone loss-is substantially higher than reported by Pope et al. Our results suggest the existence of a ClOOCl electronic state manifold leading to an absorption band similar to those of the near UV spectrum of Cl(2). The differences to previous studies can be accounted for quantitatively by contributions to the reported absorption spectra caused by impurities. The observed band in the long wavelength tail is supported by several high-level ab initio calculations. However, questions arise concerning absolute values of the ClOOCl cross sections, an issue that needs to be revisited in future studies. With calculated photolysis rates based on our spectrum scaled to previous cross sections at the peak absorption, the known polar catalytic ozone-destruction cycles to a large extent account for the observed ozone depletion in the spring polar stratosphere. PMID:19240934

  1. Absorption spectrum of the PbS-doped silica fibers fabricated by ALD and MCVD

    NASA Astrophysics Data System (ADS)

    Ye, Tang; Wen, Jianxiang; Dong, Yanhua; Wang, Tingyun

    2012-11-01

    The technique of atomic layer deposition (ALD) has been introduced to fabricate PbS-doped silica fibers, whose absorption peaks are discovered to be shifted from 1230 nm to 920 nm when the number of ALD deposition cycles varies from 80 to 30 during optical fiber preform fabrication. This is explained by suggesting that the PbS doped in fiber are under the 3D quantum confinement, i.e., quantum dots (QDs). An effective-mass approximat ion of the PbS QDs ' sizes is then made to show the shift of absorption peaks can be attributed to the change of size distribution of these dots.

  2. Solvatochromic Shifts in UV-Vis Absorption Spectra: The Challenging Case of 4-Nitropyridine N-Oxide.

    PubMed

    Budzák, Šimon; Laurent, Adéle D; Laurence, Christian; Medved', Miroslav; Jacquemin, Denis

    2016-04-12

    4-Nitropyridine N-oxide is a well-known molecular probe for which the experimental UV/vis absorption spectrum has been measured in a large number of solvents. Previous measurements and their analyses suggest a dominant role of the solvent hydrogen-bond donation (HBD) capability in the solvatochromic shifts measured for the absorption spectra. Herein, we analyze these solvatochromic effects using a series of complementary approaches, including empirical solvent parameters, high-level calculation of the excited-state dipole and polarizability, several flavors of the polarizable continuum model, as well as dynamics using an effective fragment potential (EFP) description of the solvent molecules. First, applying a recently proposed set of solvent parameters, we show the importance of dispersion interactions for non-HBD solvents. This statement confronts advanced coupled-cluster and multireference calculations of dipole moments and polarizabilities of both the ground and excited states in gas phase. We further address the pros and cons of implicit solvent models combined to time-dependent density functional theory (TD-DFT) in describing the solvents effects for all (HBD and non-HBD) media, the simplest linear-response approach turning out to be the most adequate. Finally, we show that the explicit TD-DFT/EFP2 models work correctly for HBD molecules and allow for restoration of the main experimental trends. PMID:26967198

  3. Dependence of Brillouin frequency shift on water absorption ratio in polymer optical fibers

    NASA Astrophysics Data System (ADS)

    Minakawa, Kazunari; Koike, Kotaro; Hayashi, Neisei; Koike, Yasuhiro; Mizuno, Yosuke; Nakamura, Kentaro

    2016-06-01

    We studied the dependence of the Brillouin frequency shift (BFS) on the water-absorption ratio in poly(methyl methacrylate)-based polymer optical fibers (POFs) to clarify the effect of the humidity on POF-based Brillouin sensors. The BFS, deduced indirectly using an ultrasonic pulse-echo technique, decreased monotonically as the water absorption ratio increased, mainly because of the decrease in the Young's modulus. For the same water absorption ratio, the BFS change was larger at a higher temperature. The maximal BFS changes (absolute values) at 40, 60, and 80 °C were 158, 285, and 510 MHz, respectively (corresponding to the temperature changes of ˜9 °C, ˜16 °C, and ˜30 °C). Thus, some countermeasure against the humidity is indispensable in implementing strain/temperature sensors based on Brillouin scattering in POFs, especially at a higher temperature. On the other hand, Brillouin-based distributed humidity sensors might be developed by exploiting the BFS dependence on water absorption in POFs.

  4. A laboratory investigation of a physical mechanism for the extended infrared absorption ('red shift') in wheat

    NASA Technical Reports Server (NTRS)

    Schutt, J. B.; Rowland, R. R.; Heartly, W. H.

    1984-01-01

    Laboratory spectral measurements, on the components of both greenhouse and field grown winter wheat, were performed to identify the component and its appropriate response which gave rise to the extended infrared absorption or 'red shift' reported by Collins. Results of this study indicated that inherent intraplant adaxial (upper) leaf reflectances were of sufficient variability to suggest that an admixture of mechanisms may have utility on identifying the booting and head emergence stages in the life cycle of wheat. The physical mechanism for the shift was found to be relatively independent of the inherent variability in leaf spectra, and to be dependent upon the difference in the mode of deposition of cuticle upon the abaxial (lower) surface relative to that of the adaxial (upper) surface, the position of the flag leaf, and thus the surface exposed to the incident light during heading and after emergence of the head.

  5. Thermochromic Absorption, Fluorescence Band Shifts and Dipole Moments of BADAN and ACRYLODAN

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2002-08-01

    Using the thermochromic shift method of absorption and fluorescence bands, the electric dipole moments in the ground (μg) and excited (μe) state are simultaneously determined for BADAN (6-bromoacetyl-2-dimethylamino-naphtalene) and ACRYLODAN (6-acrylolyl-2-dimethylamino-naphtalene) in ethyl acetate. For these compounds the same ratio μe/μg = 2.9 was found, which is similar to that of PRODAN (6-propionyl-2-dimethylamino-naphtalene). The estimated empirical Onsager radii afor BADAN and ACRYLODAN are the same, and they are somewhat smaller than the calculated geometrical values.

  6. Two attosecond pulse transient absorption spectroscopy and extraction of the instantaneous AC Stark shift in helium

    NASA Astrophysics Data System (ADS)

    Bækhøj, Jens E.; Bojer Madsen, Lars

    2016-07-01

    In two attosecond pulse absorption spectroscopy (TAPAS) the use of two attosecond XUV pulses allows the extraction of atomic and molecular quantum mechanical dipole phases from spectroscopic measurements. TAPAS relies on interference between processes that individually only include a single XUV photon, and therefore does not rely on high intensity attosecond pulses. To show the usefulness and limitations of the TAPAS method we investigate its capability of capturing the instantaneous AC Stark shift induced by a midinfrared 3200 nm pulse in the | 1{{s}}2{{p}}> state of helium.

  7. Two-photon absorption spectrum of the photoinitiator Lucirin TPO-L

    NASA Astrophysics Data System (ADS)

    Mendonca, C. R.; Correa, D. S.; Baldacchini, T.; Tayalia, P.; Mazur, E.

    2008-03-01

    Two-photon absorption induced polymerization provides a powerful method for the fabrication of intricate three-dimensional microstructures. Recently, Lucirin TPO-L was shown to be a photoinitiator with several advantageous properties for two-photon induced polymerization. Here we measure the two-photon absorption cross-section spectrum of Lucirin TPO-L, which presents a maximum of 1.2 GM at 610 nm. Despite its small two-photon absorption cross-section, it is possible to fabricate excellent microstructures by two-photon polymerization due to the high polymerization quantum yield of Lucirin TPO-L. These results indicate that optimization of the two-photon absorption cross-section is not the only material parameter to be considered when searching for new photoinitiators for microfabrication via two-photon absorption.

  8. Hearing Sensitivity to Shifts of Rippled-Spectrum Sound Signals in Masking Noise

    PubMed Central

    Nechaev, Dmitry I.; Milekhina, Olga N.; Supin, Alexander Ya.

    2015-01-01

    The goal of the study was to enlarge knowledge of discrimination of complex sound signals by the auditory system in masking noise. For that, influence of masking noise on detection of shift of rippled spectrum was studied in normal listeners. The signal was a shift of ripple phase within a 0.5-oct wide rippled spectrum centered at 2 kHz. The ripples were frequency-proportional (throughout the band, ripple spacing was a constant proportion of the ripple center frequency). Simultaneous masker was a 0.5-oct noise below-, on-, or above the signal band. Both the low-frequency (center frequency 1 kHz) and on-frequency (the same center frequency as for the signal) maskers increased the thresholds for detecting ripple phase shift. However, the threshold dependence on the masker level was different for these two maskers. For the on-frequency masker, the masking effect primarily depended on the masker/signal ratio: the threshold steeply increased at a ratio of 5 dB, and no shift was detectable at a ratio of 10 dB. For the low-frequency masker, the masking effect primarily depended on the masker level: the threshold increased at a masker level of 80 dB SPL, and no shift was detectable at a masker level of 90 dB (for a signal level of 50 dB) or 100 dB (for a signal level of 80 dB). The high-frequency masker had little effect. The data were successfully simulated using an excitation-pattern model. In this model, the effect of the on-frequency masker appeared to be primarily due to a decrease of ripple depth. The effect of the low-frequency masker appeared due to widening of the auditory filters at high sound levels. PMID:26462066

  9. Hearing Sensitivity to Shifts of Rippled-Spectrum Sound Signals in Masking Noise.

    PubMed

    Nechaev, Dmitry I; Milekhina, Olga N; Supin, Alexander Ya

    2015-01-01

    The goal of the study was to enlarge knowledge of discrimination of complex sound signals by the auditory system in masking noise. For that, influence of masking noise on detection of shift of rippled spectrum was studied in normal listeners. The signal was a shift of ripple phase within a 0.5-oct wide rippled spectrum centered at 2 kHz. The ripples were frequency-proportional (throughout the band, ripple spacing was a constant proportion of the ripple center frequency). Simultaneous masker was a 0.5-oct noise below-, on-, or above the signal band. Both the low-frequency (center frequency 1 kHz) and on-frequency (the same center frequency as for the signal) maskers increased the thresholds for detecting ripple phase shift. However, the threshold dependence on the masker level was different for these two maskers. For the on-frequency masker, the masking effect primarily depended on the masker/signal ratio: the threshold steeply increased at a ratio of 5 dB, and no shift was detectable at a ratio of 10 dB. For the low-frequency masker, the masking effect primarily depended on the masker level: the threshold increased at a masker level of 80 dB SPL, and no shift was detectable at a masker level of 90 dB (for a signal level of 50 dB) or 100 dB (for a signal level of 80 dB). The high-frequency masker had little effect. The data were successfully simulated using an excitation-pattern model. In this model, the effect of the on-frequency masker appeared to be primarily due to a decrease of ripple depth. The effect of the low-frequency masker appeared due to widening of the auditory filters at high sound levels. PMID:26462066

  10. Research on filling process of fuel and oxidant during detonation based on absorption spectrum technology

    NASA Astrophysics Data System (ADS)

    Lv, Xiao-Jing; Li, Ning; Weng, Chun-Sheng

    2014-12-01

    Research on detonation process is of great significance for the control optimization of pulse detonation engine. Based on absorption spectrum technology, the filling process of fresh fuel and oxidant during detonation is researched. As one of the most important products, H2O is selected as the target of detonation diagnosis. Fiber distributed detonation test system is designed to enable the detonation diagnosis under adverse conditions in detonation process. The test system is verified to be reliable. Laser signals at different working frequency (5Hz, 10Hz and 20Hz) are detected. Change of relative laser intensity in one detonation circle is analyzed. The duration of filling process is inferred from the change of laser intensity, which is about 100~110ms. The peak of absorption spectrum is used to present the concentration of H2O during the filling process of fresh fuel and oxidant. Absorption spectrum is calculated, and the change of absorption peak is analyzed. Duration of filling process calculated with absorption peak consisted with the result inferred from the change of relative laser intensity. The pulse detonation engine worked normally and obtained the maximum thrust at 10Hz under experiment conditions. The results are verified through H2O gas concentration monitoring during detonation.

  11. [Study on removing the lamp spectrum structure in differential optical absorption spectroscopy].

    PubMed

    Qu, Xiao-ying; Li, Yu-jin

    2010-11-01

    Differential optical absorption spectroscopy (DOAS) technique has been used to measure trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range, and nowadays this technique has been widely utilized to measure trace polluted gases in the atmosphere e.g. SO2, NO2, O3, HCHO, etc. However, there exists lamp (xenon lamp or deuteriumlamp) spectrum structure in the measured band (300-700 nm) of the absorption spectra of atmosphere, which badly impacts on precision of retrieving the concentration of trace gases in the atmosphere. People home and abroad generally employ two ways to handle this problem, one is segmenting band retrieving method, another is remedial retrieving method. In the present paper, a new retrieving method to deal with this trouble is introduced. The authors used moving-window average smoothing method to obtain the slow part of the absorption spectra of atmosphere, then achieved the lamp (xenon lamp in the paper) spectrum structure in the measured band of the absorption spectra of atmosphere. The authors analyzed and retrieved the measured spectrum of the atmosphere, and the result is better than the forenamed ways. Chi-square of residuum is 2.995 x 10(-4), and this method was proved to be able to avoid shortcoming of choosing narrowband and disadvantage of discovering the new component of atmosphere in retrieving the concentration of air pollutants and measuring the air pollutants. PMID:21284148

  12. Small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo

    PubMed Central

    Plamont, Marie-Aude; Billon-Denis, Emmanuelle; Maurin, Sylvie; Gauron, Carole; Pimenta, Frederico M.; Specht, Christian G.; Shi, Jian; Quérard, Jérôme; Pan, Buyan; Rossignol, Julien; Moncoq, Karine; Morellet, Nelly; Volovitch, Michel; Lescop, Ewen; Chen, Yong; Triller, Antoine; Vriz, Sophie; Le Saux, Thomas; Jullien, Ludovic; Gautier, Arnaud

    2016-01-01

    This paper presents Yellow Fluorescence-Activating and absorption-Shifting Tag (Y-FAST), a small monomeric protein tag, half as large as the green fluorescent protein, enabling fluorescent labeling of proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and nontoxic fluorogenic ligand (a so-called fluorogen). A unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, provides high labeling selectivity. Y-FAST was engineered from the 14-kDa photoactive yellow protein by directed evolution using yeast display and fluorescence-activated cell sorting. Y-FAST is as bright as common fluorescent proteins, exhibits good photostability, and allows the efficient labeling of proteins in various organelles and hosts. Upon fluorogen binding, fluorescence appears instantaneously, allowing monitoring of rapid processes in near real time. Y-FAST distinguishes itself from other tagging systems because the fluorogen binding is highly dynamic and fully reversible, which enables rapid labeling and unlabeling of proteins by addition and withdrawal of the fluorogen, opening new exciting prospects for the development of multiplexing imaging protocols based on sequential labeling. PMID:26711992

  13. Small fluorescence-activating and absorption-shifting tag for tunable protein imaging in vivo.

    PubMed

    Plamont, Marie-Aude; Billon-Denis, Emmanuelle; Maurin, Sylvie; Gauron, Carole; Pimenta, Frederico M; Specht, Christian G; Shi, Jian; Quérard, Jérôme; Pan, Buyan; Rossignol, Julien; Moncoq, Karine; Morellet, Nelly; Volovitch, Michel; Lescop, Ewen; Chen, Yong; Triller, Antoine; Vriz, Sophie; Le Saux, Thomas; Jullien, Ludovic; Gautier, Arnaud

    2016-01-19

    This paper presents Yellow Fluorescence-Activating and absorption-Shifting Tag (Y-FAST), a small monomeric protein tag, half as large as the green fluorescent protein, enabling fluorescent labeling of proteins in a reversible and specific manner through the reversible binding and activation of a cell-permeant and nontoxic fluorogenic ligand (a so-called fluorogen). A unique fluorogen activation mechanism based on two spectroscopic changes, increase of fluorescence quantum yield and absorption red shift, provides high labeling selectivity. Y-FAST was engineered from the 14-kDa photoactive yellow protein by directed evolution using yeast display and fluorescence-activated cell sorting. Y-FAST is as bright as common fluorescent proteins, exhibits good photostability, and allows the efficient labeling of proteins in various organelles and hosts. Upon fluorogen binding, fluorescence appears instantaneously, allowing monitoring of rapid processes in near real time. Y-FAST distinguishes itself from other tagging systems because the fluorogen binding is highly dynamic and fully reversible, which enables rapid labeling and unlabeling of proteins by addition and withdrawal of the fluorogen, opening new exciting prospects for the development of multiplexing imaging protocols based on sequential labeling. PMID:26711992

  14. Selectivity of the optical-absorption method based on an instrumental pick out of Fourier components in the absorption spectrum

    NASA Astrophysics Data System (ADS)

    Pisarevsky, Yu. V.; Kolesnikov, S. A.; Kolesnikova, E. S.; Turutin, Yu. A.; Konopelko, L. A.; Shor, N. B.

    2016-06-01

    The introduction of interference-polarization filters (IPFs) in the structure of an optical-absorption analyzer makes it possible to pick out a harmonic (a Fourier component of the absorption spectrum) providing measurement with the highest sensitivity. The selectivity of such a method of analysis is determined by overlapping the oscillations of the measured and interfering components. By the example of measurement in benzene in the presence of an interfering component (toluene), the possibility is considered for the optimization of selectivity due to the variation of the path-difference dispersion for ordinary and extraordinary interfering rays. The metrological characteristics of the interference-polarization analyzer of C6H6 confirming the results of calculations are given.

  15. Influence of Reduced Graphene Oxide on Effective Absorption Bandwidth Shift of Hybrid Absorbers.

    PubMed

    Ameer, Shahid; Gul, Iftikhar Hussain

    2016-01-01

    The magnetic nanoparticle composite NiFe2O4 has traditionally been studied for high-frequency microwave absorption with marginal performance towards low-frequency radar bands (particularly L and S bands). Here, NiFe2O4 nanoparticles and nanohybrids using large-diameter graphene oxide (GO) sheets are prepared via solvothermal synthesis for low-frequency wide bandwidth shielding (L and S radar bands). The synthesized materials were characterized using XRD, SEM, FTIR and microwave magneto dielectric spectroscopy. The dimension of these solvothermally synthesized pristine particles and hybrids lies within 30-58 nm. Microwave magneto-dielectric spectroscopy was performed in the low-frequency region in the 1 MHz-3 GHz spectrum. The as-synthesized pristine nanoparticles and hybrids were found to be highly absorbing for microwaves throughout the L and S radar bands (< -10 dB from 1 MHz to 3 GHz). This excellent microwave absorbing property induced by graphene sheet coupling shows application of these materials with absorption bandwidth which is tailored such that these could be used for low frequency. Previously, these were used for high frequency absorptions (typically > 4 GHz) with limited selective bandwidth. PMID:27270944

  16. Influence of Reduced Graphene Oxide on Effective Absorption Bandwidth Shift of Hybrid Absorbers

    PubMed Central

    Ameer, Shahid; Gul, Iftikhar Hussain

    2016-01-01

    The magnetic nanoparticle composite NiFe2O4 has traditionally been studied for high-frequency microwave absorption with marginal performance towards low-frequency radar bands (particularly L and S bands). Here, NiFe2O4 nanoparticles and nanohybrids using large-diameter graphene oxide (GO) sheets are prepared via solvothermal synthesis for low-frequency wide bandwidth shielding (L and S radar bands). The synthesized materials were characterized using XRD, SEM, FTIR and microwave magneto dielectric spectroscopy. The dimension of these solvothermally synthesized pristine particles and hybrids lies within 30–58 nm. Microwave magneto-dielectric spectroscopy was performed in the low-frequency region in the 1 MHz-3 GHz spectrum. The as-synthesized pristine nanoparticles and hybrids were found to be highly absorbing for microwaves throughout the L and S radar bands (< −10 dB from 1 MHz to 3 GHz). This excellent microwave absorbing property induced by graphene sheet coupling shows application of these materials with absorption bandwidth which is tailored such that these could be used for low frequency. Previously, these were used for high frequency absorptions (typically > 4 GHz) with limited selective bandwidth. PMID:27270944

  17. [Effects of LED spectrum combinations on the absorption of mineral elements of hydroponic lettuce].

    PubMed

    Chen, Xiao-Li; Guo, Wen-Zhong; Xue, Xu-Zhang; Mmanake Beauty, Morewane

    2014-05-01

    Lettuce (Lactuca sativa) was hydroponically cultured in a completely enclosed plant factory, in which spectrum proportion-adjustable LED panels were used as sole light source for plant growth. Absorption and content of eleven mineral elements such as K, P, Ca, Mg, Na, Fe, Mn, Zn, Cu, B and Mo in Lactuca sativa under different spectral component conditions were studied by ICP -AES technology. The results showed that: (1) Single or combined spectrums corresponding to the absorbing peaks of chlorophyll a and b (450, 660 nm) could enhance the absorbing ability of roots especially for mineral elements Na, Fe, Mn, Cu and Mo, the single red spectrum had the most significant promoting effect under which contents of those four elements were respectively 7. 8, 4. 2, 4. 0 and 3. 7 times more than that under FL; (2) Absorption of K and B was the highest under FL which was 10. 309 mg g-1 and 32. 6 microg g-1 while the values decreased significantly under single or combined spectrum of red and blue; (3) Plants grown under single blue spectrum had the lowest absorption of Ca and Mg which respectively decreased by 35% and 33% than FL; (4) Lettuce grown under the spectrum combination of 30% blue and 70% red had the highest accumulations of biomass while those grown under 20% blue and 80% red had the highest accumulations of the following seven elements Ca, Mg, Na, Fe, Mn, Zn and B. The results provided theoretical basis for adjusting nutrient solution formula and selecting light spectrum of hydroponic lettuce. PMID:25095445

  18. Tunable ultranarrow spectrum selective absorption in a graphene monolayer at terahertz frequency

    NASA Astrophysics Data System (ADS)

    Wu, Jun

    2016-06-01

    Complete absorption in a graphene monolayer at terahertz frequency through the critical coupling effect is investigated. It is achieved by sandwiching the graphene monolayer between a dielectric grating and a Bragg grating. The designed graphene absorber exhibits near-unity absorption at resonance but with an ultranarrow spectrum and antenna-like response, which is attributed to the combined effects of guided mode resonance with dielectric grating and the photonic band gap with Bragg grating. In addition to numerical simulation, the electric field distributions are also illustrated to provide a physical understanding of the perfect absorption effect. Furthermore, the absorption performance can be tuned by only changing the Fermi level of graphene, which is beneficial for real application. It is believed that this study may be useful for designing next-generation graphene-based optoelectronic devices.

  19. Absorption spectrum of NO in the {gamma}(O, O) band

    SciTech Connect

    Zobnin, A.V.; Korotkov, A.N.

    1995-05-01

    A promising technique for determining the concentration of nitrogen oxide in the air of an industrial zone and in process gases is the measurement of the absorption of UV radiation by this molecule in the {gamma}(O,O) band with the center of {lambda}{sub 0} = 226.5 nm. This band corresponds to the transition X{sup 2}{Pi}{yields}{Alpha}{sup 2}{Sigma} of the NO molecule and is characterized by a complex rotational structure consisting of about 400 lines. This structure cannot be resolved completely by most spectral instruments. However, if the width of the spread function of the device is perceptibly smaller than the width of the given absorption band ({approx_equal}2 nm), but larger than the characteristic space between rotational lines ({approx_equal}0.02 nm), then the recorded transmission spectra of NO are almost insensitive to a change in the form of this function. In the given case, to describe the transmission spectrum it is possible to use the absorption coefficient averaged over rotational lines. And even though the Bouger-Lambert-Beer law is not strictly applicable for this spectrum, the dependence of the transmission spectrum of NO on the optical thickness, temperature, and pressure of the broadening gas can be represented in the form of an empirical dependence that can be useful in practice, for example, when processing the absorption spectra recorded by dispersion gas analyzers. Thus, the need for complex and laborious calculations is avoided, and this simplifies considerably the instrumental implementation of this method of measuring the concentration of NO. The object of the present work is to determine the empirical dependence of the absorption spectrum of NO in the {gamma}(O, O) band on the optical thickness, temperature, and pressure of the broadening gas in the ranges most frequently encountered in operation of dispersion gas analyzers.

  20. Absorption lines in the spectrum of Q0248 + 4302 due to a foreground tidal tail

    SciTech Connect

    Sargent, W.L.W.; Steidel, C.C. California Univ., Berkeley )

    1990-08-01

    The strong absorption lines in the spectrum of the quasar Q0248 + 4302 are discussed. The absorption has been shown to be produced in a sinuous tidal tail which emanates from the nearby galaxy pair G0248 + 4302A,B. There is a velocity difference of about 260 km/s between the systemic redshift of the interacting galaxies and the redshift of the tidal tail at a galactocentric distance of about 11/h kpc. The large velocity spread observed in the tail gas is probably responsible for the unusual strength of the interstellar lines. 18 refs.

  1. Absorption-line profiles in a companion spectrum of a mass-losing cool supergiant

    NASA Technical Reports Server (NTRS)

    Rodrigues, Liliya L.; Boehm-Vitense, Erika

    1992-01-01

    Cool star winds can best be observed in resonance absorption lines seen in the spectrum of a hot companion, due to the wind passing in front of the blue star. We calculated absorption line profiles that would be seen in the ultraviolet part of the blue companion spectrum. Line profiles are derived for different radial dependences of the cool star wind and for different orbital phases of the binary. Bowen and Wilson find theoretically that stellar pulsations drive mass loss. We therefore apply our calculations to the Cepheid binary S Muscae which has a B5V companion. We find an upper limit for the Cepheid mass loss of M less than or equal to 7 x 10 (exp -10) solar mass per year provided that the stellar wind of the companion does not influence the Cepheid wind at large distances.

  2. Absorption line profiles in a companion spectrum of a mass losing cool supergiant

    NASA Technical Reports Server (NTRS)

    Rodrigues, Liliya L.; Boehm-Vitense, Erika

    1990-01-01

    Cool star winds can best be observed in resonance absorption lines seen in the spectrum of a hot companion, due to the wind passing in front of the blue star. We calculated absorption line profiles that would be seen in the ultraviolet part of the blue companion spectrum. Line profiles are derived for different radial dependences of the cool star wind and for different orbital phases of the binary. Bowen and Wilson find theoretically that stellar pulsations drive mass loss. We therefore apply our calculations to the Cepheid binary S Muscae which has a B5V companion. We find an upper limit for the Cepheid mass loss of M less than or equal to 7 x 10(exp -10) solar mass per year provided that the stellar wind of the companion does not influence the Cepheid wind at large distances.

  3. Integration of Semiconducting Sulfides for Full-Spectrum Solar Energy Absorption and Efficient Charge Separation.

    PubMed

    Zhuang, Tao-Tao; Liu, Yan; Li, Yi; Zhao, Yuan; Wu, Liang; Jiang, Jun; Yu, Shu-Hong

    2016-05-23

    The full harvest of solar energy by semiconductors requires a material that simultaneously absorbs across the whole solar spectrum and collects photogenerated electrons and holes separately. The stepwise integration of three semiconducting sulfides, namely ZnS, CdS, and Cu2-x S, into a single nanocrystal, led to a unique ternary multi-node sheath ZnS-CdS-Cu2-x S heteronanorod for full-spectrum solar energy absorption. Localized surface plasmon resonance (LSPR) in the nonstoichiometric copper sulfide nanostructures enables effective NIR absorption. More significantly, the construction of pn heterojunctions between Cu2-x S and CdS leads to staggered gaps, as confirmed by first-principles simulations. This band alignment causes effective electron-hole separation in the ternary system and hence enables efficient solar energy conversion. PMID:27062543

  4. Collision-induced absorption in the far infrared spectrum of Titan

    NASA Technical Reports Server (NTRS)

    Hunt, J. L.; Poll, J. D.; Goorvitch, D.; Tipping, R. H.

    1983-01-01

    The effects of collision-induced absorption on the far infrared spectrum of Titan have been investigated. After a review of the procedure for the theoretical calculation of the N2 translation-rotational spectrum, new results for the temperature range o 70 to 120 K are reported. These are used as input data for a simple atmospheric model in order to compute the far infrared radiance, brightness temperature, and specral limb function. This source of opacity alone is not capable of explaining the Voyager results. When the collision-induced methane is included, the results are in closer agreement in the range between 200 and 300/cm, suggesting that a more complete treatment of collision-induced absorption including particularly CH4-N2, N2-H2, and H2-H2 results, may provide sufficient opacity to reduce or obviate the need for opacities due to clouds or aerosols in order to explain the observed spectra.

  5. Light-induced changes in the absorption spectrum of bacteriorhodopsin under two-wavelength excitation

    NASA Astrophysics Data System (ADS)

    Koklyushkin, A. V.; Korolev, A. E.

    2004-09-01

    The results of spectrophotometric measurements of nonlinear light-induced changes in the absorption spectrum of bacteriorhodopsin D96N occurring upon simultaneous excitation at the wavelengths 633 and 441 nm in the excitation intensity range typical for recording of dynamic holograms are presented. The quantitative conditions under which the action of the radiation at one wavelength reduces the change in the optical density caused by the radiation at the other wavelength are determined.

  6. Chemical Shifts to Metabolic Pathways: Identifying Metabolic Pathways Directly from a Single 2D NMR Spectrum.

    PubMed

    Dubey, Abhinav; Rangarajan, Annapoorni; Pal, Debnath; Atreya, Hanudatta S

    2015-12-15

    Identifying cellular processes in terms of metabolic pathways is one of the avowed goals of metabolomics studies. Currently, this is done after relevant metabolites are identified to allow their mapping onto specific pathways. This task is daunting due to the complex nature of cellular processes and the difficulty in establishing the identity of individual metabolites. We propose here a new method: ChemSMP (Chemical Shifts to Metabolic Pathways), which facilitates rapid analysis by identifying the active metabolic pathways directly from chemical shifts obtained from a single two-dimensional (2D) [(13)C-(1)H] correlation NMR spectrum without the need for identification and assignment of individual metabolites. ChemSMP uses a novel indexing and scoring system comprised of a "uniqueness score" and a "coverage score". Our method is demonstrated on metabolic pathways data from the Small Molecule Pathway Database (SMPDB) and chemical shifts from the Human Metabolome Database (HMDB). Benchmarks show that ChemSMP has a positive prediction rate of >90% in the presence of decluttered data and can sustain the same at 60-70% even in the presence of noise, such as deletions of peaks and chemical shift deviations. The method tested on NMR data acquired for a mixture of 20 amino acids shows a success rate of 93% in correct recovery of pathways. When used on data obtained from the cell lysate of an unexplored oncogenic cell line, it revealed active metabolic pathways responsible for regulating energy homeostasis of cancer cells. Our unique tool is thus expected to significantly enhance analysis of NMR-based metabolomics data by reducing existing impediments. PMID:26556218

  7. THE SURPRISING ABSENCE OF ABSORPTION IN THE FAR-ULTRAVIOLET SPECTRUM OF Mrk 231

    SciTech Connect

    Veilleux, S.; Trippe, M.; Krug, H.; Hamann, F.; Rupke, D. S. N.; Tripp, T. M.; Netzer, H.; Lutz, D.; Genzel, R.; Sturm, E.; Tacconi, L.; Sembach, K. R.; Teng, S. H.; Maiolino, R. E-mail: veilleux@astro.umd.edu

    2013-02-10

    Mrk 231, the nearest (z = 0.0422) quasar, hosts both a galactic-scale wind and a nuclear-scale iron low-ionization broad absorption line (FeLoBAL) outflow. We recently obtained a far-ultraviolet (FUV) spectrum of this object covering {approx}1150-1470 A with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. This spectrum is highly peculiar, highlighted by the presence of faint ({approx}<2% of predictions based on H{alpha}), broad ({approx}>10,000 km s{sup -1} at the base), and highly blueshifted (centroid at {approx} -3500 km s{sup -1}) Ly{alpha} emission. The FUV continuum emission is slightly declining at shorter wavelengths (consistent with F {sub {lambda}}{proportional_to}{lambda}{sup 1.7}) and does not show the presence of any obvious photospheric or wind stellar features. Surprisingly, the FUV spectrum also does not show any unambiguous broad absorption features. It thus appears to be dominated by the AGN, rather than hot stars, and virtually unfiltered by the dusty FeLoBAL screen. The observed Ly{alpha} emission is best explained if it is produced in the outflowing BAL cloud system, while the Balmer lines arise primarily from the standard broad emission line region seen through the dusty (A{sub V} {approx} 7 mag) broad absorption line region. Two possible geometric models are discussed in the context of these new results.

  8. The Surprising Absence of Absorption in the Far-ultraviolet Spectrum of Mrk 231

    NASA Technical Reports Server (NTRS)

    Veilleux, S.; Trippe, M.; Hamann, F.; Rupke, D. S. N.; Tripp, T. M.; Netzer, H.; Lutz, D.; Sembach, K. R.; Krug, H.; Teng, Stacy H.; Genzel, R.; Maiolino, R.; Sturm, E.; Tacconi, L.

    2013-01-01

    Mrk 231, the nearest (z = 0.0422) quasar, hosts both a galactic-scale wind and a nuclear-scale iron low-ionization broad absorption line (FeLoBAL) outflow. We recently obtained a far-ultraviolet (FUV) spectrum of this object covering approx. 1150-1470A with the Cosmic Origins Spectrograph on board the Hubble Space Telescope. This spectrum is highly peculiar, highlighted by the presence of faint (< or approx.2% of predictions based on H(alpha)), broad (> or approx.10,000 km/s at the base), and highly blueshifted (centroid at approx. 3500 km/s) Ly(aplpha) emission. The FUV continuum emission is slightly declining at shorter wavelengths (consistent with F(sub lambda) Alpha Lambda(sup 1.7)) and does not show the presence of any obvious photospheric or wind stellar features. Surprisingly, the FUV spectrum also does not show any unambiguous broad absorption features. It thus appears to be dominated by the AGN, rather than hot stars, and virtually unfiltered by the dusty FeLoBAL screen. The observed Ly(alpha) emission is best explained if it is produced in the outflowing BAL cloud system, while the Balmer lines arise primarily from the standard broad emission line region seen through the dusty (Av approx. 7 mag) broad absorption line region. Two possible geometric models are discussed in the context of these new results.

  9. Matrix-Isolated Infrared Absorption Spectrum of CH2IOO Radical.

    PubMed

    Zhang, Xu; Sander, Stanley P; Cheng, Lan; Thimmakondu, Venkatesan S; Stanton, John F

    2016-01-21

    The peroxyiodomethyl radical, CH2IOO, was generated in cryogenic matrices using tandem supersonic nozzles. One hyperthermal nozzle decomposes diiodomethane (CH2I2) to generate intense beams of CH2I radicals, while the second nozzle continuously deposits O2/argon (Ar) on the matrix at 10 K. The CH2I and O2 in the Ar matrix react to produce the target peroxy radical (CH2IOO). The absorption spectra of the products are monitored with a Fourier transform infrared spectrometer. Eight of the 12 fundamental infrared bands for CH2IOO were observed in an argon matrix at 5 K. The experimental frequencies (cm(-1)) are ν3 = 1407.3, ν4 = 1230.4, ν5 = 1223.2, ν6 = 1085.3, ν7 = 919.9, ν8 = 839.9, ν9 = 567.5, and ν10 = 496.2. Additional confirmation for the vibrational assignment comes from a study of the CH2I(18)O(18)O isotopic species. The six observed frequencies (cm(-1)) for CH2I(18)O(18)O are ν3 = 1407.8, ν4 = 1228.0, ν6 = 1030.8, ν7 = 899.6, ν8 = 836.0, and ν10 = 494.6. Unlike CH2I(16)O(16)O, the ν5 and ν9 bands were not observed for CH2I(18)O(18)O. To guide the experimental analysis, ab initio calculations of the infrared spectrum based on second-order vibrational perturbation theory were performed using force fields computed with relativistic coupled-cluster methods. The experimental frequencies are shown to be in good agreement with the computed fundamental frequencies except for ν9 (for CH2IOO) and ν10 (for CH2I(18)O(18)O). Our findings were compared with the study by Lee and Lee conducted in a para-H2 matrix. The fundamental frequencies are in good agreement (within 6 cm(-1)) except for the two low-frequency modes, ν9 (for CH2IOO) and ν10 (for CH2I(18)O(18)O) likely due to different matrix shifts for para-H2 and Ar matrices. In addition, our calculations are in somewhat better agreement with the experiment values than the calculations by Lee and Lee. Our study also shows that reaction CH2I + O2 produces the peroxy radical CH2IOO in cold matrices (10

  10. Electronic structure and absorption spectrum of biexciton obtained by using exciton basis

    SciTech Connect

    Shiau, Shiue-Yuan; Combescot, Monique; Chang, Yia-Chung

    2013-09-15

    We approach the biexciton Schrödinger equation not through the free-carrier basis as usually done, but through the free-exciton basis, exciton–exciton interactions being treated according to the recently developed composite boson many-body formalism which allows an exact handling of carrier exchange between excitons, as induced by the Pauli exclusion principle. We numerically solve the resulting biexciton Schrödinger equation with the exciton levels restricted to the ground state and we derive the biexciton ground state as well as the bound and unbound excited states as a function of hole-to-electron mass ratio. The biexciton ground-state energy we find, agrees reasonably well with variational results. Next, we use the obtained biexciton wave functions to calculate optical absorption in the presence of a dilute exciton gas in quantum well. We find an asymmetric peak with a characteristic low-energy tail, identified with the biexciton ground state, and a set of Lorentzian-like peaks associated with biexciton unbound states, i.e., exciton–exciton scattering states. Last, we propose a pump–probe experiment to probe the momentum distribution of the exciton condensate. -- Highlights: •New composite boson many-body theory is used to derive exactly the biexciton Schrödinger equation using the exciton basis. •We solved the 2D and 3D biexciton ground- and excited-state binding energies for various electron-to-hole mass ratios. •The absorption spectrum shows an asymmetric low-energy peak identified with the biexciton ground state. •High-energy Lorentzian-like peaks in the absorption spectrum are associated with the exciton–exciton scattering states. •The exciton gas momentum distribution can be determined by the absorption spectrum via the biexciton wave functions.

  11. Atomic Transition Frequencies, Isotope Shifts, and Sensitivity to Variation of the Fine Structure Constant for Studies of Quasar Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Berengut, J. C.; Dzuba, V. A.; Flambaum, V. V.; King, J. A.; Kozlov, M. G.; Murphy, M. T.; Webb, J. K.

    Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, α = {e}2/hslash c , could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that α varies spatially (61). That is, in one direction on the sky α seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger.

  12. Hydrogen sulfide absorption spectrum in the 5700-6600 cm-1 spectral region

    NASA Astrophysics Data System (ADS)

    Brown, L. R.; Naumenko, O. V.; Polovtseva, E. R.; Sinitsa, Leonid N.

    2004-01-01

    High resolution FT absorption spectrum of H2S from 5700 to 6600 cm-1 was experimentally recorded and theoretically treated. As a result of the spectrum assignment 1100 precise energy levels were derived for the 2nd hexad interacting states of H232S, H233S, and H234S isotope species including the highly excited (050) state. These energy levels were modeled using Watson-type rotational Hamiltonian and taking into account Coriolis, Darling-Dennison and weak Fermi-resonance interactions inside polyad of interacting states. An average accuracy of the energy levels fitting is of 0.0019 cm-1 for the main isotope species. New evaluation of the band origin of the dark (012) state Ev = 6385.299cm-1 is obtained from the fitting process which agrees well with recent prediction by Naumenko et al. (J. Mol. Spectrosc. 50, 100-110 (2001)). Precise line intensity measurements were performed for more than 1200 absorption lines with accuracy varying from 1 to 7%. These intensities were modeled within 3.3% using wavefunctions derived in the process of the energy levels fitting. The transformed transition moment expansion with 29 terms for 1088 intensities was used. Detailed and accurate H2S absorption line list was generated in the HITRAN format for the analyzed spectral region.

  13. Surprises from a Deep ASCA Spectrum of the Broad Absorption Line Quasar PHL 5200

    NASA Technical Reports Server (NTRS)

    Mathur, Smita; Matt, G.; Green, P. J.; Elvis, M.; Singh, K. P.

    2002-01-01

    We present a deep (approx. 85 ks) ASCA observation of the prototype broad absorption line quasar (BALQSO) PHL 5200. This is the best X-ray spectrum of a BALQSO yet. We find the following: (1) The source is not intrinsically X-ray weak. (2) The line-of-sight absorption is very strong, with N(sub H) = 5 x 10(exp 23)/sq cm. (3) The absorber does not cover the source completely; the covering fraction is approx. 90%. This is consistent with the large optical polarization observed in this source, implying multiple lines of sight. The most surprising result of this observation is that (4) the spectrum of this BALQSO is not exactly similar to other radio-quiet quasars. The hard X-ray spectrum of PHL 5200 is steep, with the power-law spectral index alpha approx. 1.5. This is similar to the steepest hard X-ray slopes observed so far. At low redshifts, such steep slopes are observed in narrow-line Seyfert 1 (NLS1) galaxies, believed to be accreting at a high Eddington rate. This observation strengthens the analogy between BALQSOs and NLS1 galaxies and supports the hypothesis that BALQSOs represent an early evolutionary state of quasars. It is well accepted that the orientation to the line of sight determines the appearance of a quasar: age seems to play a significant role as well.

  14. [Application of near-infrared absorption spectrum scanning techniques in gas quantitative measurement].

    PubMed

    Ding, Hui; Liang, Jian-Qi; Cui, Jun-Hong; Wu, Xiang-Nan; Li, Xian-Li

    2010-03-01

    A practical gas sensing system utilizing absorption spectrum scanning techniques was developed. Using the narrow-band transmission of a fiber tunable filter (TOF) and wavelength modulation technique, the so-called cross-sensing effects of the traditional spectrum absorption based gas sensor were reduced effectively and thus the target gas was detected sensitively and selectively. In order to reduce the effects of nonlinearity of TOF on the measurement results and improve the system stability in operation, the reflection spectrum of a reference FBG was monitored and employed to control the modulation region and center of TOF wavelength precisely. Moreover, a kind of weak signal detecting circuits was developed to detect the weak response signal of the system with high sensitivity. The properties of the proposed system were demonstrated experimentally by detection of acetylene. Approximate linear relationships between the system responses and the input acetylene concentrations were demonstrated by experiments. The minimum detectable acetylene of 5 x 10(-6), with signal-noise ratio of 3, was also achieved by experiments. PMID:20496683

  15. NF3: UV Absorption Spectrum Temperature Dependence and the Atmospheric and Climate Forcing Implications

    NASA Technical Reports Server (NTRS)

    Papadimitriou, Vassileios C.; McGillen, Max R.; Fleming, Eric L.; Jackman, Charles H.; Burkholder, James B.

    2013-01-01

    Nitrogen trifluoride (NF3) is an atmospherically persistent greenhouse gas that is primarily removed by UV photolysis and reaction with O((sup 1)D) atoms. In this work, the NF3 gas-phase UV absorption spectrum, sigma(delta,T), was measured at 16 wavelengths between 184.95 and 250 nm at temperatures between 212 and 296 K. A significant spectrum temperature dependence was observed in the wavelength region most relevant to atmospheric photolysis (200-220 nm) with a decrease in sigma(210 nm,T) of approximately 45 percent between 296 and 212 K. Atmospheric photolysis rates and global annually averaged lifetimes of NF3 were calculated using the Goddard Space Flight Center 2-D model and the sigma(delta,T) parameterization developed in this work. Including the UV absorption spectrum temperature dependence increased the stratospheric photolysis lifetime from 610 to 762 years and the total global lifetime from 484 to 585 years; the NF3 global warming potentials on the 20-, 100-, and 500-year time horizons increased less than 0.3, 1.1, and 6.5 percent to 13,300, 17,700, and 19,700, respectively.

  16. Simulation of energy absorption spectrum in NaI crystal detector for multiple gamma energy using Monte Carlo method

    SciTech Connect

    Wirawan, Rahadi; Waris, Abdul; Djamal, Mitra; Handayani, Gunawan

    2015-04-16

    The spectrum of gamma energy absorption in the NaI crystal (scintillation detector) is the interaction result of gamma photon with NaI crystal, and it’s associated with the photon gamma energy incoming to the detector. Through a simulation approach, we can perform an early observation of gamma energy absorption spectrum in a scintillator crystal detector (NaI) before the experiment conducted. In this paper, we present a simulation model result of gamma energy absorption spectrum for energy 100-700 keV (i.e. 297 keV, 400 keV and 662 keV). This simulation developed based on the concept of photon beam point source distribution and photon cross section interaction with the Monte Carlo method. Our computational code has been successfully predicting the multiple energy peaks absorption spectrum, which derived from multiple photon energy sources.

  17. The effects of spectral shift absorbers on the design and safety of fast spectrum space reactors

    NASA Astrophysics Data System (ADS)

    King, Jeffrey Charles

    Spectral Shift Absorbers (SSAs) are incorporated into space reactors to maintain them sufficiently subcritical when submerged in seawater or wet sand and subsequently flooded, following a launch abort accident. The effect of four SSAs (samarium-149, europium-151, gadolinium-155, and gadolinium-157) on the submersion criticality, operation, and temperature reactivity feedback of the thermal spectrum reactors developed in the Systems for Nuclear Auxilary Power (SNAP) program is extensively documented. Recent work on SSAs in fast spectrum space reactors, preferred for compactness and higher powers, has focused on rhenium as the primary SSA. In addition to identifying additional SSAs, the present work investigates the effects of SSAs on the overall size and mass, temperature reactivity feedback, and operational lifetime of fast spectrum space reactors. The fast spectrum S4 reactor has a sectored Mo-14%Re solid-core, loadedwith UN fuel, cooled by He-30%Xe, and designed to avoid single point failures at a steady thermal power of 550 kWth. The addition of SSAs to the reactor core increases the fuel enrichment and decreases the size and mass of the reactor and the radiation shadow shield. SSA additions of boron-10, europium-151, gadolinium-155 and iridium result in the smallest and lightest S4 reactors. The effects of SSA additions on the operational lifetime and the temperature and burnup reactivity coefficients of the S^4 reactor are studied. An increasein fuel enrichment with SSAs markedly increases the operational lifetime by decreasing the burnup reactivity coefficient with only a slight decrease in the temperature reactivity feedback coefficient. With no SSAs, the UN fuel enrichment is lowest (58.5 wt%), the temperature and burnup reactivity coefficients are the highest (-0.2709 ¢/K and -1.3470 /atom%), and the estimated operating lifetime is the shortest (7.6 years). The temperature and burnup reactivity coefficients decrease to -0.2649 ¢/K and -1.0230 /atom%, and

  18. The Far-Infrared Absorption Spectrum of Low Temperature Hydrogen Gas.

    NASA Astrophysics Data System (ADS)

    Wishnow, Edward Hyman

    The far-infrared absorption spectrum of normal hydrogen gas has been measured from 20-320 cm^ {-1} (lambda = 500-31 mu M), over the temperature range 21-38 K, and the pressure range 0.6-3 atmospheres. The spectra cover the very weak and broad collision-induced translational absorption band of H_2 which at these low temperatures is observed well isolated from the H_2 rotational lines. Translational absorption occurs when two molecules collide and absorb a photon via a transient induced dipole moment. The molecules emerge from the collision with altered translational energies, and the rotational, vibrational, and electronic energy states remain unaffected. The present spectra are the lowest temperature, lowest pressure, and highest resolution studies of the H_2 translational spectrum. In order to observe the weak translational absorption band, a long pathlength multireflection absorption cell ('White cell'), cooled by the continuous flow of helium vapour, has been designed and constructed. The cell has an f/10 optical beam that allows long wavelength radiation to be transmitted, with low diffraction losses, over an optical path of up to 60 m. The cell is coupled to a Fourier transform interferometer and H_2^ectra are obtained at a spectral resolution of 0.24 cm ^{-1}, 10 times higher than previous experiments. Low temperature absorption spectra are due to not only transitions between molecular translational energy states, but also rotational transitions between the bound states of the van der Waals complex formed by two hydrogen molecules. The integrated absorption of the measured H _2 translational spectrum is consistent with the binary absorption coefficient calculated using the Poll and Van Kranendonk theory of collison-induced absorption. The calculation is based on the quantum mechanical pair distribution function derived from the Lennard-Jones intermolecular potential, and it includes contributions from H_2 dimer bound states. Although dimer transitions

  19. Molecular level all-optical logic with chlorophyll absorption spectrum and polarization sensitivity

    NASA Astrophysics Data System (ADS)

    Raychaudhuri, B.; Bhattacharyya (Bhaumik), S.

    2008-06-01

    Chlorophyll is suggested as a suitable medium for realizing optical Boolean logic at the molecular level in view of its wavelength-selective property and polarization sensitivity in the visible region. Spectrophotometric studies are made with solutions of total chlorophyll and chromatographically isolated components, viz. chlorophyll a and b and carotenoids extracted from pumpkin leaves of different maturity stages. The absorption features of matured chlorophyll with two characteristic absorption peaks and one transmission band are molecular properties and independent of concentration. A qualitative explanation of such an absorption property is presented in terms of a ‘particle in a box’ model and the property is employed to simulate two-input optical logic operations. If both of the inputs are either red or blue, absorption is high. If either one is absent and replaced by a wavelength of the transmission band, e.g. green, absorption is low. Assigning these values as 0 s or 1 s, AND and OR operations can be performed. A NOT operation can be simulated with the transmittance instead of the absorbance. Also, the shift in absorbance values for two different polarizations of the same monochromatic light can simulate two logical states with a single wavelength. Cyclic change in absorbance is noted over a rotation of 360° for both red and blue peaks, although the difference is not very large. Red monochromatic light with polarizations apart by 90°, corresponding to maximum and minimum absorption, respectively, may be assigned as the two logical states. The fluorescence emissions for different pigment components are measured at different excitation wavelengths and the effect of fluorescence on the red absorbance is concluded to be negligible.

  20. [Detection technology of methane gas concentration based on infrared absorption spectrum].

    PubMed

    Luo, Da-Feng; Yang, Jian-Hua; Zhong, Chong-Gui

    2011-02-01

    According to the disadvantages of current methane sensor in coal mine, the infrared methane concentration detection system based on the principle of infrared spectrum absorption was designed using differential absorption technology. In the system single light beam absorbing cell and single light beam and double wavelengths technology are adopted. Differential amplifier circuit serves as the core of faint signal processing circuit that detects the output signal of methane concentration, and linear formula fits the curve of methane concentration and output voltage, which realizes accurate and full range detection of gas concentration. Experiment shows that measurement error is less than 2%, and the system has very high measurement precision and possesses the basis of industrial applications. PMID:21510386

  1. Blue satellites of absorption spectrum study of sodium based excimer-pumped alkali vapor laser

    NASA Astrophysics Data System (ADS)

    Hu, Shu; Gai, Baodong; Guo, Jingwei; Tan, Yannan; Liu, Jinbo; Li, Hui; Cai, Xianglong; Shi, Zhe; Liu, Wanfa; Jin, Yuqi; Sang, Fengting

    2015-02-01

    Sodium based excimer-pump alkali laser (Na-XPAL) is expected to be an efficient method to generate sodium beacon light, but the information about the spectroscopic characters of Na-XPAL remains sparse so far. In this work, we utilized the relative fluorescence intensity to study the absorption spectrum of blue satellites of complexes of sodium with different collision partners. The yellow fluorescence of Na D1 and D2 line was clearly visible. After processing the fluorescence intensity and the input pumping laser relative intensity, we obtained the Na-CH4 system's blue satellites was from 553nm to 556nm. Meanwhile, we experimentally demonstrated the Na-Ar and Na-Xe system's wavelength range of blue satellites. Also, it was observed that the Na-Xe system's absorption was stronger than the other two systems.

  2. Theoretical Study of the Absorption Spectrum and the Thermochemistry of the CF3OSO3 Radical

    NASA Astrophysics Data System (ADS)

    Cobos, Carlos J.; Croce, Adela E.

    2010-09-01

    The UV-visible absorption spectrum of the recently reported CF3OSO3 radical has been studied by using the time-dependent generalization of the density functional theory (TDDFT). For this a set of eleven hybrid functionals combined with the 6-311+G(3df) basis set were employed. The main features of the three experimental absorption bands of CF3OSO3 recorded over the 220 - 530 nm range are well reproduced by the calculations. A dissociation enthalpy for the CF3O-SO3 bond of 19.1 kcal mol-1 is predicted at the BAC-G3MP2//B3LYP/6-311+G(3df) level of theory

  3. Mg I absorption features in the solar spectrum near 9 and 12 microns

    NASA Technical Reports Server (NTRS)

    Glenar, David A.; Reuter, Dennis C.; Deming, Drake; Chang, Edward S.

    1988-01-01

    High-resolution FTS observations from the Kitt Peak National Solar Observatory and the Spacelab 3 ATMOS experiment have revealed additional infrared transitions due to Mg I in the spectra of both quiet sun and sunspot penumbra. In contrast to previous observations, these transitions are seen in absorption, not emission. Absorption intensities range from 1 to 7 percent of the continuum in the quiet sun. In the penumbra, the same features appear to show Zeeman splitting. Modeling of the line profiles in the photospheric spectrum shows evidence for a factor of three overabundance in the n = 5 or more levels of Mg I in the upper photosphere, but with no deviations from a Planck source function. It is concluded that whatever the process that produces the emission (including the Lemke and Holweger mechanism), it must occur well above the tau(5000) = 0.01 level.

  4. Investigations on the 1.7 micron residual absorption feature in the vegetation reflection spectrum

    NASA Technical Reports Server (NTRS)

    Verdebout, J.; Jacquemoud, S.; Andreoli, G.; Hosgood, B.; Sieber, A.

    1993-01-01

    The detection and interpretation of the weak absorption features associated with the biochemical components of vegetation is of great potential interest to a variety of applications ranging from classification to global change studies. This recent subject is also challenging because the spectral signature of the biochemicals is only detectable as a small distortion of the infrared spectrum which is mainly governed by water. Furthermore, the interpretation is complicated by complexity of the molecules (lignin, cellulose, starch, proteins) which contain a large number of different and common chemical bonds. In this paper, we present investigations on the absorption feature centered at 1.7 micron; these were conducted both on AVIRIS data and laboratory reflectance spectra of leaves.

  5. Effect of Sn on the optical band gap determined using absorption spectrum fitting method

    SciTech Connect

    Heera, Pawan; Kumar, Anup; Sharma, Raman

    2015-05-15

    We report the preparation and the optical studies on tellurium rich glasses thin films. The thin films of Se{sub 30}Te{sub 70-x} Sn{sub x} system for x= 0, 1.5, 2.5 and 4.5 glassy alloys prepared by melt quenching technique are deposited on the glass substrate using vacuum thermal evaporation technique. The analysis of absorption spectra in the spectral range 400nm–4000 nm at room temperature obtained from UV-VIS-NIR spectrophotometer [Perkin Elmer Lamda-750] helps us in the optical characterization of the thin films under study. The absorption spectrum fitting method is applied by using the Tauc’s model for estimating the optical band gap and the width of the band tail of the thin films. The optical band gap is calculated and is found to decrease with the Sn content.

  6. INCIDENCE OF Mg II ABSORPTION SYSTEMS TOWARD FLAT-SPECTRUM RADIO QUASARS

    SciTech Connect

    Chand, Hum; Gopal-Krishna E-mail: krishna@ncra.tifr.res.in

    2012-07-20

    The conventional wisdom that the rate of incidence of Mg II absorption systems, dN/dz (excluding 'associated systems' having a velocity {beta}c relative to the active galactic nucleus (AGN) of less than {approx}5000 km s{sup -1}), is totally independent of the background AGNs has been challenged by a recent finding that dN/dz for strong Mg II absorption systems toward distant blazars is 2.2 {+-} {sup 0.8}{sub 0.6} times the value known for normal optically selected quasars (QSOs). This has led to the suggestion that a significant fraction of even the absorption systems with {beta} as high as {approx}0.1 may have been ejected by the relativistic jets in the blazars, which are expected to be pointed close to our direction. Here, we investigate this scenario using a large sample of 115 flat-spectrum radio-loud quasars (FSRQs) that also possess powerful jets, but are only weakly polarized. We show, for the first time, that dN/dz toward FSRQs is, on the whole, quite similar to that known for QSOs and that the comparative excess of strong Mg II absorption systems seen toward blazars is mainly confined to {beta} < 0.15. The excess relative to FSRQs probably results from a likely closer alignment of blazar jets with our direction; hence, any gas clouds accelerated by them are more likely to be on the line of sight to the active quasar nucleus.

  7. Discovery of a second narrow absorption feature in the near-infrared spectrum of Io

    NASA Technical Reports Server (NTRS)

    Lester, D. F.; Trafton, L. M.; Ramseyer, T. F.; Gaffney, N. I.

    1992-01-01

    A high resolution survey of the near-IR reflectance spectrum of Io has shown a sharp absorption feature centered at 5045 +/- 1/cm; this feature is not present in laboratory spectra of dilute CO2 in a matrix. Since the spectrum of cold H2S ice crystals exhibits structure near this wavelength, it is suggested that either (1) the difference in width between this feature and that of the much broader Ionian H2S ice may be due to the presence of different phases of ice at different temperatures, so that these are emphasized in the different spectral regions, or (2) H2S is trapped in an SO2 matrix.

  8. The absorption spectrum of NH 2 in the region 5300 to 6800 Å

    NASA Astrophysics Data System (ADS)

    Ross, S. C.; Birss, F. W.; Vervloet, M.; Ramsay, D. A.

    1988-06-01

    The detailed analysis of the Ã2A 1- X˜2B 1 spectrum of NH 2 in the region 5300 to 6800 Å is reported. Term values derived from the analysis are also presented. Numerous new vibronic substates have been identified. The assignment of the substates and the perturbations detected are discussed in detail, making reference to the calculations of Jungen, Hallin, and Merer and also drawing on the argon matrix absorption spectrum of Robinson and McCarty. The parameters of a simplified model Hamiltonian are reported for most of the substates. The comparison of these results to the calculations of Jungen, Hallin, and Merer, along with the tendencies in the behavior of the spin-orbit coupling constant detected in their work, facilitated the assignments in the present work.

  9. Total Absorption Spectroscopy Study of (92)Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape.

    PubMed

    Zakari-Issoufou, A-A; Fallot, M; Porta, A; Algora, A; Tain, J L; Valencia, E; Rice, S; Bui, V M; Cormon, S; Estienne, M; Agramunt, J; Äystö, J; Bowry, M; Briz, J A; Caballero-Folch, R; Cano-Ott, D; Cucoanes, A; Elomaa, V-V; Eronen, T; Estévez, E; Farrelly, G F; Garcia, A R; Gelletly, W; Gomez-Hornillos, M B; Gorlychev, V; Hakala, J; Jokinen, A; Jordan, M D; Kankainen, A; Karvonen, P; Kolhinen, V S; Kondev, F G; Martinez, T; Mendoza, E; Molina, F; Moore, I; Perez-Cerdán, A B; Podolyák, Zs; Penttilä, H; Regan, P H; Reponen, M; Rissanen, J; Rubio, B; Shiba, T; Sonzogni, A A; Weber, C

    2015-09-01

    The antineutrino spectra measured in recent experiments at reactors are inconsistent with calculations based on the conversion of integral beta spectra recorded at the ILL reactor. (92)Rb makes the dominant contribution to the reactor antineutrino spectrum in the 5-8 MeV range but its decay properties are in question. We have studied (92)Rb decay with total absorption spectroscopy. Previously unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding was found to be 87.5(25)%. The impact on the reactor antineutrino spectra calculated with the summation method is shown and discussed. PMID:26382674

  10. Absorption spectrum of the laser-populated 3D metastable levels in barium

    NASA Technical Reports Server (NTRS)

    Carlsten, J. L.; Mcilrath, T. J.; Parkinson, W. H.

    1975-01-01

    This paper deals with the details of the absorption spectrum of the 3D metastable term in barium. The 3D term was selectively populated with a tuneable dye laser. The fundamental triplet series (6s5d 3D-6snf 3F) is identified and extended out to n = 32. In addition, the absolute photoionization cross section was measured at 303 nm. The relative cross section from 303 to 250 nm was also measured with the absolute scale set by the measurement at 303 nm and was found to be nearly constant in the wavelength region measured.

  11. Water-fat imaging and general chemical shift imaging with spectrum modeling

    NASA Astrophysics Data System (ADS)

    An, Li

    from volunteers and patients in a clinical setting will be presented. In chapter 4, new improvements in the signal-to-noise-ratio (SNR) for the DPE method will be introduced and details of noise performance analysis will be discussed. In chapter 5, a special DPE sampling scheme will be introduced. With three-orthogonal phase (TOP) image acquisitions, it allows a correction of image magnitude errors caused by factors such as T2* relaxation. Details of data acquisition and signal processing will be discussed. Representative results from volunteers will be presented. In chapter 6, we will introduce a new two-point water-fat imaging method. By sampling water and fat asymmetrically and minimizing the gradient energy in a phase map, this method determines water and fat without ambiguity and handles disconnected tissues well. Details of data acquisition, signal processing, and noise performances will be discussed. Representative results from volunteers will be presented. In chapter 7, we will introduce a new general method of chemical shift imaging with spectrum modeling (CSISM). CSISM models a spectrum as several peaks with known resonance frequencies but unknown peak amplitudes which can be resolved from a set of spin-echo images. Details of data acquisition, signal processing and noise performances will be discussed. Representative results from phantom experiments and a clinical scan will be presented. In chapter 8, the general ideas, results and conclusions of all the methods we introduced in this thesis will be discussed, compared, and summarized.

  12. CFCl3 (CFC-11): UV absorption spectrum temperature dependence measurements and the impact on its atmospheric lifetime and uncertainty

    NASA Astrophysics Data System (ADS)

    McGillen, Max R.; Fleming, Eric L.; Jackman, Charles H.; Burkholder, James B.

    2013-09-01

    (CFC-11) is both an atmospheric ozone-depleting and potent greenhouse gas that is removed primarily via stratospheric UV photolysis. Uncertainty in the temperature dependence of its UV absorption spectrum is a significant contributing factor to the overall uncertainty in its global lifetime and, thus, model calculations of stratospheric ozone recovery and climate change. In this work, the CFC-11 UV absorption spectrum was measured over a range of wavelength (184.95-230 nm) and temperature (216-296 K). We report a spectrum temperature dependence that is less than that currently recommended for use in atmospheric models. The impact on its atmospheric lifetime was quantified using a 2-D model and the spectrum parameterization developed in this work. The calculated global annually averaged lifetime was 58.1 ± 0.7 years (2σ uncertainty due solely to the spectrum uncertainty). The lifetime is slightly reduced and the uncertainty significantly reduced from that obtained using current UV spectrum recommendations.

  13. CFCI3 (CFC-11): UV Absorption Spectrum Temperature Dependence Measurements and the Impact on Atmospheric Lifetime and Uncertainty

    NASA Technical Reports Server (NTRS)

    Mcgillen, Max R.; Fleming, Eric L.; Jackman, Charles H.; Burkholder, James B.

    2014-01-01

    CFCl3 (CFC-11) is both an atmospheric ozone-depleting and potent greenhouse gas that is removed primarily via stratospheric UV photolysis. Uncertainty in the temperature dependence of its UV absorption spectrum is a significant contributing factor to the overall uncertainty in its global lifetime and, thus, model calculations of stratospheric ozone recovery and climate change. In this work, the CFC-11 UV absorption spectrum was measured over a range of wavelength (184.95 - 230 nm) and temperature (216 - 296 K). We report a spectrum temperature dependence that is less than currently recommended for use in atmospheric models. The impact on its atmospheric lifetime was quantified using a 2-D model and the spectrum parameterization developed in this work. The obtained global annually averaged lifetime was 58.1 +- 0.7 years (2 sigma uncertainty due solely to the spectrum uncertainty). The lifetime is slightly reduced and the uncertainty significantly reduced from that obtained using current spectrum recommendations

  14. [Research on the influence of LED temperature shifts on differential optical absorption spectroscopy for measuring NO2].

    PubMed

    Ling, Liu-Yi; Xie, Pin-Hua; Qin, Min; Zheng, Ni-Na; Ye, Cong-Lei; Li, Ang; Hu, Ren-Zhi

    2012-11-01

    Influences of LEDs (without etalon structure and center wavelengths are respectively 370 nm (near-UV), 452 nm (blue) and 660 nm(red)) temperature shifts on differential optical absorption spectroscopy(DOAS) for measuring NO2 were studied. NO2 absorption spectra were formed using LED emitting spectra at 10 degrees C. The measured LED spectra at other temperatures were used as reference spectra of DOAS. Thus, NO2 differential optical densities under different LED temperature shifts were acquired and then NO2 differential cross-sections were fitted to the acquired differential optical densities. From fitting results, the linear relations of 0.995, 0.945 and 0.989 correlation between delta of fitting residual and near-UV, blue and red LEDs temperature shifts were found and their slopes are respectively 1.12 x 10(-3), 5.25 x 10(-5) and 7.45 x 10(-4) degrees C(-1). The fitting results show that the influence of temperature shifts of blue LED on DOAS retrieval is negligible and the temperature shifts of near-UV and red LED are impressible to DOAS measurement resulting in degradation of detection sensitivity. The retrieval results of blue LED with and without etalon with similar temperature properties were compared and showed that etalon of LED will greatly increase the influence of temperature shifts of LED on DOAS retrieval. PMID:23387143

  15. Invisible ink mark detection in the visible spectrum using absorption difference.

    PubMed

    Lee, Joong; Kong, Seong G; Kang, Tae-Yi; Kim, Byounghyun; Jeon, Oc-Yeub

    2014-03-01

    One of popular techniques in gambling fraud involves the use of invisible ink marks printed on the back surface of playing cards. Such covert patterns are transparent in the visible spectrum and therefore invisible to unaided human eyes. Invisible patterns can be made visible with ultraviolet (UV) illumination or a CCD camera installed with an infrared (IR) filter depending on the type of ink materials used. Cheating gamers often wear contact lenses or eyeglasses made of IR or UV filters to recognize the secret marks on the playing cards. This paper presents an image processing technique to reveal invisible ink patterns in the visible spectrum without the aid of special equipment such as UV lighting or IR filters. A printed invisible ink pattern leaves a thin coating on the surface with different refractive index for different wavelengths of light, which results in color dispersion or absorption difference. The proposed method finds the differences of color components caused by absorption difference to detect invisible ink patterns on the surface. Experiment results show that the proposed scheme is effective for both UV-active and IR-active invisible ink materials. PMID:24529777

  16. Efficient Algorithms for Estimating the Absorption Spectrum within Linear Response TDDFT

    SciTech Connect

    Brabec, Jiri; Lin, Lin; Shao, Meiyue; Govind, Niranjan; Yang, Chao; Saad, Yousef; Ng, Esmond

    2015-10-06

    We present two iterative algorithms for approximating the absorption spectrum of molecules within linear response of time-dependent density functional theory (TDDFT) framework. These methods do not attempt to compute eigenvalues or eigenvectors of the linear response matrix. They are designed to approximate the absorption spectrum as a function directly. They take advantage of the special structure of the linear response matrix. Neither method requires the linear response matrix to be constructed explicitly. They only require a procedure that performs the multiplication of the linear response matrix with a vector. These methods can also be easily modified to efficiently estimate the density of states (DOS) of the linear response matrix without computing the eigenvalues of this matrix. We show by computational experiments that the methods proposed in this paper can be much more efficient than methods that are based on the exact diagonalization of the linear response matrix. We show that they can also be more efficient than real-time TDDFT simulations. We compare the pros and cons of these methods in terms of their accuracy as well as their computational and storage cost.

  17. 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

  18. 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

  19. The Electronic Absorption Spectrum of Molecular Iodine: A New Fitting Procedure for the Physical Chemistry Laboratory

    NASA Astrophysics Data System (ADS)

    Pursell, Christopher J.; Doezema, Lambert

    1999-06-01

    This paper presents a different approach to the data treatment for the electronic absorption spectrum of molecular iodine, a standard experiment in the undergraduate physical chemistry laboratory. Traditionally, students analyze the transitions originating from the u'' = 0 level using a Birge-Sponer plot and thereby determine the various molecular constants and energies. Our treatment involves simply fitting the transition frequencies to a second-order polynomial. This fit then yields a direct determination of the important molecular constants along with the various energy terms. With the availability of common graphing programs such as Excel, Kaleidagraph, and SigmaPlot, students can take advantage of more advanced fitting techniques and no longer have to rely on simple linear plots. Additionally, students find this new approach more satisfying and we believe it has pedagogical advantages over the Birge-Sponer treatment.

  20. Theoretical reproduction of the Q-band absorption spectrum of free-base chlorin

    NASA Astrophysics Data System (ADS)

    Wójcik, Justyna; Ratuszna, Alicja; Peszke, Jerzy; Wrzalik, Roman

    2015-01-01

    The computational results of the features observed in the room-temperature Q-band absorption spectrum of free-base chlorin (H2Ch) are presented. The vibrational structures of the first and second excited singlet states were calculated based on a harmonic approximation using density functional theory and its time dependent extension within the Franck-Condon and Herzberg-Teller approaches. The outcome allowed to identify the experimental bands and to assign them to the specific vibrational transitions. A very good agreement between the simulated and measured wavelengths and their relative intensities provided the opportunity to predict the origin of the S0 → S2 transition which could not be determined experimentally.

  1. Theoretical reproduction of the Q-band absorption spectrum of free-base chlorin.

    PubMed

    Wójcik, Justyna; Ratuszna, Alicja; Peszke, Jerzy; Wrzalik, Roman

    2015-01-21

    The computational results of the features observed in the room-temperature Q-band absorption spectrum of free-base chlorin (H2Ch) are presented. The vibrational structures of the first and second excited singlet states were calculated based on a harmonic approximation using density functional theory and its time dependent extension within the Franck-Condon and Herzberg-Teller approaches. The outcome allowed to identify the experimental bands and to assign them to the specific vibrational transitions. A very good agreement between the simulated and measured wavelengths and their relative intensities provided the opportunity to predict the origin of the S0 → S2 transition which could not be determined experimentally. PMID:25612704

  2. The UV-vis absorption spectrum of the flavonol quercetin in methanolic solution: A theoretical investigation

    NASA Astrophysics Data System (ADS)

    Andrade-Filho, T.; Ribeiro, T. C. S.; Del Nero, J.

    2009-07-01

    The UV-vis absorption spectrum of the solvated quercetin molecule in methanol was investigated theoretically by means of an elegant type of QM/MM scheme better known as sequential Monte Carlo/quantum mechanics (S-MC/QM) methodology. A set of 125 uncorrelated Monte Carlo molecular liquid structures were properly selected through the autocorrelation function of the energy in order to be used in the quantum mechanical calculations. These molecular liquid structures were obtained by means of the radial and minimum distance distribution functions. A detailed account of the pattern of hydrogen bond structures obtained in this study is also available. The computed results obtained here were directly compared with the available experimental data in order to validate our theoretical model and through this comparison a very good conformity between theoretical and available experimental results was found.

  3. An absorption line in the ultraviolet spectrum of 40 Eridani B

    NASA Technical Reports Server (NTRS)

    Greenstein, J. L.

    1980-01-01

    Two excellent low-resolution spectra show an absorption line of equivalent width 3 A, near 1391 A, in the typical DA (hydrogen atmosphere) white dwarf 40 Eri B. The line is confirmed by a high-resolution spectrum and is the first seen in any DA star. Ultraviolet fluxes and the profile of Lyman-alpha confirm an effective temperature near 17,000 K. If the line is Si IV, it requires a temperature near 40,000 K. Unattractive possibilities are a hot circumstellar absorbing envelope dependent on accretion from companions, or formation at large optical depth in a transparent atmosphere with high Si/H. A suggestion that H2 should be considered leads to the possible interpretation as the (0, 5) transition of the Lyman band, formed at small optical depth. The band should be stronger in cooler DAs.

  4. Absorption features in the x-ray spectrum of an ordinary radio pulsar.

    PubMed

    Kargaltsev, Oleg; Durant, Martin; Misanovic, Zdenka; Pavlov, George G

    2012-08-24

    The vast majority of known nonaccreting neutron stars (NSs) are rotation-powered radio and/or γ-ray pulsars. So far, their multiwavelength spectra have all been described satisfactorily by thermal and nonthermal continuum models, with no spectral lines. Spectral features have, however, been found in a handful of exotic NSs and were thought to be a manifestation of their unique traits. Here, we report the detection of absorption features in the x-ray spectrum of an ordinary rotation-powered radio pulsar, J1740+1000. Our findings bridge the gap between the spectra of pulsars and other, more exotic, NSs, suggesting that the features are more common in the NS spectra than they have been thought so far. PMID:22923576

  5. Analysis of ultraviolet absorption spectrum of Chinese herbal medicine-Cortex Fraxini by double ANN

    NASA Astrophysics Data System (ADS)

    Bai, Lifei; Zhang, Haitao; Wang, Hongxia; Li, Junfeng; Lu, Lei; Zhang, Hanqi; Wang, Hongyan

    2006-11-01

    A fast, accurate and convenient method for the simultaneous determination of multi-component in the Chinese herbal medicine was proposed by using ultraviolet absorption spectrum. In this method, dummy components were added to training sample, and a double artificial neural network (DANN) that has the function of high self-revision and self-simulation was used. Effect of other interference components could be eliminated by adjusting concentration of dummy components. Therefore, the accuracy of concentration prediction for multi-component in the complicated Chinese herbal medicine was improved. It has been realized that two effective components of Cortex Fraxini, aesculin and aesculetin, were simultaneously determined, without any separation. The predicted accuracy was 92% within the permitted relative errors. The measurement precisions of the aesculin and aesculetin were 0.37% and 1.5%, respectively.

  6. Mechanism of Pressure-Induced Phase Transitions, Amorphization, and Absorption-Edge Shift in Photovoltaic Methylammonium Lead Iodide.

    PubMed

    Szafrański, Marek; Katrusiak, Andrzej

    2016-09-01

    Our single-crystal X-ray diffraction study of methylammonium lead triiodide, MAPbI3, provides the first comprehensive structural information on the tetragonal phase II in the pressure range to 0.35 GPa, on the cubic phase IV stable between 0.35 and 2.5 GPa, and on the isostructural cubic phase V observed above 2.5 GPa, which undergoes a gradual amorphization. The optical absorption study confirms that up to 0.35 GPa, the absorption edge of MAPbI3 is red-shifted, allowing an extension of spectral absorption. The transitions to phases IV and V are associated with the abrupt blue shifts of the absorption edge. The strong increase of the energy gap in phase V result in a spectacular color change of the crystal from black to red around 3.5 GPa. The optical changes have been correlated with the pressure-induced strain of the MAPbI3 inorganic framework and its frustration, triggered by methylammonium cations trapped at random orientations in the squeezed voids. PMID:27538989

  7. The soft X-ray absorption spectrum of the allyl free radical.

    PubMed

    Alagia, M; Bodo, E; Decleva, P; Falcinelli, S; Ponzi, A; Richter, R; Stranges, S

    2013-01-28

    The first experimental study of the X-ray absorption spectrum (XAS) of the allyl free radical, CH(2)CHCH(2), is reported. A supersonic He seeded beam of hyperthermal allyl radicals was crossed by a high resolution synchrotron radiation (SR) in the focus of a 3D ion momentum imaging time-of-flight (TOF) spectrometer to investigate the soft X-ray absorption and fragmentation processes. The XAS, recorded as Total-Ion-Yield (TIY), is dominated by C1s electron excitations from either the central carbon atom, C(C), or the two terminal carbon atoms, C(T), to the frontier orbitals, the semi-occupied-molecular-orbital (SOMO) and the lowest-unoccupied-molecular-orbital (LUMO). All of the intense features in the XAS could only be assigned with the aid of ab initio spectral simulation at the Multi-Configuration Self-Consistent-Field (MCSCF) level of theory, this level being required because of the multi-reference nature of the core-excited state wavefunctions of the open shell molecule. The ionization energies (IEs) of the singlet and triplet states of the C1s ionized allyl radical (XPS) were also calculated at the MCSCF level. PMID:23232557

  8. Tight binding model of conformational disorder effects on the optical absorption spectrum of polythiophenes.

    PubMed

    Bombile, Joel H; Janik, Michael J; Milner, Scott T

    2016-05-14

    Semiconducting polymers are soft materials with many conformational degrees of freedom. The limited understanding of how conformational disorder affects their optoelectronic properties is a key source of difficulties that limits their widespread usage in electronic devices. We develop a coarse-grained approach based on the tight binding approximation to model the electronic degrees of freedom of polythiophene chains, taking into account conformational degrees of freedom. Particularly important is dihedral disorder, which disrupts extended electronic states. Our tight binding model is parameterized using density functional theory (DFT) calculations of the one-dimensional band structures for chains with imposed periodic variations in dihedral angles. The model predicts valence and conduction bands for these chain conformations that compare well to DFT results. As an initial application of our model, we compute the optical absorption spectrum of poly(3-hexylthiophene) chains in solution. We observe a broadening of the absorption edge resulting from dihedral disorder, just shy of the experimental broadening. We conclude that the effects of molecular disorder on the optoelectronic properties of conjugated polymer single chains can be mostly accounted for by torsional disorder alone. PMID:27087455

  9. Analysis of urinary stone based on a spectrum absorption FTIR-ATR

    NASA Astrophysics Data System (ADS)

    Asyana, V.; Haryanto, F.; Fitri, L. A.; Ridwan, T.; Anwary, F.; Soekersi, H.

    2016-03-01

    This research analysed the urinary stone by measuring samples using Fourier transform infrared-attenuated total reflection spectroscopy and black box analysis. The main objective of this study is to find kinds of urinary stone and determine a total spectrum, which is a simple model of the chemical and mineral composition urinary stone through black box analysis using convolution method. The measurements result showed that kinds of urinary stone were pure calcium oxalate monohydrate, ion amino acid calcium oxalate monohydrate, a mixture of calcium oxalate monohydrate with calcium phosphate, a mixture of ion amino acid calcium oxalate monohydrate and calcium phosphate,pure uric acid, ion amino acid uric acid, and a mixture of calcium oxalate monohydrate with ion amino acid uric acid. The results of analysis of black box showed characteristics as the most accurate and precise to confirm the type of urinary stones based on theregion absorption peak on a graph, the results of the convolution, and the shape of the total spectrum on each urinary stones.

  10. Absorption spectrum analysis based on singular value decomposition for photoisomerization and photodegradation in organic dyes

    NASA Astrophysics Data System (ADS)

    Kawabe, Yutaka; Yoshikawa, Toshio; Chida, Toshifumi; Tada, Kazuhiro; Kawamoto, Masuki; Fujihara, Takashi; Sassa, Takafumi; Tsutsumi, Naoto

    2015-10-01

    In order to analyze the spectra of inseparable chemical mixtures, many mathematical methods have been developed to decompose them into the components relevant to species from series of spectral data obtained under different conditions. We formulated a method based on singular value decomposition (SVD) of linear algebra, and applied it to two example systems of organic dyes, being successful in reproducing absorption spectra assignable to cis/trans azocarbazole dyes from the spectral data after photoisomerization and to monomer/dimer of cyanine dyes from those during photodegaradation process. For the example of photoisomerization, polymer films containing the azocarbazole dyes were prepared, which have showed updatable holographic stereogram for real images with high performance. We made continuous monitoring of absorption spectrum after optical excitation and found that their spectral shapes varied slightly after the excitation and during recovery process, of which fact suggested the contribution from a generated photoisomer. Application of the method was successful to identify two spectral components due to trans and cis forms of azocarbazoles. Temporal evolution of their weight factors suggested important roles of long lifetimed cis states in azocarbazole derivatives. We also applied the method to the photodegradation of cyanine dyes doped in DNA-lipid complexes which have shown efficient and durable optical amplification and/or lasing under optical pumping. The same SVD method was successful in the extraction of two spectral components presumably due to monomer and H-type dimer. During the photodegradation process, absorption magnitude gradually decreased due to decomposition of molecules and their decaying rates strongly depended on the spectral components, suggesting that the long persistency of the dyes in DNA-complex related to weak tendency of aggregate formation.

  11. Intermolecular interaction as the origin of red shifts in absorption spectra of zinc-phthalocyanine from first-principles.

    PubMed

    Yanagisawa, Susumu; Yasuda, Taiga; Inagaki, Kouji; Morikawa, Yoshitada; Manseki, Kazuhiro; Yanagida, Shozo

    2013-11-01

    We investigate electronic origins of a redshift in absorption spectra of a dimerized zinc phthalocyanine molecule (ZnPc) by means of hybrid density functional theoretical calculations. In terms of the molecular orbital (MO) picture, the dimerization splits energy levels of frontier MOs such as the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the constituent molecules. Consequently, the absorption wavelength seems to become longer than the monomer as the overlap between the monomers becomes larger. However, for a ZnPc dimer configuration with its cofacially stacked monomer arrangement, the calculated absorption spectra within the time-dependent density functional theory indicates no redshift but blueshift in the Q-band absorption spectrum, i.e., a typical H-aggregate. The origin of the apparently contradictory result is elucidated by the conventional description of the interaction between monomer transition dipoles in molecular dimers [Kasha, M. Radiat. Res. 1963, 20, 55]. The redshift is caused by an interaction between the two head-to-tail transition dipoles of the monomers, while the side-by-side arranged transition dipoles result in a blueshift. By tuning the dipole-dipole interaction based on the electronic natures of the HOMO and the LUMO, we describe a slipped-stacked ZnPc dimer configuration in which the Q-band absorption wavelength increases by as large as 144 nm relative to the monomer Q-band. PMID:24106753

  12. The second spectrum of niobium: III. Evaluation of line isotope shifts

    NASA Astrophysics Data System (ADS)

    Bouazza, Safa

    2013-03-01

    Using isotope shift values of only one Nb II line, we propose for the first time to predict isotope shifts of all spectral lines for this ion for any pair of isotopes. For this purpose, we had recourse to ab intio calculations to determine specific mass and field shifts of all relevant Nb II configuration averages, which are respectively proportional to the Vinti integral k-factor and the charge density at the nucleus, 4л|Ψ(o)|2. With the help of very accurate level eigenvectors of these configurations and using the sharing rule, we computed specific mass and field shifts of each level. Since a transition wavenumber is the difference between two energy levels, we then deduced line isotope shifts.

  13. The core shift measurements for two-sided jets affected by Free-Free absorption using VLBA

    NASA Astrophysics Data System (ADS)

    Haga, Takafumi; Doi, Akihiro; Murata, Yasuhiro; Sudou, Hiroshi; Kameno, Seiji; Hada, Kazuhiro; Nagai, Hiroshi

    2013-12-01

    A radio core represents the peak of intensity in VLBI images and is located at the base of jets. It appears at different positions depending on frequencies. This is known as "core shift", caused by absorption of the core emission. The position of the central engine in an AGN can be estimated accurately by measuring the core shift with multifrequency and phase-referencing observations. We observed NGC 4261 using the VLBA at seven frequencies. This source is a nearby FR-I type radio galaxy at the distance of 30 Mpc and has prominent two-sided jets. We measured the core shifts in not only approaching side but also counter side of the jets. The positions of core at infinity of frequency in both side indicated to come close asymptotically to the same position, which was separated by 82±16 μas from 43 GHz core position, corresponding to 310±60 Rs (Schwarzschild radius). This source also has another feature that there is a region affected by free-free absorption (FFA) in the vicinity of the core and toward the counter jet. Moreover, we also found the same feature in other three sources, 3C 84, Cen A and Cyg A, which are also nearby galaxies with two-sided jets and with an indication of the FFA regions. We will measure the core shifts in these sources by using same technique as NGC 4261 in order to study the structure of circumnuclear plasma, to determine the position of the central engine and to test core shifts due to FFA.

  14. The integrated radio continuum spectrum of M33 - Evidence for free-free absorption by cool ionized gas

    NASA Technical Reports Server (NTRS)

    Israel, F. P.; Mahoney, M. J.; Howarth, N.

    1992-01-01

    We present measurements of the integrated radio continuum flux density of M33 at frequencies between 22 and 610 MHz and discuss the radio continuum spectrum of M33 between 22 MHz and 10 GHz. This spectrum has a turnover between 500 and 900 MHz, depending on the steepness of the high frequency radio spectrum of M33. Below 500 MHz the spectrum is relatively flat. We discuss possible mechanisms to explain this spectral shape and consider efficient free-free absorption of nonthermal emission by a cool (not greater than 1000 K) ionized gas to be a very likely possibility. The surface filling factor of both the nonthermal and the thermal material appears to be small (of order 0.001), which could be explained by magnetic field/density fluctuations in the M 33 interstellar medium. We briefly speculate on the possible presence of a nuclear radio source with a steep spectrum.

  15. Rapid pressure swing absorption cleanup of post-shift reactor synthesis gas

    SciTech Connect

    Sirkar, K.K.; Majumdar, S.; Bhaumik, S. . Dept. of Chemical Engineering, Chemistry and Environmental Science)

    1993-01-29

    The theoretical model for the absorption part of a particular type of RAPSAB cycle (Mode 3) (see Technical Progress Report No. 7) has been developed. The numerical simulations of the model compare well with the experimental results presented in the last report (Technical Progress Report No. 7). A number of experiments were carried out also for Mode 2 type of operation by varying the time for initial pressurization of the hollow fiber module as well as the total absorption time. These were done to provide a basis for comparison with the theoretical model to be developed later. We have initiated RAPSAB studies with reactive absorbents such as 19.5 % aqueous solution of diethanolamine (DEA) for the absorption of C0[sub 2] from a C0[sub 2]-N[sub 2] mixture. Six experiments were carried out using Mode 3 type of operation and a C0[sub 2]-N[sub 2] mixture containing 9.9% CO, and balance N[sub 2]. Excellent purification was obtained. No C0[sub 2] was observed in the purified high pressure gas outlet for absorption time of up to 14 seconds; the purified high pressure gas flow rate was also considerable. Module No. 5 was used for all experiments. The details of the module are given in Technical Progress Report No. 7.

  16. Attosecond transient absorption of argon atoms in the vacuum ultraviolet region: line energy shifts versus coherent population transfer

    NASA Astrophysics Data System (ADS)

    Cao, Wei; Warrick, Erika R.; Neumark, Daniel M.; Leone, Stephen R.

    2016-01-01

    Using attosecond transient absorption, the dipole response of an argon atom in the vacuum ultraviolet (VUV) region is studied when an external electromagnetic field is present. An isolated attosecond VUV pulse populates Rydberg states lying 15 eV above the argon ground state. A synchronized few-cycle near infrared (NIR) pulse modifies the oscillating dipoles of argon impulsively, leading to alterations in the VUV absorption spectra. As the NIR pulse is delayed with respect to the VUV pulse, multiple features in the absorption profile emerge simultaneously including line broadening, sideband structure, sub-cycle fast modulations, and 5-10 fs slow modulations. These features indicate the coexistence of two general processes of the light-matter interaction: the energy shift of individual atomic levels and coherent population transfer between atomic eigenstates, revealing coherent superpositions. An intuitive formula is derived to treat both effects in a unifying framework, allowing one to identify and quantify the two processes in a single absorption spectrogram.

  17. The ultraviolet absorption spectrum of the quasar PKS 0405-12 and the local density of Lyman-alpha absorption systems

    NASA Technical Reports Server (NTRS)

    Bahcall, John N.; Jannuzi, Buell T.; Schneider, Donald P.; Hartig, George F.

    1993-01-01

    A sample of 32 absorption lines has been identified in the ultraviolet spectrum of the z = 0.57 quasar PKS 0405-12. Data cover the wavelength range 1190-3260 A. There are 10 extragalactic Ly-alpha absorption lines in the complete sample, all with observed equivalent widths greater than or equal to 0.40 A; three of the Ly-alpha lines have Ly-beta counterparts. The number of Ly-alpha lines observed in the spectrum of PKS 0405-12 is within 1 sigma of the number predicted on the basis of previous HST observations of 3C 273 and of H1821 + 643. Combining the HST observations of 3C 273, H1821 + 643, and PKS 0405-12, we estimate the local number density of Ly-alpha systems with rest equivalent widths larger than 0.32 A to be about 15 +/- 4 Ly-alpha lines per unit redshift. Ground-based images reveal a rich field of galaxies in the direction of PKS 0405-12, including many galaxies with the brightnesses and sizes expected if they belong to a cluster associated with the quasar. The quasar spectrum does not show any evidence for absorption at the redshift of the emission lines, indicating a covering factor of less than unity for the halos of galaxies in the cluster around PKS 0405 - 12.

  18. Temperature sounding from the absorption spectrum of CO2 at 4.3 microns. [in stratosphere and lower mesosphere

    NASA Technical Reports Server (NTRS)

    Toth, R. A.

    1977-01-01

    A new method is described for obtaining the temperature profile in the stratosphere and lower mesosphere from observations of the absorption spectrum of the high J lines of carbon dioxide at 4.3 microns. This concept is based upon the measurement of the integrated absorption of individual CO2 lines whose strengths depend strongly on temperature and that the absorption of these lines are obtained from measurements of the solar or stellar spectrum through an atmospheric path. The technique involves a rapidly converging iterative process in which the equivalent widths of the individual vibration-rotation lines of CO2 are used. Theoretical calculations are presented for balloon and satellite observations using a model atmosphere. Experimental results are given from spectra obtained with a balloon-borne Fourier interferometer spectrometer in which the sun was observed at low zenith angles. The experimental results are compared to rocketsonde data.

  19. A variable absorption feature in the X-ray spectrum of a magnetar.

    PubMed

    Tiengo, Andrea; Esposito, Paolo; Mereghetti, Sandro; Turolla, Roberto; Nobili, Luciano; Gastaldello, Fabio; Götz, Diego; Israel, Gian Luca; Rea, Nanda; Stella, Luigi; Zane, Silvia; Bignami, Giovanni F

    2013-08-15

    Soft-γ-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slowly rotating, isolated neutron stars that sporadically undergo episodes of long-term flux enhancement (outbursts) generally accompanied by the emission of short bursts of hard X-rays. This behaviour can be understood in the magnetar model, according to which these sources are mainly powered by their own magnetic energy. This is supported by the fact that the magnetic fields inferred from several observed properties of SGRs and AXPs are greater than-or at the high end of the range of-those of radio pulsars. In the peculiar case of SGR 0418+5729, a weak dipole magnetic moment is derived from its timing parameters, whereas a strong field has been proposed to reside in the stellar interior and in multipole components on the surface. Here we show that the X-ray spectrum of SGR 0418+5729 has an absorption line, the properties of which depend strongly on the star's rotational phase. This line is interpreted as a proton cyclotron feature and its energy implies a magnetic field ranging from 2 × 10(14) gauss to more than 10(15) gauss. PMID:23955229

  20. Absorption spectrum and ultrafast response of monolayer and bilayer transition-metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Turkowski, Volodymyr; Ramirez-Torres, Alfredo; Rahman, Talat S.

    2015-03-01

    We apply a combined time-dependent density functional theory and many-body theory approach to examine the absorption spectrum and nonequilibrium response of monolayer and bilayer MoS2, MoSe2, WS2 and WSe2 systems. In particular, we evaluate the possibility of existence of bound states - excitons and trions in the undoped systems. In a previous work we have already demonstrated that the binding energies of these states in the monolayer systems are large which makes them available for room temperature applications. We analyze the possibility of ultrafast electron-hole separation in bilayer systems through inter-layer hole transfer, and show that such a possibility exists, in agreement with experimental observations. For doped systems we consider the possibility of Mahan excitonic states in monolayers and show that the binding energy for these states is of the order of 10 meV. We perform a detailed analysis of the relaxation of doped monolayers excited by ultrafast laser pulse by taking into account electron-phonon scattering effects, and demonstrate that ultrafast (10-100fs) processes, including luminescence, may be relevant for these materials. Work supported in part by DOE Grant No. DOE-DE-FG02-07ER46354.

  1. Rapid pressure swing absorption cleanup of post-shift reactor synthesis gas

    SciTech Connect

    Sirkar, K.K.; Majumdar, S.; Bhaumik, S.

    1992-09-24

    This investigation is concerned with the separation of gas mixtures using a novel concept of rapid pressure swing absorption (RAPSAB) of gas in a stationary absorbent liquid through gas-liquid interfaces immobilized in the pore mouths of hydrophobic microporous membranes. The process is implemented in a module well-packed with hydrophobic microporous hollow fiber membranes. Before we proceed to RAPSAB studies with reactive absorbents, it is necessary to make an effort to compare experimental results with those predicted by the models. The only model developed so far involved a type of RAPSAB cycle (Mode 3) for which limited data were acquired earlier. A number of experiments have, therefore, been conducted in this mode to characterize the absorption part of the cycle. A new and more compact module (Module No. 5) was made using 840 fibers and a teflon casing inside the stainless steel shell to exactly define the fiber packing density. This allows an exact calculation of Happel's free surface radius. Experiments were carried out using a CO[sub 2]-N[sub 2] mixture of around 10% CO[sub 2] and balanced N[sub 2] using both modules 4 and 5 over a wide range of absorption times.

  2. Design of Time-Resolved Shifted Dual Transmission Grating Spectrometer for the X-Ray Spectrum Diagnostics

    NASA Astrophysics Data System (ADS)

    Wang, Baoqing; Yi, Tao; Wang, Chuanke; Zhu, Xiaoli; Li, Tingshuai; Li, Jin; Liu, Shenye; Jiang, Shaoen; Ding, Yongkun

    2016-07-01

    A new time-resolved shifted dual transmission grating spectrometer (SDTGS) is designed and fabricated in this work. This SDTGS uses a new shifted dual transmission grating (SDTG) as its dispersive component, which has two sub transmission gratings with different line densities, of 2000 lines/mm and 5000 lines/mm. The axes of the two sub transmission gratings in SDTG are horizontally and vertically shifted a certain distance to measure a broad range of 0.1-5 keV time-resolved X-ray spectra. The SDTG has been calibrated with a soft X-ray beam of the synchrotron radiation facility and its diffraction efficiency is also measured. The designed SDTGS can take full use of the space on a record panel and improve the precision for measuring spatial and temporal spectrum simultaneously. It will be a promising application for accurate diagnosis of the soft X-ray spectrum in inertial confinement fusion. supported by National Natural Science Foundation of China (Nos. 11405158 and 11435011) and Development Foundation of China Academy of Engineering Physics (Nos. 2014B0102011 and 2014B0102012)

  3. CFCl3 (CFC-11): UV Absorption Spectrum Temperature Dependence Measurements and the Impact on Atmospheric Lifetime Uncertainty

    NASA Astrophysics Data System (ADS)

    McGillen, M.; Fleming, E. L.; Jackman, C. H.; Burkholder, J. B.

    2013-12-01

    CFCl3 (CFC-11) is both a major ozone-depleting substance and a potent greenhouse gas that is removed primarily via stratospheric UV photolysis. Uncertainty in the temperature dependence of its UV absorption spectrum is a significant contributing factor to the overall uncertainty in its global lifetime and, thus, model calculations of stratospheric ozone recovery and climate change. In this work, the CFC-11 UV absorption spectrum was measured over a range of wavelength (184.95-230 nm) and temperature (216-296 K). We report a spectrum temperature dependence that is less than currently recommended for use in atmospheric models. The impact on its atmospheric lifetime was quantified using the NASA Goddard Space Flight Center 2-D coupled chemistry-radiation-dynamics model and the spectrum parameterization developed in this work. The modeled global annually averaged lifetime was 58.1 × 0.7 years (2σ uncertainty due solely to the spectrum uncertainty). The lifetime is slightly reduced and the uncertainty significantly reduced from that obtained using current UV spectrum recommendations. CFCl 3 (CFC-11) 2-D model results: Left: Global annually averaged loss rate coefficient (local lifetime) and photolysis and reaction contributions (see legend). Middle: Molecular loss rate and uncertainty limits; the slow and fast profiles were calculated using the 2σ uncertainty estimates in the CFC-11 UV absorption spectrum from this work. Right: CFC-11 concentration profile. CFC-11 loss process contribution to the overall local lifetime uncertainty (2σ) calculated using the 2-D model (see text). Left: Results obtained from this work. Right: Results obtained using model input from Sander et al. [2011] and updates in SPARC [2013].

  4. Hydrophilic Indolium Cycloruthenated Complex System for Visual Detection of Bisulfite with a Large Red Shift in Absorption.

    PubMed

    Su, Xianlong; Hu, Rongrong; Li, Xianghong; Zhu, Jun; Luo, Facheng; Niu, Xuehu; Li, Mei; Zhao, Qiang

    2016-01-19

    Bisulfite, as an important additive in foodstuffs, is one of the most widely distributed environmental pollutants. The excessive intake of bisulfite may cause asthmatic attacks and allergic reactions. Therefore, the determination and visual detection of bisulfite are very important. Herein, a newly designed hydrophilic indolium cycloruthenated complex, [Ru(mepbi)(bpy)2](+) [1; bpy = 2,2'-bipyridine and Hmepbi = 3,3-dimethyl-1-ethyl-2-[4-(pyridin-2-yl)styryl]benzo[e]indolium iodide (3)], was successfully synthesized and used as a bisulfite probe. The bisulfite underwent a 1,4-addition reaction with complex 1 in PBS buffer (10 mM, pH 7.40), resulting in a dramatic change in absorption spectra with a red shift of over 100 nm and a remarkable change in solution color from yellow to pink. It is worth noting that this obvious bathochromic shift is rarely observed in the detection of bisulfite through an addition reaction. The detection limit was calculated to be as low as 0.12 μM by UV-vis absorption spectroscopy. Moreover, complex 1 was also used to detect bisulfite in sugar samples (granulated and crystal sugar) with good recovery. PMID:26700219

  5. Eye Direction, Not Movement Direction, Predicts Attention Shifts in Those with Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Rutherford, M. D.; Krysko, Kristen M.

    2008-01-01

    Experiments suggesting that a change in eye gaze creates a reflexive attention shift tend to confound motion direction and terminal eye direction. However, motion and the onset of motion are known to capture attention. Current thinking about social cognition in autism suggests that there might be a deficit in responding to social (eye gaze) cues…

  6. The Hubble Space Telescope Quasar Absorption Line Key Project: The Unusual Absorption-Line System in the Spectrum of PG 2302+029--Ejected or Intervening?

    NASA Technical Reports Server (NTRS)

    Jannuzi, B. T.; Hartig, G. F.; Kirhakos, S.; Sargent, W. L. W.; Turnshek, D. A.; Weymann, R. J.; Bahcall, J. N.; Bergeron, J.; Boksenberg, A.; Savage, B. D.; Schneider, D. P.; Wolfe, A. M.

    1996-01-01

    We report the discovery of a high-ionization broad absorption line system at a redshift of z(sub abs) = 0.695 in the spectrum of the z(sub em) = 1.052 radio-quiet quasar PG 2302+029. Broad absorption with FWHM from 3000 to 5000 km/s is detected from C iv, N v, and O vi in Hubble Space Telescope (HST) Faint Object Spectrograph spectra of the quasar. A narrow-line system (FWHM approx. 250 km/s) at z(sub abs) = 0.7016 is resolved from the broad blend and includes absorption by Ly alpha and the C iv, N v, and O vi doublets. No absorption by low-ionization metal species (e.g., Si II and Mg II) is detected in the HST or ground-based spectra for either the broad or the narrow system. The centroids of the broad system lines are displaced by approx. 56,000 km/s to the blue of the quasar's broad emission lines. The reddest extent of the broad-line absorption is more than 50,000 km/s from the quasar. The properties of this system are unprecedented, whether it is an intervening or an ejected system.

  7. On the absorption and electromagnetic field spectral shifts in plasmonic nanotriangle arrays.

    PubMed

    Vedraine, Sylvain; Hou, Renjie; Norton, Peter R; Lagugné-Labarthet, François

    2014-06-01

    The behavior of the electromagnetic field interaction with gold nanotriangles organized in bow-tie arrays is investigated. A side-by-side comparison between the measured absorbance of the array and the modelled integrated electric field resonances confined around the gold structures is presented and discussed to explain the spectral shift between both parameters. Finite difference time domain calculations and Raman measurements of gold triangles of different sizes and periodicity are systematically performed. Numerical calculations show that the spectral maximum of the electric field varies in distinct areas over the metallic structures. PMID:24921524

  8. Vibronic and Rydberg series assignments in the vacuum ultraviolet absorption spectrum of nitrous oxide

    NASA Astrophysics Data System (ADS)

    Shastri, Aparna; Singh, Param Jeet; Krishnakumar, Sunanda; Mandal, Anuvab; Raja Sekhar, B. N.; D'Souza, R.; Jagatap, B. N.

    2014-11-01

    We report a comprehensive photoabsorption study of nitrous oxide (N2O) in the vacuum ultraviolet (45,000-95,000 cm-1) region using synchrotron radiation. The observed spectrum comprises of a few valence transitions and low lying Rydberg series converging to the two spin-orbit components (2П1/2,3/2) of the ground state of N2O+. Spectral analysis is aided by extensive quantum chemical calculations of vertical excited states, oscillator strengths and potential energy curves using the time dependent density functional theory. Vibronic bands observed in the first absorption system (45,000-60,000 cm-1) are assigned to hot band progressions in υ2‧ originating from v″=1 or 2. New insights into the assignment of the well-formed progression of bands in the X1Σ+→C1П system (60,000-72,000 cm-1) are afforded by consideration of the Renner-Teller interaction. A set of molecular vibrational parameters (ω2=467 cm-1, x22=-2.9, ε=-0.24) for the C1П state are derived from a fitting of the experimental data. The 3pπ1Σ+ state at ~77,600 cm-1 shows a large quantum defect (0.96) which is explained as arising due to mixed valence-Rydberg character. In the 85,000-95,000 cm-1 region, a number of absorption features are observed with greater clarity than in earlier photoabsorption studies and assigned to Rydberg series of type nlλ (n=3,4; l=s,p,d; λ=σ,π,δ) and accompanying vibronic bands. This work has resulted in clarification of several discrepancies in earlier Rydberg series assignments. Additionally, the 3pπ 3Σ- Rydberg state at 85,788 cm-1, the valence transition 7σ→3π (1П) at 87,433 cm-1 and the 3dλ Rydberg series in the 91,700-92,600 cm-1 region are assigned for the first time.

  9. Interpretation of the optical absorption spectrum of Co3O4 with normal spinel structure from first principles calculations

    NASA Astrophysics Data System (ADS)

    Lima, A. F.

    2014-01-01

    First principles calculations based on density functional theory have been employed to study the electronic, magnetic and optical properties of Co3O4 in a cubic normal spinel structure. Exchange and correlation effects between electrons were treated by a B3PW91 hybrid functional, which produced better results than others scheme, such as GGA+U or PBE0 hybrid functionals or mBJ semilocal potential. The work focuses on clarifying the nature of the optical absorption bands, which have motivated various theoretical and experimental works in the literature. The calculated optical absorption spectrum was compared with available experimental data. On the basis of this calculated electronic and magnetic structure, the optical absorption peaks (theoretical and experimental) could be satisfactorily explained in terms of d3d charge transfer transitions between both CO2+→CO2+ and CO3+→CO3+ ions. The calculations also predicted that the crystal field splittings at both octahedral and tetrahedral sites in the Co3O4 compound are of the same magnitude. First principles calculations were used to predict optical properties of Co3O4. Exchange-correlation electronic effects were treated by a B3PW91 hybrid functional. Calculated optical absorption spectrum was compared with experimental data. Optical absorption peaks could be satisfactorily explained.

  10. Failure of Energy Transfer between Identical Aromatic Molecules on Excitation at the Long Wave Edge of the Absorption Spectrum

    PubMed Central

    Weber, Gregorio; Shinitzky, Meir

    1970-01-01

    Electronic energy transfer among identical molecules has been followed by the depolarization of the fluorescence in concentrated solutions as well as in dimers, polymers, and micelle systems. In the many aromatic fluorophores examined, unlike a few nonaromatic ones, transfer is much decreased or altogether undetectable on excitation at the red edge of the absorption spectrum. The phenomenon is not due to the transfer taking place during a small fraction of the total fluorescence lifetime, nor is it explainable by a decrease in overlap of absorption and emission upon edge excitation. PMID:16591825

  11. Design of microresonator quantum well intensity modulators based on an absorption blue-shift

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Pile, B.; Taylor, G. W.

    2011-09-01

    A micro resonator quantum well intensity modulator for operation in the wavelength band around 1μm is described. High efficiency 90° bends are used to form the resonator and also provide optimal coupling to the external waveguide. The benefits are to reduce loss, to relax the lithography requirements and to provide more flexible contact designs to the modulator. The characteristics of modulator are analyzed using optical simulation tools and based on measured absorption parameters. The modulator operates with two distinctly different electrode configurations which are both based on the index change calculated using Kramers-Kronig relations. A model including parasitic is developed for HSPICE transient simulations and run in the AGILENT ADS environment. The performance parameters are determined to be an extinction ratio of 10.4dB, a bandwidth of 33GHz, and a dc power less than 1mW for device dimensions of 16×6μm2.

  12. 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.

  13. An equivalent n-source for WGPu derived from a spectrum-shifted PuBe source

    NASA Astrophysics Data System (ADS)

    Ghita, Gabriel; Sjoden, Glenn; Baciak, James; Walker, Scotty; Cornelison, Spring

    2008-04-01

    We have designed, built, and laboratory-tested a unique shield design that transforms the complex neutron spectrum from PuBe source neutrons, generated at high energies, to nearly exactly the neutron signature leaking from a significant spherical mass of weapons grade plutonium (WGPu). This equivalent "X-material shield assembly" (Patent Pending) enables the harder PuBe source spectrum (average energy of 4.61 MeV) from a small encapsulated standard 1-Ci PuBe source to be transformed, through interactions in the shield, so that leakage neutrons are shifted in energy and yield to become a close reproduction of the neutron spectrum leaking from a large subcritical mass of WGPu metal (mean energy 2.11 MeV). The utility of this shielded PuBe surrogate for WGPu is clear, since it directly enables detector field testing without the expense and risk of handling large amounts of Special Nuclear Materials (SNM) as WGPu. Also, conventional sources using Cf-252, which is difficult to produce, and decays with a 2.7 year half life, could be replaced by this shielded PuBe technology in order to simplify operational use, since a sealed PuBe source relies on Pu-239 (T½=24,110 y), and remains viable for more than hundreds of years.

  14. Trifluoro methyl peroxynitrate (CF 3OONO 2): Temperature dependence of the UV absorption spectrum and atmospheric implications

    NASA Astrophysics Data System (ADS)

    Malanca, Fabio E.; Chiappero, Malisa S.; Argüello, Gustavo A.; Wallington, Timothy J.

    The ultraviolet absorption spectrum of gas phase CF 3OONO 2 has been measured over the wavelength range 200-340 nm at 233-300 K. Absorption cross-sections at wavelengths of 290-340 nm were found to increase significantly with increasing temperature. The UV spectra of CF 3C(O)Cl and CF 3C(O)F were measured and were consistent with previous work [Rattigan et al., 1993. Temperature-dependent absorption cross-sections of CF 3COCl, CF 3COF, CH 3COF, CCl 3CHO and CF 3COOH. Journal of Photochemistry and Photobiology A: Chemistry 73, 1-9]. Implications for the atmospheric chemistry of CF 3OONO 2 are discussed.

  15. Electronic absorption spectra and solvatochromic shifts by the vertical excitation model: solvated clusters and molecular dynamics sampling.

    PubMed

    Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G

    2015-01-22

    A physically realistic treatment of solvatochromic shifts in liquid-phase electronic absorption spectra requires a proper account for various short- and long-range equilibrium and nonequilibrium solute-solvent interactions. The present article demonstrates that such a treatment can be accomplished using a mixed discrete-continuum approach based on the two-time-scale self-consistent state-specific vertical excitation model (called VEM) for electronic excitation in solution. We apply this mixed approach in combination with time-dependent density functional theory to compute UV/vis absorption spectra in solution for the n → π* ((1)A2) transition for acetone in methanol and in water, the π → π* ((1)A1) transition for para-nitroaniline (PNA) in methanol and in water, the n → π* ((1)B1) transition for pyridine in water, and the n → π* ((1)B1) transition for pyrimidine in water. Hydrogen bonding and first-solvation-shell-specific complexation are included by means of explicit solvent molecules, and solute-solvent dispersion is included by using the solvation model with state-specific polarizability (SMSSP). Geometries of microsolvated clusters were treated in two different ways, (i) using single liquid-phase global-minimum solute-solvent clusters containing up to two explicit solvent molecules and (ii) using solute-solvent cluster snapshots derived from molecular dynamics (MD) trajectories. The calculations in water involve using VEM/TDDFT excitation energies and oscillator strengths computed over 200 MD-derived solute-solvent clusters and convoluted with Gaussian functions. We also calculate ground- and excited-state dipole moments for interpretation. We find that inclusion of explicit solvent molecules generally improves the agreement with experiment and can be recommended as a way to include the effect of hydrogen bonding in solvatochromic shifts. PMID:25159827

  16. Ultraviolet (250-550  nm) absorption spectrum of pure water.

    PubMed

    Mason, John D; Cone, Michael T; Fry, Edward S

    2016-09-01

    Data for the spectral light absorption of pure water from 250 to 550 nm have been obtained using an integrating cavity made from a newly developed diffuse reflector with a very high UV reflectivity. The data provide the first scattering-independent measurements of absorption coefficients in the spectral gap between well-established literature values for the absorption coefficients in the visible (>400  nm) and UV (<200  nm). A minimum in the absorption coefficient has been observed in the UV at 344 nm; the value is 0.000811±0.000227  m-1. PMID:27607297

  17. Using optical parametric oscillators (OPO) for wavelength shifting IR images to visible spectrum

    SciTech Connect

    McDonald, T.E. Jr.; Numkena, D.M.; Payton, J.; Yates, G.J.; Zagarino, P.

    1998-12-31

    The authors have carried out preliminary investigations into coherent imaging using Optical Parametric Oscillators (OPO) for wavelength conversion of near IR images to visible spectrum. A nonlinear crystal, second harmonic generator (SHG), was used for degenerate optical parametric up-conversion. A Potassium Titanyl Phosphate (KTP) doubling crystal was used to convert incident 1,540 nm flux to 772 nm. Experiments included investigation of spatial resolution and responsivity of the OPO. Spatial resolution of 1.3 1p/mm was attained in both horizontal and vertical axis. Measured responsivity for this OPO configuration compared well with that attained from image intensifier-based systems. Equipment used for this experiment included an ORION SB2-2R pulsed solid state laser used as a light source and a CCD camera and frame grabber to capture and record all data. The experiment and results are discussed.

  18. The origin of blueshifted absorption features in the X-ray spectrum of PG 1211+143: outflow or disc

    NASA Astrophysics Data System (ADS)

    Gallo, L. C.; Fabian, A. C.

    2013-07-01

    In some radio-quiet active galactic nuclei (AGN), high-energy absorption features in the X-ray spectra have been interpreted as ultrafast outflows (UFOs) - highly ionized material (e.g. Fe XXV and Fe XXVI) ejected at mildly relativistic velocities. In some cases, these outflows can carry energy in excess of the binding energy of the host galaxy. Needless to say, these features demand our attention as they are strong signatures of AGN feedback and will influence galaxy evolution. For the same reason, alternative models need to be discussed and refuted or confirmed. Gallo and Fabian proposed that some of these features could arise from resonance absorption of the reflected spectrum in a layer of ionized material located above and corotating with the accretion disc. Therefore, the absorbing medium would be subjected to similar blurring effects as seen in the disc. A priori, the existence of such plasma above the disc is as plausible as a fast wind. In this work, we highlight the ambiguity by demonstrating that the absorption model can describe the ˜7.6 keV absorption feature (and possibly other features) in the quasar PG 1211+143, an AGN that is often described as a classic example of a UFO. In this model, the 2-10 keV spectrum would be largely reflection dominated (as opposed to power law dominated in the wind models) and the resonance absorption would be originating in a layer between about 6 and 60 gravitational radii. The studies of such features constitute a cornerstone for future X-ray observatories like Astro-H and Athena+. Should our model prove correct, or at least important in some cases, then absorption will provide another diagnostic tool with which to probe the inner accretion flow with future missions.

  19. Terahertz absorption spectrum of para and ortho water vapors at different humidities at room temperature

    NASA Astrophysics Data System (ADS)

    Xin, X.; Altan, H.; Saint, A.; Matten, D.; Alfano, R. R.

    2006-11-01

    Terahertz time-domain spectroscopy has been used to measure the absorption of water vapor in 0.2-2.4THz range from low to high humidity at room temperature. The observed absorption lines are due to the water molecular rotations in the ground vibrational state. We find that the absorption strength of para transitions increases as humidity increases, while the absorption strength of ortho transitions increases and then decreases in intensity with increasing humidity. We explain this difference based on the nuclear spin statistics based ratio of ortho to para water monomer populations at room temperature. The preferential adsorption on the solid surfaces of para water leads to an ortho dominated vapor cloud whose monomer rotational absorption intensity decreases due to the effects of dimerization, molecular collisions, clustering, and interactions with liquid droplets at high concentrations.

  20. Spread-spectrum code acquisition in the presence of Doppler shift and data modulation

    NASA Technical Reports Server (NTRS)

    Cheng, Unjeng; Hurd, William J.; Statman, Joseph I.

    1990-01-01

    A spread-spectrum code acquisition technique for a direct-sequence (DS) system in the presence of Doppler effect and data modulation is investigated. Both the carrier-frequency offset and code-frequency offset due to severe Doppler effect are considered. The code-chip slipping during the correlation process caused by code-frequency offset can degrade the acquisition performance significantly. However, this issue can be alleviated by compensating code-frequency offset in an appropriate manner. Results are presented for the cases with and without data modulation. Coherent detection is considered when there is no data modulation. If data modulation is present, the authors partition the correlation time into subintervals and the integration results in these subintervals are square-law noncoherently combined for detection. The implementation of this code acquisition technique using the fast Fourier transform (FFT) algorithm is described. The use of theoretical results to estimate the hardware complexity of an actual system is illustrated step by step, showing that implementation is feasible with existing technology. The tradeoff between hardware complexity and acquisition performance is discussed.

  1. Mutagenesis of mNeptune Red-Shifts Emission Spectrum to 681-685 nm

    PubMed Central

    Li, ZhaoYang; Zhang, ZhiPing; Bi, LiJun; Cui, ZongQiang; Deng, JiaoYu; Wang, DianBing; Zhang, Xian-En

    2016-01-01

    GFP-like fluorescent proteins with diverse emission wavelengths have been developed through mutagenesis, offering many possible choices in cellular and tissue imaging, such as multi-targets imaging, deep tissue imaging that require longer emission wavelength. Here, we utilized a combined approach of random mutation and structure-based rational design to develop new NIR fluorescent proteins on the basis of a far-red fluorescent protein, mNeptune (Ex/Em: 600/650 nm). We created a number of new monomeric NIR fluorescent proteins with the emission range of 681–685 nm, which exhibit the largest Stocks shifts (77–80 nm) compared to other fluorescent proteins. Among them, mNeptune681 and mNeptune684 exhibit more than 30 nm redshift in emission relative to mNeptune, owing to the major role of the extensive hydrogen-bond network around the chromophore and contributions of individual mutations to the observed redshift. Furthermore, the two variants still maintain monomeric state in solution, which is a trait crucial for their use as protein tags. In conclusion, our results suggest that there is untapped potential for developing fluorescent proteins with desired properties. PMID:27119418

  2. Mutagenesis of mNeptune Red-Shifts Emission Spectrum to 681-685 nm.

    PubMed

    Li, ZhaoYang; Zhang, ZhiPing; Bi, LiJun; Cui, ZongQiang; Deng, JiaoYu; Wang, DianBing; Zhang, Xian-En

    2016-01-01

    GFP-like fluorescent proteins with diverse emission wavelengths have been developed through mutagenesis, offering many possible choices in cellular and tissue imaging, such as multi-targets imaging, deep tissue imaging that require longer emission wavelength. Here, we utilized a combined approach of random mutation and structure-based rational design to develop new NIR fluorescent proteins on the basis of a far-red fluorescent protein, mNeptune (Ex/Em: 600/650 nm). We created a number of new monomeric NIR fluorescent proteins with the emission range of 681-685 nm, which exhibit the largest Stocks shifts (77-80 nm) compared to other fluorescent proteins. Among them, mNeptune681 and mNeptune684 exhibit more than 30 nm redshift in emission relative to mNeptune, owing to the major role of the extensive hydrogen-bond network around the chromophore and contributions of individual mutations to the observed redshift. Furthermore, the two variants still maintain monomeric state in solution, which is a trait crucial for their use as protein tags. In conclusion, our results suggest that there is untapped potential for developing fluorescent proteins with desired properties. PMID:27119418

  3. New channelrhodopsin with a red-shifted spectrum and rapid kinetics from Mesostigma viride.

    PubMed

    Govorunova, Elena G; Spudich, Elena N; Lane, C Elizabeth; Sineshchekov, Oleg A; Spudich, John L

    2011-01-01

    Light control of motility behavior (phototaxis and photophobic responses) in green flagellate algae is mediated by sensory rhodopsins homologous to phototaxis receptors and light-driven ion transporters in prokaryotic organisms. In the phototaxis process, excitation of the algal sensory rhodopsins leads to generation of transmembrane photoreceptor currents. When expressed in animal cells, the algal phototaxis receptors function as light-gated cation channels, which has earned them the name "channelrhodopsins." Channelrhodopsins have become useful molecular tools for light control of cellular activity. Only four channelrhodopsins, identified in Chlamydomonas reinhardtii and Volvox carteri, have been reported so far. By screening light-induced currents among algal species, we identified that the phylogenetically distant flagellate Mesostigma viride showed photoelectrical responses in vivo with properties suggesting a channelrhodopsin especially promising for optogenetic use. We cloned an M. viride channelrhodopsin, MChR1, and studied its channel activity upon heterologous expression. Action spectra in HEK293 cells match those of the photocurrents observed in M. viride cells. Comparison of the more divergent MChR1 sequence to the previously studied phylogenetically clustered homologs and study of several MChR1 mutants refine our understanding of the sequence determinants of channelrhodopsin function. We found that MChR1 has the most red-shifted and pH-independent spectral sensitivity so far reported, matches or surpasses known channelrhodopsins' channel kinetics features, and undergoes minimal inactivation upon sustained illumination. This combination of properties makes MChR1 a promising candidate for optogenetic applications. PMID:21693637

  4. Shift of optical absorption edge in SnO2 films with high concentrations of nitrogen grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jiang, Jie; Lu, Yinmei; Meyer, Bruno K.; Hofmann, Detlev M.; Eickhoff, Martin

    2016-06-01

    The optical and electrical properties of n-type SnO2 films with high concentrations of nitrogen (SnO2:N) grown by chemical vapor deposition are studied. The carrier concentration increases from 4.1 × 1018 to 3.9 × 1019 cm-3 and the absorption edge shifts from 4.26 to 4.08 eV with increasing NH3 flow rate. Typical Urbach tails were observed from the absorption spectra and the Urbach energy increases from 0.321 to 0.526 eV with increasing NH3 flow rate. An "effective" absorption edge of about 4.61 eV was obtained for all investigated samples from fitting the extrapolations of the Urbach tails. Burstein-Moss effect, electron-impurity, and electron-electron interactions are shown to play a minor role for the shift of the absorption edges in SnO2:N thin films.

  5. Shifted Coupling of EEG Driving Frequencies and fMRI Resting State Networks in Schizophrenia Spectrum Disorders

    PubMed Central

    Razavi, Nadja; Jann, Kay; Koenig, Thomas; Kottlow, Mara; Hauf, Martinus; Strik, Werner; Dierks, Thomas

    2013-01-01

    Introduction The cerebral resting state in schizophrenia is altered, as has been demonstrated separately by electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) resting state networks (RSNs). Previous simultaneous EEG/fMRI findings in healthy controls suggest that a consistent spatiotemporal coupling between neural oscillations (EEG frequency correlates) and RSN activity is necessary to organize cognitive processes optimally. We hypothesized that this coupling is disorganized in schizophrenia and related psychotic disorders, in particular regarding higher cognitive RSNs such as the default-mode (DMN) and left-working-memory network (LWMN). Methods Resting state was investigated in eleven patients with a schizophrenia spectrum disorder (n = 11) and matched healthy controls (n = 11) using simultaneous EEG/fMRI. The temporal association of each RSN to topographic spectral changes in the EEG was assessed by creating Covariance Maps. Group differences within, and group similarities across frequencies were estimated for the Covariance Maps. Results The coupling of EEG frequency bands to the DMN and the LWMN respectively, displayed significant similarities that were shifted towards lower EEG frequencies in patients compared to healthy controls. Conclusions By combining EEG and fMRI, each measuring different properties of the same pathophysiology, an aberrant relationship between EEG frequencies and altered RSNs was observed in patients. RSNs of patients were related to lower EEG frequencies, indicating functional alterations of the spatiotemporal coupling. Significance The finding of a deviant and shifted coupling between RSNs and related EEG frequencies in patients with a schizophrenia spectrum disorder is significant, as it might indicate how failures in the processing of internal and external stimuli, as commonly seen during this symptomatology (i.e. thought disorders, hallucinations), arise. PMID:24124576

  6. Quantitative Nature of Social Vulnerability and Autism: An Important Paradigm Shift in the DSM-5 for Autism Spectrum Disorder

    PubMed Central

    Ijichi, Shinji; Ijichi, Naomi; Ijichi, Yukina; Hirotaki, Kazumi; Sameshima, Hisami; Kawaike, Yoichi; Morioka, Hirofumi

    2013-01-01

    In the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV), autistic characteristics in social interaction and communication are described as qualitative impairments. However, the difference between autistics and nonautistics in the draft of the 5th edition (DSM-5 draft) is quantitative rather than qualitative. The word “qualitative” is deleted in the draft text, and it is specified that the relation between social demands and individual limited capacities is critical for symptom manifestation (criterion C). Because the proposed levels of support requirement in the draft are mere observable outcomes of social vulnerability, the boundary between level 1 and nonautistic condition is determined by the relation between social demands and individual capacities. In addition to the introduction of the single category (autism spectrum disorder (ASD)) to cover the entire case spectrum, the DSM-5 draft is clearly based on a conviction that ASD is indistinguishable from the normal behavioral range. This concise review provides an explanation for this implicit paradigm shift from qualitative to quantitative. Importantly, the conditional role of social demands for symptom manifestation in the draft can be plausibly interpreted using a unique liability-probability model. PMID:23762602

  7. Surface vs. atmospheric origin of 2.1-2.5 micron absorption features in the Martian spectrum

    NASA Technical Reports Server (NTRS)

    Bell, James F., III; Crisp, David

    1992-01-01

    For 20 years the origin of subtle absorption features in the spectrum of Mars near 2.3 micro-m ('K' band: 1.9-2.5 micro-m) has been debated. This spectral region contains gaseous absorption features predominantly from CO2 and CO on Mars and from telluric H2O and CO2. The authors have obtained new higher spectral resolution telescopic K band spectra of 10 surface regions using the Infrared Telescope Facility (IRTF) at Mauna Kea during 1990. The goals were to confirm the existence of broad features seen at lower spectral resolution and to determine whether these bands are caused by atmospheric gases, surface (or airborne dust) minerals, or a combination of both.

  8. Quantum Monte Carlo for the x-ray absorption spectrum of pyrrole at the nitrogen K-edge

    SciTech Connect

    Zubarev, Dmitry Yu.; Austin, Brian M.; Lester, William A. Jr.

    2012-04-14

    Fixed-node diffusion Monte Carlo (FNDMC) is used to simulate the x-ray absorption spectrum of a gas-phase pyrrole molecule at the nitrogen K-edge. Trial wave functions for core-excited states are constructed from ground-state Kohn-Sham determinants substituted with singly occupied natural orbitals from configuration interaction with single excitations calculations of the five lowest valence-excited triplet states. The FNDMC ionization potential (IP) is found to lie within 0.3 eV of the experimental value of 406.1 {+-} 0.1 eV. The transition energies to anti-bonding virtual orbitals match the experimental spectrum after alignment of IP values and agree with the existing assignments.

  9. Detection of the 1400 A absorption in the ultraviolet spectrum of the DA white dwarf LB 3303

    NASA Technical Reports Server (NTRS)

    Wegner, G.

    1982-01-01

    Low-resolution ultraviolet International Ultraviolet Explorer spectra of the southern white dwarf LB 3303 show the presence of the wavelength 1400 absorption feature reported by Greenstein in the spectrum of 40 Eri B. The equivalent width is 5.7 A, and the measured wavelength is 1394 A. A comparison of the ultraviolet fluxes with model atmospheres confirms that LB 3303 has an effective temperature near 16,000 K, as found earlier from visual wavelength data. There are still problems with the identification of this line. The star is not hot enough to explain the presence of Si IV, and the agreement with the spectrum of the H2 molecule is not convincing.

  10. A photon counting and a squeezing measurement method by the exact absorption and dispersion spectrum of Λ-type Atoms.

    PubMed

    Naeimi, Ghasem; Alipour, Samira; Khademi, Siamak

    2016-01-01

    Recently, the master equations for the interaction of two-mode photons with a three-level Λ-type atom are exactly solved for the coherence terms. In this paper the exact absorption spectrum is applied for the presentation of a non-demolition photon counting method, for a few number of coupling photons, and its benefits are discussed. The exact scheme is also applied where the coupling photons are squeezed and the photon counting method is also developed for the measurement of the squeezing parameter of the coupling photons. PMID:27610321

  11. H216O absorption spectrum between 22250 and 22800 cm-1: Fourier transform spectroscopy with bright light source

    NASA Astrophysics Data System (ADS)

    Serduykov, V. I.; Sinitsa, L. N.; Vasil'chenko, S. S.; Bykov, A. D.; Kruglova, T. V.; Polovtseva, E. R.; Scherbakov, A. P.

    2014-11-01

    Measurements of water vapor absorption spectra in the visible spectral region near 0.44 mkm are performed using FTspectrometer IFS-125M and Light-emitting diode (LED) as source of radiation. Water vapor spectrum has been obtained by averaging over 17136 scans recorded at 34,8 m optical path length, temperature 24 ± 1 C and pressure of sample 24,8 mBar. Due to strong emission of LED source it was possible to achieve signal-to-noise ratio about 104 and to record weak lines with intensities of 6 10-27 cm/molecule. Comparisons with results of early works are made.

  12. Variable Doppler shifts of the thermal wind absorption lines in low-mass X-ray binaries

    NASA Astrophysics Data System (ADS)

    Madej, O. K.; Jonker, P. G.; Díaz Trigo, M.; Miškovičová, I.

    2014-02-01

    In this paper, we address the general applicability of the method pioneered by Zhang, Liao & Yao in which the motion of the compact object can be tracked using wind X-ray absorption lines. We present the velocity measurements of the thermal wind lines observed in the X-ray spectrum of a few low-mass X-ray binaries: GX 13+1, H 1743-322, GRO J1655-40 and GRS 1915+105. We find that the variability in the velocity of the wind lines in about all of the sources is larger than conceivable radial velocity variations of the compact object. GX 13+1 provides a potential exception, although it would require the red giant star to be massive with a mass of ≈5-6 M⊙. We conclude that the variability of the source luminosity occurring on a time-scale of days/months can affect the outflow properties making it difficult to track the orbital motion of the compact object using current observations. Given the intrinsic variability of the outflows we suggest that low-mass X-ray binaries showing stable coronae instead of an outflow (e.g. 4U 1254-69, MXB 1659-29, 4U 1624-49) could be more suitable targets for tracking the orbital motion of the compact object.

  13. Predicting the Shifts of Absorption Maxima of Azulene Derivatives Using Molecular Modeling and ZINDO CI Calculations of UV-Vis Spectra

    ERIC Educational Resources Information Center

    Patalinghug, Wyona C.; Chang, Maharlika; Solis, Joanne

    2007-01-01

    The deep blue color of azulene is drastically changed by the addition of substituents such as CH[subscript 3], F, or CHO. Computational semiempirical methods using ZINDO CI are used to model azulene and azulene derivatives and to calculate their UV-vis spectra. The calculated spectra are used to show the trends in absorption band shifts upon…

  14. Crafting Core/Graded Shell-Shell Quantum Dots with Suppressed Re-absorption and Tunable Stokes Shift as High Optical Gain Materials.

    PubMed

    Jung, Jaehan; Lin, Chun Hao; Yoon, Young Jun; Malak, Sidney T; Zhai, Yaxin; Thomas, Edwin L; Vardeny, Valy; Tsukruk, Vladimir V; Lin, Zhiqun

    2016-04-11

    The key to utilizing quantum dots (QDs) as lasing media is to effectively reduce non-radiative processes, such as Auger recombination and surface trapping. A robust strategy to craft a set of CdSe/Cd1-x Znx Se1-y Sy /ZnS core/graded shell-shell QDs with suppressed re-absorption, reduced Auger recombination rate, and tunable Stokes shift is presented. In sharp contrast to conventional CdSe/ZnS QDs, which have a large energy level mismatch between CdSe and ZnS and thus show strong re-absorption and a constrained Stokes shift, the as-synthesized CdSe/Cd1-x Znx Se1-y Sy /ZnS QDs exhibited the suppressed re-absorption of CdSe core and tunable Stokes shift as a direct consequence of the delocalization of the electron wavefunction over the entire QD. Such Stokes shift-engineered QDs with suppressed re-absorption may represent an important class of building blocks for use in lasers, light emitting diodes, solar concentrators, and parity-time symmetry materials and devices. PMID:26990250

  15. Solvent effects on the electronic absorption spectrum of camphor using continuum, discrete or explicit approaches

    NASA Astrophysics Data System (ADS)

    Kongsted, Jacob; Mennucci, Benedetta; Coutinho, Kaline; Canuto, Sylvio

    2010-01-01

    We address the effect of solvation on the lowest electronic excitation energy of camphor. The solvents considered represent a large variation in-solvent polarity. We consider three conceptually different ways of accounting for the solvent using either an implicit, a discrete or an explicit solvation model. The solvatochromic shifts in polar solvents are found to be in good agreement with the experimental data for all three solvent models. However, both the implicit and discrete solvation models are less successful in predicting solvatochromic shifts for solvents of low polarity. The results presented suggest the importance of using explicit solvent molecules in the case of nonpolar solvents.

  16. Concerted single-nanowire absorption and emission spectroscopy: Explaining the origin of the size-dependent Stokes shift in single cadmium selenide nanowires

    NASA Astrophysics Data System (ADS)

    Vietmeyer, F.; Chatterjee, R.; McDonald, M. P.; Kuno, M.

    2015-02-01

    Concerted single-nanowire (NW) absorption and emission spectroscopies have been used to measure Stokes shifts in the optical response of individual CdSe NWs. Obtained spectra are free of inhomogeneous broadening inherent to ensemble measurements. They reveal apparent size-dependent NW Stokes shifts with magnitudes on the order of 30 meV. Given that an effective mass model previously used to explain CdSe NW excited state progressions predicts no sizable emission Stokes shift, we have investigated modifications to the theory to rationalize their existence. This has entailed better accounting for the effects of crystal field splitting on NW band edge states. What results are important changes to the spectroscopic assignment of NW band edge transitions that arise from the crossing of hole levels. Furthermore, these modifications simultaneously predict Stokes shifts with size-dependent magnitudes up to 20 meV. However, quantitative agreement with experiment is only achieved by accounting for the role of exciton trap states. Consequently, we conclude that CdSe NW Stokes shifts contain both intrinsic and extrinsic contributions—the latter arising from band edge exciton potential energy fluctuations. At a broader level, these concerted absorption and emission measurements have provided detailed insight into the electronic structure of CdSe NWs, beyond what could be obtained using either single-particle absorption or emission spectroscopies alone.

  17. Doping dependent blue shift and linewidth broadening of intersubband absorption in non-polar m-plane AlGaN/GaN multiple quantum wells

    SciTech Connect

    Kotani, Teruhisa; Arita, Munetaka; Arakawa, Yasuhiko

    2015-09-14

    Blue shift and broadening of the absorption spectra of mid-infrared intersubband transition in non-polar m-plane AlGaN/GaN 10 quantum wells were observed with increasing doping density. As the doping density was increased from 6.6 × 10{sup 11} to 6.0 × 10{sup 12 }cm{sup −2} per a quantum well, the intersubband absorption peak energy shifted from 274.0 meV to 302.9 meV, and the full width at half maximum increased from 56.4 meV to 112.4 meV. Theoretical calculations reveal that the blue shift is due to many body effects, and the intersubband linewidth in doped AlGaN/GaN QW is mainly determined by scattering due to interface roughness, LO phonons, and ionized impurities.

  18. Doping dependent blue shift and linewidth broadening of intersubband absorption in non-polar m-plane AlGaN/GaN multiple quantum wells

    NASA Astrophysics Data System (ADS)

    Kotani, Teruhisa; Arita, Munetaka; Arakawa, Yasuhiko

    2015-09-01

    Blue shift and broadening of the absorption spectra of mid-infrared intersubband transition in non-polar m-plane AlGaN/GaN 10 quantum wells were observed with increasing doping density. As the doping density was increased from 6.6 × 1011 to 6.0 × 1012 cm-2 per a quantum well, the intersubband absorption peak energy shifted from 274.0 meV to 302.9 meV, and the full width at half maximum increased from 56.4 meV to 112.4 meV. Theoretical calculations reveal that the blue shift is due to many body effects, and the intersubband linewidth in doped AlGaN/GaN QW is mainly determined by scattering due to interface roughness, LO phonons, and ionized impurities.

  19. FUSE Detection of Galactic and Intrinsic Absorption in the Spectrum of the Seyfert 1 Galaxy 2MASX J21362313-6224008

    NASA Technical Reports Server (NTRS)

    Bonamente, Massimiliano; VanDykeDixon, W.

    2003-01-01

    We present the far-ultraviolet spectrum of the Seyfert 1 galaxy 2MASX 521362313-6224008 obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). The spectrum features absorption from Galactic O VI at two velocities and redshifted H I Lyman beta and gamma, C II, C III, and O VI. The redshifted absorption features represent a single kinematic component blueshifted by approx. 310 km/s relative to the AGN. We use photoionization models to derive the physical parameters of the absorbing gas. An alternative interpretation for the absorption lines is also proposed, whereby the absorbing gas is associated with an intervening galaxy cluster.

  20. FUSE Observations of Galactic and Intrinsic Absorption in the Spectrum of the Seyfert 1 Galaxy 2MASX J21362313-6224008

    NASA Technical Reports Server (NTRS)

    Bonamente, Massimiliano; Dixon, W. Van Dyke

    2004-01-01

    We present the far-ultraviolet spectrum of the Seyfert 1 galaxy 2MASX J21362313-6224008 obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). The spectrum features absorption from Galactic O VI at two velocities and redshifted H I Ly beta and gamma, C II, CIII, and O VI. The redshifted absorption features represent a single kinematic component blueshifted by approx. 310 km/s relative to the active galactic nucleus. We use photoionization models to derive constraints on the physical parameters of the absorbing gas. An alternative interpretation for the absorption lines is also proposed, wherein the absorbing gas is associated with an intervening galaxy cluster.

  1. Photodissociation of carbon dioxide in singlet valence electronic states. II. Five state absorption spectrum and vibronic assignment

    NASA Astrophysics Data System (ADS)

    Grebenshchikov, Sergy Yu.

    2013-06-01

    The absorption spectrum of CO2 in the wavelength range 120-160 nm is analyzed by means of quantum mechanical calculations performed using vibronically coupled potential energy surfaces of five singlet valence electronic states and the coordinate dependent transition dipole moment vectors. The thermally averaged spectrum, calculated for T = 190 K via Boltzmann averaging of optical transitions from many initial rotational states, accurately reproduces the experimental spectral envelope, consisting of a low and a high energy band, the positions of the absorption maxima, their FWHMs, peak intensities, and frequencies of diffuse structures in each band. Contributions of the vibronic interactions due to Renner-Teller coupling, conical intersections, and the Herzberg-Teller effect are isolated and the calculated bands are assigned in terms of adiabatic electronic states. Finally, diffuse structures in the calculated bands are vibronically assigned using wave functions of the underlying resonance states. It is demonstrated that the main progressions in the high energy band correspond to consecutive excitations of the pseudorotational motion along the closed loop of the CI seam, and progressions differ in the number of nodes along the radial mode perpendicular to the closed seam. Irregularity of the diffuse peaks in the low energy band is interpreted as a manifestation of the carbene-type "cyclic" OCO minimum.

  2. Two-photon-absorption spectrum of poly(di- n -hexylsilane) films

    SciTech Connect

    Soos, Z.G. ); Kepler, R.G. )

    1991-05-15

    Two-photon-absorption (TPA) spectra of poly(di-{ital n}-hexylsilane) (PDHS) films are obtained from 605 to 410 nm at 295 and 11 K, where the intensity is an order of magnitude higher. A strong TPA band is found above 5 eV and interpreted in terms of interacting {sigma} electrons in a Pariser-Parr-Pople (PPP) model. PPP models for (Si){sub {ital n}} chains relate the excitonic (one-photon) absorption at {ital E}{sub {ital g}}=3.4 in PDHS to the 4.2-eV TPA at the alternation gap and the high-energy TPA derived from two-electron excitations at {ital E}{sub {ital g}}. The smaller alternation gap in {pi}-conjugated polymers and their intense TPA above {ital E}{sub {ital g}} also indicate correlated states and differ qualitatively from single-particle descriptions.

  3. Near-infrared spectrum of ZrF by intracavity laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Harms, Jack C.; O'Brien, Leah C.; Ni, Ann; Mahkdoom, Bilal; O'Brien, James J.

    2015-04-01

    The (1, 1) band of the CΩ = 3/2 - X2Δ3/2 transition of ZrF has been recorded at high resolution using intracavity laser absorption spectroscopy. The ZrF molecules were produced using a Zr-lined copper hollow cathode sputter source with a trace amount of SF6 as a fluoride source. Molecular constants from the analysis are presented and compared with previous work.

  4. High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride

    SciTech Connect

    Hughes, Patrick P.; Thompson, Alan K.; Vest, Robert E.; Sprague, Matthew K.; Irikura, Karl K.; Beasten, Amy; McComb, Jacob C.; Al-Sheikhly, Mohamad; Coplan, Michael A.; Clark, Charles W.

    2014-11-21

    In the course of investigations of thermal neutron detection based on mixtures of {sup 10}BF{sub 3} with other gases, knowledge was required of the photoabsorption cross sections of {sup 10}BF{sub 3} for wavelengths between 135 and 205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements reported in this communication. The measurements were made at the SURF III Synchrotron Ultraviolet Radiation Facility at the National Institute of Standards and Technology. The measured absorption cross sections vary from 10{sup −20} cm{sup 2} at 135 nm to less than 10{sup −21} cm{sup 2} in the region from 165 to 205 nm. Three previously unreported absorption features with resolvable structure were found in the regions 135–145 nm, 150–165 nm, and 190–205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise from symmetry-changing adiabatic transitions.

  5. Visible-band (390-940nm) monitoring of the Pluto absorption spectrum during the New Horizons encounter

    NASA Astrophysics Data System (ADS)

    Smith, Robert J.; Marchant, Jonathan M.

    2015-11-01

    Whilst Earth-based observations obviously cannot compete with New Horizons’ on-board instrumentation in most regards, the New Horizons data set is essentially a snapshot of Pluto in July 2015. The New Horizons project team therefore coordinated a broad international observing campaign to provide temporal context and to take advantage of the once-in-a-lifetime opportunity to directly link our Earth-based view of Pluto with “ground truth” provided by in situ measurements. This both adds value to existing archival data sets and forms the basis of long term, monitoring as we watch Pluto recede from the Sun over the coming years. We present visible-band (390-940nm) monitoring of the Pluto absorption spectrum over the period July - October 2015 from the Liverpool Telescope (LT). In particular we wished to understand the well-known 6-day fluctuation in the methane ice absorption spectrum which is observable from Earth in relation to the never-before-available high resolution maps of the Pluto surface. The LT is a fully robotic 2.0m optical telescope that automatically and dynamically schedules observations across 30+ observing programmes with a broad instrument suite. It is ideal for both reactive response to dynamic events (such as the fly-by) and long term, stable monitoring with timing constraints individually optimised to the science requirements of each programme. For example past studies of the observed CH4 absorption variability have yielded ambiguity of whether they were caused by real physical changes or geometric observation constraints, in large part because of the uneven time sampling imposed by traditional telescope scheduling.

  6. Fourier-analytic technique for the separation of the signature of atmospheric ClO absorption from the solar background spectrum in the near ultraviolet

    SciTech Connect

    Burnett, E.B.

    1989-02-01

    The high-resolution ClO absorption signature in the region of 308.1 nm has a very low absorption fraction, of the order of 6 x 10/sup -5/, and linewidths comparable with those of the solar background spectrum. Because of the need for reliable absorption measurements of the abundance of this species, which is important in ozone photochemistry, a Fourier-analysis-based technique for the deconvolution of atmospheric solar absorption spectra in this region has been developed. The technique utilizes the regularity of the ClO spectrum and results in a significant reduction in the minimum signal-to-noise required for the retrieval of ClO abundances from absorption spectra.

  7. Excited state dipole moments of chloroanilines and chlorophenols from solvatochromic shifts in electronic absorption spectra: Support for the concept of excited state group moments

    NASA Astrophysics Data System (ADS)

    Prabhumirashi, L. S.; Satpute, R. S.

    The dipole moments of isomeric o-, m- and p-chloroanilines and chlorophenols in electronically excited L a and L b states are estimated from solvent induced polarization shifts in electronic absorption spectra. It is observed that μ e( L a) > μ e( L b) > μ g, which is consistent with the general theory of polarization red shift. The μ es are found to be approximately co-linear with the corresponding μ gs. The concept of group moments is extended to aromatic molecules in excited states. This approach is found to be useful in understanding correlations among the excited states of mono- and disubstituted benzenes.

  8. Research of fiber carbon dioxide sensing system based laser absorption spectrum

    NASA Astrophysics Data System (ADS)

    Wei, Yubin; Zhang, Tingting; Li, Yanfang; Zhao, Yanjie; Wang, Chang; Liu, Tongyu

    2012-02-01

    Carbon dioxide is one of the important gas need to be detected in coal mine safety. In the mine limited ventilation environment, Concentration of carbon dioxide directly affects the health of coal miners. Carbon dioxide is also one of important signature Gas in spontaneous combustion forecasting of coal goaf area, it is important to accurately detect concentration of carbon dioxide in coal goaf area. This paper proposed a fiber carbon dioxide online sensing system based on tunable diode laser spectroscopy. The system used laser absorption spectroscopy and optical fiber sensors combined, and a near-infrared wavelength 1608nm fiber-coupled distributed feedback laser (DFB) as a light source and a 7cm length gas cell, to achieve a high sensitivity concentration detection of carbon dioxide gas. The technical specifications of sensing system can basically meet the need of mine safety.

  9. A Near-Infrared Spectrometer to Measure Zodiacal Light Absorption Spectrum

    NASA Technical Reports Server (NTRS)

    Kutyrev, A. S.; Arendt, R.; Dwek, E.; Kimble, R.; Moseley, S. H.; Rapchun, D.; Silverberg, R. F.

    2010-01-01

    We have developed a high throughput infrared spectrometer for zodiacal light fraunhofer lines measurements. The instrument is based on a cryogenic dual silicon Fabry-Perot etalon which is designed to achieve high signal to noise Fraunhofer line profile measurements. Very large aperture silicon Fabry-Perot etalons and fast camera optics make these measurements possible. The results of the absorption line profile measurements will provide a model free measure of the zodiacal Light intensity in the near infrared. The knowledge of the zodiacal light brightness is crucial for accurate subtraction of zodiacal light foreground for accurate measure of the extragalactic background light after the subtraction of zodiacal light foreground. We present the final design of the instrument and the first results of its performance.

  10. Detection of a Deep 3-μm Absorption Feature in the Spectrum of Amalthea (JV)

    NASA Astrophysics Data System (ADS)

    Takato, Naruhisa; Bus, Schelte J.; Terada, Hiroshi; Pyo, Tae-Soo; Kobayashi, Naoto

    2004-12-01

    Near-infrared spectra of Jupiter's small inner satellites Amalthea and Thebe are similar to those of D-type asteroids in the 0.8- to 2.5-micrometer wavelength range. A deep absorption feature is detected at 3 micrometers in the spectra of the trailing side of Amalthea, which is similar to that of the non-ice components of Callisto and can be attributed to hydrous minerals. These surface materials cannot be explained if the satellite formed at its present orbit by accreting from a circumjovian nebula. Amalthea and Thebe may be the remnants of Jupiter's inflowing building blocks that formed in the outer part or outside of the circumjovian nebula.

  11. Detection of a deep 3-microm absorption feature in the spectrum of Amalthea (JV).

    PubMed

    Takato, Naruhisa; Bus, Schelte J; Terada, Hiroshi; Pyo, Tae-Soo; Kobayashi, Naoto

    2004-12-24

    Near-infrared spectra of Jupiter's small inner satellites Amalthea and Thebe are similar to those of D-type asteroids in the 0.8- to 2.5-micrometer wavelength range. A deep absorption feature is detected at 3 micrometers in the spectra of the trailing side of Amalthea, which is similar to that of the non-ice components of Callisto and can be attributed to hydrous minerals. These surface materials cannot be explained if the satellite formed at its present orbit by accreting from a circumjovian nebula. Amalthea and Thebe may be the remnants of Jupiter's inflowing building blocks that formed in the outer part or outside of the circumjovian nebula. PMID:15618511

  12. Anomalously Broad Diffuse Interstellar Bands and Excited CH+ Absorption in the Spectrum of Herschel 36

    NASA Astrophysics Data System (ADS)

    York, D. G.; Dahlstrom, J.; Welty, D. E.; Oka, T.; Hobbs, L. M.; Johnson, S.; Friedman, S. D.; Jiang, Z.; Rachford, B. L.; Snow, T. P.; Sherman, R.; Sonnentrucker, P.

    2014-02-01

    Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 Å are found in absorption along the line of sight to Herschel 36, an O star system next to the bright Hourglass nebula of the Hii region Messier 8. Excited lines of CH and CH+ are seen as well. We show that the region is very compact and itemize other anomalies of the gas. An infrared-bright star within 400 AU is noted. The combination of these effects produces anomalous DIBs, interpreted by Oka et al. (2013, see also this volume) as being caused predominantly by infrared pumping of rotational levels of relatively small molecules.

  13. o-nitrobenzyl photolabile protecting groups with red-shifted absorption: syntheses and uncaging cross-sections for one- and two-photon excitation.

    PubMed

    Aujard, Isabelle; Benbrahim, Chouaha; Gouget, Marine; Ruel, Odile; Baudin, Jean-Bernard; Neveu, Pierre; Jullien, Ludovic

    2006-09-01

    We evaluated the o-nitrobenzyl platform for designing photolabile protecting groups with red-shifted absorption that could be photolyzed upon one- and two-photon excitation. Several synthetic pathways to build different conjugated o-nitrobenzyl backbones, as well as to vary the benzylic position, are reported. Relative to the reference 4,5-dimethoxy-2-nitrobenzyl group, several o-nitrobenzyl derivatives exhibit a large and red-shifted one-photon absorption within the near-UV range. Uncaging after one-photon excitation was studied by measuring UV-visible absorption and steady-state fluorescence emission on model caged ethers and esters. In the whole series investigated, the caged substrates were released cleanly upon photolysis. Quantum yields of uncaging after one-photon absorption lie within the 0.1-1 % range. We observed that these drop as the maximum wavelength absorption of the o-nitrobenzyl protecting group is increased. A new method based on fluorescence correlation spectroscopy (FCS) after two-photon excitation was used to measure the action uncaging cross section for two-photon excitation. The series of o-nitrobenzyl caged fluorescent coumarins investigated exhibit values within the 0.1-0.01 Goeppert-Mayer (GM) range. Such results are in line with the low quantum yields of uncaging associated with cross-sections of 1-50 GM for two-photon absorption. Although the cross-sections for one- and two-photon absorption of o-nitrobenzyl photolabile protecting groups can be readily improved, we emphasize the difficulty in enlarging the corresponding action uncaging cross-sections in view of the observed trend of their quantum yield of uncaging. PMID:16763952

  14. Theory and experiment of coherent wave packet dynamics in rare earth solids: Absorption spectrum vs femtosecond fringe-resolved interferogram

    NASA Astrophysics Data System (ADS)

    Luo, Q.; Dai, D. C.; Wang, G. Q.; Ninulescu, V.; Yu, X. Y.; Luo, L.; Zhou, J. Y.; Yan, YiJing

    2001-01-01

    Coherent dynamic property of neodymium yttrium aluminum garnet (Nd:YAG) crystal at 77 K is studied via the conventional absorption, the femtosecond fringe-resolved wave packet interferometry, and the related difference-phase spectrum. The recorded interferogram exhibits beatings in subpicosecond time scale arising from the interferences among various weakly split 4f-electronic states and the coupled vibronic optical phonon sidebands. The electron-phonon coupling in Nd:YAG can be well described by multiple Brownian oscillators model involving in each individual electronic transition. The parameters for characterizing material coherence and relaxation are determined via the theoretical modelings of both the frequency and the time-domain experimental signals.

  15. Signature OH Absorption Spectrum from cluster Models of Solvation: a solvent-to-solute charge transfer state

    SciTech Connect

    Tsai, Ming Kang; Kowalski, Karol; Valiev, Marat; Dupuis, Michel

    2007-10-25

    ab initio electronic structure theories applied to cluster models support the characterization of the signature of the OH absorption spectrum to be a solvent-to-solute charge transfer state affected by the hydrogen bonding environment in the region of 250 nm (calculated). The vertical excited states were calculated at the TDDFT level of theory with using OH(H2O)n clusters (n = 0-7, 16) with companion calculations at the EOM-CCSD level of theory for n ≤ 7. An intense solvent-to-solute charge transfer transition was calculated for n = 16 cluster where the donor and acceptor molecular orbitals are in favorable alignment. In the other smaller clusters the transitions in this region were found to be weak. The present findings are consistent with the experimental absorption at 230 nm suggested to be a solvent-to-solute charge transfer and provide insight into the electronic states and orbitals that give rise to the intensity of the band. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program, and was performed in part using the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a DOE national scientific user facility located at the Pacific Northwest National Laboratory (PNNL). PNNL is operated by Battelle for DOE.

  16. Highly Ionized Iron Absorption Lines from Outflowing Gases in the X-ray Spectrum of NGC 1365

    NASA Technical Reports Server (NTRS)

    Risaliti, G.; Bianchi, S.; Matt, G.; Baldi, A.; Elvis, M.; Fabbiano, G.; Zezas, A.

    2006-01-01

    We present the discovery of four absorption lines in the X-ray spectrum of the Seyfert galaxy NGC 1365, at energies between 6.7 and 8.3 keV. The lines are detected with high statistical confidence (from >20 sigma for the strongest to -4 sigma for the weakest) in two XMM-Newton observations 60 ks long. We also detect the same lines, with a lower signal-to-noise ratio (but still >2 sigma for each line), in two previous shorter (-10 ks) XMM-Newton observations. The spectral analysis identifies these features as Fe XXV and Fe XXVI Kalpha and Kbeta lines, outflowing with velocities varying between -1000 and -5000 km/s among the observations. These are the highest quality detections of such lines so far. The high equivalent widths [EW (Kalpha) approximately 100 eV] and the Kalpha/Kbeta ratios imply that the lines are due to absorption of the AGN continuum by a highly ionized gas with column density NH-5?1023 cm(exp -2) at a distance of -(50-100)RS from the continuum source.

  17. The origin of the unusual Qy red shift in LH1-RC complexes from purple bacteria Thermochromatium tepidum as revealed by Stark absorption spectroscopy.

    PubMed

    Ma, Fei; Yu, Long-Jiang; Wang-Otomo, Zheng-Yu; van Grondelle, Rienk

    2015-12-01

    Native LH1-RC of photosynthetic purple bacteria Thermochromatium (Tch.) tepidum, B915, has an ultra-red BChl a Qy absorption. Two blue-shifted complexes obtained by chemical modification, B893 and B882, have increasing full widths at half maximum (FWHM) and decreasing transition dipole oscillator strength. 77K Stark absorption spectroscopy studies were employed for the three complexes, trying to understand the origin of the 915 nm absorption. We found that Tr(∆α) and |∆μ| of both Qy and carotenoid (Car) bands are larger than for other purple bacterial LH complexes reported previously. Moreover, the red shifts of the Qy bands are associated with (1) increasing Tr(∆α) and |∆μ| of the Qy band, (2) the red shift of the Car Stark signal and (3) the increasing |∆μ| of the Car band. Based on the results and the crystal structure, a combined effect of exciton-charge transfer (CT) states mixing, and inhomogeneous narrowing of the BChl a site energy is proposed to be the origin of the 915 nm absorption. CT-exciton state mixing has long been found to be the origin of strong Stark signal in LH1 and special pair, and the more extent of the mixing in Tch. tepidum LH1 is mainly the consequence of the shorter BChl-BChl distances. The less flexible protein structure results in a smaller site energy disorder (inhomogeneous narrowing), which was demonstrated to be able to influence |∆μ| and absorption. PMID:26341015

  18. The Fourier transform absorption spectrum of acetylene between 8280 and 8700 cm-1

    NASA Astrophysics Data System (ADS)

    Lyulin, O. M.; Vander Auwera, J.; Campargue, A.

    2016-07-01

    High resolution (0.011 cm-1) room temperature (295 K) Fourier transform absorption spectra (FTS) of acetylene have been analyzed in the 8280-8700 cm-1 range dominated by the ν1+ν2+ν3 band at 8512 cm-1. Line positions and intensities were retrieved from FTS spectra recorded at 3.84 and 56.6 hPa. As a result, a list of 1001 lines was constructed with intensities ranging between about 2×10-26 and 10-22 cm/molecule. Comparison with accurate predictions provided by a global effective operator model led to the assignment of 629 12C2H2 lines. In addition, 114 lines of the 13C12CH2 isotopologue were assigned using information available in the literature. The 12C2H2 lines belong to thirteen bands, nine of which being newly reported. The 13C12CH2 lines belong to three bands, the intensities of which being reported for the first time. Spectroscopic parameters of the 12C2H2 upper vibrational levels were derived from band-by-band analyses of the line positions (typical rms are on the order of 0.002 cm-1). Three of the analyzed bands were found to be affected by rovibrational perturbations, which are discussed in the frame of a global effective Hamiltonian. The obtained line parameters are compared with those of the two bands included in the HITRAN 2012 database.

  19. [Measurements of IR absorption across section and spectrum simulation of lewisite].

    PubMed

    Zhang, Yuan-peng; Wang, Hai-tao; Zhang, Lin; Yang, Liu; Guo, Xiao-di; Bai, Yun; Sun, Hao

    2015-02-01

    The vapor infrared transmission spectra of varied concentration of lewisite-1 were measured by a long-path FT-IR spectrometer, and its characteristic frequencies are 814, 930, 1563 cm(-1); their infrared absorption cross section (a) were determined using Beer-Lambert law. The corresponding sigma values are 3.89 +/- 0.01, 1.43 +/- 0.06, 4.47 +/- 0.05 ( X 10(-20) cm2 x molecule(-1)). Two little teeny peaks, 1158, 1288 cm(-1) were found in the measured spectra. Density Functional Theory (DFT) was applied to calculated the infrared spectra of lewisite-1, -2, -3 on a b3lyp/6-311+g(d, p) level by Gauss09 package. The vibration modes were assigned by Gaussview5. 08. The calculated spectra and experimental spectra are in good agreement with each other in 600-1600 cm(-1) range, for the Person's r is 0.9991. The calculated spectra also showed three characteristic frequencies (293, 360, 374 cm(-1)) related to As atom. 0.977 was a scaling factor we determined for lewisite-1 through least-square error and its performance to scale lewisite-1, -2, -3 was acceptable. The results of this work are useful for monitoring environmental atmospheric concentrations of lewisite. PMID:25970914

  20. Theory of the electronic states and absorption spectrum of the LiCl:Ag+ impurity system

    NASA Astrophysics Data System (ADS)

    Jackson, Koblar A.; Lin, Chun C.

    1990-01-01

    The impurity absorption spectra of Ag+ and Cu+ impurities in alkali halide hosts show characteristically different features, despite the similar nature of the corresponding free ions. We use the self-interaction-corrected local-spin-density (SIC-LSD) theory to calculate the electronic structure of the ground state (4d) and the 5s and 5p excited states of the LiCl:Ag+ impurity ion. The method of linear combinations of atomic orbitals is used to determine the wave functions and energy levels. By comparing with previous calculations for LiCl:Cu+, we are able to attribute the differences in the d-->s and d-->p transitions in the ultraviolet spectra of these systems to the increased bonding between host crystal and impurity orbitals in LiCl:Ag+, due to the more extensive nature of the Ag+ 4d orbitals. A modification of the earlier SIC-LSD impurity-crystal procedure is introduced to treat the strongly mixed impurity states.

  1. 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.

  2. Total Absorption Spectroscopy Study of ⁹²Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape

    DOE PAGESBeta

    Sonzogni, A.; Zakari-Issoufou, A. -A.; Fallot, M.; Porta, A.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; et al

    2015-03-09

    The accurate determination of the emitted reactor antineutrino flux is still a major challenge for actual and future neutrino experiments at reactors, especially after the evidence of a disagreement between the measured antineutrino energy spectrum by Double Chooz, Daya Bay, and Reno and calculated antineutrino spectra obtained from the conversion of the unique integral beta spectra measured at the ILL reactor. Using nuclear data to compute reactor antineutrino spectra may help understanding this bias, with the study of the underlying nuclear physics. Summation calculations allow identifying a list of nuclei that contribute importantly to the antineutrino energy spectra emitted aftermore » the fission of ²³⁹,²⁴¹Pu and ²³⁵,²³⁸U, and whose beta decay properties might deserve new measurements. Among these nuclei, ⁹²Rb exhausts by itself about 16% of of the antineutrino energy spectrum emitted by Pressurized Water Reactors in the 5 to 8 MeV range. In this Letter, we report new Total Absorption Spectroscopy (TAS) results for this important contributor. The obtained beta feeding from ⁹²Rb shows beta intensity unobserved before in the 4.5 to 5.5 MeV energy region and gives a ground state to ground state branch of 87.5 % ± 3%. These new data induce a dramatic change in recent summation calculations where a 51% GS to GS branch was considered for ⁹²Rb, increasing the summation antineutrino spectrum in the region nearby the observed bias.The new data still have an important impact on other summation calculations in which more recent data were considered« less

  3. Total Absorption Spectroscopy Study of ⁹²Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape

    SciTech Connect

    Sonzogni, A.; Zakari-Issoufou, A. -A.; Fallot, M.; Porta, A.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; Estienne, M.; Agramunt, J.; Aysto, J.; Bowry, M.; Briz Monago, J. A.; Caballero-Folch, R.; Cano-Ott, D.; Cucoanes, A.; Eloma, V.; Estvez, E.; Farrelly, G. F.; Garcia, A.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez, A.; Podolyak, Zs.; Penttil, H.; Regan, P. H.; Shiba, T.; Rissanen, J.; Rubio, B.; Weber, C.

    2015-03-09

    The accurate determination of the emitted reactor antineutrino flux is still a major challenge for actual and future neutrino experiments at reactors, especially after the evidence of a disagreement between the measured antineutrino energy spectrum by Double Chooz, Daya Bay, and Reno and calculated antineutrino spectra obtained from the conversion of the unique integral beta spectra measured at the ILL reactor. Using nuclear data to compute reactor antineutrino spectra may help understanding this bias, with the study of the underlying nuclear physics. Summation calculations allow identifying a list of nuclei that contribute importantly to the antineutrino energy spectra emitted after the fission of ²³⁹,²⁴¹Pu and ²³⁵,²³⁸U, and whose beta decay properties might deserve new measurements. Among these nuclei, ⁹²Rb exhausts by itself about 16% of of the antineutrino energy spectrum emitted by Pressurized Water Reactors in the 5 to 8 MeV range. In this Letter, we report new Total Absorption Spectroscopy (TAS) results for this important contributor. The obtained beta feeding from ⁹²Rb shows beta intensity unobserved before in the 4.5 to 5.5 MeV energy region and gives a ground state to ground state branch of 87.5 % ± 3%. These new data induce a dramatic change in recent summation calculations where a 51% GS to GS branch was considered for ⁹²Rb, increasing the summation antineutrino spectrum in the region nearby the observed bias.The new data still have an important impact on other summation calculations in which more recent data were considered

  4. 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.

  5. Global Properties of the Ejecta Absorptions in the Spectrum of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Gull, T. R.; Vieira, G. L.; Danks, A. C.

    2002-12-01

    Between 2400A to 3160A, we have identified approximately 500 absorption line complexes, each with up to 20 velocity components. Lines of Fe I, Fe II, Ti II, V II, Ni II, Co II, Mn II, Mg I, Mg II and Na I have been identified. Surprisingly, most of the lines originate from energy levels significantly above the ground level. This is indicative of optical pumping from the Central Source. Line widths and population of various levels are non-thermal. The relative column densities change with velocity. For example, Fe II column densities for one transition arising from 0.1eV increase with ejecta velocity while Fe II column densities for another transition decreases with velocity. This may be due to softening of the ultraviolet radiation that pumps the various ions (neutrals) with velocity. If we assume that the distance of each system scales with distance from the Central Source, only a thirty percent change in distance is noted; yet the ratio of column densities for the Fe II examples given above changes by nearly thirty-fold. If the ejecta distance scales with distance from Eta Carinae, then it is likely that this ejecta originated at nearly the same time. The geometry of the Homunculus has been determined to be a double-lobed structure tilted out of the plane of the sky. We interpret the ejecta as being in the wall of the Southwest lobe, and that this wall just happens to be in line of sight from Eta Carinae to the observer. As Eta Carinae enters into the upcoming minimum, we are already seeing some evidence for changes in column densities due to changes in ultraviolet fluxes. This is reinforced by IUE observations that we have recently re-analyzed with respect to the 5.52 year (2020+/-10 days) spectroscopic period. Observations were done through STScI and funding was through the STIS GTO resources.

  6. Global Properties of the Ejecta Absorptions in the Spectrum of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Gull, T. R.; Vieira, G.; Danks, A.

    2003-01-01

    Between 2400A to 3160A, we have identified approximately 500 absorption line complexes, each with up to 20 velocity components. Lines of Fe I, Fe II, Ti II, V II, Ni II, Co II, Mn II, Mg I, Mg II and Na I have been identified. Surprisingly, most of the lines originate from energy levels significantly above the ground level. This is indcative of optical pumping from the Central Source. Line widths and population of various levels are non-thermal. The relative column densities change with velocity. For example, Fe 11 column densities for one transition arising from approx. 0.l ev increase with ejecta velocity while Fe 11 column densities for another transition decreases with velocity. This may be due to softening of the ultraviolet radiation that pumps the various ions (neutrals) with velocity. If we assume that the distance of each system scales with distance from the Central Source, only a thirty percent change in distance is noted; yet the ratio of column densities for the Fe I1 examples given above changes by nearly thirty-fold. If the ejecta distance scales with distance from Eta Carinae, then it is likely that this ejecta originated at nearly the same time. The geometry of the Homunculus has been determined to be a double-lobed structure tilted out of the plane of the sky. We interpret the ejecta as being in the wall of the Southwest lobe, and that this wall just happens to be in line of sight from Eta Carinae to the observer. As Eta Carinae enters into the upcoming minimum, we are already seeing some evidence for changes in column densities due to changes in ultraviolet fluxes. This is reinforced by IUE observations that we have recently re-analyzed with respect to the 5.52 year (2020 +/- 10 days) spectroscopic period. Observations were done through STScI and funding was through the STIS GTO resources.

  7. Hydrogen bonding between acetate-based ionic liquids and water: Three types of IR absorption peaks and NMR chemical shifts change upon dilution

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Cao, Yuanyuan; Zhang, Yuwei; Mu, Tiancheng

    2014-01-01

    The hydrogen-bonding interaction between acetate-based ionic liquids (AcIL) and water was investigated by attenuated total reflection infrared (ATR-IR) and 1H NMR. Interestingly, the relative change of chemical shift δ of 1H NMR upon dilution could be divided into three regions. All the H show an upfield shift in Regions 1 and 2 while a different tendency in Region 3 (upfield, no, and downfield shift classified as Types 1, 2, 3, respectively). For ATR-IR, the red, no, or blue shift of νOD (IR absorption peak of OD in D2O) and ν± (IR absorption peak of AcILs) also have three types, respectively. Two-Times Explosion Mechanism (TTEM) was proposed to interpret the dynamic processes of AcILs upon dilution macroscopically, meanwhile an Inferior Spring Model (ISM) was proposed to help to understand the TTEM microscopically, All those indicate that AcILs present the state of network, sub-network, cluster, sub-cluster, ion pairs and sub-ion pairs in sequence upon dilution by water and the elongation of hydrogen bonding between AcILs-water, between cation-anion of AcILs is plastic deformation rather than elastic deformation.

  8. Reconstruction of a 6-MeV bremsstrahlung spectrum by multi-layer absorption based on LiF:Mg, Cu, P

    NASA Astrophysics Data System (ADS)

    Huang, Jian-Wei; Wang, Nai-Yan

    2014-10-01

    In this paper, TLD (LiF: Mg, Cu, P) is used as detector. A multi-layer absorption (MLA) model is designed. Combined with Monte-Carlo processes, a bremsstrahlung X-ray spectrum is reconstructed by an iterative method; the reconstructed results agree with the results of simulations by the MCNP process essentially, especially in middle energy region.

  9. On the Putative Detection of Z>0 X-Ray Absorption Features in the Spectrum of Mrk 421

    SciTech Connect

    Rasmussen, Andrew P.; Kahn, Steven M.; Paerels, Frits; Herder, Jan Willem den; Kaastra, Jelle; de Vries, Cor; /SRON, Utrecht

    2006-04-28

    In a series of papers, Nicastro et al. have claimed the detection of z > 0 O VII absorption features in the spectrum of Mrk 421 obtained with the Chandra Low Energy Transmission Grating Spectrometer (LETGS). We evaluate those claims in the context of a high quality spectrum of the same source obtained with the Reflection Grating Spectrometer (RGS) on XMM-Newton. The data comprise over 955 ksec of usable exposure time and more than 2.6 x 10{sup 4} counts per 50 m{angstrom} at 21.6 {angstrom}. We concentrate on the spectrally clean region (21.3 < {lambda} < 22.5 {angstrom}) where sharp features due to the astrophysically abundant O VII may reveal an intervening, warm-hot intergalactic medium (WHIM). In spite of the fact that the sensitivity of the RGS data is higher than that of the original LETGS data presented by Nicastro et al., we do not confirm detection of any of the intervening systems claimed to date. Rather, we detect only three unsurprising, astrophysically expected features down to the log (N{sub i}) {approx} 14.6 (3{sigma}) sensitivity level. Each of the two purported WHIM features is rejected with a statistical confidence that exceeds that reported for its initial detection. While we can not rule out the existence of fainter, WHIM related features in these spectra, we suggest that previous discovery claims were premature. A more recent paper by Williams et al. claims to have demonstrated that the RGS data we analyze here do not have the resolution or statistical quality required to confirm or deny the LETGS detections. We show that the Williams et al. reduction of the RGS data was highly flawed, leading to an artificial and spurious degradation of the instrument response. We carefully highlight the differences between our analysis presented here and those published by Williams et al.

  10. Water-vapor absorption line measurements in the 940-nm band by using a Raman-shifted dye laser

    NASA Technical Reports Server (NTRS)

    Chu, Zhiping; Wilkerson, Thomas D.; Singh, Upendra N.

    1993-01-01

    We report water-vapor absorption line measurements that are made by using the first Stokes radiation (930-982 nm) with HWHM 0.015/cm generated by a narrow-linewidth, tunable dye laser. Forty-five absorption line strengths are measured with an uncertainty of 6 percent and among them are fourteen strong lines that are compared with previous measurements for the assessment of spectral purity of the light source. Thirty air-broadened linewidths are measured with 8 percent uncertainty at ambient atmospheric pressure with an average of 0.101/cm. The lines are selected for the purpose of temperature-sensitive or temperature-insensitive lidar measurements. Results for these line strengths and linewidths are corrected for broadband radiation and finite laser linewidth broadening effects and compared with the high-resolution transmission molecular absorption.

  11. Quick measurement of continuous absorption spectrum in ion beam pulse radiolysis: Application of optical multi-channel detector into transient species observation

    NASA Astrophysics Data System (ADS)

    Iwamatsu, Kazuhiro; Muroya, Yusa; Yamashita, Shinichi; Kimura, Atsushi; Taguchi, Mitsumasa; Katsumura, Yosuke

    2016-02-01

    A quick measurement system of a continuous absorption spectrum covering a wide range from 200 to 950 nm was constructed by employing an optical multi-channel detector. Ion beam pulse radiolysis with 12.5 MeV/u He, 18.3 MeV/u C and 17.5 MeV/u Ne ions were performed with the measurement system. Transient absorption spectrum of (S C N) 2 • - was clearly observed in KSCN aqueous solutions within a few minutes in spite of their very small absorbance, demonstrating high sensitivity of 0.001-0.003 in absorbance in the range from 260 to 660 nm as well as short measurement time of a few minutes. Two different absorption peaks attributed to Br2 • - and Br3 - were observed simultaneously in NaBr aqueous solutions, showing powerfulness of the measurement system in overviewing chemical kinetics under ion beam irradiation especially in not well investigated chemical systems.

  12. Infrared Pulse-laser Long-path Absorption Measurement of Carbon Dioxide Using a Raman-shifted Dye Laser

    NASA Technical Reports Server (NTRS)

    Minato, Atsushi; Sugimoto, Nobuo; Sasano, Yasuhiro

    1992-01-01

    A pulsed laser source is effective in infrared laser long-path absorption measurements when the optical path length is very long or the reflection from a hard target is utilized, because higher signal-to-noise ratio is obtained in the detection of weak return signals. We have investigated the performance of a pulse-laser long-path absorption system using a hydrogen Raman shifter and a tunable dye laser pumped by a Nd:YAG laser, which generates second Stokes radiation in the 2-micron region.

  13. Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source

    SciTech Connect

    Wada, M. Doi, K.; Kisaki, M.; Nakano, H.; Tsumori, K.; Nishiura, M.

    2015-04-08

    Balmer-α light emission from the extraction region of the LHD one-third ion source has shown a characteristic Doppler broadening in the wavelength spectrum detected by a high resolution spectrometer. The spectrum resembles Gaussian distribution near the wavelength of the intensity peak, while it has an additional component of a broader foot. The measured broadening near the wavelength of the intensity peak corresponds to 0.6 eV hydrogen atom temperature. The spectrum exhibits a larger expansion in the blue wing which becomes smaller when the line of sight is tilted toward the driver region from the original observation axis parallel to the plasma grid. A surface collision simulation model predicts the possibility of hydrogen reflection at the plasma grid surface to form a broad Balmer-α light emission spectrum.

  14. Accurate calculation of the x-ray absorption spectrum of water via the GW/Bethe-Salpeter equation

    NASA Astrophysics Data System (ADS)

    Gilmore, Keith; Vinson, John; Kas, Josh; Vila, Fernando; Rehr, John

    2014-03-01

    We calculate x-ray absorption spectra (XAS) of water within the OCEAN code, which combines plane-wave, pseudopotential electronic structure, PAW transition elements, GW self-energy corrections, and the NIST BSE solver. Due to the computational demands of this approach, our initial XAS calculations were limited to 17 molecule super cells. This lead to unphysical, size dependent effects in the calculated spectra. To treat larger systems, we extended the OCEAN interface to support well-parallelized codes such as QuantumESPRESSO. We also implemented an efficient interpolation scheme of Shirley. We applied this large-scale GW/BSE approach to 64 molecule unit cell structures of water obtained from classical DFT/MD and PIMD simulations. In concurrence with previous work, we find the calculated spectrum both qualitatively and quantitatively reproduces the experimental features. The agreement implies that structures based on PIMD, which are similar to the traditional distorted tetrahedral view, are consistent with experimental observations. Supported by the DOE CMCSN through DOE award DE-SC0005180 (Princeton University) and in part by DOE Grant No. DE-FG03-97ER45623 (JJR) with computer support from NERSC.

  15. Communication: Does a single CH3CN molecule attached to Ru(bipy)3(2+) affect its absorption spectrum?

    PubMed

    Stockett, M H; Brøndsted Nielsen, S

    2015-05-01

    Tris(bipyridine)ruthenium(II) (Ru(bipy)3 (2+)) is a prototypical transition metal coordination complex whose photophysical properties have attracted considerable attention. A much debated issue is whether the metal-to-ligand charge transfer (MLCT) transition that accounts for the complex's beautiful red color is fully delocalized across all three bipyridine ligands or located on just one ligand. Here, we show based on gas-phase action spectroscopy that attachment of a single acetonitrile molecule does not change the absorption spectrum from that of the bare ions, which is indicative of a delocalized state. However, the gas-phase spectra of the bare and one solvent molecule complexes are significantly blueshifted relative to that obtained in bulk acetonitrile, which suggests that in solution the polarizability of many solvent molecules working together can localize the MLCT state. Our data clearly show that more than one solvent molecule is needed to break the symmetry of the MLCT excited state and reproduce its solution-phase characteristics. PMID:25956080

  16. Communication: Does a single CH3CN molecule attached to Ru(bipy)32+ affect its absorption spectrum?

    NASA Astrophysics Data System (ADS)

    Stockett, M. H.; Brøndsted Nielsen, S.

    2015-05-01

    Tris(bipyridine)ruthenium(II) (Ru(bipy)32+) is a prototypical transition metal coordination complex whose photophysical properties have attracted considerable attention. A much debated issue is whether the metal-to-ligand charge transfer (MLCT) transition that accounts for the complex's beautiful red color is fully delocalized across all three bipyridine ligands or located on just one ligand. Here, we show based on gas-phase action spectroscopy that attachment of a single acetonitrile molecule does not change the absorption spectrum from that of the bare ions, which is indicative of a delocalized state. However, the gas-phase spectra of the bare and one solvent molecule complexes are significantly blueshifted relative to that obtained in bulk acetonitrile, which suggests that in solution the polarizability of many solvent molecules working together can localize the MLCT state. Our data clearly show that more than one solvent molecule is needed to break the symmetry of the MLCT excited state and reproduce its solution-phase characteristics.

  17. Investigation of broadening and shift of vapour absorption lines of H{sub 2}{sup 16}O in the frequency range 7184 – 7186 cm{sup -1}

    SciTech Connect

    Nadezhdinskii, A I; Pereslavtseva, A A; Ponurovskii, Ya Ya

    2014-10-31

    We present the results of investigation of water vapour absorption spectra in the 7184 – 7186 cm{sup -1} range that is of particular interest from the viewpoint of possible application of the data obtained for monitoring water vapour in the Earth's stratosphere. The doublet of H{sub 2}{sup 16}O near ν = 7185.596 cm{sup -1} is analysed. The coefficients of broadening and shift of water vapour lines are found in the selected range in mixtures with buffer gases and compared to those obtained by other authors. (laser spectroscopy)

  18. A Giant Metrewave Radio Telescope search for associated H I 21 cm absorption in high-redshift flat-spectrum sources

    NASA Astrophysics Data System (ADS)

    Aditya, J. N. H. S.; Kanekar, Nissim; Kurapati, Sushma

    2016-02-01

    We report results from a Giant Metrewave Radio Telescope search for `associated' redshifted H I 21 cm absorption from 24 active galactic nuclei (AGNs), at 1.1 < z < 3.6, selected from the Caltech-Jodrell Bank Flat-spectrum (CJF) sample. 22 out of 23 sources with usable data showed no evidence of absorption, with typical 3σ optical depth detection limits of ≈0.01 at a velocity resolution of ≈30 km s-1. A single tentative absorption detection was obtained at z ≈ 3.530 towards TXS 0604+728. If confirmed, this would be the highest redshift at which H I 21 cm absorption has ever been detected. Including 29 CJF sources with searches for redshifted H I 21 cm absorption in the literature, mostly at z < 1, we construct a sample of 52 uniformly selected flat-spectrum sources. A Peto-Prentice two-sample test for censored data finds (at ≈3σ significance) that the strength of H I 21 cm absorption is weaker in the high-z sample than in the low-z sample; this is the first statistically significant evidence for redshift evolution in the strength of H I 21 cm absorption in a uniformly selected AGN sample. However, the two-sample test also finds that the H I 21 cm absorption strength is higher in AGNs with low ultraviolet or radio luminosities, at ≈3.4σ significance. The fact that the higher luminosity AGNs of the sample typically lie at high redshifts implies that it is currently not possible to break the degeneracy between AGN luminosity and redshift evolution as the primary cause of the low H I 21 cm opacities in high-redshift, high-luminosity AGNs.

  19. Discovery of the double Doppler-shifted emission-line systems in the X-ray spectrum of SS 433

    NASA Technical Reports Server (NTRS)

    Kotani, Taro; Kawai, Nobuyuki; Aoki, Takashi; Doty, John; Matsuoka, Masaru; Mitsuda, Kazuhisa; Nagase, Fumiaki; Ricker, George; White, Nick E.

    1994-01-01

    We have used the CCD X-ray spectrometers on ASCA and resolved the X-ray emission line from the jet of SS 433 both into Doppler-shifted components with two distinct velocities, and into emission from different ionization states of iron, i.e., Fe XXV and Fe XXVI. This is the first direct detection of the two Doppler shifted beams in the X-ray spectra of SS 433 and allows the radial velocity of the jet along the line of sight to be determined with an accuracy comparable to the optical spectroscopy. We also found pairs of emission lines from other atomic species, such as ionized silicon and sulfur, with the Doppler shifts consistent with each other. This confirms the origin of the X-ray emission in the high temperature plasma in the jets.

  20. The absorption spectrum of the QSO PKS 2126-158 (z_em =3.27) at high resolution

    NASA Astrophysics Data System (ADS)

    D'Odorico, V.; Cristiani, S.; D'Odorico, S.; Fontana, A.; Giallongo, E.

    1998-01-01

    Spectra of the z_em = 3.268 quasar PKS 2126-158 have been obtained in the range lambda lambda 4300-6620 Angstroms with a resolution Rsmallimeq27000 and an average signal-to-noise ratio s/nsmallimeq 25 per resolution element. The list of the identified absorption lines is given together with their fitted column densities and Doppler widths. The modal value of the Doppler parameter distribution for the Lyalpha lines is smallimeq 25 km s(-1) . The column density distribution can be described by a power-law dn / dN ~ N(-beta ) with beta smallimeq 1.5. 12 metal systems have been identified, two of which were previously unknown. In order to make the column densities of the intervening systems compatible with realistic assumptions about the cloud sizes and the silicon to carbon overabundance, it is necessary to assume a jump beyond the He II edge in the spectrum of the UV ionizing background at z smallim 3 a factor 10 larger than the standard predictions for the integrated quasar contribution. An enlarged sample of C IV absorptions (71 doublets) has been used to analyze the statistical properties of this class of absorbers strictly related to galaxies. The column density distribution is well described by a single power-law, with beta =1.64 and the Doppler parameter distribution shows a modal value b_CIV smallimeq 14 km s(-1) . The two point correlation function has been computed in the velocity space for the individual components of C IV features. A significant signal is obtained for scales smaller than 200- 300 km s(-1) , xi (30< Delta v < 90 km\\ s(-1) ) = 33 +/- 3. A trend of decreasing clustering amplitude with decreasing column density is apparent, analogously to what has been observed for Lyalpha lines. Based on observations collected at the European Southern Observatory, La Silla, Chile (ESO No. 2-013-49K). Table 2 is only available in electronic from via anonymous ftp 130.79.128.5 or http://cdsweb.u-strasbg.fr/Abstract.html

  1. 5f3 --> 5f 26d1 absorption spectrum analysis of U3+-SrCl2.

    PubMed

    Karbowiak, Mirosław

    2005-04-28

    The 5f3--> 5f26d1 absorption spectra of the U3+ ions incorporated in SrCl2 single crystals were recorded at 4.2 K in the 15,000-50,000 cm(-1) spectral range. From an analysis of the vibronic structure, 32 zero-phonon lines corresponding to transitions from the 4I9/2 ground multiplet of the 5f3 configuration to the 5f26d(eg)1 excited levels were assigned. A theoretical model proposed by Reid et al. (Reid, H. F.; van Pieterson, L.; Wegh, R. T.; Meijerink, A. Phys. Rev. B 2000, 62, 14744) that extends the established model for energy-level calculations of nf N states has been applied for analysis of the spectrum. The Fk(ff) (k = 2, 4), zeta(5f)(ff), B0(4)(ff), B0(6)(ff), Fk(fd) (k = 2, 4), and Gj(fd) (j = 1, 3) Hamiltonian parameters were determined by a least-squares fitting of the calculated energies to the experimental data. A good overall agreement between the calculated and experimentally observed energy levels has been achieved, with the root-mean-square (rms) deviation equal to 95 cm(-1) for 32 fitted levels and 9 varied parameters. Adjusted values of Fk(ff) and zeta(5f)(ff) parameters for the 5f2 core electrons are closer to the values characteristic of the 5f2 (U4+) configuration than to those of the 5f3 (U3+) configuration. For the U3+ ion, the f-d Coulomb interaction parameters are significantly more reduced from the values calculated using Cowan's computer code than they are for lanthanide ions. Moreover, because of weaker f-d Coulomb interactions for the U3+ ion than for the isoelectronic Nd3+ lanthanide ion, the very simple model assuming the coupling of crystal-field levels of the 6d1 electron with the lattice and the multiplet structure of the 5f2 configuration may be employed for the qualitative description of the general structure of the U3+ ion f-d spectrum. PMID:16839023

  2. Cavity Ringdown Absorption Spectrum of the T_1 (n,π^{*}) ← S_0 Transition of 2-CYCLOHEXEN-1-ONE

    NASA Astrophysics Data System (ADS)

    Zabronsky, Katherine L.; McAnally, Michael O.; Stupca, Daniel J.; Pillsbury, Nathan R.; Drucker, Stephen

    2013-06-01

    The cavity ringdown (CRD) absorption spectrum of 2-cyclohexen-1-one (CHO) was recorded over the range 401.5-410.5 nm in a room-temperature gas cell. The very weak band system (ɛ ≤ 0.02 dm^3 mol^{-1} {cm}^{-1}) in this region is due to the T_1(n, π*) ← S_0 electronic transition. The 0^0_0 origin band was assigned to the feature observed at {24,558.6 ± 0.3 {cm}^{-1}}. We have assigned about 25 vibronic transitions in a region extending from {-200 to +350 cm^{-1}} relative to the origin band. From these assignments we determined fundamental frequencies for several vibrational modes in the T_1 excited state. The table below compares their frequencies to corresponding values measured for CHO vapor in the S_0 electronic ground state (via far-IR spectroscopy) and the S_1(n, π*) excited state (via near-UV CRD spectroscopy). Low-frequency fundamentals (cm^{-1}) of CHO vapor Mode Description S_0 S_1(n,π^*) T_1(n,π^*) 39 ring twist 99.2 122.1 99.5 38 bend (inversion of C-5) 247 251.9 253.2 37 C=C twist 304.1 303.3 247.8 36 C=O wag 485 343.9 345.5 For ν_{39} and ν_{37}, the differences between S_1 and T_1 frequencies are noteworthy. These differences suggest that the electron delocalization associated with the π^* ← n chromophore in CHO is substantially different for singlet vs. triplet excitation. T. L. Smithson and H. Wieser, J. Chem. Phys. {73}, 2518 (1980) M. Z. M. Rishard and J. Laane, J. Molec. Struct. {976}, 56 (2010). M. Z. M. Rishard, E. A. Brown, L. K. Ausman, S. Drucker and J. Laane, J. Phys. Chem. A {112}, 38 (2008).

  3. Full-Quantum chemical calculation of the absorption maximum of bacteriorhodopsin: a comprehensive analysis of the amino acid residues contributing to the opsin shift

    PubMed Central

    Hayashi, Tomohiko; Matsuura, Azuma; Sato, Hiroyuki; Sakurai, Minoru

    2012-01-01

    Herein, the absorption maximum of bacteriorhodopsin (bR) is calculated using our recently developed method in which the whole protein can be treated quantum mechanically at the level of INDO/S-CIS//ONIOM (B3LYP/6-31G(d,p): AMBER). The full quantum mechanical calculation is shown to reproduce the so-called opsin shift of bR with an error of less than 0.04 eV. We also apply the same calculation for 226 different bR mutants, each of which was constructed by replacing any one of the amino acid residues of the wild-type bR with Gly. This substitution makes it possible to elucidate the extent to which each amino acid contributes to the opsin shift and to estimate the inter-residue synergistic effect. It was found that one of the most important contributions to the opsin shift is the electron transfer from Tyr185 to the chromophore upon excitation. We also indicate that some aromatic (Trp86, Trp182) and polar (Ser141, Thr142) residues, located in the vicinity of the retinal polyene chain and the β-ionone ring, respectively, play an important role in compensating for the large blue-shift induced by both the counterion residues (Asp85, Asp212) and an internal water molecule (W402) located near the Schiff base linkage. In particular, the effect of Trp86 is comparable to that of Tyr185. In addition, Ser141 and Thr142 were found to contribute to an increase in the dipole moment of bR in the excited state. Finally, we provide a complete energy diagram for the opsin shift together with the contribution of the chromophore-protein steric interaction. PMID:27493528

  4. Two-Photon Absorption of Bacteriorhodopsin: Formation of a Red-Shifted Thermally Stable Photoproduct F620

    PubMed Central

    Fischer, Thorsten; Hampp, Norbert A.

    2005-01-01

    By means of high-intensity 532 nm laser pulses, a photochemical conversion of the initial B570 state of bacteriorhodopsin (BR) to a stable photoproduct absorbing maximally at ≈620 nm in BR suspensions and at ≈610 nm in BR films is induced. This state, which we named F620, is photochemically further converted to a group of three products with maximal absorptions in the wavelength range from 340 nm to 380 nm, which show identical spectral properties to the so-called P360 state reported in the literature. The photoconversion from B570 to F620 is most likely a resonant two-photon absorption induced step. The formation of F620 and P360 leads to a distinguished photo-induced permanent optical anisotropy in BR films. The spectral dependence of the photo-induced anisotropy and the anisotropy orientations at the educt (B570) and product (F620) wavelengths are strong indicators that F620 is formed in a direct photochemical step from B570. The chemical nature of the P360 products probably is that of a retro-retinal containing BR, but the structural characteristics of the F620 state are still unclear. The photo-induced permanent anisotropy induced by short laser pulses in BR films helps to better understand the photochemical pathways related to this transition, and it is interesting in view of potential applications as this feature is the molecular basis for permanent optical data storage using BR films. PMID:15894635

  5. Solvent effects on the absorption spectrum and first hyperpolarizability of keto-enol tautomeric forms of anil derivatives: A Monte Carlo/quantum mechanics study

    NASA Astrophysics Data System (ADS)

    Adriano Junior, L.; Fonseca, T. L.; Castro, M. A.

    2016-06-01

    Theoretical results for the absorption spectrum and electric properties of the enol and keto tautomeric forms of anil derivatives in the gas-phase and in solution are presented. The electronic properties in chloroform, acetonitrile, methanol, and water were determined by carrying out sequential Monte Carlo simulations and quantum mechanics calculations based on the time dependent density functional theory and on the second-order Møller-Plesset perturbation theory method. The results illustrate the role played by electrostatic interactions in the electronic properties of anil derivatives in a liquid environment. There is a significant increase of the dipole moment in solution (20%-100%) relative to the gas-phase value. Solvent effects are mild for the absorption spectrum and linear polarizability but they can be particularly important for first hyperpolarizability. A large first hyperpolarizability contrast between the enol and keto forms is observed when absorption spectra present intense lowest-energy absorption bands. Dynamic results for the first hyperpolarizability are in qualitative agreement with the available experimental results.

  6. Solvent effects on the absorption spectrum and first hyperpolarizability of keto-enol tautomeric forms of anil derivatives: A Monte Carlo/quantum mechanics study.

    PubMed

    Adriano Junior, L; Fonseca, T L; Castro, M A

    2016-06-21

    Theoretical results for the absorption spectrum and electric properties of the enol and keto tautomeric forms of anil derivatives in the gas-phase and in solution are presented. The electronic properties in chloroform, acetonitrile, methanol, and water were determined by carrying out sequential Monte Carlo simulations and quantum mechanics calculations based on the time dependent density functional theory and on the second-order Møller-Plesset perturbation theory method. The results illustrate the role played by electrostatic interactions in the electronic properties of anil derivatives in a liquid environment. There is a significant increase of the dipole moment in solution (20%-100%) relative to the gas-phase value. Solvent effects are mild for the absorption spectrum and linear polarizability but they can be particularly important for first hyperpolarizability. A large first hyperpolarizability contrast between the enol and keto forms is observed when absorption spectra present intense lowest-energy absorption bands. Dynamic results for the first hyperpolarizability are in qualitative agreement with the available experimental results. PMID:27334183

  7. Effect of a Single Water Molecule on the Electronic Absorption by o- and p-Nitrophenolate: A Shift to the Red or to the Blue?

    PubMed

    Houmøller, Jørgen; Wanko, Marius; Rubio, Angel; Nielsen, Steen Brøndsted

    2015-11-25

    Many photoactive biomolecules are anions and exhibit ππ* optical transitions but with a degree of charge transfer (CT) character determined by the local environment. The phenolate moiety is a common structural motif among biochromophores and luminophores, and nitrophenolates are good model systems because the nitro substituent allows for CT-like transitions. Here we report gas-phase absorption spectra of o- and p-nitrophenolate·H2O complexes to decipher the effect of just one H2O and compare them with ab initio calculations of vertical excitation energies. The experimental band maximum is at 3.01 and 3.00 eV for ortho and para isomers, respectively, and is red-shifted by 0.10 and 0.13 eV relative to the bare ions, respectively. These shifts indicate that the transition has become more CT-like because of localization of negative charge on the phenolate oxygen, i.e., diminished delocalization of the negative excess charge. However, the transition bears less CT than that of m-nitrophenolate·H2O because this complex absorbs further to the red (2.56 eV). Our work emphasizes the importance of local perturbations: one water causes a larger shift than experienced in bulk for para isomer and almost the full shift for ortho isomer. Predicting microenvironmental effects in the boundary between CT and non-CT with high accuracy is nontrivial. However, in agreement with experiment, our calculations show a competition between the effects of electronic delocalization and electrostatic interaction with the solvent molecule. As a result, the excitation energy of ortho and para isomers is less sensitive to hydration than that of the meta isomer because donor and acceptor orbitals are only weakly coupled in the meta isomer. PMID:26549521

  8. Acceleration of convergence by shifting the spectrum of implicit finite difference operators associated with the equations of gas dynamics

    NASA Technical Reports Server (NTRS)

    Cheer, A.; Saleem, M.

    1991-01-01

    Eigensystem analysis techniques are applied to finite difference formulations of the Navier-Stokes equations in one dimension. Spectra of the resulting implicit difference operators are computed. The largest eigenvalues are calculated by using a combination of the Frechet derivative of the operators and Arnoldi's method. The accuracy of Arnoldi's method is tested by comparing the rate of convergence of the iterative method with the dominant eigenvalue of the original iteration matrix. On the basis of the pattern of eigenvalue distributions for various flow configurations, a shifting of the implicit operators in question is devised. This procedure has improved the rates of convergence of CFD codes by 20 - 50 percent.

  9. Relative amplitudes of external satellites of superfine-structure multiplets in the saturated absorption spectrum of SiF4

    NASA Astrophysics Data System (ADS)

    Krylov, I. R.; Akulinin, D. A.; Chubykin, A. D.

    2015-08-01

    Variation of amplitudes of Doppler-free saturated absorption resonances as a result of changes in the gas pressure and power of light waves is studied theoretically and experimentally. The results of the investigation are used for the interpretation of weak satellites of superfine-structure multiplets in the spectrum related to tunnel transitions between energy states of a molecule corresponding to its rotation about equivalent symmetry axes. Relative amplitudes of satellites of the AFE and FEF multiplets of the superfine structure of the SiF4 molecule in the frequency tuning interval of a CO2 laser operating at the P(38) line of the 9.7-µm band are studied experimentally. It is confirmed that the variation of relative amplitudes of the satellites is caused mainly by the fact that the magnitudes of the self-induced transparency of the medium that are created by each light wave for itself are different for the main resonances of the multiplet and for their satellites. The discrepancy between the experimental and theoretical dependences of the relative amplitudes of the satellites upon variation of the gas pressure and power of light waves is analyzed. Based on the discovered discrepancy, it is suggested that molecular collisions with Bennett dip or peak transfer contribute to the formation of satellites of the FEF multiplet. Multiphoton processes participate in the formation of one of the multiplets of the FEF multiplet. It is suggested that the power of the light field partially lifts the ban on transitions participating in the formation of satellites of both studied multiplets. Processing of the experimental curves by the leastsquares method revealed spectrally unresolved satellites within the FEF multiplet, which represent crossover resonances between allowed and forbidden transitions. For these satellites, no additional dependence of the amplitude on the laser power or gas pressure was found. The dependence of the amplitude of these satellites is completely

  10. Temperature and strain measurements using the power, line-width, shape, and frequency shift of the Brillouin loss spectrum

    NASA Astrophysics Data System (ADS)

    Bao, Xiaoyi; Smith, Jeffrey; Brown, Anthony W.

    2002-09-01

    A Brillouin scattering based fiber sensor system has been developed by our Fiber Optics Group for the structural monitoring and civil engineering related applications. In this paper, the Brillouin loss spectrum has been characterized in terms of its center frequency, peak power, line-width and shape. These parameters have been considered as a function of the input pump and probe laser powers, the pump pulse duration, strain and temperature. The measurement accuracy has been studied at different Brillouin frequency steps to study the uncertainty of the Brillouin frequency, line-width, peak power and shape factor vs. signal to noise ratio, so that we can optimize the system performance. Characterization of the Brillouin loss spectrum led to the development of an innovative technique to measure the strain and temperature simultaneously using the strain and temperature dependence on the peak power in conjunction with the Brillouin frequency for the single mode fiber with 3m spatial resolution, 3°C temperature resolution and 200 me (mm/m) strain accuracy.

  11. Temperature dependence of the absorption edge of vitreous silica

    NASA Technical Reports Server (NTRS)

    Bates, C. W., Jr.

    1976-01-01

    During an investigation of the optical properties of high-purity vitreous silica (fused quartz), which is being developed by NASA as a reflective and ablative heat shield, some interesting properties of theoretical and experimental nature have become apparent which otherwise may have remained unnoticed. Of particular interest for the NASA application is the shift of the absorption edge toward longer wavelengths with increasing temperature. The results of studies of this shift and of the spectral dependence of the absorption edge are summarized in the present paper. Plots of the absorption edge and the absorption spectrum of fused quartz vs temperature are given and discussed.

  12. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  13. The effect of deformation and intermolecular interaction on the absorption spectrum of 5-aminotetrazole and hydrazine: A computational molecular spectroscopy study on hydrazinium 5-aminotetrazolate

    NASA Astrophysics Data System (ADS)

    Farrokhpour, H.; Dehbozorgi, A.; Manassir, M.; Najafi Chermahini, A.

    2016-03-01

    In the present work, the UV absorption spectra of seven complexes of hydrazinium 5-aminotetrazolate (HY-5AT), in the range of 4-12 eV, were calculated in both gas and water. The UV absorption spectra of the selected HY-5AT complexes were also calculated in the absence of the intermolecular interaction between 5-aminotetrazole (5AT) and hydrazine (HY) and compared with the calculated UV absorption spectra of isolated HY and 5AT in the gas phase to see the effect of deformation on the electronic structures of the fragments. In addition, the calculated spectra of HY-5AT complexes were compared with the corresponding calculated spectra of HY-5AT complexes in the absence of the interaction between HY and 5AT to see the effect of interaction between two fragments on the absorption spectra of the complexes. Similar studies were performed on the most stable structure of HY-5AT complex in water and different trend was observed for the effect of deformation and interaction on the absorption spectrum of complex compared to the gas phase.

  14. The HD spectrum near 2.3 μm by CRDS-VECSEL: Electric quadrupole transition and collision-induced absorption

    NASA Astrophysics Data System (ADS)

    Vasilchenko, S.; Mondelain, D.; Kassi, S.; Čermák, P.; Chomet, B.; Garnache, A.; Denet, S.; Lecocq, V.; Campargue, A.

    2016-08-01

    The HD absorption spectrum is investigated near 2.3 μm with the help of a newly developed Cavity Ring Down Spectrometer (CRDS) using a VECSEL (Vertical External Cavity Surface Emitting Laser) as light source. The HD CRDS spectra were recorded for a series of ten pressure values in the range 50-650 Torr. The sensitivity of the recordings - noise equivalent absorption of the spectra on the order of αmin ≈ 5 × 10-10 cm-1 - has allowed for the first detection of the S(3) quadrupole electric transition of the HD fundamental band, at 4359.940 cm-1. The line center determined with an uncertainty of 0.002 cm-1 agrees with the most recent theoretical calculations. The retrieved value of the line intensity (2.5 × 10-27 cm/molecule at 296 K) agrees within 12% with the ab initio values included in the HITRAN spectroscopic database. We take the opportunity of this contribution to provide an exhaustive review of seventy-three HD absorption lines previously detected up to 20,000 cm-1. From the pressure dependence of the baseline of the CRDS spectra, the binary absorption coefficient of the HD collision induced absorption band is determined to be 1.17(4) × 10-6 cm-1amagat-2 at 4360 cm-1.

  15. The set-shifting profiles of anorexia nervosa and autism spectrum disorder using the Wisconsin Card Sorting Test: a systematic review and meta-analysis.

    PubMed

    Westwood, H; Stahl, D; Mandy, W; Tchanturia, K

    2016-07-01

    Difficulties in set-shifting are commonly reported in both autism spectrum disorder (ASD) and anorexia nervosa (AN) populations. Despite this, it is not known whether this cognitive profile persists across different ages, or whether the profiles seen in ASD and AN are comparable. This systematic review and meta-analyses aimed to compare the set-shifting profiles, as measured by the Wisconsin Card Sorting Test (WCST) in adults and younger people with either ASD or AN, relative to healthy controls (HCs) and to statistically compare performance on the WCST between ASD and AN. In all, 24 studies on ASD and 22 studies on AN were identified. In ASD, there were significant differences between the clinical group and HCs, with the ASD group making significantly more perseverative errors, indicating greater difficulty in set-shifting [pooled effect size of d = 0.67, 95% confidence interval (CI) 0.53-0.81, p ⩽ 0.001]. This effect was consistent across the age span. For AN studies, there was a significant difference between adults with AN and HCs (d = 0.52, 95% CI 0.36-0.68, p ⩽ 0.001) but a non-significant effect in child studies (d = 0.25, 95% CI -0.05 to 0.55, z = 1.66, p = 0.096). Meta-regression indicated no effect of diagnosis (AN or ASD) on performance in adult studies but there was a non-significant trend (p = 0.053) towards children with ASD performing worse than children with AN. While difficulties with set-shifting appear to be stable in ASD, there may be differences between children and adults with AN, which warrant further investigation. PMID:27109830

  16. The influence of hyperfine structure and isotope shift on the detection of Rb by 2 f-wavelength modulation diode laser absorption spectrometry—experimental verification of simulations

    NASA Astrophysics Data System (ADS)

    Gustafsson, Jörgen; Axner, Ove

    1998-12-01

    This work presents an experimental verification of a previously developed methodology for simulation of the 2 f-wavelength modulation diode laser absorption spectrometry technique (2 f-WM-DLAS) when the influence of hyperfine structure, isotope shift and collisional broadening and shift of an atomic transition is taken into account [J. Gustafsson, D. Rojas and O. Axner, Spectrochim. Acta, 52B, 1937-1953 (1997)]. The pilot element in the simulations was Rb, detected at the 780 nm 5s 2S 1/2-5p 2P 3/2 transition, in low-pressure cells and atmospheric-pressure reservoirs (e.g. graphite furnaces). This experimental investigation verifies that the simulations are able to predict, with good accuracy, experimental 2 f-WM signals from Rb atoms under both low-pressure, room-temperature conditions and atmospheric-pressure, high-temperature conditions. This implies that the previously published simulation methodology can be used for predicting and optimizing 2 f-WM signal strengths and shapes from Rb atoms (and thereby presumably also from other atoms) under a variety of pressure and temperature conditions.

  17. Direction dependence of the magneto-optical absorption in nanowires with Rashba interaction

    NASA Astrophysics Data System (ADS)

    Sakr, M. R.

    2016-09-01

    We study the directional dependence of the absorption spectrum of ballistic nanowires in the presence of gate-controlled Rashba spin-orbit interaction and an in-plane magnetic field. In the weak Rashba regime, our analytical and numerical results show that the absorption peaks associated with the first and third intersubband transitions exhibit frequency shifts and strong amplitude modulations as the direction of the magnetic field changes. If the field is parallel to the nanowire axis, these peaks disappear and the resonance frequencies of the whole absorption spectrum are given merely in terms of the Zeeman splitting and the energy scale characterizing the confinement potential. The second transition has an absorption peak that suffers an opposite frequency shift with amplitude that is largely direction independent. The amplitude modulation and frequency shift of the absorption spectrum is periodic in the angle that the magnetic field makes with the nanowire axis.

  18. The 13CH4 absorption spectrum in the Icosad range (6600-7692 cm-1) at 80 K and 296 K: Empirical line lists and temperature dependence

    NASA Astrophysics Data System (ADS)

    Campargue, A.; Béguier, S.; Zbiri, Y.; Mondelain, D.; Kassi, S.; Karlovets, E. V.; Nikitin, A. V.; Rey, M.; Starikova, E. N.; Tyuterev, Vl. G.

    2016-08-01

    The 13CH4 absorption spectrum has been recorded at 296 K and 80 K in the Icosad range between 6600 and 7700 cm-1. The achieved noise equivalent absorption of the spectra recorded by differential absorption spectroscopy (DAS) is about αmin ≈ 1.5 × 10-7 cm-1. Two empirical line lists were constructed including 17,792 and 24,139 lines at 80 K and 296 K, respectively. For comparison, the HITRAN database provides only 1040 13CH4 lines in the region determined from methane spectra with natural isotopic abundance. Empirical values of the lower state energy level, Eemp, were systematically derived from the intensity ratios of the lines measured at 80 K and 296 K. Overall 10,792 Eemp values were determined providing accurate temperature dependence for most of the 13CH4 absorption in the region (93% and 82% at 80 K and 296 K, respectively). The quality of the derived empirical values of the lower state rotational quantum number, Jemp, is illustrated by their clear propensity to be close to an integer. A good agreement is achieved between our small Jemp values, with previous accurate determinations obtained by applying the 2T method to jet and 80 K spectra. The line lists at 296 K and 80 K which are provided as Supplementary material will be used for future rovibrational assignments based on accurate variational calculations.

  19. Electronic Absorption Spectra from MM and ab initio QM/MM Molecular Dynamics: Environmental Effects on the Absorption Spectrum of Photoactive Yellow Protein

    PubMed Central

    Isborn, Christine M.; Götz, Andreas W.; Clark, Matthew A.; Walker, Ross C.; Martínez, Todd J.

    2012-01-01

    We describe a new interface of the GPU parallelized TeraChem electronic structure package and the Amber molecular dynamics package for quantum mechanical (QM) and mixed QM and molecular mechanical (MM) molecular dynamics simulations. This QM/MM interface is used for computation of the absorption spectra of the photoactive yellow protein (PYP) chromophore in vacuum, aqueous solution, and protein environments. The computed excitation energies of PYP require a very large QM region (hundreds of atoms) covalently bonded to the chromophore in order to achieve agreement with calculations that treat the entire protein quantum mechanically. We also show that 40 or more surrounding water molecules must be included in the QM region in order to obtain converged excitation energies of the solvated PYP chromophore. These results indicate that large QM regions (with hundreds of atoms) are a necessity in QM/MM calculations. PMID:23476156

  20. Gas cell based on optical contacting for fundamental spectroscopy studies with initial reference absorption spectrum of H2O vapor at 1723 K and 0.0235 bar

    NASA Astrophysics Data System (ADS)

    Melin, Scott T.; Sanders, Scott T.

    2016-09-01

    A gas cell, using optically contacted sapphire windows to form a hot vapor seal, has been created for high temperature fundamental spectroscopy studies. It is designed to operate at temperatures from 280-2273 K and pressures from vacuum to 1.3 bar. Using the cell in conjunction with an external cavity diode laser spectrometer, a reference H2O vapor absorption spectrum at P=0.0235±0.0036 bar and T=1723±6 K was measured with 0.0001 cm-1 resolution over the 7326-7598 cm-1 range. Comparison of the measured spectrum to simulations reveals errors in both the HITEMP and BT2 databases. This work establishes heated static cell capabilities at temperatures well above the typical limit of approximately 1300 K set by quartz material properties. This paper addresses the design of the cell as well as the cell's limitations.

  1. Rotationally resolved à 2Πg←X˜2Πu electronic spectrum of triacetylene cation by frequency modulation absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Sinclair, Wayne E.; Pfluger, David; Linnartz, Harold; Maier, John P.

    1999-01-01

    The spectrum of the à 2Πg←X˜2Πu 000 band system of the triacetylene cation and isotopic derivatives DC6H+ and C6D2+ have been studied at Doppler-limited resolution using frequency modulation absorption spectroscopy. The ions were generated in a liquid-nitrogen-cooled hollow cathode discharge incorporated in a White cell. A discharge modulation in combination with the frequency modulation technique was used to enhance the detection sensitivity. Analyses of the rotational structure yield accurate rotational and spin-orbit interaction constants of triacetylene cation in the two electronic states and information on its geometry.

  2. Pressure Swing Absorption Device and Process for Separating CO{sub 2} from Shifted Syngas and its Capture for Subsequent Storage

    SciTech Connect

    Sirkar, Kamalesh; Jie, Xingming; Chau, John; Obuskovic, Gordana

    2013-03-31

    Using the ionic liquid (IL) 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]) as the absorbent on the shell side of a membrane module containing either a porous hydrophobized ceramic tubule or porous hydrophobized polyether ether ketone (PEEK) hollow fiber membranes, studies for CO{sub 2} removal from hot simulated pre-combustion shifted syngas were carried out by a novel pressure swing membrane absorption (PSMAB) process. Helium was used as a surrogate for H{sub 2} in a simulated shifted syngas with CO{sub 2} around 40% (dry gas basis). In this cyclic separation process, the membrane module was used to achieve non-dispersive gas absorption from a high-pressure feed gas (689-1724 kPag; 100-250 psig) at temperatures between 25-1000C into a stationary absorbent liquid on the module shell side during a certain part of the cycle followed by among other cycle steps controlled desorption of the absorbed gases from the liquid in the rest of the cycle. Two product streams were obtained, one He-rich and the other CO{sub 2}-rich. Addition of polyamidoamine (PAMAM) dendrimer of generation 0 to IL [bmim][DCA] improved the system performance at higher temperatures. The solubilities of CO{sub 2} and He were determined in the ionic liquid with or without the dendrimer in solution as well as in the presence or absence of moisture; polyethylene glycol (PEG) 400 was also studied as a replacement for the IL. The solubility selectivity of the ionic liquid containing the dendrimer for CO{sub 2} over helium was considerably larger than that for the pure ionic liquid. The solubility of CO{sub 2} and CO{sub 2}-He solubility selectivity of PEG 400 and a solution of the dendrimer in PEG 400 were higher than the corresponding ones in the IL, [bmim][DCA]. A mathematical model was developed to describe the PSMAB process; a numerical solution of the governing equations described successfully the observed performance of the PSMAB process for the pure ionic liquid-based system.

  3. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Basavaraja, Jana; Suresh Kumar, H. M.; Inamdar, S. R.; Wari, M. N.

    2016-02-01

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π → π* transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μe). It is observed that dipole moment value of excited state (μe) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state.

  4. Contribution of a visual pigment absorption spectrum to a visual function: depth perception in a jumping spider

    PubMed Central

    Nagata, Takashi; Arikawa, Kentaro; Terakita, Akihisa

    2013-01-01

    Absorption spectra of visual pigments are adaptively tuned to optimize informational capacity in most visual systems. Our recent investigation of the eyes of the jumping spider reveals an apparent exception: the absorption characteristics of a visual pigment cause defocusing of the image, reducing visual acuity generally in a part of the retina. However, the amount of defocus can theoretically provide a quantitative indication of the distance of an object. Therefore, we proposed a novel mechanism for depth perception in jumping spiders based on image defocus. Behavioral experiments revealed that the depth perception of the spider depended on the wavelength of the ambient light, which affects the amount of defocus because of chromatic aberration of the lens. This wavelength effect on depth perception was in close agreement with theoretical predictions based on our hypothesis. These data strongly support the hypothesis that the depth perception mechanism of jumping spiders is based on image defocus.

  5. Diagnosing the reionization of the universe - The absorption spectrum of the intergalactic medium and Lyman alpha clouds

    NASA Technical Reports Server (NTRS)

    Giroux, Mark L.; Shapiro, Paul R.

    1991-01-01

    The thermal and ionization evolution of a uniform intergalactic medium composed of H and He and undergoing reionization is studied. The diagnosis of the metagalactic ionizing radiation background at z of about three using metal line ratios for Lyman limit quasar absorption line systems is addressed. The use of the He II Gunn-Peterson effect to diagnose the reionization source and/or nature of the Hy-alpha forest clouds is considered.

  6. Ultrafast transient absorption spectrum of the room temperature Ionic liquid 1-hexyl-3-methylimidazolium bromide: Confounding effects of photo-degradation

    NASA Astrophysics Data System (ADS)

    Musat, Raluca M.; Crowell, Robert A.; Polyanskiy, Dmitriy E.; Thomas, Marie F.; Wishart, James F.; Katsumura, Yosuke; Takahashi, Kenji

    2015-12-01

    The photochemistry of the charge transfer (CT) band of the room temperature ionic liquid (RTIL) 1-hexyl-3-methylimidazolium bromide (HMIm+/Br-) is investigated using near-IR to vis ultrafast transient absorption (TA) and steady-state UV absorption spectroscopies. Continuous irradiation of the CT band at 266 nm results in the formation of photo-products that absorb strongly at 266 nm. It is shown that these photo-products, which are apparently very stable, adversely affect ultrafast TA measurements. Elimination of these effects reveals at least two transient species that exist within the TA detection window of 100 fs to 3 ns and 500-1250 nm. One of the components is a short-lived (<1 ps) species that absorbs at 1080 nm. The second band exhibits a multicomponent spectrum that is very broad with an absorption maximum around 600 nm and a lifetime that is longer than the 3 ns window of our TA spectrometer. Within the signal to noise ratio of the TA spectrometer little to no solvated electron is generated by the CT mechanism.

  7. Influence of the size and protonation state of acidic residue 85 on the absorption spectrum and photoreaction of the bacteriorhodopsin chromophore

    NASA Technical Reports Server (NTRS)

    Lanyi, J. K.; Tittor, J.; Varo, G.; Krippahl, G.; Oesterhelt, D.

    1992-01-01

    The consequences of replacing Asp-85 with glutamate in bacteriorhodopsin, as expressed in Halobacterium sp. GRB, were investigated. Similarly to the in vitro mutated and in Escherichia coli expressed protein, the chromophore was found to exist as a mixture of blue (absorption maximum 615 nm) and red (532 nm) forms, depending on the pH. However, we found two widely separated pKa values (about 5.4 and 10.4 without added salt), arguing for two blue and two red forms in separate equilibria. Both blue and red forms of the protein are in the two-dimensional crystalline state. A single pKa, such as in the E. coli expressed protein, was observed only after solubilization with detergent. The photocycle of the blue forms was determined at pH 4.0 with 610 nm photoexcitation, and that of the red forms at pH 10.5 and with 520 nm photoexcitation, in the time-range of 100 ns to 1 s. The blue forms produced no M, but a K- and an L-like intermediate, whose spectra and kinetics resembled those of blue wild-type bacteriorhodopsin below pH 3. The red forms produced a K-like intermediate, as well as M and N. Only the red forms transported protons. Specific perturbation of the neighborhood of the Schiff base by the replacement of Asp-85 with glutamate was suggested by (1) the shift and splitting of the pKa for what is presumably the protonation of residue 85, (2) a 36 nm blue-shift in the absorption of the all-trans red chromophore and a 25 nm red-shift of the 13-cis N chromophore, as compared to wild-type bacteriorhodopsin and its N intermediate, and (3) significant acceleration of the deprotonation of the Schiff base at pH 7, but not of its reprotonation and the following steps in the photocycle.

  8. Low-temperature high-resolution absorption spectrum of 14NH3 in the ν1+ν3 band region (1.51 μm)

    NASA Astrophysics Data System (ADS)

    Földes, T.; Golebiowski, D.; Herman, M.; Softley, T. P.; Di Lonardo, G.; Fusina, L.

    2014-09-01

    Jet-cooled spectra of 14NH3 and 15NH3 in natural abundance were recorded using cavity ring-down (CRDS, 6584-6670 cm-1) and cavity enhanced absorption (CEAS, 6530-6700 cm-1) spectroscopy. Line broadening effects in the CRDS spectrum allowed lines with J″-values between 0 and 3 to be identified. Intensity ratios in 14NH3 between the jet-cooled CRDS and literature room-temperature data from Sung et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1066) further assisted the line assignments. Ground state combination differences were extensively used to support the assignments, providing reliable values for J, K and inversion symmetry of the ground state vibrational levels. CEAS data helped in this respect for the lowest J lines, some of which are saturated in the CRDS spectrum. Further information on a/s doublets arose from the observed spectral structures. Thirty-two transitions of 14NH3 were assigned in this way and a limited but significant number (19) of changes in the assignments results, compared to Sung et al. or to Cacciani et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1084). Sixteen known and 25 new low-J transitions were identified for 15NH3 in the CRDS spectrum but the much scarcer literature information did not allow for any more refined assignment. The present line position measurements improve on literature values published for 15NH3 and on some line positions for 14NH3.

  9. VizieR Online Data Catalog: Absorption spectrum of the QSO PKS2126-158 (D'Odorico+ 1998)

    NASA Astrophysics Data System (ADS)

    D'Odorico, V.; Cristiani, S.; D'Odorico, S.; Fontana, A.; Giallongo, E.

    1997-10-01

    Spectra of the zem=3.268 quasar PKS 2126-158 have been obtai the wavelength range 430-662nm with a resolution R=27000 and an average signal to noise ratio s/n=25 per resolution element. 12 metal absorption systems have been identified, two of which were previously unknown. All the lines shortward of the Lymanα emission not identified as due to metals have been fitted as Lymanα and Lymanβ. We reported statistical analysis of this sample of lines. In particular, the two-point correlation function for metal systems has been computed. (1 data file).

  10. UV and VUV spectrum of matrix-isolated In: an investigation by absorption, magnetic circular dichroism and emission yield spectroscopy

    NASA Astrophysics Data System (ADS)

    Schroeder, W.; Rotermund, H.-H.; Wiggenhauser, H.; Schrittenlacher, W.; Hormes, J.; Krebs, W.; Laaser, W.

    1986-05-01

    The electronic absorption spectra of In atoms isolated in neon, argon, krypton and xenon matrices have been measured in the energy range between 2.5 and 9.0 eV. This region includes the 5s 25p → 5s 26s and 5s 25p → 5s 25d resonance transitions, higher members of the corresponding s- and d-Rydberg series and the inner shell 5s 25p → 5s5p 2 transitions. A correlation of the absorption spectra with results obtained from magnetic circular dichroism and fluorescence measurements has made it possible to provide a detailed assignment of most of the features in the spectra in spite of the complexities associated with their behavior. For example, the transition to 5s 26s could not be detected in any of the matrices and the 5s 25d configuration was found to be strongly quenched in intensity as compared to the other transitions. In contrast, several Rydberg transitions could be observed for In in Ne. These were satisfactorily interpreted within the Frenkel formalism. Some of these observations have been rationalized by assuming that the average radius of the wavefunction for the excited state is the dominant parameter for the matrix interaction.

  11. 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

  12. 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

  13. Cl{sub 2}O photochemistry: Ultraviolet/vis absorption spectrum temperature dependence and O({sup 3}P) quantum yield at 193 and 248 nm

    SciTech Connect

    Papanastasiou, Dimitrios K.; Feierabend, Karl J.; Burkholder, James B.

    2011-05-28

    The photochemistry of Cl{sub 2}O (dichlorine monoxide) was studied using measurements of its UV/vis absorption spectrum temperature dependence and the O({sup 3}P) atom quantum yield, {Phi}{sub Cl{sub 2}O}{sup O}({lambda}), in its photolysis at 193 and 248 nm. The Cl{sub 2}O UV/vis absorption spectrum was measured over the temperature range 201-296 K between 200 and 500 nm using diode array spectroscopy. Cl{sub 2}O absorption cross sections, {sigma}{sub Cl{sub 2}O}({lambda},T), at temperatures <296 K were determined relative to its well established room temperature values. A wavelength and temperature dependent parameterization of the Cl{sub 2}O spectrum using the sum of six Gaussian functions, which empirically represent transitions from the ground {sup 1}A{sub 1} electronic state to excited states, is presented. The Gaussian functions are found to correlate well with published theoretically calculated vertical excitation energies. O({sup 3}P) quantum yields in the photolysis of Cl{sub 2}O at 193 and 248 nm were measured using pulsed laser photolysis combined with atomic resonance fluorescence detection of O({sup 3}P) atoms. O({sup 3}P) quantum yields were measured to be 0.85 {+-} 0.15 for 193 nm photolysis at 296 K and 0.20 {+-} 0.03 at 248 nm, which was also found to be independent of temperature (220-352 K) and pressure (17 and 28 Torr, N{sub 2}). The quoted uncertainties are at the 2{sigma} (95% confidence) level and include estimated systematic errors. ClO radical temporal profiles obtained following the photolysis of Cl{sub 2}O at 248 nm, as reported previously in Feierabend et al.[J. Phys. Chem. A 114, 12052, (2010)], were interpreted to establish a <5% upper-limit for the O + Cl{sub 2} photodissociation channel, which indicates that O({sup 3}P) is primarily formed in the three-body, O + 2Cl, photodissociation channel at 248 nm. The analysis also indirectly provided a Cl atom quantum yield of 1.2 {+-} 0.1 at 248 nm. The results from this work are compared

  14. A HIRES Detection of NA I D Absorption in the Spectrum of the QSO PKS 2020-370 Due to the Galaxy Klemola 31A

    NASA Astrophysics Data System (ADS)

    Junkkarinen, V. T.; Barlow, T. A.

    1994-12-01

    By using the Keck telescope and HIRES spectrograph we have detected Na I D absorption lines in the spectrum of the QSO PKS 2020-370 (V = 17.5, z = 1.048) due to the galaxy Klemola 31A (z = 0.0288). The PKS 2020-370 line of sight is near an apparent spiral arm only 20" from the nucleus of Klemola 31A which corresponds to 17 kpc (H_o = 50 km s(-1) Mpc(-1) ). The spectrum of PKS 2020-370 has strong Ca II absorption lines (W_λ ~ 350 m Angstroms \\ for the K line) at the galaxy redshift (Boksenberg et al, 1980, ApJ, 242, L145), but previous attempts to detect Na I have resulted in upper limits (Boisse et al. 1988, A&A, 191, 193, Womble, 1992, thesis UCSD). We observed PKS 2020-370 with HIRES in May 1994 at a resolution of 8 km s(-1) FWHM for a total of 90 minutes. The Na I D doublet is detected with a total W_λ for the Na I 5891.6 Angstroms \\ (vac) absorption line of about 160 m Angstroms . The absorption appears as two main velocity components separated by 23 km s(-1) . The optically thin estimate for N(Na I) = 1.0 times 10(12) cm(-2) gives an estimated N(Ca II)/N(Na I) = 5. This value suggests that the gas in Klemola 31A along the QSO line of sight is ``halo like''. Along ``disk like'' lines of sight where Ca is thought to be depleted onto grains in our Galaxy, the N(Ca II)/N(Na I) ratio is usually small (<= 1). Other QSO--galaxy pairs often show disk like N(Ca II)/N(Na I) ratios when the line of sight intersects starlight at 25 mag per sq. arcsec (Womble, 1992 thesis UCSD). The PKS 2020-370 sightline is near the optical extent of Klemola 31A but the N(Ca II)/N(Na I) is consistent with the sightline passing through two clouds in the halo. This research has been supported in part by NASA NAS5--29293 and NAG5--1630.

  15. FE K EMISSION AND ABSORPTION FEATURES IN THE XMM-EPIC SPECTRUM OF THE SEYFERT GALAXY IC 4329A

    NASA Technical Reports Server (NTRS)

    Markowitz, A.; Reeves, J. N.; Braito, V.

    2001-01-01

    We present a re-analysis of the XMM-Newton long-look of the X-ray bright Seyfert galaxy IC 4329a. The Fe K bandpass is dominated by two peaks, consistent with emission from neutral or near-neutral Fe Ka and KP. A relativistic diskline model whereby both peaks are the result of one doubly-peaked diskline profile is found to be a poor description of the data. Models using two relativistic disklines are found to describe the emission profile well. A low-inclination, moderately-relativistic dual-diskline model is possible if the contribution from narrow components, due to distant material, is small or absent. A high-inclination, moderately relativistic profile for each peak is possible if there are roughly equal contributions from both the broad and narrow components. Upper limits on Fe XXV and Fe XXVI emission and absorption at the systemic velocity of IC 4329a are obtained. We also present the results of RXTE monitoring of this source obtained so far; the combined XMM-Newton and RXTE data sets allow us to explore the time-resolved spectral behavior of this source on time scales ranging from hours to 2 years. We find no strong evidence for variability of the Fe Ka emission line on any time scale probed, likely due to the minimal level of continuum variability. We detect a narrow absorption line, at a energy of 7.68 keV in the rest frame of the source; its significance has been confirmed using Monte Carlo simulations. This feature is most likely due to absorption from Fe XXVI blueshifted to approximately 0.1c relative to the systemic velocity, making IC 4329a the lowest-redshift AGN known with a high-velocity, highly-ionized outflow component. As is often the case with similar outflows seen in high-luminosity quasars, the estimated mass outflow rate is larger than the inflow accretion rate, signaling that the outflow represents a substantial portion of the total energy budget of the AGN. The outflow could arise from a radiatively-driven disk wind, or it may be in the

  16. A New Search for Carbon Monoxide Absorption in the Transmission Spectrum of the Extrasolar Planet HD 209458b

    NASA Astrophysics Data System (ADS)

    Deming, Drake; Brown, Timothy M.; Charbonneau, David; Harrington, Joseph; Richardson, L. Jeremy

    2005-04-01

    We have revisited the search for carbon monoxide absorption features in transmission during the transit of the extrasolar planet HD 209458b. In 2002 August-September we acquired a total of 1077 high-resolution spectra (λ/δλ~25,000) in the K-band (2 μm) wavelength region using NIRSPEC on the Keck II telescope during three transits. These data are more numerous and of better quality than the data analyzed in an initial search by Brown et al. Our analysis achieves a sensitivity sufficient to test the degree of CO absorption in the first-overtone bands during transit on the basis of plausible models of the planetary atmosphere. We analyze our observations by comparison with theoretical tangent geometry absorption spectra, computed by adding height-invariant ad hoc temperature perturbations to the model atmosphere of Sudarsky et al. and by treating cloud height as an adjustable parameter. We do not detect CO absorption. The strong 2-0 R-branch lines between 4320 and 4330 cm-1 have depths during transit less than 1.6 parts in 104 in units of the stellar continuum (3 σ limit) at a spectral resolving power of 25,000. Our analysis indicates a weakening similar to that found in the case of sodium, suggesting that a general masking mechanism is at work in the planetary atmosphere. Under the interpretation that this masking is provided by high clouds, our analysis defines the maximum cloud-top pressure (i.e., minimum height) as a function of the model atmospheric temperature. For the relatively hot model used by Charbonneau et al. to interpret their sodium detection, our CO limit requires cloud tops at or above 3.3 mbar, and these clouds must be opaque at a wavelength of 2 μm. High clouds comprised of submicron-sized particles are already present in some models but may not provide sufficient opacity to account for our CO result. Cooler model atmospheres, having smaller atmospheric scale heights and lower CO mixing ratios, may alleviate this problem to some extent

  17. Discovery of a cyclotron absorption line in the spectrum of the binary X-ray pulsar 4U 1538 - 52 observed by Ginga

    NASA Technical Reports Server (NTRS)

    Clark, George W.; Woo, Jonathan W.; Nagase, Fumiaki; Makishima, Kazuo; Sakao, Taro

    1990-01-01

    A cyclotron absorption line near 20 keV has been found in the spectrum of the massive eclipsing binary X-ray pulsar 4U 1538 - 52 in observations with the Ginga observatory. The line is detected throughout the 529 s pulse cycle with a variable equivalent width that has its maximum value during the smaller peak of the two-peak pulse profile. It is found that the profile of the pulse and the phase-dependence of the cyclotron line can be explained qualitatively by a pulsar model based on recent theoretical results on the properties of pencil beams emitted by accretion-heated slabs of magnetized plasma at the magnetic poles of a neutron star. The indicated field at the surface of the neutron star is 1.7 (1 + z) x 10 to the 12th G, where z is the gravitational redshift.

  18. The 5 f r arrow 6 d absorption spectrum of Pa sup 4+ /Cs sub 2 ZrCl sub 6

    SciTech Connect

    Edelstein, N.; Kot, W.K. ); Krupa, J. )

    1992-01-01

    The 5{ital f}{sup 1}{r arrow}6{ital d}{sup 1} absorption spectrum of {sup 231}Pa{sup 4+} diluted in a single crystal of Cs{sub 2}ZrCl{sub 6} has been measured at 4.2 K. Three bands corresponding to the 6{ital d}({Gamma}{sub 8{ital g}}, {Gamma}{sub 7{ital g}}, and {Gamma}{sup {prime}}{sub 8{ital g}} ) levels are assigned. Extensive vibronic structure has been observed for the lowest 5{ital f}{r arrow}6{ital d} transition and this structure is compared to that recently reported for the 6{ital d}{sup 1}{r arrow}5{ital f}{sup 1} emission spectra in the same system.

  19. A full-dimensional multilayer multiconfiguration time-dependent Hartree study on the ultraviolet absorption spectrum of formaldehyde oxide.

    PubMed

    Meng, Qingyong; Meyer, Hans-Dieter

    2014-09-28

    Employing the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method in conjunction with the multistate multimode vibronic coupling Hamiltonian (MMVCH) model, we perform a full dimensional (9D) quantum dynamical study on the simplest Criegee intermediate, formaldehyde oxide, in five lower-lying singlet electronic states. The ultraviolet (UV) spectrum is then simulated by a Fourier transform of the auto-correlation function. The MMVCH model is built based on extensive MRCI(8e,8o)/aug-cc-pVTZ calculations. To ensure a fast convergence of the final calculations, a large number of ML-MCTDH test calculations is performed to find an appropriate multilayer separations (ML-trees) of the ML-MCTDH nuclear wave functions, and the dynamical calculations are carefully checked to ensure that the calculations are well converged. To compare the computational efficiency, standard MCTDH simulations using the same Hamiltonian are also performed. A comparison of the MCTDH and ML-MCTDH calculations shows that even for the present not-too-large system (9D here) the ML-MCTDH calculations can save a considerable amount of computational resources while producing identical spectra as the MCTDH calculations. Furthermore, the present theoretical B̃(1)A'←X̃(1)A' UV spectral band and the corresponding experimental measurements [J. M. Beames, F. Liu, L. Lu, and M. I. Lester, J. Am. Chem. Soc. 134, 20045-20048 (2012); L. Sheps, J. Phys. Chem. Lett. 4, 4201-4205 (2013); W.-L. Ting, Y.-H. Chen, W. Chao, M. C. Smith, and J. J.-M. Lin, Phys. Chem. Chem. Phys. 16, 10438-10443 (2014)] are discussed. To the best of our knowledge, this is the first theoretical UV spectrum simulated for this molecule including nuclear motion beyond an adiabatic harmonic approximation. PMID:25273439

  20. A full-dimensional multilayer multiconfiguration time-dependent Hartree study on the ultraviolet absorption spectrum of formaldehyde oxide

    NASA Astrophysics Data System (ADS)

    Meng, Qingyong; Meyer, Hans-Dieter

    2014-09-01

    Employing the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method in conjunction with the multistate multimode vibronic coupling Hamiltonian (MMVCH) model, we perform a full dimensional (9D) quantum dynamical study on the simplest Criegee intermediate, formaldehyde oxide, in five lower-lying singlet electronic states. The ultraviolet (UV) spectrum is then simulated by a Fourier transform of the auto-correlation function. The MMVCH model is built based on extensive MRCI(8e,8o)/aug-cc-pVTZ calculations. To ensure a fast convergence of the final calculations, a large number of ML-MCTDH test calculations is performed to find an appropriate multilayer separations (ML-trees) of the ML-MCTDH nuclear wave functions, and the dynamical calculations are carefully checked to ensure that the calculations are well converged. To compare the computational efficiency, standard MCTDH simulations using the same Hamiltonian are also performed. A comparison of the MCTDH and ML-MCTDH calculations shows that even for the present not-too-large system (9D here) the ML-MCTDH calculations can save a considerable amount of computational resources while producing identical spectra as the MCTDH calculations. Furthermore, the present theoretical tilde{B}{}^1A^' }leftarrow tilde{X}{}^1A^' } UV spectral band and the corresponding experimental measurements [J. M. Beames, F. Liu, L. Lu, and M. I. Lester, J. Am. Chem. Soc. 134, 20045-20048 (2012); L. Sheps, J. Phys. Chem. Lett. 4, 4201-4205 (2013); W.-L. Ting, Y.-H. Chen, W. Chao, M. C. Smith, and J. J.-M. Lin, Phys. Chem. Chem. Phys. 16, 10438-10443 (2014)] are discussed. To the best of our knowledge, this is the first theoretical UV spectrum simulated for this molecule including nuclear motion beyond an adiabatic harmonic approximation.

  1. A full-dimensional multilayer multiconfiguration time-dependent Hartree study on the ultraviolet absorption spectrum of formaldehyde oxide

    SciTech Connect

    Meng, Qingyong; Meyer, Hans-Dieter

    2014-09-28

    Employing the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method in conjunction with the multistate multimode vibronic coupling Hamiltonian (MMVCH) model, we perform a full dimensional (9D) quantum dynamical study on the simplest Criegee intermediate, formaldehyde oxide, in five lower-lying singlet electronic states. The ultraviolet (UV) spectrum is then simulated by a Fourier transform of the auto-correlation function. The MMVCH model is built based on extensive MRCI(8e,8o)/aug-cc-pVTZ calculations. To ensure a fast convergence of the final calculations, a large number of ML-MCTDH test calculations is performed to find an appropriate multilayer separations (ML-trees) of the ML-MCTDH nuclear wave functions, and the dynamical calculations are carefully checked to ensure that the calculations are well converged. To compare the computational efficiency, standard MCTDH simulations using the same Hamiltonian are also performed. A comparison of the MCTDH and ML-MCTDH calculations shows that even for the present not-too-large system (9D here) the ML-MCTDH calculations can save a considerable amount of computational resources while producing identical spectra as the MCTDH calculations. Furthermore, the present theoretical B{sup ~} {sup 1}A{sup ′}←X{sup ~} {sup 1}A{sup ′} UV spectral band and the corresponding experimental measurements [J. M. Beames, F. Liu, L. Lu, and M. I. Lester, J. Am. Chem. Soc. 134, 20045–20048 (2012); L. Sheps, J. Phys. Chem. Lett. 4, 4201–4205 (2013); W.-L. Ting, Y.-H. Chen, W. Chao, M. C. Smith, and J. J.-M. Lin, Phys. Chem. Chem. Phys. 16, 10438–10443 (2014)] are discussed. To the best of our knowledge, this is the first theoretical UV spectrum simulated for this molecule including nuclear motion beyond an adiabatic harmonic approximation.

  2. New narrow infrared absorption features in the spectrum of Io between 3600 and 3100 cm (2.8-3.2 micrometers)

    NASA Technical Reports Server (NTRS)

    Sandford, Scott A.; Geballe, Thomas R.; Salama, Farid; Goorvitch, David

    1994-01-01

    We report the discovery of a series of infrared absorption bands between 3600 and 3100/cm (2.8-3.2 micrometers) in the spectrum of Io. Individual narrow bands are detected at 3553, 3514.5, 3438, 3423, 3411.5, and 3401/cm (2.815, 2.845, 2.909, 2.921, 2.931, and 2.940 micrometers, respectively). The positions and relative strengths of these bands, and the difference of their absolute strengths between the leading and trailing faces of Io, indicate that they are due to SO2. The band at 3438/cm (2.909 micrometers) could potentially have a contribution from an additional molecular species. The existence of these bands in the spectrum of Io indicates that a substantial fraction of the SO2 on Io must reside in transparent ices having relatively large crystal sizes. The decrease in the continuum observed at the high frequency ends of the spectra is probably due to the low frequency side of the recently detected, strong 3590/cm (2.79 micrometer) feature. This band is likely due to the combination of a moderately strong SO2 band and an additional absorption from another molecular species, perhaps H2O isolated in SO2 at low concentrations. A broad (FWHM approximately = 40-60/cm), weak band is seen near 3160/cm (3.16 micrometers) and is consistent with the presence of small quantities of H2O isolated in SO2-rich ices. There is no evidence in the spectra for the presence of H2O vapor on Io. Thus, the spectra presented here neither provide unequivocal evidence for the presence of H2O on Io nor preclude it at the low concentrations suggested by past studies.

  3. AN Fe XXIV ABSORPTION LINE IN THE PERSISTENT SPECTRUM OF THE DIPPING LOW-MASS X-RAY BINARY 1A 1744-361

    SciTech Connect

    Gavriil, Fotis P.; Strohmayer, Tod E.; Bhattacharyya, Sudip

    2012-07-01

    We report on Chandra X-ray Observatory (Chandra) High Energy Transmission Grating spectra of the dipping low-mass X-ray binary 1A 1744-361 during its 2008 July outburst. We find that its persistent emission is well modeled by a blackbody (kT {approx} 1.0 keV) plus power law ({Gamma} {approx} 1.7) with an absorption edge. In the residuals of the combined spectrum, we find a significant absorption line at 6.961 {+-} 0.002 keV, consistent with the Fe XXVI (hydrogen-like Fe) 2-1 transition. We place an upper limit on the velocity of a redshifted flow of v < 221 km s{sup -1}. We find an equivalent width for the line of 27{sup +2}{sub -3} eV, from which we determine a column density of (7 {+-} 1) Multiplication-Sign 10{sup 17} cm{sup -2} via a curve-of-growth analysis. Using XSTAR simulations, we place a lower limit on the ionization parameter of >10{sup 3.6} erg cm s{sup -1}. We discuss what implications the feature has on the system and its geometry. We also present Rossi X-ray Timing Explorer data accumulated during this latest outburst and, via an updated color-color diagram, clearly show that 1A 1744-361 is an 'atoll' source.

  4. Assignment and modeling of the absorption spectrum of 13CH4 at 80 K in the region of the 2ν3 band (5853-6201 cm-1)

    NASA Astrophysics Data System (ADS)

    Starikova, E.; Nikitin, A. V.; Rey, M.; Tashkun, S. A.; Mondelain, D.; Kassi, S.; Campargue, A.; Tyuterev, Vl. G.

    2016-07-01

    The absorption spectrum of the 13CH4 methane isotopologue has been recently recorded by Differential Absorption Spectroscopy (DAS) at 80 K in the 5853-6201 cm-1 spectral range. An empirical list of 3717 lines was constructed for this spectral range corresponding to the upper part of the Tetradecad dominated by the 2ν3 band near 5987 cm-1. In this work, we present rovibrational analyses of these spectra obtained via two theoretical approaches. Assignments of strong and medium lines were achieved with variational calculations using ab initio potential energy (PES) and dipole moment surfaces. For further analysis a non-empirical effective Hamiltonian (EH) of the methane polyads constructed by high-order Contact Transformations (CT) from an ab initio PES was employed. Initially predicted values of EH parameters were empirically optimized using 2898 assigned line positions fitted with an rms deviation of 5×10-3 cm-1. More than 1860 measured line intensities were modeled using the effective dipole transition moments approach with the rms deviation of about 10%. These new data were used for the simultaneous fit of the 13CH4 Hamiltonian parameters of the {Ground state/Dyad/Pentad/Octad/Tetradecad} system and the dipole moment parameters of the {Ground state-Tetradecad} system. Overall, 10 vibrational states and 28 vibration sublevels of the 13CH4 Tetradecad are determined. The comparison of their energy values with corresponding theoretical calculations is discussed.

  5. An Fe XXIV Absorption Line in the Persistent Spectrum of the Dipping Low-Mass X-Ray Binary 1A 1744-361

    NASA Technical Reports Server (NTRS)

    Gavriil, Fotis P.; Strohmayer, Tod E.; Bhattacharyya, Sudip

    2012-01-01

    We report on Chandra X-ray Observatory (Chandra) High Energy Transmission Grating spectra of the dipping low-mass X-ray binary 1A 1744-361 during its 2008 July outburst. We find that its persistent emission is well modeled by a blackbody (kT approx. 1.0 keV) plus power law (Gamma approx. 1.7) with an absorption edge. In the residuals of the combined spectrum, we find a significant absorption line at 6.961 +/- 0.002 keV, consistent with the Fe xxvi (hydrogen-like Fe) 2-1 transition.We place an upper limit on the velocity of a redshifted flow of nu < 221 km/s. We find an equivalent width for the line of 27+2/-3 eV, from which we determine a column density of (7 +/- 1)×10(exp 17) /sq. cm via a curve-of-growth analysis. Using XSTAR simulations, we place a lower limit on the ionization parameter of >103.6 erg cm/s. We discuss what implications the feature has on the system and its geometry. We also present Rossi X-ray Timing Explorer data accumulated during this latest outburst and, via an updated color-color diagram, clearly show that 1A 1744-361 is an "atoll" source

  6. A Combination of Chemometrics and Quantum Mechanics Methods Applied to Analysis of Femtosecond Transient Absorption Spectrum of Ortho-Nitroaniline

    PubMed Central

    Yi, Jing; Xiong, Ying; Cheng, Kemei; Li, Menglong; Chu, Genbai; Pu, Xuemei; Xu, Tao

    2016-01-01

    A combination of the advanced chemometrics method with quantum mechanics calculation was for the first time applied to explore a facile yet efficient analysis strategy to thoroughly resolve femtosecond transient absorption spectroscopy of ortho-nitroaniline (ONA), served as a model compound of important nitroaromatics and explosives. The result revealed that the ONA molecule is primarily excited to S3 excited state from the ground state and then ultrafast relaxes to S2 state. The internal conversion from S2 to S1 occurs within 0.9 ps. One intermediate state S* was identified in the intersystem crossing (ISC) process, which is different from the specific upper triplet receiver state proposed in some other nitroaromatics systems. The S1 state decays to the S* one within 6.4 ps and then intersystem crossing to the lowest triplet state within 19.6 ps. T1 was estimated to have a lifetime up to 2 ns. The relatively long S* state and very long-lived T1 one should play a vital role as precursors to various nitroaromatic and explosive photoproducts. PMID:26781083

  7. A Combination of Chemometrics and Quantum Mechanics Methods Applied to Analysis of Femtosecond Transient Absorption Spectrum of Ortho-Nitroaniline.

    PubMed

    Yi, Jing; Xiong, Ying; Cheng, Kemei; Li, Menglong; Chu, Genbai; Pu, Xuemei; Xu, Tao

    2016-01-01

    A combination of the advanced chemometrics method with quantum mechanics calculation was for the first time applied to explore a facile yet efficient analysis strategy to thoroughly resolve femtosecond transient absorption spectroscopy of ortho-nitroaniline (ONA), served as a model compound of important nitroaromatics and explosives. The result revealed that the ONA molecule is primarily excited to S3 excited state from the ground state and then ultrafast relaxes to S2 state. The internal conversion from S2 to S1 occurs within 0.9 ps. One intermediate state S* was identified in the intersystem crossing (ISC) process, which is different from the specific upper triplet receiver state proposed in some other nitroaromatics systems. The S1 state decays to the S* one within 6.4 ps and then intersystem crossing to the lowest triplet state within 19.6 ps. T1 was estimated to have a lifetime up to 2 ns. The relatively long S* state and very long-lived T1 one should play a vital role as precursors to various nitroaromatic and explosive photoproducts. PMID:26781083

  8. Ascites-induced shift along epithelial-mesenchymal spectrum in ovarian cancer cells: enhancement of their invasive behavior partly dependant on αv integrins.

    PubMed

    Carduner, L; Leroy-Dudal, J; Picot, C R; Gallet, O; Carreiras, F; Kellouche, S

    2014-08-01

    At least one-third of patients with epithelial ovarian cancer (OC) present ascites at diagnosis and almost all have ascites at recurrence. The presence of ascites, which acts as a dynamic reservoir of active molecules and cellular components, correlates with the OC peritoneal metastasis and is associated with poor prognosis. Since epithelial-mesenchymal transition (EMT) is involved in different phases of OC progression, we have investigated the effect of the unique ascitic tumor microenvironment on the EMT status and the behavior of OC cells. The exposure of three OC cell lines to ascites leads to changes in cellular morphologies. Within ascites, OC cells harboring an initial intermediate epithelial phenotype are characterized by marked dislocation of epithelial markers (E-cadherin, ZO-1 staining) while OC cells initially harboring an intermediate mesenchymal phenotype strengthen their mesenchymal markers (N-cadherin, vimentin). Ascites differentially triggers a dissemination phenotype related to the initial cell features by either allowing the proliferation and the formation of spheroids and the extension of colonies for cells that present an initial epithelial intermediate phenotype, or favoring the migration of cells with a mesenchymal intermediate phenotype. In an ascitic microenvironment, a redeployment of αv integrins into cells was observed and the ascites-induced accentuation of the two different invasive phenotypes (i.e. spheroids formation or migration) was shown to involve αv integrins. Thus, ascites induces a shift toward an unstable intermediate state of the epithelial-mesenchymal spectrum and confers a more aggressive cell behavior that takes on a different pathway based on the initial epithelial-mesenchymal cell features. PMID:24946950

  9. Electromagnetic resonance modes on a two-dimensional tandem grating and its application for broadband absorption in the visible spectrum.

    PubMed

    Han, Sunwoo; Lee, Bong Jae

    2016-01-25

    In this work, we numerically investigate the electromagnetic resonances on two-dimensional tandem grating structures. The base of a tandem grating consists of an opaque Au substrate, a SiO(2) spacer, and a Au grating (concave type); that is, a well-known fishnet structure forming Au/SiO(2)/Au stack. A convex-type Au grating (i.e., topmost grating) is then attached on top of the base fishnet structure with or without additional SiO(2) spacer, resulting in two types of tandem grating structures. In order to calculate the spectral reflectance and local magnetic field distribution, the finite-difference time-domain method is employed. When the topmost Au grating is directly added onto the base fishnet structure, the surface plasmon and magnetic polariton in the base structure are branched out due to the geometric asymmetry with respect to the SiO(2) spacer. If additional SiO(2) spacer is added between the topmost Au grating and the base fishnet structure, new magnetic resonance modes appear due to coupling between two vertically aligned Au/SiO(2)/Au stacks. With the understanding of multiple electromagnetic resonance modes on the proposed tandem grating structures, we successfully design a broadband absorber made of Au and SiO(2) in the visible spectrum. PMID:26832574

  10. High-resolution absorption spectrum of jet-cooled CH3Cl between 70 000 and 85 000 cm-1: New assignments

    NASA Astrophysics Data System (ADS)

    Cossart-Magos, Claudina; Jungen, Martin; Stalder, Joerg; Launay, Françoise

    2005-09-01

    The absorption spectrum of jet-cooled CH3Cl was photographed from 165to117nm (or 60000-85000cm-1, 7.5-10.5eV) at a resolution limit of 0.0008nm (0.3-0.6cm-1 or 0.04-0.08meV). Even in the best structured region of the spectrum, from 70000to85000cm-1 (8.7-10.5eV ), observed bandwidths (full width at half maximum) are large, from 50to150cm-1. No rotational feature could be resolved. The spectrum is dominated by two strong bands near 9eV, 140nm, the D and E bands of Mulliken [J. Chem. Phys. 8, 382 (1940)] or the spectral region D of Price [J. Chem. Phys.4, 539 (1936)]. Their relative intensity is incompatible with previous assignments, namely, to a triplet and a singlet state belonging to the same configuration. On the basis of the present ab initio calculations, those bands are now assigned to two singlet states, the A11 and E1 excited states resulting from the 2e34pe Rydberg configuration. The present calculations also reveal that the two E1 states issued from 2e34sa1 and 2e34pa1 are quasidegenerate and strongly mixed. They should be assigned to the two broad bands near 8eV, 160nm, the B and C bands of Mulliken and Price. Three vibrational modes are observed to be active: the CCl bond stretch ν3(a1), and the CH3 umbrella and rocking vibrations, respectively, ν2(a1) and ν6(e ). The fundamental frequencies deduced are well within the ranges defined by the corresponding values in the neutral and ion ground states. The possibility of a dynamical Jahn-Teller effect induced by the ν6(e) vibrational mode in the E1 Rydberg states is discussed.

  11. The 5f2-->5f16d1 absorption spectrum of Cs2GeF6:U4+ crystals: A quantum chemical and experimental study.

    PubMed

    Ordejón, Belén; Karbowiak, Miroslaw; Seijo, Luis; Barandiarán, Zoila

    2006-08-21

    Single crystals of U(4+)-doped Cs2GeF6 with 1% U4+ concentration have been obtained by the modified Bridgman-Stockbarger method in spite of the large difference in ionic radii between Ge4+ and U4+ in octahedral coordination. Their UV absorption spectrum has been recorded at 7 K, between 190 and 350 nm; it consists of a first broad and intense band peaking at about 38,000 cm(-1) followed by a number of broad bands of lower intensity from 39,000 to 45,000 cm(-1). None of the bands observed shows appreciable fine vibronic structure, so that the energies of experimental electronic origins cannot be deduced and the assignment of the experimental spectrum using empirical methods based on crystal field theory cannot be attempted. Alternatively, the profile of the absorption spectrum has been obtained theoretically using the U-F bond lengths and totally symmetric vibrational frequencies of the ground 5f2 - 1A(1g) and 5f16d(t(2g))1 - iT(1u) excited states, their energy differences, and their corresponding electric dipole transition moments calculated using the relativistic ab initio model potential embedded cluster method. The calculations suggest that the observed bands are associated with the lowest five 5f2 - 1A(1g)-->5f16d(t(2g))1 - iT(1u) (i = 1-5) dipole allowed electronic origins and their vibrational progressions. In particular, the first broad and intense band peaking at about 38,000 cm(-1) can be safely assigned to the 0-0 and 0-1 members of the a(1g) progression of the 5f2 - 1A(1g)-->5f16d(t(2g))1 - 1T(1u) electronic origin. The electronic structure of all the states with main configurational character 5f16d(t(2g))1 has been calculated as well. The results show that the lowest crystal level of this manifold is 5f16d(t(2g))1 - 1E(u) and lies about 6200 cm(-1) above the 5f2 level closest in energy, which amounts to some 11 vibrational quanta. This large energy gap could result in low nonradiative decay and efficient UV emission, which suggest the interest of

  12. Infrared absorption spectrum of free carriers in polar semiconductors. Progress report, July 1, 1979-June 30, 1980

    SciTech Connect

    Jensen, B.

    1980-02-01

    The Drude Zener theory of the absorption of high frequency radiation by free carriers (inverse bremsstrahlung) has been extended into the quantum region (h-bar omega > k/sub 0/T) in terms of a frequency dependent relaxation time which predicts the dc mobility in the quasiclassical limit. Numerical calculations of the frequency and concentration dependent electron scattering rate have been completed for InP, InAs, Ga/sub 0/ /sub 47/In/sub 0/ /sub 53/As, and previous results for GaAs extended to high carrier concentrations. When starting from a quantum statistical theory, the fact that n/sub q/oh-bar omega ..-->.. k/sub 0/T at low frequencies can be used to prevent the divergence of the coulomb scattering rate without inclusion of a screening radius. A result containing no adjustable parameters is found which predicts a mobility for uncompensated samples that decreases strongly at high concentrations. This has been observed in GaAs, and is not accounted for by the usual dc calculation which assumes h-bar omega = 0 and a screening parameter. Calculated results for GaAs are in good agreement with experimental measurements of the mobility which are found to be independent of a wide variety of conditions of material preparation. This indicates that disagreement with previous theoretical calculations was not due to compensation. Calculations for ZnSe and further investigation of the modification of the optical constants by the presence of an intense laser field and by a static magnetic field are currently planned.

  13. Theoretical analysis of the two-photon absorption spectrum of Tb3+ in Cs2NaTbCl6

    NASA Astrophysics Data System (ADS)

    Wang, Dianyuan; Ning, Lixin; Xia, Shangda; Tanner, Peter A.

    2003-05-01

    Eighteen selected two-photon absorption (TPA) transition line strengths with polarization angles theta = 0° and 45°, spanning several orders of magnitude, have been calculated for the Tb3+ ion in the cubic host Cs2NaTbCl6. The results are in reasonable agreement with experimental results in the literature. The calculation utilized the crystal field (CF) wavefunctions for the initial and final states of the 4f8 configuration, and utilized free ion or CF wavefunctions (with the corresponding energies) for 4f7 core states of the whole intermediate 4f7 5d configuration comprising 34 320 states. The intensities of certain transitions were found to be very sensitive to the inclusion of the CF interaction within the 4f7 core. In contrast to previous fourth- or third-order calculations of the TPA transition line strength of the strong transition (7F 6)A1g rightarrow (5D 4)A1g using pure Russell-Saunders (RS) wavefunctions for the |7F 6 rangle initial and langle5D 4 | final states, our second-order direct calculation shows that the admixed RS wavefunctions |[7F 6 ]rangle and langle[5D 4 ]| must be used to account for its high intensity. The effects of CF interactions within the 4f7 core, i.e. J-mixing and CF energy level splitting, upon the (7F 6)A1g rightarrow (5D 4)Eg TPA transition line strength have been separated, and the latter effect is shown to be more important for the transition investigated.

  14. Absorption intensity changes and frequency shifts of fundamental and first overtone bands for OH stretching vibration of methanol upon methanol-pyridine complex formation in CCl4: analysis by NIR/IR spectroscopy and DFT calculations.

    PubMed

    Futami, Yoshisuke; Ozaki, Yasushi; Ozaki, Yukihiro

    2016-02-21

    Infrared (IR) and near infrared (NIR) spectra were measured for methanol and the methanol-pyridine complex in carbon tetrachloride. Upon the formation of the methanol-pyridine complex, the frequencies of both the fundamental and first overtone bands of the OH stretching vibration shifted to lower frequencies, and the absorption intensity of the fundamental increased significantly, while that of the first overtone decreased markedly. By using quantum chemical calculations, we estimated the absorption intensities and frequencies of the fundamental and first overtone bands for the OH stretching vibration based on the one-dimensional Schrödinger equation. The calculated results well reproduced the experimental results. The molecular vibration potentials and dipole moment functions of the OH stretching vibration modes were compared between methanol and the methanol-pyridine complex in terms of absorption intensity changes and frequency shifts. The large change in the dipole moment function was found to be the main cause for the variations in absorption intensity for the fundamental and first overtone bands. PMID:26862859

  15. Local Effects in the X-ray Absorption Spectrum of CaCl2, MgCl2, and NaCl Solutions

    SciTech Connect

    Kulik, H J; Correa Tedesco, A A; Schwegler, E; Prendergast, D; Galli, G

    2010-04-12

    Both first principles molecular dynamics and theoretical X-ray absorption spectroscopy have been used to investigate the aqueous solvation of cations in 0.5 M MgCl{sub 2}, CaCl{sub 2}, and NaCl solutions. We focus here on the species-specific effects that Mg{sup 2+}, Ca{sup 2+}, and Na{sup +}, have on the X-ray absorption spectrum of the respective solutions. For the divalent cations, we find that the hydrogen bonding characteristics of the more rigid magnesium first shell water molecules differ from those in the more flexible solvation shell surrounding calcium. In particular, the first solvation shell water molecules of calcium are accessible to forming acceptor hydrogen bonds, and this results in an enhancement of a post-edge peak near 540 eV. The absence of acceptor hydrogen bonds for magnesium first shell water molecules provides an explanation for the experimental and theoretical observation of a lack of enhancement at the post-main-edge peak. For the sodium monovalent cation we find that the broad tilt angle distribution results in a broadening of post-edge features, despite populations in donor-and-acceptor configurations consistent with calcium. We also present the re-averaged spectra of the MgCl{sub 2}, CaCl{sub 2}, and NaCl solutions and show that trends apparent with increasing concentration (0.5 M, 2.0 M, 4.0 M) are consistent with experiment. Finally, we examine more closely both the effect that cation coordination number has on the hydrogen bonding network and the relative perturbation strength of the cations on lone pair oxygen orbitals.

  16. Inertial solvent dynamics and the analysis of spectral line shapes: Temperature-dependent absorption spectrum of beta-carotene in nonpolar solvent.

    PubMed

    Burt, Jim A; Zhao, Xihua; McHale, Jeanne L

    2004-03-01

    The influence of solvent dynamics on optical spectra is often described by a stochastic model which assumes exponential relaxation of the time-correlation function for solvent-induced frequency fluctuations. In contrast, theory and experiment suggest that the initial (subpicosecond) phase of solvent relaxation, resulting from inertial motion of the solvent, is a Gaussian function of time. In this work, we employ numerical and analytical calculations to compare the predicted absorption line shapes and the derived solvent reorganization energies obtained from exponential (Brownian oscillator) versus Gaussian (inertial) solvent dynamics. Both models predict motional narrowing as the ratio kappa = Lambda/Delta is increased, where Lambda and Delta are the frequency and variance, respectively, of the solvent-induced frequency fluctuations. However, the motional narrowing limit is achieved at lower values of kappa for the Brownian oscillator model compared to the inertial model. For a given line shape, the derived value of the solvent reorganization energy lambdasolv is only weakly dependent on the solvent relaxation model employed, though different solvent parameters Lambda and Delta are obtained. The two models are applied to the analysis of the temperature-dependent absorption spectrum of beta-carotene in isopentane and CS2. The derived values of lambdasolv using the Gaussian model are found to be in better agreement with the high temperature limit of Delta2/2kBT than are the values obtained using the Brownian oscillator model. In either approach, the solvent reorganization energy is found to increase slightly with temperature as a result of an increase in the variance Delta of the solvent-induced frequency fluctuations. PMID:15268604

  17. Inertial solvent dynamics and the analysis of spectral line shapes: Temperature-dependent absorption spectrum of β-carotene in nonpolar solvent

    NASA Astrophysics Data System (ADS)

    Burt, Jim A.; Zhao, Xihua; McHale, Jeanne L.

    2004-03-01

    The influence of solvent dynamics on optical spectra is often described by a stochastic model which assumes exponential relaxation of the time-correlation function for solvent-induced frequency fluctuations. In contrast, theory and experiment suggest that the initial (subpicosecond) phase of solvent relaxation, resulting from inertial motion of the solvent, is a Gaussian function of time. In this work, we employ numerical and analytical calculations to compare the predicted absorption line shapes and the derived solvent reorganization energies obtained from exponential (Brownian oscillator) versus Gaussian (inertial) solvent dynamics. Both models predict motional narrowing as the ratio κ=Λ/Δ is increased, where Λ and Δ are the frequency and variance, respectively, of the solvent-induced frequency fluctuations. However, the motional narrowing limit is achieved at lower values of κ for the Brownian oscillator model compared to the inertial model. For a given line shape, the derived value of the solvent reorganization energy λsolv is only weakly dependent on the solvent relaxation model employed, though different solvent parameters Λ and Δ are obtained. The two models are applied to the analysis of the temperature-dependent absorption spectrum of β-carotene in isopentane and CS2. The derived values of λsolv using the Gaussian model are found to be in better agreement with the high temperature limit of Δ2/2kBT than are the values obtained using the Brownian oscillator model. In either approach, the solvent reorganization energy is found to increase slightly with temperature as a result of an increase in the variance Δ of the solvent-induced frequency fluctuations.

  18. An Fe XXVI Absorption Line in the Persistent Spectrum of the Dipping Low Mass X-ray Binary 1A 1744-361

    NASA Technical Reports Server (NTRS)

    Gavriil, Fotis P.; Strohmayer, Tod E.; Bhattacharyya, Sudip

    2009-01-01

    We report on Chandra X-ray Observatory (CXO) High-Energy Transmission Grating (HETG) spectra of the dipping Low Mass X-ray Binary (LMXB) 1A 1744-361 during its July 2008 outburst. We find that its persistent emission is well modeled by a blackbody (kT approx. 1.0 keV) plus power-law (Gamma approx. 1.7) with an absorption edge at 7.6 keV. In the residuals of the combined spectrum we find a significant absorption line at 6.961+/-0.002 keV, consistent with the Fe XXVI (hydrogen-like Fe) 2 - 1 transition. We place an upper limit on the velocity of a redshifted flow of v < 221 km/s. We find an equivalent width for the line of 27+2/-3 eV, from which we determine a column density of 7+/-1 x 10(exp 17)/sq cm via a curve-of-growth analysis. Using XSTAR simulations, we place a lower limit on the ionization parameter of > 10(exp 3.6) erg cm/s. The properties of this line are consistent with those observed in other dipping LMXBs. Using Rossi X-ray Timing Explorer (RXTE) data accumulated during this latest outburst we present an updated color-color diagram which clearly shows that IA 1744-361 is an "atoll" source. Finally, using additional dips found in the RXTE and CXO data we provide an updated orbital period estimate of 52+/-5 minutes.

  19. The enhancement of 21.2%-power conversion efficiency in polymer photovoltaic cells by using mixed Au nanoparticles with a wide absorption spectrum of 400 nm-1000 nm

    NASA Astrophysics Data System (ADS)

    Hao, Jing-Yu; Xu, Ying; Zhang, Yu-Pei; Chen, Shu-Fen; Li, Xing-Ao; Wang, Lian-Hui; Huang, Wei

    2015-04-01

    Au nanoparticles (NPs) mixed with a majority of bone-like, rod, and cube shapes and a minority of irregular spheres, which can generate a wide absorption spectrum of 400 nm-1000 nm and three localized surface plasmon resonance peaks, respectively, at 525, 575, and 775 nm, are introduced into the hole extraction layer poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) to improve optical-to-electrical conversion performances in polymer photovoltaic cells. With the doping concentration of Au NPs optimized, the cell performance is significantly improved: the short-circuit current density and power conversion efficiency of the poly(3-hexylthiophene): [6,6]-phenyl-C60-butyric acid methyl ester cell are increased by 20.54% and 21.2%, reaching 11.15 mA·cm-2 and 4.23%. The variations of optical, electrical, and morphology with the incorporation of Au NPs in the cells are analyzed in detail, and our results demonstrate that the cell performance improvement can be attributed to a synergistic reaction, including: 1) both the localized surface plasmon resonance- and scattering-induced absorption enhancement of the active layer, 2) Au doping-induced hole transport/extraction ability enhancement, and 3) large interface roughness-induced efficient exciton dissociation and hole collection. Project supported by the National Basic Research Program of China (Grant Nos. 2015CB932202 and 2012CB933301), the National Natural Science Foundation of China (Grant Nos. 61274065, 51173081, 61136003, BZ2010043, 51372119, and 51172110), the Science Fund from the Ministry of Education of China (Grant No. IRT1148), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20113223110005), the Priority Academic Program Development of Jiangsu Provincial Higher Education Institutions (Grant No. YX03001), and the National Synergistic Innovation Center for Advanced Materials and the Synergetic Innovation Center for Organic Electronics and

  20. Hybrid Ab initio/EFP approach for calculating d-d absorption spectrum of hexaammineruthenium(II) ion in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Yurenev, P. V.; Scherbinin, A. V.; Stepanov, N. F.

    Ab initio quantum chemical strategies for quantitatively predicting the lowest (1Ag rarr 1T1g) vertical d-d excitation energy of hexaammineruthenium(II) ion in aqueous solution are discussed. The scalar-relativistic ECP/valence basis set on Ru atom developed by the Stuttgart group in a combination with the state-average CASSCF(d) approach, followed by multiconfigurational quasi-degenerate second-order perturbation theory (MCQDPT2) to account for differential correlation effects is proved to be an adequate tool to reproduce the experimental absorption spectrum of the complex for a variety of AO basis sets on ligand atoms. In addition, different ab initio methodologies are examined in order to predict the ground state geometry which is consistent with the follow-up excitation spectrum calculations. It is observed that the use of the optimized structures of a hypothetical gas-phase complex lead to substantial underestimation of excitation energies. Solvent effects strongly influence the excitation energy though indirectly, mainly by means of changing the ground state geometry of the solvated complex when compared with the vacuum one. In particular, the ground state structure of the complex surrounded by effective fragments simulating water molecules provides the lowest CASSCF/MCQDPT excitation energy estimate to be within 25,500-26,400 cm-1, in a fair agreement with the experimentally measured value of 25,600 cm-1. At the same time, direct incorporation of solvation effects causes only minor change in the estimated transition energies, within several hundred cm-1.

  1. Revisiting the Paradigm Shift from the "Versus" to the "Non-Versus" Notion of Mosston's Spectrum of Teaching Styles in Physical Education Pedagogy: A Critical Pedagogical Perspective

    ERIC Educational Resources Information Center

    Sicilia-Camacho, Alvaro; Brown, David

    2008-01-01

    Background: Teaching styles in physical education (PE) found prominence through Muska Mosston's teaching styles "Spectrum" model. Mosston's Spectrum has been remarkably successful and its logic currently underpins the conceptualisation of teaching styles in many PE practices in Western education systems, including those in the United States,…

  2. K- and L-edge X-ray absorption spectrum calculations of closed-shell carbon, silicon, germanium, and sulfur compounds using damped four-component density functional response theory.

    PubMed

    Fransson, Thomas; Burdakova, Daria; Norman, Patrick

    2016-05-21

    X-ray absorption spectra of carbon, silicon, germanium, and sulfur compounds have been investigated by means of damped four-component density functional response theory. It is demonstrated that a reliable description of relativistic effects is obtained at both K- and L-edges. Notably, an excellent agreement with experimental results is obtained for L2,3-spectra-with spin-orbit effects well accounted for-also in cases when the experimental intensity ratio deviates from the statistical one of 2 : 1. The theoretical results are consistent with calculations using standard response theory as well as recently reported real-time propagation methods in time-dependent density functional theory, and the virtues of different approaches are discussed. As compared to silane and silicon tetrachloride, an anomalous error in the absolute energy is reported for the L2,3-spectrum of silicon tetrafluoride, amounting to an additional spectral shift of ∼1 eV. This anomaly is also observed for other exchange-correlation functionals, but it is seen neither at other silicon edges nor at the carbon K-edge of fluorine derivatives of ethene. Considering the series of molecules SiH4-XFX with X = 1, 2, 3, 4, a gradual divergence from interpolated experimental ionization potentials is observed at the level of Kohn-Sham density functional theory (DFT), and to a smaller extent with the use of Hartree-Fock. This anomalous error is thus attributed partly to difficulties in correctly emulating the electronic structure effects imposed by the very electronegative fluorines, and partly due to inconsistencies in the spurious electron self-repulsion in DFT. Substitution with one, or possibly two, fluorine atoms is estimated to yield small enough errors to allow for reliable interpretations and predictions of L2,3-spectra of more complex and extended silicon-based systems. PMID:27136720

  3. Titanium Dioxide/Upconversion Nanoparticles/Cadmium Sulfide Nanofibers Enable Enhanced Full-Spectrum Absorption for Superior Solar Light Driven Photocatalysis.

    PubMed

    Zhang, Fu; Zhang, Chuan-Ling; Wang, Wan-Ni; Cong, Huai-Ping; Qian, Hai-Sheng

    2016-06-22

    In this work, we demonstrate an electrospinning technique to fabricate TiO2 /upconversion nanoparticles (UCNPs)/CdS nanofibers on large scale. In addition, the as-prepared TiO2 nanofibers are incorporated with a high population of UCNPs and CdS nanospheres; this results in Förster resonance energy-transfer configurations of the UCNPs, TiO2 , and CdS nanospheres that are in close proximity. Hence, strong fluorescent emissions for the Tm(3+) ions including the (1) G4 →(3) H6 transition are efficiently transferred to TiO2 and the CdS nanoparticles through an energy-transfer process. The as-prepared TiO2 /UCNPs/CdS nanofibers exhibit full-spectrum solar-energy absorption and enable the efficient degradation of organic dyes by fluorescence resonance energy transfer between the UCNPs and TiO2 (or CdS). The UCNPs/TiO2 /CdS nanofibers may also have enhanced energy-transfer efficiency for wide applications in solar cells, bioimaging, photodynamics, and chemotherapy. PMID:27214754

  4. Communication: Does a single CH{sub 3}CN molecule attached to Ru(bipy){sub 3}{sup 2+} affect its absorption spectrum?

    SciTech Connect

    Stockett, M. H.; Brøndsted Nielsen, S.

    2015-05-07

    Tris(bipyridine)ruthenium(II) (Ru(bipy){sub 3}{sup 2+}) is a prototypical transition metal coordination complex whose photophysical properties have attracted considerable attention. A much debated issue is whether the metal-to-ligand charge transfer (MLCT) transition that accounts for the complex’s beautiful red color is fully delocalized across all three bipyridine ligands or located on just one ligand. Here, we show based on gas-phase action spectroscopy that attachment of a single acetonitrile molecule does not change the absorption spectrum from that of the bare ions, which is indicative of a delocalized state. However, the gas-phase spectra of the bare and one solvent molecule complexes are significantly blueshifted relative to that obtained in bulk acetonitrile, which suggests that in solution the polarizability of many solvent molecules working together can localize the MLCT state. Our data clearly show that more than one solvent molecule is needed to break the symmetry of the MLCT excited state and reproduce its solution-phase characteristics.

  5. Slow light and saturable absorption

    NASA Astrophysics Data System (ADS)

    Selden, A. C.

    2009-06-01

    Quantitative analysis of slow light experiments utilising coherent population oscillation (CPO) in a range of saturably absorbing media, including ruby and alexandrite, Er3+:Y2SiO5, bacteriorhodopsin, semiconductor quantum devices and erbium-doped optical fibres, shows that the observations may be more simply interpreted as saturable absorption phenomena. A basic two-level model of a saturable absorber displays all the effects normally associated with slow light, namely phase shift and modulation gain of the transmitted signal, hole burning in the modulation frequency spectrum and power broadening of the spectral hole, each arising from the finite response time of the non-linear absorption. Only where hole-burning in the optical spectrum is observed (using independent pump and probe beams), or pulse delays exceeding the limits set by saturable absorption are obtained, can reasonable confidence be placed in the observation of slow light in such experiments. Superluminal (“fast light”) phenomena in media with reverse saturable absorption (RSA) may be similarly explained.

  6. Rapid pressure swing absorption cleanup of post-shift reactor synthesis gas. Technical progress report, August 1, 1992--October 31, 1992

    SciTech Connect

    Sirkar, K.K.; Majumdar, S.; Bhaumik, S.

    1993-01-29

    The theoretical model for the absorption part of a particular type of RAPSAB cycle (Mode 3) (see Technical Progress Report No. 7) has been developed. The numerical simulations of the model compare well with the experimental results presented in the last report (Technical Progress Report No. 7). A number of experiments were carried out also for Mode 2 type of operation by varying the time for initial pressurization of the hollow fiber module as well as the total absorption time. These were done to provide a basis for comparison with the theoretical model to be developed later. We have initiated RAPSAB studies with reactive absorbents such as 19.5 % aqueous solution of diethanolamine (DEA) for the absorption of C0{sub 2} from a C0{sub 2}-N{sub 2} mixture. Six experiments were carried out using Mode 3 type of operation and a C0{sub 2}-N{sub 2} mixture containing 9.9% CO, and balance N{sub 2}. Excellent purification was obtained. No C0{sub 2} was observed in the purified high pressure gas outlet for absorption time of up to 14 seconds; the purified high pressure gas flow rate was also considerable. Module No. 5 was used for all experiments. The details of the module are given in Technical Progress Report No. 7.

  7. Negligible shift of 3Ag- potential in longer-chain carotenoids as revealed by a single persistent peak of 3Ag-→1Ag- stimulated emission followed by 3Ag-←1Ag- transient-absorption

    NASA Astrophysics Data System (ADS)

    Li, Chunyong; Miki, Takeshi; Kakitani, Yoshinori; Koyama, Yasushi; Nagae, Hiroyoshi

    2007-12-01

    Upon excitation of lycopene, anhydrorhodovibrin or spirilloxanthin to the 1Bu+(0) state, stimulated emission followed by transient-absorption was observed as a single peak with the 3Ag-(0) energy that had been determined by measurement of resonance-Raman excitation profiles. This observation was explained in terms of negligible shift of the 3Ag- potential, in reference to the 1Ag- potential, where only the 3Ag-(υ)→1Ag-(υ) emission and the 3Ag-(υ)←1Ag-(υ) absorption become allowed during the vibrational relaxation of υ = 2 → 1 → 0, starting from the 3Ag-(2) level generated by diabatic internal conversion from the 1Bu+(0) level, in anhydrorhodovibrin, for example.

  8. A new model for pressure-induced shifts of electronic absorption bands as applied to neat CS sub 2 and CS sub 2 in n-hexane and dichloromethane solutions

    SciTech Connect

    Agnew, S.F.; Swanson, B.I. )

    1990-01-25

    The authors propose a model for the pressure dependence of electronic absorption spectra and apply it to the authors data on CS{sub 2} both in neat phase and in hexane and dichloromethane solid solutions. They believe that their data represent a rather severe test of this model and argue that any model for the pressure dependence of electronic absorption spectra must include certain minimal effects - dispersive or dielectric and repulsive or volume effects - in order to adequately represent the data. They discuss previous models at some length in order to delineate the limits of their applicability. They further acknowledge and define the limits of the applicability of their model to solvent-induced shifts in general.

  9. The application of new methane line absorption data to Gemini-N/NIFS and KPNO/FTS observations of Uranus' near-infrared spectrum

    NASA Astrophysics Data System (ADS)

    Irwin, P. G. J.; de Bergh, C.; Courtin, R.; Bézard, B.; Teanby, N. A.; Davis, G. R.; Fletcher, L. N.; Orton, G. S.; Calcutt, S. B.; Tice, D.; Hurley, J.

    2012-08-01

    New line data describing the absorption of CH4 and CH3D from 1.26 to 1.71 μm (Campargue, A., Wang, L., Mondelain, D., Kassi, S., Bézard, B., Lellouch, E., Coustenis, A., de Bergh, C., Hirtzig, M., Drossart, P. [2012]. Icarus 219, 110-128), building upon previous papers by Campargue et al. (Campargue, A., Wang, L., Kassi, S., Masat, M., Votava, O. [2010]. J. Quant. Spectrosc. Radiat. Transfer 111, 1141-1151; Wang, L., Kassi, S., Campargue, A. [2010]. J. Quant. Spectrosc. Radiat. Transfer 111, 1130-1140; Wang, L., Kassi, S., Liu, A.W., Hu, S.M., Campargue, A. [2011]. J. Quant. Spectrosc. Radiat. Transfer 112, 937-951)) have been applied to the analysis of Gemini-N/NIFS observations of Uranus made in 2010 and compared with earlier disc-averaged observations made by KPNO/FTS in 1982. The new line data are found to improve greatly the fit to the observed spectra and present a huge advance over previous methane absorption tables by allowing us to determine the CH3D/CH4 ratio and also start to break the degeneracy between methane abundance and cloud top height. The best fits are obtained if the cloud particles in the main cloud deck at the 2-3 bar level become less scattering with wavelength across the 1.4-1.6 μm region and we have modelled this variation here by varying the extinction cross-section and single-scattering albedo of the particles. Applying the new line data to the NIFS spectra of Uranus, we determine a new estimate of the CH3D/CH4 ratio of 2.9-0.5+0.9×10-4, which is consistent with the estimate of de Bergh et al. (de Bergh, C., Lutz, B.L., Owen, T., Brault, J., Chauville, J. [1986]. Astrophys. J. 311, 501-510) of 3.6-2.8+3.6×10-4, made by fitting a disc-averaged KPNO/FTS spectrum measured in 1982, but much better constrained. The NIFS observations made in 2010 have been disc-averaged and compared with the 1982 KPNO/FTS spectrum and found to be in excellent agreement. Using k-tables fitted to the new line data, the central meridian observations of

  10. Rapid pressure swing absorption cleanup of post-shift reactor synthesis gas. Technical progress report, April 1, 1992--July 31, 1992

    SciTech Connect

    Sirkar, K.K.; Majumdar, S.; Bhaumik, S.

    1992-09-24

    This investigation is concerned with the separation of gas mixtures using a novel concept of rapid pressure swing absorption (RAPSAB) of gas in a stationary absorbent liquid through gas-liquid interfaces immobilized in the pore mouths of hydrophobic microporous membranes. The process is implemented in a module well-packed with hydrophobic microporous hollow fiber membranes. Before we proceed to RAPSAB studies with reactive absorbents, it is necessary to make an effort to compare experimental results with those predicted by the models. The only model developed so far involved a type of RAPSAB cycle (Mode 3) for which limited data were acquired earlier. A number of experiments have, therefore, been conducted in this mode to characterize the absorption part of the cycle. A new and more compact module (Module No. 5) was made using 840 fibers and a teflon casing inside the stainless steel shell to exactly define the fiber packing density. This allows an exact calculation of Happel`s free surface radius. Experiments were carried out using a CO{sub 2}-N{sub 2} mixture of around 10% CO{sub 2} and balanced N{sub 2} using both modules 4 and 5 over a wide range of absorption times.

  11. A new highly selective, ratiometric and colorimetric fluorescence sensor for Cu(2+) with a remarkable red shift in absorption and emission spectra based on internal charge transfer.

    PubMed

    Goswami, Shyamaprosad; Sen, Debabrata; Das, Nirmal Kumar

    2010-02-19

    A new 1,8-diaminonaphthalene based ratiometric and highly selective colorimetric "off-on" type of fluorescent probe, receptor 2 has been designed and synthesized that senses only Cu(2+) among the other heavy and transition metal ions examined on the basis of internal charge transfer (ICT). The visual sensitivity of the receptor 2 is remarkable, showing dual color changes from colorless (receptor) to purple followed by blue and a large red shift in emission upon Cu(2+) complexation. PMID:20104900

  12. Detection and characterization of hyperfine-shifted resonances in the proton nuclear magnetic resonance spectrum of Anabaena 7120 ferredoxin at high magnetic fields.

    PubMed

    Skjeldal, L; Westler, W M; Markley, J L

    1990-05-01

    This paper presents previously unobserved signals in the 1H NMR spectra of oxidized and reduced [2Fe-2S]-ferredoxin from Anabaena 7120 detected at 400, 500, and 600 MHz. The signals shifted to low field exhibited longitudinal relaxation (T1) values in the range of 100-400 microseconds and line widths in the range of 1-10 kHz (at 400 MHz), and the chemical shifts of all signals showed strong temperature dependence. Although the line widths were smaller at lower magnetic fields, the resolution was better at higher magnetic fields. In the oxidized state, a broad signal was detected at 37 ppm, which corresponds to at least 6 protons, and whose chemical shift exhibits positive temperature dependence. This signal also was found in oxidized ferredoxin reconstituted in 2H2O, which excludes the signal as arising from solvent-exchangeable amide protons. In the reduced state, four signals detected between 90 and 140 ppm exhibited negative temperature dependence. These consisted of two pairs of signals, each pair having one component with half the linewidth of the other. On the basis of their chemical shifts, linewidths, longitudinal relaxation properties, and temperature dependence we assigned these resonances to four of the beta hydrogens of the ligated cysteines. Two solvent-exchangeable hyperfine-shifted signals were found in the reduced state; these are located upfield of the diamagnetic region. The low-field hyperfine resonances of half-reduced ferredoxin in the presence of sodium dithionite showed a self electron transfer exchange rate that was slow on the NMR scale as observed earlier (Chan, T., and Markley, J. L. (1983) Biochemistry 22, 5982-5987), but the exchange rate was accelerated in the presence of methyl viologen. PMID:2327800

  13. Enhanced squeezing by absorption

    NASA Astrophysics Data System (ADS)

    Grünwald, P.; Vogel, W.

    2016-04-01

    Absorption is usually expected to be detrimental to quantum coherence effects. However, there have been few studies into the situation for complex absorption spectra. We consider the resonance fluorescence of excitons in a semiconductor quantum well. The creation of excitons requires absorption of the incoming pump-laser light. Thus, the absorption spectrum of the medium acts as a spectral filter for the emitted light. Surprisingly, absorption can even improve quantum effects, as is demonstrated for the squeezing of the resonance fluorescence of the quantum-well system. This effect can be explained by an improved phase matching due to absorption.

  14. Water absorption lines, 931-961 nm - Selected intensities, N2-collision-broadening coefficients, self-broadening coefficients, and pressure shifts in air

    NASA Technical Reports Server (NTRS)

    Giver, L. P.; Gentry, B.; Schwemmer, G.; Wilkerson, T. D.

    1982-01-01

    Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.

  15. The absorption spectrum of water vapor in the 1.25 μm atmospheric window (7911-8337 cm-1)

    NASA Astrophysics Data System (ADS)

    Campargue, A.; Mikhailenko, S. N.; Lohan, Benoit Guillo; Karlovets, E. V.; Mondelain, D.; Kassi, S.

    2015-05-01

    The absorption spectrum of water vapor in "natural" isotopic abundance has been recorded at room temperature by high sensitivity Continuous Wave Cavity Ring Down Spectroscopy (CW-CRDS) between 7911 and 8337 cm-1. The investigated region covers most of the 1.25 μm transparency window of importance for atmospheric applications. The recordings were performed with sensitivity on the order of αmin~2×10-11 cm-1, more than two orders of magnitude better than previous investigations by Fourier Transform Spectroscopy (FTS). Measured line intensities cover a range of seven orders of magnitude (3×10-30-2×10-23 cm/molecule at room temperature). The experimental line list provided as Supplementary Material includes more than 5000 transitions. As a result of the achieved sensitivity, more than 1150 lines of the experimental list were identified as being due to ammonia present as an impurity at the 5 ppm concentration level in the water sample. Although incomplete, the obtained ammonia line list seems to be the first one in the region. More than 3193 water lines were assigned to 3560 transitions of five water isotopologues (H216O, H218O, H217O, HD16O and HD18O). The assignments were performed using known experimental energy levels and calculated spectra based on variational calculations by Schwenke and Partridge. The obtained results are compared to the most relevant previous studies by Fourier Transform Spectroscopy in the region and to the exhaustive review of rovibrational line positions and levels performed recently by an IUPAC sponsored task group. Two-hundred and sixty-six levels are newly determined and 46 are corrected by more than 0.015 cm-1 compared to those recommended by the water IUPAC task group. The overall agreement between variational and measured intensities is satisfactory. A complete empirical list of 4473 transitions incorporating all the experimental information at disposal was constructed for water in the studied region. The intensity cut-off was fixed

  16. Infrared absorption spectra of molecular crystals: Possible evidence for small-polaron formation?

    NASA Astrophysics Data System (ADS)

    Pržulj, Željko; Čevizović, Dalibor; Zeković, Slobodan; Ivić, Zoran

    2008-09-01

    The temperature dependence of the position of the so-called anomalous band peaked at 1650cm in the IR-absorption spectrum of crystalline acetanilide (ACN) is theoretically investigated within the small-polaron theory. Its pronounced shift towards the position of the normal band is predicted with the rise of temperature. Interpretation of the IR-absorption spectra in terms of small-polaron model has been critically assessed on the basis of these results.

  17. Absorption of surface acoustic waves by topological insulator thin films

    SciTech Connect

    Li, L. L.; Xu, W.

    2014-08-11

    We present a theoretical study on the absorption of the surface acoustic waves (SAWs) by Dirac electrons in topological insulator (TI) thin films (TITFs). We find that due to momentum and energy conservation laws, the absorption of the SAWs in TITFs can only be achieved via intra-band electronic transitions. The strong absorption can be observed up to sub-terahertz frequencies. With increasing temperature, the absorption intensity increases significantly and the cut-off frequency is blue-shifted. More interestingly, we find that the absorption of the SAWs by the TITFs can be markedly enhanced by the tunable subgap in the Dirac energy spectrum of the TI surface states. Such a subgap is absent in conventional two-dimensional electron gases (2DEGs) and in the gapless Dirac 2DEG such as graphene. This study is pertinent to the exploration of the acoustic properties of TIs and to potential application of TIs as tunable SAW devices working at hypersonic frequencies.

  18. Energy Spectrum of La3Lu2Ga3O12:Cr3+ and Its Pressure-Induced R-Line-Shift Reversal

    NASA Astrophysics Data System (ADS)

    Ma, Dong-Ping; Chen, Ju-Rong

    2005-12-01

    By means of both the theory for pressure-induced shifts (PS) of energy spectra and the theory for shifts of energy spectra due to electron-phonon interaction (EPI), the normal-pressure energy spectra of α and β centers of Cr3+ ions for LLGG:Cr3+ and the PS's of R1 lines and U band of these centers have been calculated at 10 K, respectively. The total calculated results are in very good agreement with the experimental data. For LLGG:Cr3+, the pressure-induced low-high crystal-field transition and the reversal of R1-line PS take place. The pressure-dependent variation of Rmixel (2E-4T2) [mixing-degree of |t22(3T1)e4T2 rangle and |t23 2Erangle base-wavefunctions in the wavefunction of R1 state without EPI] plays a key role for the reversal of R1-line PS. The behavior of the pure electronic PS of R1 line is quite different from that of the PS of R1 line due to EPI. It is the combined effect of them that gives rise to the total PS of R1 line. The comparison between R1-line PS's of GSGG:Cr3+ and LLGG:Cr3+ has been made. It is found that a peak of R1-line PS appears at Rmixel (2E-4T2) ≈ 0.08.

  19. Inhomogeneous broadening and peak shift of the 7.6 eV optical absorption band of oxygen vacancies in SiO{sub 2}

    SciTech Connect

    Kajihara, Koichi; Skuja, Linards; Hosono, Hideo

    2014-10-21

    The peak parameters of radiation-induced 7.6 eV optical absorption band of oxygen vacancies (Si-Si bonds) were examined for high-purity synthetic α-quartz and amorphous SiO{sub 2} (a‐SiO{sub 2}) exposed to {sup 60}Co γ-rays. The peak shape is asymmetric with the steeper edge at the lower energy side both in α-quartz and a‐SiO{sub 2}, and the peak energy is larger for α-quartz than that for a‐SiO{sub 2}. The full width at half maximum for a‐SiO{sub 2} is larger by ∼40-60% than that for α-quartz, and it increases with an increase in the disorder of the a‐SiO{sub 2} network, which is enhanced by raising the temperature of preannealing before irradiation, i.e., fictive temperature. These data are interpreted from the viewpoint of the site-to-site distribution of the Si-Si bond length in a‐SiO{sub 2}.

  20. Ultraviolet to near-infrared absorption spectrum of carbon dioxide ice from 0.174 to 1.8 μm

    NASA Astrophysics Data System (ADS)

    Hansen, Gary B.

    2005-11-01

    A laboratory experiment was devised to measure transmission at fine spectral resolution through thick, high-quality samples of CO2 ice over an extended wavelength range. The absorption coefficient throughout the ultraviolet and near-infrared spectral ranges 0.174-1.8 μm (5555-57,470 cm-1 in wave number) is presented here. CO2 ice samples were grown at a temperature of 150 K, typical of the Martian polar caps. The path length of the samples varied from 1.6 to 107.5 mm, allowing the measurement of absorption from <0.1 to 4000 m-1. The experiment used both a grating monochromator (with spectral resolution 0.1-0.3 nm) and a Fourier transform spectrometer (with an effective resolution of <1.0 cm-1). The transmission data for five thicknesses are used to estimate both the scattering losses for each sample and the absorption coefficient at each wavelength. The uncertainty in the most transparent wavelength regions (<10 m-1) is due to scattering extinction. Measurement noise and data scatter produce significant uncertainty only where absorption coefficients exceed 1000 m-1. Between 1.0 and 1.8 μm there are several weak to moderate absorption lines. Only an upper limit to the absorption can be determined in many places; e.g., the absorption from ~0.25 to 1.0 μm is below the detection limit. The estimated visible absorption, ~10-2 m-1, is a factor of 1000 smaller than the values reported by Egan and Spagnolo, which have been used previously to compute albedos of CO2 snow. The new results should be useful for studies of the seasonal polar caps of Mars.

  1. TURBULENCE SPECTRA FROM DOPPLER-BROADENED SPECTRAL LINES: TESTS OF THE VELOCITY CHANNEL ANALYSIS AND VELOCITY COORDINATE SPECTRUM TECHNIQUES

    SciTech Connect

    Chepurnov, A.; Lazarian, A.

    2009-03-10

    Turbulent motions induce Doppler shifts of observable emission and absorption lines motivating studies of turbulence using precision spectroscopy. We provide numerical testing of the two most promising techniques, velocity channel analysis and velocity coordinate spectrum (VCS). We obtain an expression for the shot noise that the discretization of the numerical data entails and successfully test it. We show that the numerical resolution required for recovering the underlying turbulent spectrum from observations depend on the spectral index of velocity fluctuations, which makes low-resolution testing misleading. We demonstrate numerically that, when dealing with absorption lines, sampling of turbulence along just a dozen directions provides a high quality spectrum with the VCS technique.

  2. Studies on external electric field effects on absorption and fluorescence spectra of NADH

    NASA Astrophysics Data System (ADS)

    Nakabayashi, Takakazu; Islam, Md. Serajul; Li, Liming; Yasuda, Masahide; Ohta, Nobuhiro

    2014-03-01

    Electric field effects on absorption and fluorescence spectra have been investigated for NADH that is a representative autofluorescent chromophore in cells. The change in electric dipole moment following absorption is significant in the electroabsorption spectrum, indicating charge transfer character in the excited state. The fluorescence intensity decreases in the presence of an electric field, which arises from the field-induced increase in the rate of the non-radiative process. The blue shift of the fluorescence spectrum and the increase in the fluorescence lifetime of NADH are measured in yeast cells, which is discussed in terms of a local electric field around NADH.

  3. Shifting tools

    SciTech Connect

    Fisher, E.P.; Welch, W.R.

    1984-03-13

    An improved shifting tool connectable in a well tool string and useful to engage and position a slidable sleeve in a sliding sleeve device in a well flow conductor. The selectively profiled shifting tool keys provide better fit with and more contact area between keys and slidable sleeves. When the engaged slidable sleeve cannot be moved up and the shifting tool is not automatically disengaged, emergency disengagement means may be utilized by applying upward force to the shifting tool sufficient to shear pins and cause all keys to be cammed inwardly at both ends to completely disengage for removal of the shifting tool from the sliding sleeve device.

  4. Absorption of ac fields in amorphous indium-oxide films

    NASA Astrophysics Data System (ADS)

    Ovadyahu, Z.

    2014-08-01

    Absorption data from applied ac fields in Anderson-localized amorphous indium-oxide (InxO) films are shown to be frequency and disorder dependent. The absorption shows a roll-off at a frequency which is much lower than the electron-electron scattering rate of the material when it is in the diffusive regime. This is interpreted as evidence for discreteness of the energy spectrum of the deeply localized regime. This is consistent with recent many-body localization scenarios. As the metal-insulator transition is approached, the absorption shifts to higher frequencies. Comparing with the previously obtained results on the crystalline version of indium-oxide (In2O3-x) implies a considerably higher inelastic electron-phonon scattering rate in the amorphous material. The range over which the absorption versus frequency decreases may indicate that a wide distribution of localization length is a common feature in these systems.

  5. Stark shift of the absorption spectra in Ge/Ge1-xSnx/Ge type-I single QW cell for mid-wavelength infra-red modulators

    NASA Astrophysics Data System (ADS)

    Yahyaoui, N.; Sfina, N.; Lazzari, J.-L.; Bournel, A.; Said, M.

    2015-09-01

    For mid-wavelength infra-red (MWIR) modulation or detection applications, we propose α-Sn rich Ge/Ge1-xSnx/Ge a type-I single quantum wells (SQW) partially strain compensated on Ge1-ySny relaxed layers grown onto (0 0 1)-oriented Ge substrate. Such elementary cells with W-like potential profiles of conduction and valence bands have been modeled by solving the one-dimensional Schrödinger equation under an applied external electrical field. First, strain effects on electrons, heavy holes (hh) and light holes (lh) energy bands for strained/relaxed Ge1-xSnx/Ge1-ySny heterointerfaces are investigated using the model-solid theory in the whole ranges (0 ⩽ x, y ⩽ 1) of Sn compositions. From the obtained band-discontinuities, band gaps and effective masses, Ge1-ySny/Ge/Ge0.80Sn0.20/Ge/Ge1-ySny cells are computed as a function of the Ge0.80Sn0.20 well width for three compositions of the Ge1-ySny buffer layer (y = 0.05, 0.07 and 0.09) in order to get the optimum quantum confinement of electrons and holes levels while keeping a reasonable amount of averaged strain in the cell. The electric field effect on the absorption spectra is given. An absorption coefficient in the 6× to 3 × 103 cm-1 range is reasonably obtained for a SQW at room temperature with a rather large Stark shift of the direct transition between 0.46 and 0.38 eV (i.e., λ = 3.26-2.70 μm) at large external fields (50 kV/cm). These characteristics are attractive for the design of MWIR optical modulators.

  6. XMM-Newton/Reflection Grating Spectrometer detection of the missing interstellar O VII Kα absorption line in the spectrum of Cyg X-2

    NASA Astrophysics Data System (ADS)

    Cabot, Samuel H. C.; Wang, Q. Daniel; Yao, Yangsen

    2013-05-01

    The hot interstellar medium is an important part of the Galactic ecosystem and can be effectively characterized through X-ray absorption line spectroscopy. However, in a study of the hot medium using the accreting neutron star X-ray binary, Cyg X-2, as a background light source, a mystery came about when the putatively strong O VII Kα line was not detected in Chandra grating observations, while other normally weaker lines such as O VII Kβ as well as O VI and O VIII Kα are clearly present. We have investigated the grating spectra of Cyg X-2 from 10 XMM-Newton observations, in search of the missing line. We detect it consistently in nine of these observations, but the line is absent in the remaining one observation or is inconsistent with the detection in others at a ˜4σ confidence level. This absence of the line resembles that seen in the Chandra observations. Similarly, the O VI Kα line is found to disappear occasionally, but not in concert with the variation of the O VII Kα line. All these variations are most likely due to the presence of changing O VII and O VI Kα emission lines of Cyg X-2, which are blurred together with the absorption ones in the X-ray spectra. A re-examination of the Chandra grating data indeed shows evidence for a narrow emission line slightly off the O VI Kα absorption line. We further show that narrow N V emission lines with varying centroids and fluxes are present in far-ultraviolet spectra from the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. These results provide new constraints on the accretion around the neutron star and on the X-ray-heating of the stellar companion. The understanding of these physical processes is also important to the fidelity of using such local X-ray binaries for interstellar absorption line spectroscopy.

  7. LED-Based Fourier Transform Spectroscopy: the HD16O Absorption Spectrum in the Range of 11200-12400 cm-1

    NASA Astrophysics Data System (ADS)

    Sinitsa, L. N.; Serdyukov, V. I.; Polovtseva, E. R.; Shcherbakov, A. P.; Voronin, B. A.; Bykov, A. D.

    2016-03-01

    The vibrational—rotational spectrum of the HD16O molecule is studied within the range of 11200-12400 cm-1. The spectrum is recorded by an IFS-125M Fourier spectrometer with a resolution of 0.05 cm-1. The measurements are performed using a multipass White cell. A light-emitting diode is used as a radiation source. The signal-to-noise ratio was about 104. The centers, intensities, and half-widths of the spectral lines are determined by fitting to the experimental data by the least-squares method. A linelist containing more than 1500 lines is created. The results obtained are compared with the experimental data of other authors.

  8. Attenuation analysis of real GPR wavelets: The equivalent amplitude spectrum (EAS)

    NASA Astrophysics Data System (ADS)

    Economou, Nikos; Kritikakis, George

    2016-03-01

    Absorption of a Ground Penetrating Radar (GPR) pulse is a frequency dependent attenuation mechanism which causes a spectral shift on the dominant frequency of GPR data. Both energy variation of GPR amplitude spectrum and spectral shift were used for the estimation of Quality Factor (Q*) and subsequently the characterization of the subsurface material properties. The variation of the amplitude spectrum energy has been studied by Spectral Ratio (SR) method and the frequency shift by the estimation of the Frequency Centroid Shift (FCS) or the Frequency Peak Shift (FPS) methods. The FPS method is more automatic, less robust. This work aims to increase the robustness of the FPS method by fitting a part of the amplitude spectrum of GPR data with Ricker, Gaussian, Sigmoid-Gaussian or Ricker-Gaussian functions. These functions fit different parts of the spectrum of a GPR reference wavelet and the Equivalent Amplitude Spectrum (EAS) is selected, reproducing Q* values used in forward Q* modeling analysis. Then, only the peak frequencies and the time differences between the reference wavelet and the subsequent reflected wavelets are used to estimate Q*. As long as the EAS is estimated, it is used for Q* evaluation in all the GPR section, under the assumption that the selected reference wavelet is representative. De-phasing and constant phase shift, for obtaining symmetrical wavelets, proved useful in the sufficiency of the horizons picking. Synthetic, experimental and real GPR data were examined in order to demonstrate the effectiveness of the proposed methodology.

  9. The Complete Ultraviolet Spectrum of the Archetypal "Wind-dominated" Quasar Mrk 231: Absorption and Emission from a High-speed Dusty Nuclear Outflow

    NASA Astrophysics Data System (ADS)

    Veilleux, S.; Meléndez, M.; Tripp, T. M.; Hamann, F.; Rupke, D. S. N.

    2016-07-01

    New near- and far-ultraviolet (NUV and FUV) Hubble Space Telescope spectra of Mrk 231, the nearest quasar known, are combined with ground-based optical spectra to study the remarkable dichotomy between the FUV and NUV–optical spectral regions in this object. The FUV emission-line features are faint, broad, and highly blueshifted (up to ˜7000 km s‑1), with no significant accompanying absorption. In contrast, the profiles of the NUV absorption features resemble those of the optical Na i D, He i, and Ca ii H and K lines, exhibiting broad blueshifted troughs that overlap in velocity space with the FUV emission-line features and indicate a dusty, high-density and patchy broad absorption line (BAL) screen covering ˜90% of the observed continuum source at a distance ≲2–20 pc. The FUV continuum emission does not show the presence of any obvious stellar features and is remarkably flat compared with the steeply declining NUV continuum. The NUV (FUV) features and continuum emission have not varied significantly over the past ˜22 (3) years and are unresolved on scales ˜40 (170) pc. These results favor an active galactic nucleus origin for the NUV–FUV line and continuum emission. The observed FUV line emission is produced in the outflowing BAL cloud system, while the Balmer lines arise primarily from the standard broad line region seen through the dusty BAL screen. Our data are inconsistent with the recently proposed binary black hole model. We argue instead that Mrk 231 is the nearest example of weak-lined “wind-dominated” quasars with high Eddington ratios and geometrically thick (“slim”) accretion disks; these quasars are likely more common in the early universe.

  10. Experimental and theoretical study of absorption spectrum of the (CH3)2CO···HF complex. Influence of anharmonic interactions on the frequency and intensity of the C=O and H-F stretching bands.

    PubMed

    Bulychev, V P; Svishcheva, E A; Tokhadze, K G

    2014-01-01

    IR absorption spectra of mixtures (CH3)2CO/HF and free (CH3)2CO molecules are recorded in the region of 4000-900 cm(-1) with a Bruker IFS-125 HR vacuum Fourier spectrometer at room temperature with a resolution up to 0.02 cm(-1). Spectral characteristics of the 2ν(C=O) overtone band of free acetone are reliably measured. The ν1(HF) and ν(C=O) absorption bands of the (CH3)2CO···HF complex are obtained by subtracting the absorption bands of free HF and acetone and absorption lines of atmospheric water from the experimental spectrum of mixtures. The experimental data are compared with theoretical results obtained from variational solutions of 1D-4D vibrational Schrödinger equations. The anharmonic potential energy and dipole moment surfaces used in the calculations were computed in the MP2/6-311++G(2d,2p) approximation with corrections for the basis set superposition error. Comparison of the data derived from solutions for different combinations of vibrational degrees of freedom shows that taking the inter-mode anharmonic interactions into account has different effects on the transition frequencies and intensities. Particular attention has been given to elucidation of the influence of anharmonic coupling of the H-F and C=O stretches with the low-frequency intermolecular modes on their frequencies and intensities and the strength of resonance between the fundamental H-F and the first overtone C=O transitions. PMID:24128921

  11. Shifting Attention

    ERIC Educational Resources Information Center

    Ingram, Jenni

    2014-01-01

    This article examines the shifts in attention and focus as one teacher introduces and explains an image that represents the processes involved in a numeric problem that his students have been working on. This paper takes a micro-analytic approach to examine how the focus of attention shifts through what the teacher and students do and say in the…

  12. The X-ray absorption spectrum of 4U1700-37 and its implications for the stellar wind of the companion HD153919

    NASA Technical Reports Server (NTRS)

    White, N. E.; Kallman, T. R.; Swank, J. H.

    1982-01-01

    The first high resolution non-dispersive 2-60 KeV X-ray spectra of 4U1700-37 is presented. The continuum is typical of that found from X-ray pulsars; that is a flat power law between 2 and 10 keV and, beyond 10 keV, an exponential decay of characteristic energy varying between 10 and 20 keV. No X-ray pulsations were detected between 160 ms and 6 min with an amplitude greater than approximately 2%. The absorption measured at binary phases approximately 0.72 is comparable to that expected from the stellar wind of the primary. The gravitational capture of material in the wind is found to be more than enough to power the X-ray source. The increase in the average absorption after phi o approximately 0.5 is confirmed. The minimum level of adsorption is a factor of 2 or 3 lower than that reported by previous observers, which may be related to a factor of approximately 10 decline in the average X-ray luminosity over the same interval. Short term approximately 50% variations in adsorption are seen for the first time which appear to be loosely correlated with approximately 10 min flickering activity in the X-ray flux. These most likely originate from inhomogeneities in the stellar wind of the primary.

  13. Pressure-dependence on the absorption spectrum of CuMoO 4: study of the green→brownish-red piezochromic phase transition at 2.5 kbar

    NASA Astrophysics Data System (ADS)

    Hernández, D.; Rodríguez, F.; Garcia-Jaca, J.; Ehrenberg, H.; Weitzel, H.

    1999-04-01

    The optical properties of CuMoO 4 are investigated by means of hydrostatic pressure techniques in the 0-60 kbar range. Attention is paid to the piezochromism exhibited by this crystal at the α (green)→γ (brownish red) structural phase transition. The variation of the absorption spectra with pressure indicates that the piezochromic transition takes place at 2.5 kbar. The associated change of colour is due to the broadening of the first O 2-→Cu 2+ charge transfer band and the disappearance of an intense band at 12000 cm -1, related to the presence of pyramidal CuO 5 complexes in α-CuMoO 4. The measured oscillator strength suggests that this band corresponds to the e→b 1 crystal field transition rather than to a charge transfer within CuO 5. The structural correlation with the absorption spectra performed in this work explains the strong dichroism exhibited by the crystal in the high-pressure γ-CuMoO 4.

  14. Single-particle absorption spectroscopy by photothermal contrast.

    PubMed

    Yorulmaz, Mustafa; Nizzero, Sara; Hoggard, Anneli; Wang, Lin-Yung; Cai, Yi-Yu; Su, Man-Nung; Chang, Wei-Shun; Link, Stephan

    2015-05-13

    Removing effects of sample heterogeneity through single-molecule and single-particle techniques has advanced many fields. While background free luminescence and scattering spectroscopy is widely used, recording the absorption spectrum only is rather difficult. Here we present an approach capable of recording pure absorption spectra of individual nanostructures. We demonstrate the implementation of single-particle absorption spectroscopy on strongly scattering plasmonic nanoparticles by combining photothermal microscopy with a supercontinuum laser and an innovative calibration procedure that accounts for chromatic aberrations and wavelength-dependent excitation powers. Comparison of the absorption spectra to the scattering spectra of the same individual gold nanoparticles reveals the blueshift of the absorption spectra, as predicted by Mie theory but previously not detectable in extinction measurements that measure the sum of absorption and scattering. By covering a wavelength range of 300 nm, we are furthermore able to record absorption spectra of single gold nanorods with different aspect ratios. We find that the spectral shift between absorption and scattering for the longitudinal plasmon resonance decreases as a function of nanorod aspect ratio, which is in agreement with simulations. PMID:25849105

  15. Communication: THz absorption spectrum of the CO{sub 2}–H{sub 2}O complex: Observation and assignment of intermolecular van der Waals vibrations

    SciTech Connect

    Andersen, J.; Mahler, D. W.; Larsen, R. Wugt; Heimdal, J.; Nelander, B.

    2014-03-07

    Terahertz absorption spectra have been recorded for the weakly bound CO{sub 2}–H{sub 2}O complex embedded in cryogenic neon matrices at 2.8 K. The three high-frequency van der Waals vibrational transitions associated with out-of-plane wagging, in-plane rocking, and torsional motion of the isotopic H{sub 2}O subunit have been assigned and provide crucial observables for benchmark theoretical descriptions of this systems’ flat intermolecular potential energy surface. A (semi)-empirical value for the zero-point energy of 273 ± 15 cm{sup −1} from the class of intermolecular van der Waals vibrations is proposed and the combination with high-level quantum chemical calculations provides a value of 726 ± 15 cm{sup −1} for the dissociation energy D{sub 0}.

  16. THE 3-5 {mu}m SPECTRUM OF NGC 1068 AT HIGH ANGULAR RESOLUTION: DISTRIBUTION OF EMISSION AND ABSORPTION FEATURES ACROSS THE NUCLEAR CONTINUUM SOURCE

    SciTech Connect

    Geballe, T. R.; Mason, R. E.; Rodriguez-Ardila, A.; Axon, D. J.

    2009-08-20

    We report moderate resolution 3-5 {mu}m spectroscopy of the nucleus of NGC 1068 obtained at 0.''3 (20 pc) resolution with the spectrograph slit aligned approximately along the ionization cones of the active galactic nucleus. The deconvolved full width at half-maximum of the nuclear continuum source in this direction is 0.''3. Four coronal lines of widely different excitations were detected; the intensity of each peaks near radio knot C, approximately 0.''3 north of the infrared continuum peak, where the radio jet changes direction. Together with the broadened line profiles observed near that location, this suggests that shock ionization is the dominant excitation mechanism of the coronal lines. The depth of the 3.4 {mu}m hydrocarbon absorption is maximum at and just south of the continuum peak, similar to the 10 {mu}m silicate absorption. That and the similar and rapid variations of the optical depths of both features across the nucleus suggest that substantial portions of both arise in a dusty environment just in front of the continuum source(s). A new and tighter limit is set on the column density of CO. Although clumpy models of the dust screen might explain the shallowness of the silicate feature, the presence of the 3.4 {mu}m feature and the absence of CO are strongly reminiscent of Galactic diffuse cloud environments and a consistent explanation for them and the observed silicate feature is found if all three phenomena occur in such an environment, existing as close as 10 pc to the central engine.

  17. Novel Technique for Improving the Signal-to-Background Ratio of X-ray Absorption Near-Edge Structure Spectrum in Fluorescence Mode and Its Application to the Chemical State Analysis of Magnesium Doped in GaN

    NASA Astrophysics Data System (ADS)

    Yonemura, Takumi; Iihara, Junji; Saito, Yoshihiro; Ueno, Masaki

    2013-12-01

    A novel measurement technique for an X-ray absorption near-edge structure (XANES) for magnesium (Mg) doped in gallium nitride (GaN) has been developed. XANES spectra from Mg at very low concentrations of 1 ×1018/cm3 doped in GaN have successfully been obtained by optimizing the region of interest (ROI) and by using highly brilliant synchrotron radiation X-rays of SPring-8. The ROI is the limited energy region from an X-ray fluorescence spectrum to elicit signals of particular atoms. Using this new technique, we have investigated the effect of the annealing process for Mg-doped GaN on the XANES spectra. It has been found that the XANES spectra of Mg significantly changed as the annealing temperature increased. This indicates that the local structure around Mg atoms in GaN was modified by the annealing process.

  18. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, Michael B.; Hargens, Alan R.; Dulchavsky, Scott A.; Ebert, Douglas J.; Lee, Stuart M. C.; Laurie, Steven S.; Garcia, Kathleen M.; Sargsyan, Ashot E.; Martin, David S.; Liu, John; Macias, Brandon R.; Arbeille, Philippe; Danielson, Richard; Chang, Douglas; Gunga, Hanns-Christian; Johnston, Smith L.; Westby, Christian M.; Ploutz-Snyder, Robert J.; Smith, Scott M.

    2016-01-01

    We hypothesize that microgravity-induced cephalad fluid shifts elevate intracranial pressure (ICP) and contribute to VIIP. We will test this hypothesis and a possible countermeasure in ISS astronauts.

  19. Spectral shifts and switches in random fields upon interaction with negative-phase materials

    SciTech Connect

    Tong Zhisong; Korotkova, Olga

    2010-07-15

    Spectral shifts in stochastic beam-like fields on interaction with layers of positive- and negative-phase materials are examined on the basis of the ABCD-matrix approach and generalized Huygens-Fresnel principle. It is found that boundaries between such materials may cause spectral switches. Effect of absorption of negative-phase materials on the beam spectrum is discussed. Our results may find applications in connection with spectrum-selection optical interconnects, spectrally encoded information transfer, image formation in systems involving negative-phase materials, and geometrically tunable metamaterials.

  20. Structural and optical study of core–shell InGaN layers of nanorod arrays with multiple stacks of InGaN/GaN superlattices for absorption of longer solar spectrum

    NASA Astrophysics Data System (ADS)

    Bae, Si-Young; Jung, Byung Oh; Lekhal, Kaddour; Lee, Dong-Seon; Deki, Manato; Honda, Yoshio; Amano, Hiroshi

    2016-05-01

    We report on the material and optical properties of core–shell InGaN layers grown on GaN nanorod arrays. The core–shell InGaN layers were well grown on polarization-reduced surfaces such as semipolar pyramids and nonpolar sidewalls. In addition, to compensate the biaxial strain between GaN and InGaN layers, we grew interlayers underneath a thick InGaN layer. Here, the interlayers were composed of multiple superlattice structures. We could observe that the indium composition of core–shell InGaN structures increased with the number of interlayers. This indicates that the absorption energy band of InGaN alloys can be better matched to the spectral irradiance of the solar spectrum in nature. We also implemented a simulation of Ga-polar and nonpolar InGaN-based solar cells based on the indium composition obtained from the experiments. The result showed that nonpolar InGaN solar cells had a much higher efficiency than Ga-polar InGaN solar cells with the same thickness of the absorption layer.

  1. ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. I. OBSERVATIONS OF ROTATIONALLY EXCITED CH AND CH{sup +} ABSORPTION AND STRONG, EXTENDED REDWARD WINGS ON SEVERAL DIBs

    SciTech Connect

    Dahlstrom, Julie; York, Donald G.; Welty, Daniel E.; Oka, Takeshi; Johnson, Sean; Jiang Zihao; Sherman, Reid; Hobbs, L. M.; Friedman, Scott D.; Sonnentrucker, Paule; Rachford, Brian L.; Snow, Theodore P.

    2013-08-10

    Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 A are found in absorption along the line of sight to Herschel 36, the star illuminating the bright Hourglass region of the H II region Messier 8. Interstellar absorption from excited CH{sup +} in the J = 1 level and from excited CH in the J = 3/2 level is also seen. To our knowledge, neither those excited molecular lines nor such strongly extended DIBs have previously been seen in absorption from interstellar gas. These unusual features appear to arise in a small region near Herschel 36 which contains most of the neutral interstellar material in the sight line. The CH{sup +} and CH in that region are radiatively excited by strong far-IR radiation from the adjacent infrared source Her 36 SE. Similarly, the broadening of the DIBs toward Herschel 36 may be due to radiative pumping of closely spaced high-J rotational levels of relatively small, polar carrier molecules. If this picture of excited rotational states for the DIB carriers is correct and applicable to most DIBs, the 2.7 K cosmic microwave background may set the minimum widths (about 0.35 A) of known DIBs, with molecular processes and/or local radiation fields producing the larger widths found for the broader DIBs. Despite the intense local UV radiation field within the cluster NGC 6530, no previously undetected DIBs stronger than 10 mA in equivalent width are found in the optical spectrum of Herschel 36, suggesting that neither dissociation nor ionization of the carriers of the known DIBs by this intense field creates new carriers with easily detectable DIB-like features. Possibly related profile anomalies for several other DIBs are noted.

  2. Two-photon solvatochromism II: experimental and theoretical study of solvent effects on the two-photon absorption spectrum of Reichardt's dye.

    PubMed

    Wielgus, Małgorzata; Zaleśny, Robert; Murugan, N Arul; Kongsted, Jacob; Ågren, Hans; Samoc, Marek; Bartkowiak, Wojciech

    2013-11-11

    In this study, we report on the influence of solvent on the two-photon absorption (2PA) spectra of Reichardt's dye (RD). The measurement of 2PA cross-sections is performed for three solvents (chloroform, dimethyl formamide, and dimethyl sulfoxide) using the Z-scan technique. The key finding of this study is the observation that the cross-section, corresponding to the 2PA of the intramolecular charge-transfer state, diminishes substantially upon increasing the solvent polarity. To unravel the solvent dependence of the 2PA cross-section, the electronic structure of RD is determined using a hybrid quantum mechanics/molecular mechanics (QM/MM) approach, in which polarization between the solute and solvent is taken into account by using a self-consistent scheme in the solvent polarization. The two-state approximation proves to be adequate for the studied system, and allowed the observed solvent-polarity-induced decrease of the 2PA cross-section to be related to the decrease of the transition moment and the increase in the excitation energy. PMID:24106066

  3. Enhanced Hydrogen Evolution in the Presence of Plasmonic Au-Photo-Sensitized g-C3N4 with an Extended Absorption Spectrum from 460 to 640 nm.

    PubMed

    Xie, Lihong; Ai, Zhuyu; Zhang, Meng; Sun, Runze; Zhao, Weirong

    2016-01-01

    Extensively spectral-responsive photocatalytic hydrogen production was achieved over g-C3N4 photo-sensitized by Au nanoparticles. The photo-sensitization, which was achieved by a facile photo-assisted reduction route, resulted in an extended spectral range of absorption from 460 to 640 nm. The photo-sensitized g-C3N4 (Au/g-C3N4) photocatalysts exhibit significantly enhanced photocatalytic hydrogen evolution with a TOF value of 223 μmol g-1 h-1, which is a 130-fold improvement over g-C3N4. The hydrogen production result confirms that Au nanoparticles are effective photo-sensitizers for the visible light-responsive substrate g-C3N4. UV-vis diffuse reflection spectra (DRS), photoluminescence spectra (PL), electron spin resonance (ESR), and electrochemical measurements were used to investigate the transfer process of photogenerated electrons. The optimal Au/g-C3N4 photocatalyst displays the lowest charge transfer resistance of 18.45 Ω cm-2 and a high electron transfer efficiency, as determined by electrochemical impedance spectroscopy (EIS). The photo-sensitized g-C3N4 shows a broad range of response to visible light (400-640 nm), with significantly high incident photon-to-current efficiency (IPCE) values of 14.52%, 2.9%, and 0.74% under monochromatic light irradiation of 400, 550, and 640 nm, respectively. ESR characterization suggests that Au nanoparticles are able to absorb visible light of wavelengths higher than 460 nm and to generate hot electrons due to the SPR effect. PMID:27575246

  4. Enhanced Hydrogen Evolution in the Presence of Plasmonic Au-Photo-Sensitized g-C3N4 with an Extended Absorption Spectrum from 460 to 640 nm

    PubMed Central

    Xie, Lihong; Ai, Zhuyu; Zhang, Meng; Sun, Runze; Zhao, Weirong

    2016-01-01

    Extensively spectral-responsive photocatalytic hydrogen production was achieved over g-C3N4 photo-sensitized by Au nanoparticles. The photo-sensitization, which was achieved by a facile photo-assisted reduction route, resulted in an extended spectral range of absorption from 460 to 640 nm. The photo-sensitized g-C3N4 (Au/g-C3N4) photocatalysts exhibit significantly enhanced photocatalytic hydrogen evolution with a TOF value of 223 μmol g-1 h-1, which is a 130-fold improvement over g-C3N4. The hydrogen production result confirms that Au nanoparticles are effective photo-sensitizers for the visible light-responsive substrate g-C3N4. UV–vis diffuse reflection spectra (DRS), photoluminescence spectra (PL), electron spin resonance (ESR), and electrochemical measurements were used to investigate the transfer process of photogenerated electrons. The optimal Au/g-C3N4 photocatalyst displays the lowest charge transfer resistance of 18.45 Ω cm-2 and a high electron transfer efficiency, as determined by electrochemical impedance spectroscopy (EIS). The photo-sensitized g-C3N4 shows a broad range of response to visible light (400–640 nm), with significantly high incident photon-to-current efficiency (IPCE) values of 14.52%, 2.9%, and 0.74% under monochromatic light irradiation of 400, 550, and 640 nm, respectively. ESR characterization suggests that Au nanoparticles are able to absorb visible light of wavelengths higher than 460 nm and to generate hot electrons due to the SPR effect. PMID:27575246

  5. [PHOSPHOLIPIDS AND FATTY ACIDS IN ERYTHROCYTES OF THE LAMPREY LAMPETRA FLUVIATILIS DURING AUTUMN PRESPAWNING PERIOD AND THE ABSORPTION SPECTRUM OF THEIR LIPID EXTRACT].

    PubMed

    Zabelinskii, S A; Chebotareva, M A; Shukolyukova, E P; Krivchenko, A I

    2015-01-01

    The content of some classes of phospholipids and their fatty acid composition in erythrocytes of the lamprey Lampetrafluviatilis during the autumn period of its prespawning migration are investigated. It is found that the phospholipid spectrum of erythrocytes of the lamprey, the oldest representative of vertebrates, is similar to that of many mammals. A four-fold prevalence of phosphatidilcholine content over sphingomyelin content as well as prevalence of (ω3-acids over ω6-acids indicates the of lamprey's erythrocyte membranes - an important indicator of deformational ability of lamprey's erythrocytes. Phosphatidilethanol amine and its plasmalogenic form are the most unsaturated phospholipids (their unsaturation indices are 230 and 342, correspondingly). Phosphatidilcholine is the most saturated one (UI is 167). It is found that the basic acid indicators characterizing the fluidity of erythrocyte membranes remain unchanged during the whole period of prespawning migration of lampreys up to spawning. The blood contains several buffer systems, in particular, membrane phospholipids which neutralize acids and alkali incoming into the blood. In the process of organism life a change of pH inside erythrocytes occurs. One can suppose that the base of the system associated with buffer properties of the blood is water dissociation. Inside thin vessels of the circulatory system the hemoglobin attaches and returns molecules of oxygen due to interaction of the buffer systems with water. The property of water to dissociate as well as ion transfer produce in erythrocytes, lying within narrow vessels of the circulatory system, a local pH alteration allowing displacing/attaching the molecule of oxygen from hemoglobin. PMID:26547949

  6. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Gunga, H.; Johnston, S.; Westby, C.; Ribeiro, L.; Ploutz-Snyder, R.; Smith, S.

    2015-01-01

    INTRODUCTION: Mechanisms responsible for the ocular structural and functional changes that characterize the visual impairment and intracranial pressure (ICP) syndrome (VIIP) are unclear, but hypothesized to be secondary to the cephalad fluid shift experienced in spaceflight. This study will relate the fluid distribution and compartmentalization associated with long-duration spaceflight with VIIP symptoms. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, can be predicted preflight with acute hemodynamic manipulations, and also if lower body negative pressure (LBNP) can reverse the VIIP effects. METHODS: Physiologic variables will be examined pre-, in- and post-flight in 10 International Space Station crewmembers including: fluid compartmentalization (D2O and NaBr dilution); interstitial tissue thickness (ultrasound); vascular dimensions and dynamics (ultrasound and MRI (including cerebrospinal fluid pulsatility)); ocular measures (optical coherence tomography, intraocular pressure, ultrasound); and ICP measures (tympanic membrane displacement, otoacoustic emissions). Pre- and post-flight measures will be assessed while upright, supine and during 15 deg head-down tilt (HDT). In-flight measures will occur early and late during 6 or 12 month missions. LBNP will be evaluated as a countermeasure during HDT and during spaceflight. RESULTS: The first two crewmembers are in the preflight testing phase. Preliminary results characterize the acute fluid shifts experienced from upright, to supine and HDT postures (increased stroke volume, jugular dimensions and measures of ICP) which are reversed with 25 millimeters Hg LBNP. DISCUSSION: Initial results indicate that acute cephalad fluid shifts may be related to VIIP symptoms, but also may be reversible by LBNP. The effect of a chronic fluid shift has yet to be evaluated. Learning Objectives: Current spaceflight VIIP research is described

  7. Petawatt laser absorption bounded

    PubMed Central

    Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

    2014-01-01

    The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656

  8. Petawatt laser absorption bounded

    NASA Astrophysics Data System (ADS)

    Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

    2014-06-01

    The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials.

  9. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Lauriie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Ribeiro, L.; Lui, J.; Macias, B.; Arbeille, P.; Danielson, R.; Chang, D.; Johnston, S.; Ploutz-Snyder, R.; Smith, S.

    2016-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low-Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 50% of ISS astronauts experienced more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's preflight conditions and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. METHODS: We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by

  10. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, Michael; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; Platts, S.

    2014-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 30% of ISS astronauts experience more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the space flight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration space flight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during space flight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's pre-flight condition and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by ultrasound

  11. How to distinguish elastically scattered light from Stokes shifted light for solid-state lighting?

    NASA Astrophysics Data System (ADS)

    Meretska, M. L.; Lagendijk, A.; Thyrrestrup, H.; Mosk, A. P.; IJzerman, W. L.; Vos, W. L.

    2016-03-01

    We have studied the transport of light through phosphor diffuser plates that are used in commercial solid-state lighting modules (Fortimo). These polymer plates contain YAG:Ce+3 phosphor particles that both elastically scatter and Stokes shift light in the visible wavelength range (400-700 nm). We excite the phosphor with a narrowband light source and measure spectra of the outgoing light. The Stokes shifted light is spectrally separated from the elastically scattered light in the measured spectra, and using this technique, we isolate the elastic transmission of the plates. This result allows us to extract the transport mean free path ltr over the full wavelength range by employing diffusion theory. Simultaneously, we determine the absorption mean free path labs in the wavelength range 400 to 530 nm where YAG:Ce+3 absorbs. The diffuse absorption (μa=1/labs ) spectrum is qualitatively similar to the absorption coefficient of YAG:Ce+3 in powder, with the diffuse spectrum being wider than the absorption coefficient. We propose a design rule for the solid-state lighting diffuser plates.

  12. X-ray Absorption Studies in Spinel-Type LiMn 2O 4

    NASA Astrophysics Data System (ADS)

    Liu, R. S.; Jang, L. Y.; Chen, J. M.; Tsai, Y. C.; Hwang, Y. D.; Liu, R. G.

    1997-02-01

    The electronic structure of the spinel-type LiMn2O4as the cathode material for the application in secondary batteries was probed using both MnK- andL23-edge X-ray absorption near edge structure (XANES) spectra. Based on the energy shifts of the absorption peaks in the XANES spectrum correlated to the effective charge, the valence of Mn in LiMn2O4was determined to be ∼4+. This suggests that the chemical substitution of low valent Li+ions into the Mn sites is possible to result in high valence of Mn.

  13. Absorption spectra of monolayer MoS2 in high magnetic field

    NASA Astrophysics Data System (ADS)

    Yang, Hung-Duen; Her, Jim-Long; Takeyama, Shojiro; Matsuda, Yasuhiro; Wang, Kai-Hsuan

    2015-03-01

    We have measured the absorption spectra of monolayer MoS2 film at several temperatures in pulsed high magnetic fields up to 52 T. At room temperature, the observed spectrum dominated by two main peaks, which are located at 660 nm and 606 nm. These peaks are ascribed to excition and trion absorption peaks respectively [1]. At low temperature (4.2 K), two peaks show the blue shift to 633 nm and 588 nm, respectively. Irrespective of the temperature, applying magnetic field does not show pronounced influence on the peaks even in 52 T.

  14. Fractal morphology of black carbon aerosol enhances absorption in the thermal infrared wavelengths.

    PubMed

    Heinson, William R; Chakrabarty, Rajan K

    2016-02-15

    In this Letter, we numerically calculate the mass absorption cross sections (MACs) of black carbon fractal aggregates in the thermal infrared solar spectrum. Compared to equivalent-size spheres, the MAC values of aggregates show a percent enhancement of ≈150 and 400 at small and large length scales, respectively. The absorption properties of aggregates with size parameters >1 surprisingly continued to remain in the Rayleigh optics regime. We explain this phenomenon using the Maxwell-Garnett effective medium theory and the concept of phase shift parameter. PMID:26872194

  15. Shuttle spectrum despreader

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The results of the spread spectrum despreader project are reported and three principal products are designed and tested. The products are, (1) a spread spectrum despreader breadboard, (2) associated test equipment consisting of a spectrum spreader and bit reconstruction/error counter and (3) paper design of a Ku-band receiver which would incorporate the despreader as a principal subsystem. The despreader and test set are designed for maximum flexibility. A choice of unbalanced quadriphase or biphase shift keyed data modulation is available. Selectable integration time and threshold voltages on the despreader further lend true usefulness as laboratory test equipment to the delivered hardware.

  16. EXAFS Energy Shift and Structural Parameters

    NASA Astrophysics Data System (ADS)

    Kelly, Shelly D.; Ravel, Bruce

    2007-02-01

    In EXAFS analysis, the energy shift parameter is used to align the theoretical calculated spectrum to the energy grid of the measured spectrum. Unrealistically large energy shift values, sometimes in excess of 20 eV, are at times published in research articles. We therefore see the need for a concise discussion of the EXAFS energy shift parameter. This paper is intended as a learning tool for the proper alignment of theory to measured EXAFS spectra and proper interpretation of the energy shift parameter.

  17. The effect of different particle sizes of polyethylene on the absorption of myrrh in mixtures

    NASA Astrophysics Data System (ADS)

    Xu, Lei; Li, Bin; Zuo, Jian; Zhang, Cunlin

    2015-08-01

    Terahertz radiation lies between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Absorption spectra of different mass ratio of the myrrh and polyethylene can be gained by Fourier transform infrared spectrometer in this paper. It is found that absorption spectra show a slight red-shift with the decrease of the mass ratio of myrrh and polyethylene. On the other hand, different particle sizes of polyethylene (PE) mixed with myrrh absorption spectra were measured. Due to the different sizes of polyethylene particles, there are some differences in the vibration peak intensity, peak position and peak numbers in the absorption spectra. The experimental results show that the scattering effect leads to this phenomenon.

  18. Multiplasmon Absorption in Graphene

    NASA Astrophysics Data System (ADS)

    Jablan, Marinko; Chang, Darrick E.

    2015-06-01

    We show that graphene possesses a strong nonlinear optical response in the form of multiplasmon absorption, with exciting implications in classical and quantum nonlinear optics. Specifically, we predict that graphene nanoribbons can be used as saturable absorbers with low saturation intensity in the far-infrared and terahertz spectrum. Moreover, we predict that two-plasmon absorption and extreme localization of plasmon fields in graphene nanodisks can lead to a plasmon blockade effect, in which a single quantized plasmon strongly suppresses the possibility of exciting a second plasmon.

  19. Chaotic Systems with Absorption

    NASA Astrophysics Data System (ADS)

    Altmann, Eduardo G.; Portela, Jefferson S. E.; Tél, Tamás

    2013-10-01

    Motivated by applications in optics and acoustics we develop a dynamical-system approach to describe absorption in chaotic systems. We introduce an operator formalism from which we obtain (i) a general formula for the escape rate κ in terms of the natural conditionally invariant measure of the system, (ii) an increased multifractality when compared to the spectrum of dimensions Dq obtained without taking absorption and return times into account, and (iii) a generalization of the Kantz-Grassberger formula that expresses D1 in terms of κ, the positive Lyapunov exponent, the average return time, and a new quantity, the reflection rate. Simulations in the cardioid billiard confirm these results.

  20. The Compton Effect Red Shift

    NASA Astrophysics Data System (ADS)

    Kierein, John

    2004-05-01

    In 1923 (Phil Mag. 46, 897.) A. H. Compton noted that the Compton effect produces a red shift for all wavelengths when the scattered electron is free and not bound to an atom or molecule. He suggested that the red shift in the visible spectrum at the limb of the sun is larger than that at the center due to the Compton effect from the greater number of free electrons in the sun's atmosphere along the line of sight. Kierein and Sharp (1968, Solar Physics 3, 450) quantified this and showed a good correlation of red shift observations with the variation in the number of these electrons along the line of sight from center to limb and suggested that the quasar red shift and cosmological red shift could be similarly explained. Grote Reber mapped and measured the background hectometric radiation and found it to be unexpectedly bright. In 1968 (J. Franklin Inst. 285,1), while describing these measurements and maps he explained this brightness as being due to the Compton effect causing the cosmological red shift and accelerating intergalactic electrons. The resulting universe is static. The predicted red shift from the Compton effect deviates from Hubble's law only at large red shifts.

  1. Enhancement of spectrum strength in holographic sensing in nanozeolites dispersed acrylamide photopolymer.

    PubMed

    Yu, Dan; Liu, Hongpeng; Mao, Dongyao; Geng, Yaohui; Wang, Weibo; Sun, Liping; Lv, Jiang

    2015-11-01

    Holographic sensing of organic vapor is characterized at transmission and reflection geometries in ZSM-5 nanozeolites dispersed acrylamide photopolymer. Nano-zeolites as absorption medium are dispersed into the polymer to enhance the absorptivity to organic vapor. Obvious enhancements of spectrum strength are observed during the sensing process. Two primary factors causing the enhancement, absorption of nanozeolites and photopolymerization induced by broadband white light, are analyzed experimentally. Significant increment provides a quick and intuitive identification strategy for holographic sensing. Accompanying with the wavelength blue-shift, the shrinkage of sample is measured quantitatively under homogeneous white light. It is further demonstrated that the significance of nanozeolites absorption. Finally a theoretical model with mutual diffusion is used to simulate the swelling process. This study provides significant foundation for the application of holographic sensor. PMID:26561180

  2. Zellweger Spectrum

    MedlinePlus

    ... the Zellweger spectrum result from defects in the assembly of a cellular structure called the peroxisome, and ... Zellweger spectrum are caused by defects in the assembly of the peroxisome. There are at least 12 ...

  3. Cholesterol absorption.

    PubMed

    Ostlund, Richard E

    2002-03-01

    Cholesterol absorption is a key regulatory point in human lipid metabolism because it determines the amount of endogenous biliary as well as dietary cholesterol that is retained, thereby influencing whole body cholesterol balance. Plant sterols (phytosterols) and the drug ezetimibe reduce cholesterol absorption and low-density lipoprotein cholesterol in clinical trials, complementing the statin drugs, which inhibit cholesterol biosynthesis. The mechanism of cholesterol absorption is not completely known but involves the genes ABC1, ABCG5, and ABCG8, which are members of the ATP-binding cassette protein family and appear to remove unwanted cholesterol and phytosterols from the enterocyte. ABC1 is upregulated by the liver X (LXR) and retinoid X (RXR) nuclear receptors. Acylcholesterol acytransferase-2 is an intestinal enzyme that esterifies absorbed cholesterol and increases cholesterol absorption when dietary intake is high. New clinical treatments based on better understanding of absorption physiology are likely to substantially improve clinical cholesterol management in the future. PMID:17033296

  4. Computational design of small organic dyes with strong visible absorption by controlled quinoidization of the thiophene unit

    NASA Astrophysics Data System (ADS)

    Tan, Yi Yin; Tu, Wei Han; Manzhos, Sergei

    2014-02-01

    We present rational design of phenothiazine dyes by controlled quinoidization of the thiophene unit. We systematically study the effect of electron-withdrawing functional groups including pseudo- and super-halogens. We propose a new dye where a fumaronitrile unit induces an increase in the bond length alternation and a concurrent red shift in the absorption spectrum vs. the parent dye. The visible absorption peak is predicted at 520 nm, in CH2Cl2 vs. 450 nm for the parent dye. The LUMO and HOMO levels of the new dye are suitable for injection into TiO2 and regeneration by available redox shuttles, respectively.

  5. Petawatt laser absorption bounded

    NASA Astrophysics Data System (ADS)

    Levy, Matthew; Wilks, Scott; Tabak, Max; Libby, Stephen; Baring, Matthew

    2014-10-01

    The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top relativistic particle accelerators, ultrafast charged particle imaging systems and fast ignition inertial confinement fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. In this presentation, using a relativistic Rankine-Hugoniot-like analysis, we show how to derive the theoretical maximum and minimum of f. These boundaries constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. Close agreement is shown with several dozens of published experimental data points and simulation results, helping to confirm the theory. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials.

  6. Effect of impurity on the absorption of a parabolic quantum dot with including Rashba spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Hosseinpour, Parinaz; Soltani-Vala, Ali; Barvestani, Jamal

    2016-06-01

    In this paper, the influence of impurity parameters on the electron energy spectrum and absorption coefficients in a parabolic quantum dot and in the presence of Rashba spin-orbit interaction subjected to a perpendicular magnetic field is studied. The impurity potential is approximated by a Gaussian form. We have shown that in the both cases of a repulsive and attractive Gaussian impurity, the absorption coefficients are strongly affected by the decay length. These coefficients show blue (red) shift as the decay length of repulsive (attractive) impurity is increased. The dependence of the absorption coefficients on the impurity position is also examined for different polarizations. Our results show that the absorption coefficient has local maximum (minimum) for a given value of impurity position for Y-polarized (X-polarized) light.

  7. X-shaped Electro-Optic Chromophore with Remarkably Blue-Shifted Optical Absorption. Synthesis, Characterization, Linear/Nonlinear Optical Properties, Self-Assembly, and Thin Film Microstructural Characteristics

    SciTech Connect

    Kang,H.; Evmenenko, G.; Dutta, P.; Clays, K.; Song, K.; Marks, T.

    2006-01-01

    A novel type of 'X-shaped' two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH{sub 2}Cl{sub 2}) while maintaining a very large first hyperpolarizability ({beta}). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a {beta}{sub zzz} value of 1840 x 10{sup -30} esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response ({chi}({sup 2}){sub 333} {approx} 232 pm/V at 1064 nm; r{sub 33} {approx} 45 pm/V at 1310 nm). This work demonstrates an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs.

  8. X-Shaped electro-optic chromophore with remarkably blue-shifted optical absorption. Synthesis, characterization, linear/nonlinear optical properties, self-assembly, and thin film microstructural characteristics.

    PubMed

    Kang, Hu; Evmenenko, Guennadi; Dutta, Pulak; Clays, Koen; Song, Kai; Marks, Tobin J

    2006-05-10

    A novel type of "X-shaped" two-dimensional electro-optic (EO) chromophore with extended conjugation has been synthesized and characterized. This chromophore is found to exhibit a remarkably blue-shifted optical maximum (357 nm in CH(2)Cl(2)) while maintaining a very large first hyperpolarizability (beta). Hyper-Rayleigh Scattering (HRS) measurements at 800 nm provide a beta(zzz) value of 1840 x 10(-30) esu. Self-assembled thin films of this chromophore were fabricated via a layer-by-layer chemisorptive siloxane-based approach. The chromophoric multilayers have been characterized by transmission optical spectroscopy, advancing contact angle measurements, synchrotron X-ray reflectivity, atomic force microscopy, and angle-dependent polarized second harmonic generation spectroscopy. The self-assembled chromophoric films exhibit a dramatically blue-shifted optical maximum (325 nm) while maintaining a large EO response (chi(2)(333) approximately 232 pm/V at 1064 nm; r(33) approximately 45 pm/V at 1310 nm). This work demonstrates an attractive approach to developing EO materials offering improved nonlinearity-transparency trade-offs. PMID:16669690

  9. Optical absorption signature of a self-assembled dye monolayer on graphene

    PubMed Central

    Sghaier, Tessnim; Le Liepvre, Sylvain; Fiorini, Céline; Douillard, Ludovic

    2016-01-01

    Summary A well-organized monolayer of alkylated perylene-3,4,9,10-tetracarboxylic-3,4,9,10-diimide (PTCDI) has been formed onto CVD graphene transferred on a transparent substrate. Its structure has been probed by scanning tunnelling microscopy and its optical properties by polarized transmission spectroscopy at varying incidence. The results show that the transition dipoles of adsorbed PTCDI are all oriented parallel to the substrate. The maximum absorption is consistent with the measured surface density of molecules and their absorption cross section. The spectrum presents mainly a large red-shift of the absorption line compared with the free molecules dispersed in solution, whereas the relative strengths of the vibronic structures are preserved. These changes are attributed to non-resonant interactions with the graphene layer and the neighbouring molecules. PMID:27547603

  10. Absorption and fluorescence of alexandrite and of titanium in sapphire and glass

    NASA Technical Reports Server (NTRS)

    Byvik, C. E.; Hess, R. V.; Buoncristiani, A. M.

    1985-01-01

    The fluorescence and absorption data for titanium in crystalline sapphire and titanium doped into two silicate and one phosphate glass structures are analyzed. It is observed that the Ti-doped silicate glass sample exhibits no absorption related to the Ti(III) ion, the Ti-doped phosphate glass is deep blue, the absorption line width of the glass samples are a factor of two larger than that of sapphire, and the absorption peak for the Ti in the glass shifted about 100 nm to the red from the Ti:sapphire absorption peak. This shift reveals that the Ti(III) ion is sensitive to the crystalline environment and not to the glass environment. The photoluminescence spectra for Ti-doped sapphire and alexandrite are compared. It is detected that the Ti:sapphire exhibits a broader spectrum than that for alexandrite with a peak at 750 nm. The three zero phonon transitions of Ti:Al2O3 at liquid nitrogen temperatures are studied.

  11. Absorption of ac fields in amorphous indium-oxide films

    SciTech Connect

    Ovadyahu, Z.

    2014-08-20

    Absorption data from applied ac fields in Anderson-localized amorphous indium-oxide (In{sub x}O) films are shown to be frequency and disorder dependent. The absorption shows a roll-off at a frequency which is much lower than the electron-electron scattering rate of the material when it is in the diffusive regime. This is interpreted as evidence for discreteness of the energy spectrum of the deeply localized regime. This is consistent with recent many-body localization scenarios. As the metal-insulator transition is approached, the absorption shifts to higher frequencies. Comparing with the previously obtained results on the crystalline version of indium-oxide (In{sub 2}O{sub 3−x}) implies a considerably higher inelastic electron-phonon scattering rate in the amorphous material. The range over which the absorption versus frequency decreases may indicate that a wide distribution of localization length is a common feature in these systems.

  12. A study of a high resolution IUE spectrum of AM Canum Venaticorum

    NASA Technical Reports Server (NTRS)

    Solheim, J.-E.; Sion, E. M.

    1994-01-01

    We have obtained the first high resolution IUE spectrum of the helium-rich, cataclysmic variable star AM CVn. The spectrum is greatly underexposed, but we can still detect both wide and narrow line profiles. We report broad, shortward-shifted, P-Cygni-like absorption and in some cases emission lines in the far UV high ionization resonance lines of C, N, O, and Si, but the profiles are considerably disk/boundary layer outflows, absorption disk continuum light in H-rich CVs. The highest ionizations show evidence of a narrow jet or conical flow. For other, lower ionized lines, we find some evidence of a stellar origin. The broad He II (lambda 1640 A) absorption profile with blue shifted emission core has a remarkably similar overall structure to the He II (lambda 1640 A) broad absorption trough in the IUE spectrum of the prototypical cool DO white dwarf HZ 21. The sharp absorption lines seem most convincingly in the resonance doublets of N V (lambda 1238 A, lambda 1242 A) and C IV (lambda 1548 A, lambda 1550 A) and in He II (lambda 1640 A) exhibit a precise velocity coincidence. These sharp features are almost certainly due to circumbinary matter because they are obviously unaffected by the rapid orbital motion (or rapid stellar rotation) in this short period system during the long (9.3 hour) IUE echelle exposure. Our observations support an evolution through shell episodes of a close binary system which ends up with an expanding envelope as seen for HZ 21, and suggests one possible evolutionary channel for production of DOs (DBs).

  13. Spectral broadening of interacting pigments: polarized absorption by photosynthetic proteins.

    PubMed Central

    Somsen, O J; van Grondelle, R; van Amerongen, H

    1996-01-01

    Excitonic interaction between pigment molecules is largely responsible for the static and dynamic spectroscopic properties of photosynthetic pigment-proteins. This paper provides a new description of its effect on polarized absorption spectroscopy, in particular on circular dichroism (CD). We investigate excitonic spectra of finite width and use "spectral moments" to compare 1) inhomogeneously broadened excitonic spectra, 2) spectra that are (homogeneously broadened by vibrations or electron-phonon interaction, and 3) spectra that are simulated by applying convolution after the interaction has been evaluated. Two cases are distinguished. If the excitonic splitting is smaller than the width of the interacting absorption bands, the broadening of the excitonic spectrum can be approximated by a convolution approach, although a correction is necessary for CD spectra. If the excitonic splitting exceeds the bandwidth, the well-known exchange narrowing occurs. We demonstrate that this is accompanied by redistribution of dipole strength and spectral shifts. The magnitude of a CD spectrum is conveniently expressed by its first spectral moment. As will be shown, this is independent of spectral broadening as well as dispersive shifts induced by pigment-protein interactions. Consequently, it provides a simple tool to relate the experimental CD spectrum of a pigment complex to the excitonic interactions from which it originates. To illustrate the potential of the presented framework, the spectroscopy of the LH2 pigment-protein complex from purple bacteria is analyzed and compared for dimer-like and ring-like structures. Furthermore, it is demonstrated that the variability of the CD of chlorosomes from green bacteria can be explained by small changes in the structure of their cylindrical bacteriochlorophyll c subunits. Images FIGURE 3 FIGURE 4 PMID:8889168

  14. Spectrum Recombination.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1984-01-01

    Describes several methods of executing lecture demonstrations involving the recombination of the spectrum. Groups the techniques into two general classes: bringing selected portions of the spectrum together using lenses or mirrors and blurring the colors by rapid movement or foreshortening. (JM)

  15. Precise Determination of Brillouin Scattering Spectrum Using a Virtually Imaged Phase Array (VIPA) Spectrometer and Charge-Coupled Device (CCD) Camera.

    PubMed

    Meng, Zhaokai; Yakovlev, Vladislav V

    2016-08-01

    Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows noninvasive assessment of viscoelastic properties of materials. The use of atomic-molecular absorption cells as ultra-narrow notch filters allows acquisition of Brillouin spectra from turbid samples despite their strong elastic scattering. However, such systems alter the shapes of the Brillouin lines, making the precise determination of the Brillouin shift difficult. In this report, we propose a simple method for analyzing the Brillouin spectrum using a customized least-square fitting algorithm. The absorption spectrum induced by the atomic-molecular cell was taken into consideration. The capability of the method is confirmed by processing experimental spectroscopic data from the pure water at different temperatures. The accuracy of the measurements of ±1 MHz spectral line shift is experimentally demonstrated. PMID:27296309

  16. Chaotic systems with absorption.

    PubMed

    Altmann, Eduardo G; Portela, Jefferson S E; Tél, Tamás

    2013-10-01

    Motivated by applications in optics and acoustics we develop a dynamical-system approach to describe absorption in chaotic systems. We introduce an operator formalism from which we obtain (i) a general formula for the escape rate κ in terms of the natural conditionally invariant measure of the system, (ii) an increased multifractality when compared to the spectrum of dimensions D(q) obtained without taking absorption and return times into account, and (iii) a generalization of the Kantz-Grassberger formula that expresses D(1) in terms of κ, the positive Lyapunov exponent, the average return time, and a new quantity, the reflection rate. Simulations in the cardioid billiard confirm these results. PMID:24138240

  17. Isotope shifts in methane near 6000/cm

    NASA Technical Reports Server (NTRS)

    Fox, K.; Halsey, G. W.; Jennings, D. E.

    1976-01-01

    Isotope shifts for cleanly resolved vibrational-rotational absorption lines of CH4-12 and CH4-13 were measured by a 5-m focal length Littrow spectrometer in the 6000/cm range. The methane isotopes were held in separate absorption cells: 20 torr of CH4-13 in a 1-m cell, and 5 torr of CH4-12 in a White cell of 4-m optical path length. Measured shifts for the cleanly resolved singlets R(0), R(1), Q(1) and P(1) are summarized in tabular form.

  18. Micro acoustic spectrum analyzer

    DOEpatents

    Schubert, W. Kent; Butler, Michael A.; Adkins, Douglas R.; Anderson, Larry F.

    2004-11-23

    A micro acoustic spectrum analyzer for determining the frequency components of a fluctuating sound signal comprises a microphone to pick up the fluctuating sound signal and produce an alternating current electrical signal; at least one microfabricated resonator, each resonator having a different resonant frequency, that vibrate in response to the alternating current electrical signal; and at least one detector to detect the vibration of the microfabricated resonators. The micro acoustic spectrum analyzer can further comprise a mixer to mix a reference signal with the alternating current electrical signal from the microphone to shift the frequency spectrum to a frequency range that is a better matched to the resonant frequencies of the microfabricated resonators. The micro acoustic spectrum analyzer can be designed specifically for portability, size, cost, accuracy, speed, power requirements, and use in a harsh environment. The micro acoustic spectrum analyzer is particularly suited for applications where size, accessibility, and power requirements are limited, such as the monitoring of industrial equipment and processes, detection of security intrusions, or evaluation of military threats.

  19. A simple levulinate-based ratiometric fluorescent probe for sulfite with a large emission shift.

    PubMed

    Liu, Caiyun; Wu, Huifang; Yang, Wen; Zhang, Xiaoling

    2014-01-01

    A simple 4-hydroxynaphthalimide-derived colorimetric and ratiometric fluorescent probe (1) containing a receptor of levulinate moiety was designed and synthesized to monitor sulfite. Probe 1 could quantificationally detect sulfite by a ratiometric fluorescence spectroscopy method with high selectivity and sensitivity. Specially, probe 1 exhibited a 100 nm red-shifted absorption spectrum along with the color changes from colorless to yellow, and 103 nm red-shifted emission spectra upon the addition of sulfite. Thus, 1 can serve as a "naked-eye" probe for sulfite. Further, the recognition mechanism of probe 1 for sulfite was confirmed using nuclear magnetic resonance and electrospray ionization mass spectrometry. Also, the preliminary practical application demonstrated that our proposed probe provided a promising method for the determination of sulfite. PMID:24813958

  20. Real-time bilinear rotation decoupling in absorptive mode J-spectroscopy: Detecting low-intensity metabolite peak close to high-intensity metabolite peak with convenience.

    PubMed

    Verma, Ajay; Baishya, Bikash

    2016-05-01

    "Pure shift" NMR spectra display singlet peak per chemical site. Thus, high resolution is offered at the cost of valuable J-coupling information. In the present work, real-time BIRD (BIlinear Rotation Decoupling) is applied to the absorptive-mode 2D J-spectroscopy to provide pure shift spectrum in the direct dimension and J-coupling information in the indirect dimension. Quite often in metabolomics, proton NMR spectra from complex bio-fluids display tremendous signal overlap. Although conventional J-spectroscopy in principle overcomes this problem by separating the multiplet information from chemical shift information, however, only magnitude mode of the experiment is practical, sacrificing much of the potential high resolution that could be achieved. Few J-spectroscopy methods have been reported so far that produce high-resolution pure shift spectrum along with J-coupling information for crowded spectral regions. In the present work, high-quality J-resolved spectrum from important metabolomic mixture such as tissue extract from rat cortex is demonstrated. Many low-intensity metabolite peaks which are obscured by the broad dispersive tails from high-intensity metabolite peaks in regular magnitude mode J-spectrum can be clearly identified in real-time BIRD J-resolved spectrum. The general practice of removing such spectral overlap is tedious and time-consuming as it involves repeated sample preparation to change the pH of the tissue extract sample and subsequent spectra recording. PMID:27026651

  1. Real-time bilinear rotation decoupling in absorptive mode J-spectroscopy: Detecting low-intensity metabolite peak close to high-intensity metabolite peak with convenience

    NASA Astrophysics Data System (ADS)

    Verma, Ajay; Baishya, Bikash

    2016-05-01

    "Pure shift" NMR spectra display singlet peak per chemical site. Thus, high resolution is offered at the cost of valuable J-coupling information. In the present work, real-time BIRD (BIlinear Rotation Decoupling) is applied to the absorptive-mode 2D J-spectroscopy to provide pure shift spectrum in the direct dimension and J-coupling information in the indirect dimension. Quite often in metabolomics, proton NMR spectra from complex bio-fluids display tremendous signal overlap. Although conventional J-spectroscopy in principle overcomes this problem by separating the multiplet information from chemical shift information, however, only magnitude mode of the experiment is practical, sacrificing much of the potential high resolution that could be achieved. Few J-spectroscopy methods have been reported so far that produce high-resolution pure shift spectrum along with J-coupling information for crowded spectral regions. In the present work, high-quality J-resolved spectrum from important metabolomic mixture such as tissue extract from rat cortex is demonstrated. Many low-intensity metabolite peaks which are obscured by the broad dispersive tails from high-intensity metabolite peaks in regular magnitude mode J-spectrum can be clearly identified in real-time BIRD J-resolved spectrum. The general practice of removing such spectral overlap is tedious and time-consuming as it involves repeated sample preparation to change the pH of the tissue extract sample and subsequent spectra recording.

  2. Absorption Characteristics of Vertebrate Non-Visual Opsin, Opn3

    PubMed Central

    Sugihara, Tomohiro; Nagata, Takashi; Mason, Benjamin; Koyanagi, Mitsumasa; Terakita, Akihisa

    2016-01-01

    Most animals possess multiple opsins which sense light for visual and non-visual functions. Here, we show spectral characteristics of non-visual opsins, vertebrate Opn3s, which are widely distributed among vertebrates. We successfully expressed zebrafish Opn3 in mammalian cultured cells and measured its absorption spectrum spectroscopically. When incubated with 11-cis retinal, zebrafish Opn3 formed a blue-sensitive photopigment with an absorption maximum around 465 nm. The Opn3 converts to an all-trans retinal-bearing photoproduct with an absorption spectrum similar to the dark state following brief blue-light irradiation. The photoproduct experienced a remarkable blue-shift, with changes in position of the isosbestic point, during further irradiation. We then used a cAMP-dependent luciferase reporter assay to investigate light-dependent cAMP responses in cultured cells expressing zebrafish, pufferfish, anole and chicken Opn3. The wild type opsins did not produce responses, but cells expressing chimera mutants (WT Opn3s in which the third intracellular loops were replaced with the third intracellular loop of a Gs-coupled jellyfish opsin) displayed light-dependent changes in cAMP. The results suggest that Opn3 is capable of activating G protein(s) in a light-dependent manner. Finally, we used this assay to measure the relative wavelength-dependent response of cells expressing Opn3 chimeras to multiple quantally-matched stimuli. The inferred spectral sensitivity curve of zebrafish Opn3 accurately matched the measured absorption spectrum. We were unable to estimate the spectral sensitivity curve of mouse or anole Opn3, but, like zebrafish Opn3, the chicken and pufferfish Opn3-JiL3 chimeras also formed blue-sensitive pigments. These findings suggest that vertebrate Opn3s may form blue-sensitive G protein-coupled pigments. Further, we suggest that the method described here, combining a cAMP-dependent luciferase reporter assay with chimeric opsins possessing the third

  3. The spatio-temporal spectrum of turbulent flows.

    PubMed

    Clark di Leoni, P; Cobelli, P J; Mininni, P D

    2015-12-01

    Identification and extraction of vortical structures and of waves in a disorganised flow is a mayor challenge in the study of turbulence. We present a study of the spatio-temporal behavior of turbulent flows in the presence of different restitutive forces. We show how to compute and analyse the spatio-temporal spectrum from data stemming from numerical simulations and from laboratory experiments. Four cases are considered: homogeneous and isotropic turbulence, rotating turbulence, stratified turbulence, and water wave turbulence. For homogeneous and isotropic turbulence, the spectrum allows identification of sweeping by the large-scale flow. For rotating and for stratified turbulence, the spectrum allows identification of the waves, precise quantification of the energy in the waves and in the turbulent eddies, and identification of physical mechanisms such as Doppler shift and wave absorption in critical layers. Finally, in water wave turbulence the spectrum shows a transition from gravity-capillary waves to bound waves as the amplitude of the forcing is increased. PMID:26701711

  4. The action spectrum for vitamin D3: initial skin reaction and prolonged exposure.

    PubMed

    van Dijk, Arjan; den Outer, Peter; van Kranen, Henk; Slaper, Harry

    2016-07-01

    Vitamin D3 photosynthesis in the skin is formulated as a set of reaction equations, including side-reactions to lumisterol, tachysterol and toxisterols, and the accompanying reverse reactions, isomerisation of previtamin D3 to vitamin D3 and photodegradation of vitamin D3. The solution of this set is given for the stationary irradiance spectrum. The effective action spectrum for the instantaneous vitamin D3 production changes shape as a function of exposure, and therefore, no single action spectrum can be used. We assessed the action spectrum for unexposed skin and for skin that has been exposed to 7.5 Standard Erythemal Doses (SED). We constructed two new estimates: (1) the RIVM action spectrum, based on absorption spectra, quantum yields and skin transmission spectra, and (2) the modified QUT action spectrum, which is adjusted for self-absorption and skin transmission. For previously unexposed skin, the modified QUT action spectrum gives a qualitatively similar, but larger estimate than the RIVM action spectrum. We have not been able to solve the lack of quantitative agreement between the vitamin D production estimates from the three action spectrum estimates (RIVM, modified QUT and CIE). All new action spectra have stronger emphasis on the short wavelengths than the CIE action spectrum. We showed that, for wavelengths larger than 300 nm, the bandwidth that was used in the experiment that formed the basis of the CIE action spectrum, gives a red-shift of about 1 nm. Generally, with the formation of previtamin D3, the return reaction to provitamin D3 limits the production of vitamin D3. After some exposure, the new action spectrum has negative values for the longer wavelengths in the UVB. For the RIVM action spectrum, this happens after 7.5 SED, for the modified QUT action spectrum already after 1.25 SED, and after 7.5 SED the net production rate is largely cancelled. Thus prolonged exposure of previously unexposed skin saturates vitamin D3 formation. For maximum

  5. Polarization of the Sun's continuous spectrum

    NASA Astrophysics Data System (ADS)

    Stenflo, J. O.

    2005-01-01

    The Sun's spectrum is linearly polarized by coherent scattering processes. Here we develop the theory for the formation of the polarized continuum, identify the relevant physical mechanisms, and clarify their relative roles. The polarized photons are produced by scattering at neutral hydrogen in its ground state (Lyman scattering), and to a smaller degree by scattering at free electrons (Thomson scattering). The polarized photons are diluted by the unpolarized photons from the H- opacity and radiative absorption from the Balmer bound-bound and bound-free transitions. Due to pressure broadening of the Balmer lines from the statistical Stark effect the polarized Balmer jump is shifted from the series limit to substantially longer wavelengths. In the second part of the paper the Atlas of the Second Solar Spectrum that covers 3161-6995 Å for disk position μ =0.1 (where μ is the cosine of the heliocentric angle) is used to extract the empirical values of the continuum polarization with the help of a model for the behavior of the depolarizing lines. The empirically determined continuum polarization lies systematically lower than the values that have been predicted for λ >4000 Å from radiative-transfer modelling. The Balmer jump is found to be shifted as expected from pressure-broadening theory. Through scaling of the relative center-to-limb variations obtained from radiative-transfer theory with the empirically determined values (valid for μ=0.1) we finally obtain the semi-empirical function that describes the variation of the continuum polarization with both wavelength and disk position μ. The empirically determined continuum polarization can be used to constrain model atmospheres as well as to fix the zero point of the polarization scale in observations of the scattering polarization and the Hanle effect.

  6. Line Identifications in the Far Ultraviolet Spectrum of the Eclipsing Binary System 31 Cygni

    NASA Astrophysics Data System (ADS)

    Hagen Bauer, Wendy; Bennett, P. D.

    2011-05-01

    The eclipsing binary system 31 Cygni (K4 Ib + B3 V) was observed at several phases with the Far Ultraviolet Spectrosocopic Explorer (FUSE) satellite. During total eclipse, a rich emission spectrum was observed, produced by scattering of hot star photons in the extended wind of the K supergiant. The system was observed during deep chromospheric eclipse, and 2.5 months after total eclipse ended. We present an atlas of line identifications in these spectra. During total eclipse, emission features from C II , C III, N I, N II, N III, O I, Si II, P II, P III, S II, S III, Ar I, Cr III, Fe II, Fe III, and Ni II were detected. The strongest emission features arise from N II. These lines appear strongly in absorption during chromospheric eclipse, and even 2.5 months after total eclipse, the absorption bottoms out on the underlying emission seen during total eclipse. The second strongest features in the emission spectrum arise from Fe III. Any chromospheric Fe III absorption is buried within strong chromospheric absorption from other species, mainly Fe II. The emission profiles of most of the doubly-ionized species are red-shifted relative to the systemic velocity, with asymmetric profiles with a steeper long-wavelength edge. Emission profiles from singly-ionized species tend to be more symmetric and centered near the systemic velocity. In deep chromospheric eclipse, absorption features are seen from neutral and singly-ionized species, arising from lower levels up to 3 eV. Many strong chromospheric features are doubled in the observation obtained during egress from eclipse. The 31 Cygni spectrum taken 2.5 months after total eclipse ended ws compared to single-star B spectra from the FUSE archives. There was still some additional chromospheric absorption from strong low-excitation Fe II, O I and Ar I.

  7. Psychopathology of Shift Work.

    ERIC Educational Resources Information Center

    Akinnawo, Ebenezer Olutope

    1989-01-01

    Examined incidence and nature of general psychopathology among Nigerian shift workers (N=320). Found shift workers more significantly psychopathological than non-shift workers (p<0.001). Prominent disorders among shift workers were intellectual, sleep, mood, and general somatic disorders. No significant difference could be attributed to gender and…

  8. A combined strategy of mass fragmentation, post-column cobalt complexation and shift in ultraviolet absorption spectra to determine the uridine 5'-diphospho-glucuronosyltransferase metabolism profiling of flavones after oral administration of a flavone mixture in rats.

    PubMed

    Li, Qiang; Wang, Liping; Dai, Peimin; Zeng, Xuejun; Qi, Xiaoxiao; Zhu, Lijun; Yan, Tongmeng; Wang, Ying; Lu, Linlin; Hu, Ming; Wang, Xinchun; Liu, Zhongqiu

    2015-05-22

    The use of dietary flavones is becoming increasingly popular for their prevention of cancers, cardiovascular diseases, and other diseases. Despite many pharmacokinetic studies on flavone mixtures, the position(s) of glucuronidation sites on the flavone skeleton in vivo remain(s) uncertain because of the lack of a convenient method to differentiate the isomers in biological samples. Accordingly, this study aimed to develop a new strategy to identify the position of the mono-O-glucuronide of flavones in vivo and to simultaneously determine the parent agent and its major metabolites responsible for complex pharmacokinetic characteristics. The novel strategy involves accurate mass measurements of flavone glucuronides, their [Co(II) (flavone glucuronide-H) (4,7-diphenyl-1,10-phenanthroline)2](+) complexes generated via the post-column addition of CoBr2 and 4,7-diphenyl-1,10-phenanthroline, and their mass spectrometric fragmentation by UPLC-DAD-Q-TOF and the comparison of retention times with biosynthesized standards of different isomers that were identified by analyzing the shift in UV spectra compared with the spectra of their respective aglycones. We successfully generated a metabolite profiling of flavones in rat plasma after oral administration of a flavone mixture from Dracocephalum moldavica L., which was used here as the model to demonstrate the strategy. Twelve flavone glucuronides, which were glucuronidated derivatives of acacetin, apigenin, luteolin, diosmetin, chrysoeriol and cirsimaritin, were detected and identified. Glucuronidation of the flavone skeleton at the 3'-/7-position was more prevalent, however, luteolin 4'-glucuronide levels exceeded luteolin 7-glucuronide levels. Based on the UDP-glucuronosyltransferase (UGT) metabolism profiling of flavones in rat plasma, six main compounds (tilianin, acacetin 7-glucuronide, apigenin 7-glucuronide, luteolin 3'-glucuronide, acacetin, and apigenin) were selected as pharmacokinetic markers. Pharmacokinetic

  9. Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction

    PubMed Central

    2015-01-01

    We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift Δm is mainly caused by dispersion effects and depends sensitively on the molecule’s specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide Δm= −QWm in two factors, where Q depends only on the molecular species and accounts for all nonresonant electronic transitions contributing to the dispersion while Wm is a geometry factor expressing the site dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI). PMID:25834658

  10. Optical Absorption Spectra of Hydrous Wadsleyite to 32 GPa

    NASA Astrophysics Data System (ADS)

    Thomas, S.; Goncharov, A. F.; Jacobsen, S. D.; Bina, C. R.; Frost, D. J.

    2009-05-01

    Optical absorption spectra of high-pressure minerals can be used as indirect tools to calculate radiative conductivity of the Earth's interior [e.g., 1]. Recent high-pressure studies show that e.g. ringwoodite, γ-(Mg,Fe)2SiO4, does not become opaque in the near infrared and visible region, as previously assumed, but remains transparent to 21.5 GPa [2]. Therefore, it has been concluded that radiative heat transfer does not necessarily become blocked at high pressures of the mantle and ferromagnesian minerals actually could contribute to the heat flow in the Earth's interior [2]. In this study we use gem-quality single-crystals of hydrous Fe-bearing wadsleyite, β-(Mg,Fe)2SiO4, that were synthesized at 18 GPa and 1400 °C in a multianvil apparatus. Crystals were analyzed by Mössbauer and Raman spectroscopy, electron microprobe analysis and single-crystal X-ray diffraction. For absorption measurements a double-polished 50 μm sized single-crystal of wadsleyite was loaded in a diamond-anvil cell with neon as pressure medium. Optical absorption spectra were recorded at ambient conditions as well as up to 32 GPa from 400 to 50000 cm-1. At ambient pressure the absorption spectrum reveals two broad bands at - 10000 cm-1 and -15000 cm-1, and an absorption edge in the visible-ultraviolet range. With increasing pressure the absorption spectrum changes, both bands continuously shift to higher frequencies as has been observed for ringwoodite [2], but is contrary to earlier presumptions for wadsleyite [3]. Here, we will discuss band assignment along with the influence of iron, compare our results to previous absorption studies of mantle materials [2], and analyze possible implications for radiative conductivity of the transition zone. References: [1] Goncharov et al. (2008), McGraw Yearbook Sci. Tech., 242-245. [2] Keppler & Smyth (2005), Am. Mineral., 90 1209-1212. [3] Ross (1997), Phys. Chem. Earth, 22 113-118.

  11. Looping through the Lamb Shift

    SciTech Connect

    Hazi, A U

    2007-02-06

    Sometimes in science, a small measurement can have big ramifications. For a team of Livermore scientists, such was the case when they measured a small shift in the spectrum of extremely ionized atoms of uranium. The measurement involves the Lamb shift, a subtle change in the energy of an electron orbiting an atom's nucleus. The precision of the Livermore result was 10 times greater than that of existing measurements, making it the best measurement to date of a complicated correction to the simplest quantum description of how atoms behave. The measurement introduces a new realm in the search for deviations between the theory of quantum electrodynamics (QED), which is an extension of quantum mechanics, and the real world. Such deviations, if discovered, would have far-reaching consequences, indicating that QED is not a fundamental theory of nature.

  12. Tunable absorption resonances in the ultraviolet for InP nanowire arrays.

    PubMed

    Aghaeipour, Mahtab; Anttu, Nicklas; Nylund, Gustav; Samuelson, Lars; Lehmann, Sebastian; Pistol, Mats-Erik

    2014-11-17

    The ability to tune the photon absorptance spectrum is an attracting way of tailoring the response of devices like photodetectors and solar cells. Here, we measure the reflectance spectra of InP substrates patterned with arrays of vertically standing InP nanowires. Using the reflectance spectra, we calculate and analyze the corresponding absorptance spectra of the nanowires. We show that we can tune absorption resonances for the nanowire arrays into the ultraviolet by decreasing the diameter of the nanowires. When we compare our measurements with electromagnetic modeling, we generally find good agreement. Interestingly, the remaining differences between modeled and measured spectra are attributed to a crystal-phase dependence in the refractive index of InP. Specifically, we find indication of significant differences in the refractive index between the modeled zinc-blende InP nanowires and the measured wurtzite InP nanowires in the ultraviolet. We believe that such crystal-phase dependent differences in the refractive index affect the possibility to excite optical resonances in the large wavelength range of 345 < λ < 390 nm. To support this claim, we investigated how resonances in nanostructures can be shifted in wavelength by geometrical tuning. We find that dispersion in the refractive index can dominate over geometrical tuning and stop the possibility for such shifting. Our results open the door for using crystal-phase engineering to optimize the absorption in InP nanowire-based solar cells and photodetectors. PMID:25402159

  13. Field shifts in hafnium II

    NASA Astrophysics Data System (ADS)

    Aufmuth, P.; Henneberg, I.; Siminski, A.; Steudel, A.

    1991-03-01

    By means of classical interference spectroscopy, using enriched isotope samples, the isotope shift between178Hf and180Hf has been measured for 33 transitions in the Hf II spectrum. For the pure Russell-Saunders terms 5 d 26 s 4 F and2 F the parametric analysis yields a field-shift difference of 17(2) mK produced by the second-order interaction of the electrostatic operator and the field-shift operator. Semi-empirical calculations based on the non-relativistic Hartree-Fock method reproduce this value as well as the experimental field shifts if a factor of 1.68(6) is used to scale the ab initio electron densities at the nucleus. The corresponding factor for the Hf atom is much smaller. This leads to a re-evaluation of screening ratios for Hf and to a more accurate value of the nuclear parameter λ178,180 (Hf)=0.072(4) fm2.

  14. Absorption of Sunlight in Clear and Cloudy Atmospheres: A Solution to the Cloud Absorption Anomaly

    NASA Technical Reports Server (NTRS)

    Crisp, D.

    1997-01-01

    To identify the origin of this mission absorption, a spectrum-resolving (line-by-line) multiple scattering model was used to derive solar radiances, fluxes, and heating rates for realistic clear and cloudy atmospheres.

  15. Relic Neutrino Absorption Spectroscopy

    SciTech Connect

    Eberle, b

    2004-01-28

    Resonant annihilation of extremely high-energy cosmic neutrinos on big-bang relic anti-neutrinos (and vice versa) into Z-bosons leads to sizable absorption dips in the neutrino flux to be observed at Earth. The high-energy edges of these dips are fixed, via the resonance energies, by the neutrino masses alone. Their depths are determined by the cosmic neutrino background density, by the cosmological parameters determining the expansion rate of the universe, and by the large redshift history of the cosmic neutrino sources. We investigate the possibility of determining the existence of the cosmic neutrino background within the next decade from a measurement of these absorption dips in the neutrino flux. As a by-product, we study the prospects to infer the absolute neutrino mass scale. We find that, with the presently planned neutrino detectors (ANITA, Auger, EUSO, OWL, RICE, and SalSA) operating in the relevant energy regime above 10{sup 21} eV, relic neutrino absorption spectroscopy becomes a realistic possibility. It requires, however, the existence of extremely powerful neutrino sources, which should be opaque to nucleons and high-energy photons to evade present constraints. Furthermore, the neutrino mass spectrum must be quasi-degenerate to optimize the dip, which implies m{sub {nu}} 0.1 eV for the lightest neutrino. With a second generation of neutrino detectors, these demanding requirements can be relaxed considerably.

  16. Gear shift control mechanism

    SciTech Connect

    Janson, D.A.

    1987-03-10

    A gear shift control mechanism is described comprising: multiple shift rods directed substantially parallel to one another, each rod carrying a shift fork for axial movement; a shift lever supported for pivotal movement about a first axis directed parallel to the axes of the shift rods and for pivotal movement about a second axis directed substantially perpendicular to the axes of the shift rods. The lever is moveable about the first axis and the second axis into engagement with a selected shift fork; interlock means located on each lateral side of the shift lever and mounted for pivotal movement about the first axis for blocking engagement with the shift forks; detent means for holding the shift lever in multiple predetermined angular positions about the second axis; and spring means located on a lateral side of the shift lever and mounted for pivotal movement about the first axis into interference contact with the shift forks for producing a force tending to resiliently bias the shift lever out of engagement with the selected shift fork.

  17. Red and blue shift of liquid water's excited states: A many body perturbation study

    NASA Astrophysics Data System (ADS)

    Ziaei, Vafa; Bredow, Thomas

    2016-08-01

    In the present paper, accurate optical absorption spectrum of liquid H2O is calculated in the energy range of 5-20 eV to probe the nature of water's excited states by means of many body perturbation approach. Main features of recent inelastic X-ray measurements are well reproduced, such as a bound excitonic peak at 7.9 eV with a shoulder at 9.4 eV as well as the absorption maximum at 13.9 eV, followed by a broad shoulder at 18.4 eV. The spectrum is dominated by excitonic effects impacting the structures of the spectrum at low and higher energy regimes mixed by single particle effects at high energies. The exciton distribution of the low-energy states, in particular of S1, is highly anisotropic and localized mostly on one water molecule. The S1 state is essentially a HOCO-LUCO (highest occupied crystal orbital - lowest unoccupied crystal orbital) transition and of intra-molecular type, showing a localized valence character. Once the excitation energy is increased, a significant change in the character of the electronically excited states occurs, characterized through emergence of multiple quasi-particle peaks at 7.9 eV in the quasi-particle (QP) transition profile and in the occurring delocalized exciton density distribution, spread over many more water molecules. The exciton delocalization following a change of the character of excited states at around 7.9 eV causes the blue shift of the first absorption band with respect to water monomer S1. However, due to reduction of the electronic band gap from gas to liquid phase, following enhanced screening upon condensation, the localized S1 state of liquid water is red-shifted with respect to S1 state of water monomer. For higher excitations, near vertical ionization energy (11 eV), quasi-free electrons emerge, in agreement with the conduction band electron picture. Furthermore, the occurring red and blue shift of the excited states are independent of the coupling of resonant and anti-resonant contributions to the

  18. Electro-absorption of silicene and bilayer graphene quantum dots

    NASA Astrophysics Data System (ADS)

    Abdelsalam, Hazem; Talaat, Mohamed H.; Lukyanchuk, Igor; Portnoi, M. E.; Saroka, V. A.

    2016-07-01

    We study numerically the optical properties of low-buckled silicene and AB-stacked bilayer graphene quantum dots subjected to an external electric field, which is normal to their surface. Within the tight-binding model, the optical absorption is calculated for quantum dots, of triangular and hexagonal shapes, with zigzag and armchair edge terminations. We show that in triangular silicene clusters with zigzag edges a rich and widely tunable infrared absorption peak structure originates from transitions involving zero energy states. The edge of absorption in silicene quantum dots undergoes red shift in the external electric field for triangular clusters, whereas blue shift takes place for hexagonal ones. In small clusters of bilayer graphene with zigzag edges the edge of absorption undergoes blue/red shift for triangular/hexagonal geometry. In armchair clusters of silicene blue shift of the absorption edge takes place for both cluster shapes, while red shift is inherent for both shapes of the bilayer graphene quantum dots.

  19. 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

  20. Further advancement of differential optical absorption spectroscopy: theory of orthogonal optical absorption spectroscopy.

    PubMed

    Liudchik, Alexander M

    2014-08-10

    A modified version of the differential optical absorption spectroscopy (DOAS) method is presented. The technique is called orthogonal optical absorption spectroscopy (OOAS). A widespread variant of DOAS with smoothing of the registered spectrum and absorption cross sections being made employing a polynomial regression is a particular case of OOAS. The concept of OOAS provides a variety of new possibilities for constructing computational schemes and analyzing the influence of different error sources on calculated concentrations. PMID:25320931

  1. ABSORPTION ANALYZER

    DOEpatents

    Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.

    1961-11-14

    A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)

  2. Tuning the electronic absorption of protein-embedded all-trans-retinal.

    PubMed

    Wang, Wenjing; Nossoni, Zahra; Berbasova, Tetyana; Watson, Camille T; Yapici, Ipek; Lee, Kin Sing Stephen; Vasileiou, Chrysoula; Geiger, James H; Borhan, Babak

    2012-12-01

    Protein-chromophore interactions are a central component of a wide variety of critical biological processes such as color vision and photosynthesis. To understand the fundamental elements that contribute to spectral tuning of a chromophore inside the protein cavity, we redesigned human cellular retinol binding protein II (hCRBPII) to fully encapsulate all-trans-retinal and form a covalent bond as a protonated Schiff base. This system, using rational mutagenesis designed to alter the electrostatic environment within the binding pocket of the host protein, enabled regulation of the absorption maximum of the pigment in the range of 425 to 644 nanometers. With only nine point mutations, the hCRBPII mutants induced a systematic shift in the absorption profile of all-trans-retinal of more than 200 nanometers across the visible spectrum. PMID:23224553

  3. Tuning the Electronic Absorption of Protein-Embedded All-trans-Retinal

    SciTech Connect

    Wang, Wenjing; Nossoni, Zahra; Berbasova, Tetyana; Watson, Camille T.; Yapici, Ipek; Lee, Kin Sing Stephen; Vasileiou, Chrysoula; Geiger, James H.; Borhan, Babak

    2014-10-02

    Protein-chromophore interactions are a central component of a wide variety of critical biological processes such as color vision and photosynthesis. To understand the fundamental elements that contribute to spectral tuning of a chromophore inside the protein cavity, we redesigned human cellular retinol binding protein II (hCRBPII) to fully encapsulate all-trans-retinal and form a covalent bond as a protonated Schiff base. The system, using rational mutagenesis designed to alter the electrostatic environment within the binding pocket of the host protein, enabled regulation of the absorption maximum of the pigment in the range of 425 to 644 nanometers. Moreover, with only nine point mutations, the hCRBPII mutants induced a systematic shift in the absorption profile of all-trans-retinal of more than 200 nanometers across the visible spectrum.

  4. Ultra-violet and visible absorption characterization of explosives by differential reflectometry.

    PubMed

    Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E

    2013-03-15

    This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R(2)>0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and π-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials. PMID:23299022

  5. Ultra-violet and visible absorption characterization of explosives by differential reflectometry

    NASA Astrophysics Data System (ADS)

    Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E.

    2013-03-01

    This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R2 > 0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and π-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials.

  6. Observation of confinement effects through liner and nonlinear absorption spectroscopy in cuprous oxide

    NASA Astrophysics Data System (ADS)

    Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.

    2015-02-01

    Cuprous oxide nano clusters, micro cubes and micro particles were successfully synthesized by reducing copper (II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction studies revealed the formation of pure single phase cubic. Raman spectrum shows the inevitable presence of CuO on the surface of the Cu2O powders which may have an impact on the stability of the phase. Transmission electron microscopy (TEM) data revealed that the morphology evolves from nanoclusters to micro cubes and micro particles by increasing the concentration of NaOH. Linear optical measurements show that the absorption peak maximum shifts towards red with changing morphology from nano clusters to micro cubes and micro particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm, 6 ns laser pulses. Samples exhibited saturable as well as reverse saturable absorption. The results show that the transition from SA to RSA is ascribed to excited-state absorption (ESA) induced by two-photon absorption (TPA) process. Due to confinement effects (enhanced band gap) we observed enhanced nonlinear absorption coefficient (βeff) in the case of nano-clusters compared to their micro-cubes and micro-particles.

  7. Absorption spectra and photolysis of methyl peroxide in liquid and frozen water.

    PubMed

    Epstein, Scott A; Shemesh, Dorit; Tran, Van T; Nizkorodov, Sergey A; Gerber, R Benny

    2012-06-21

    Methyl peroxide (CH(3)OOH) is commonly found in atmospheric waters and ices in significant concentrations. It is the simplest organic peroxide and an important precursor to hydroxyl radical. Many studies have examined the photochemical behavior of gaseous CH(3)OOH; however, the photochemistry of liquid and frozen water solutions is poorly understood. We present a series of experiments and theoretical calculations designed to elucidate the photochemical behavior of CH(3)OOH dissolved in liquid water and ice over a range of temperatures. The molar extinction coefficients of aqueous CH(3)OOH are different from the gas phase, and they do not change upon freezing. Between -12 and 43 °C, the quantum yield of CH(3)OOH photolysis is described by the following equation: Φ(T) = exp((-2175 ± 448)1/T) + 7.66 ± 1.56). We use on-the-fly ab initio molecular dynamics simulations to model structures and absorption spectra of a bare CH(3)OOH molecule and a CH(3)OOH molecule immersed inside 20 water molecules at 50, 200, and 220 K. The simulations predict large sensitivity in the absorption spectrum of CH(3)OOH to temperature, with the spectrum narrowing and shifting to the blue under cryogenic conditions because of constrained dihedral motion around the O-O bond. The shift in the absorption spectrum is not observed in the experiment when the CH(3)OOH solution is frozen suggesting that CH(3)OOH remains in a liquid layer between the ice grains. Using the extinction coefficients and photolysis quantum yields obtained in this work, we show that under conditions with low temperatures, in the presence of clouds with a high liquid-water content and large solar zenith angles, the loss of CH(3)OOH by aqueous photolysis is responsible for up to 20% of the total loss of CH(3)OOH due to photolysis. Gas phase photolysis of CH(3)OOH dominates under all other conditions. PMID:22217262

  8. Decays of the Three Top Contributors to the Reactor ν[over ¯]_{e} High-Energy Spectrum, ^{92}Rb, ^{96gs}Y, and ^{142}Cs, Studied with Total Absorption Spectroscopy.

    PubMed

    Rasco, B C; Wolińska-Cichocka, M; Fijałkowska, A; Rykaczewski, K P; Karny, M; Grzywacz, R K; Goetz, K C; Gross, C J; Stracener, D W; Zganjar, E F; Batchelder, J C; Blackmon, J C; Brewer, N T; Go, S; Heffron, B; King, T; Matta, J T; Miernik, K; Nesaraja, C D; Paulauskas, S V; Rajabali, M M; Wang, E H; Winger, J A; Xiao, Y; Zachary, C J

    2016-08-26

    We report total absorption spectroscopy measurements of ^{92}Rb, ^{96gs}Y, and ^{142}Cs β decays, which are the most important contributors to the high energy ν[over ¯]_{e} spectral shape in nuclear reactors. These three β decays contribute 43% of the ν[over ¯]_{e} flux near 5.5 MeV emitted by nuclear reactors. This ν[over ¯]_{e} energy is particularly interesting due to spectral features recently observed in several experiments including the Daya Bay, Double Chooz, and RENO Collaborations. Measurements were conducted at Oak Ridge National Laboratory by means of proton-induced fission of ^{238}U with on-line mass separation of fission fragments and the Modular Total Absorption Spectrometer. We observe a β-decay pattern that is similar to recent measurements of ^{92}Rb, with a ground-state to ground-state β feeding of 91(3)%. We verify the ^{96gs}Y ground-state to ground-state β feeding of 95.5(20)%. Our measurements substantially modify the β-decay feedings of ^{142}Cs, reducing the β feeding to ^{142}Ba states below 2 MeV by 32% when compared with the latest evaluations. Our results increase the discrepancy between the observed and the expected reactor ν[over ¯]_{e} flux between 5 and 7 MeV, the maximum excess increases from ∼10% to ∼12%. PMID:27610847

  9. Visible Spectrum Incandescent Selective Emitter

    SciTech Connect

    Sonsight Inc.

    2004-04-30

    The purpose of the work performed was to demonstrate the feasibility of a novel bi-layer selective emitter. Selective emitters are incandescent radiant bodies with emissivities that are substantially larger in a selected part of the radiation spectrum, thereby significantly shifting their radiated spectral distribution from that of a blackbody radiating at the same temperature. The major research objectives involved answering the following questions: (1) What maximum VIS/NIR radiant power and emissivity ratios can be attained at 2650 K? (2) What is the observed emitter body life and how does its performance vary with time? (3) What are the design tradeoffs for a dual heating approach in which both an internally mounted heating coil and electrical resistance self-heating are used? (4) What are the quantitative improvements to be had from utilizing a bi-layer emitter body with a low emissivity inner layer and a partially transmissive outer layer? Two approaches to obtaining selective emissivity were investigated. The first was to utilize large optical scattering within an emitter material with a spectral optical absorption that is much greater within the visible spectrum than that within the NIR. With this approach, an optically thick emitter can radiate almost as if optically thin because essentially, scattering limits the distance below the surface from which significant amounts of internally generated radiation can emerge. The performance of thin emitters was also investigated (for optically thin emitters, spectral emissivity is proportional to spectral absorptivity). These emitters were fabricated from thin mono-layer emitter rods as well as from bi-layer rods with a thin emitter layer mounted on a substrate core. With an initially estimated energy efficiency of almost three times that of standard incandescent bulbs, a number of energy, economic and environmental benefits such as less energy use and cost, reduced CO{sub 2} emissions, and no mercury contamination

  10. Etched-multilayer phase shifting masks for EUV lithography

    DOEpatents

    Chapman, Henry N.; Taylor, John S.

    2005-04-05

    A method is disclosed for the implementation of phase shifting masks for EUV lithography. The method involves directly etching material away from the multilayer coating of the mask, to cause a refractive phase shift in the mask. By etching into the multilayer (for example, by reactive ion etching), rather than depositing extra material on the top of the multilayer, there will be minimal absorption loss associated with the phase shift.

  11. Impedance Characteristics of the Plasma Absorption Probe

    NASA Astrophysics Data System (ADS)

    Yamazawa, Yohei

    2009-10-01

    The plasma absorption probe (PAP) is a diagnostics for determination of spatially resolved electron density.footnotetextH. Kokura, et al., Jpn. J. Appl. Phys. 38 5262 (1999). PAP has attracted considerable interest because of its applicability in a reactive plasma. The simple structure of the probe allows us a robust measurement while the mechanism of the absorption is complicated and there are still some uncertainty.footnotetextM. Lapke, et al., Appl. Phys. Lett. 90, 121502 (2007) In this study, we focus on the frequency characteristics of the impedance instead of the absorption spectrum. An electromagnetic field simulation reveals that there is only one parallel resonance in the impedance characteristics even in a case there are many peaks in absorption spectrum. Thus, the impedance characteristics provide a clue to understanding the mechanism.

  12. Fission Spectrum

    DOE R&D Accomplishments Database

    Bloch, F.; Staub, H.

    1943-08-18

    Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951

  13. Temperature dependence of the HNO3 UV absorption cross sections

    NASA Technical Reports Server (NTRS)

    Burkholder, James B.; Talukdar, Ranajit K.; Ravishankara, A. R.; Solomon, Susan

    1993-01-01

    The temperature dependence of the HNO3 absorption cross sections between 240 and 360 K over the wavelength range 195 to 350 nm has been measured using a diode array spectrometer. Absorption cross sections were determined using both (1) absolute pressure measurements at 298 K and (2) a dual absorption cell arrangement in which the absorption spectrum at various temperatures is measured relative to the room temperature absorption spectrum. The HNO3 absorption spectrum showed a temperature dependence which is weak at short wavelengths but stronger at longer wavelengths which are important for photolysis in the lower stratosphere. The 298 K absorption cross sections were found to be larger than the values currently recommended for atmospheric modeling (DeMore et al., 1992). Our absorption cross section data are critically compared with the previous measurements of both room temperature and temperature-dependent absorption cross sections. Temperature-dependent absorption cross sections of HNO3 are recommended for use in atmospheric modeling. These temperature dependent HNO3 absorption cross sections were used in a two-dimensional dynamical-photochemical model to demonstrate the effects of the revised absorption cross sections on loss rate of HNO3 and the abundance of NO2 in the stratosphere.

  14. The electronic absorption edge of petroleum

    SciTech Connect

    Mullins, O.C.; Mitra-Kirtley, S.; Zhu, Yifu

    1992-09-01

    The electronic absorption spectra of more than 20 crude oils and asphaltenes are examined. The spectral location of the electronic absorption edge varies over a wide range, from the near-infrared for heavy oils and asphaltenes to the near-UV for gas condensates. The functional form of the electronic absorption edge for all crude oils (measured) is characteristic of the {open_quotes}Urbach tail,{close_quotes} a phenomenology which describes electronic absorption edges in wide-ranging materials. The crude oils all show similar Urbach widths, which are significantly larger than those generally found for various materials but are similar to those previously reported for asphaltenes. Monotonically increasing absorption at higher photon energy continues for all crude oils until the spectral region is reached where single-ring aromatics dominate absorption. However, the rate of increasing absorption at higher energies moderates, thereby deviating from the Urbach behavior. Fluorescence emission spectra exhibit small red shifts from the excitation wavelength and small fluorescence peak widths in the Urbach regions of different crude oils, but show large red shifts and large peak widths in spectral regions which deviate from the Urbach behavior. This observation implies that the Urbach spectral region is dominated by lowest-energy electronic absorption of corresponding chromophores. Thus, the Urbach tail gives a direct measure of the population distribution of chromophores in crude oils. Implied population distributions are consistent with thermally activated growth of large chromophores from small ones. 12 refs., 8 figs.

  15. Nuclear quantum effects in the structure and lineshapes of the N2 NEXAFS spectrum

    SciTech Connect

    Fatehi, Shervin; Schwartz, Craig P.; Saykally, Richard J.; Prendergast, David

    2009-12-04

    We study the relative ability of several models of the X-ray absorption spectrum to capture the Franck-Condon structure apparent from an experiment on gaseous nitrogen. In doing so, we adopt the Born-Oppenheimer approximation and a constrained density functional theory method for computing the energies of the X-ray-excited molecule. Starting from an otherwise classical model for the spectrum, we systematically introduce more realistic physics, first by substituting the quantum mechanical nuclear radial density in the bond separation R for the classical radial density, then by adding the effect of zero-point energy and other level shifts, and finally by including explicit rovibrational quantization of both the ground and excited states. The quantization is determined exactly, using a discrete variable representation. We show that the NEXAFS spectrum can be predicted semiquantiatively within this framework. We also address the possibility of non-trivial temperature dependence in the spectrum. Finally, we show that it is possible to improve the predicted spectrum by using constrained DFT in combination with more accurate potentials.

  16. Primordial power spectrum from Planck

    NASA Astrophysics Data System (ADS)

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun

    2014-11-01

    Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near l ~ 750-850 represents the most prominent feature in the data. Feature near l ~ 1800-2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ~ 2.5%. In this context low-l and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.

  17. Primordial power spectrum from Planck

    SciTech Connect

    Hazra, Dhiraj Kumar; Shafieloo, Arman; Souradeep, Tarun E-mail: arman@apctp.org

    2014-11-01

    Using modified Richardson-Lucy algorithm we reconstruct the primordial power spectrum (PPS) from Planck Cosmic Microwave Background (CMB) temperature anisotropy data. In our analysis we use different combinations of angular power spectra from Planck to reconstruct the shape of the primordial power spectrum and locate possible features. Performing an extensive error analysis we found the dip near ℓ ∼ 750–850 represents the most prominent feature in the data. Feature near ℓ ∼ 1800–2000 is detectable with high confidence only in 217 GHz spectrum and is apparently consequence of a small systematic as described in the revised Planck 2013 papers. Fixing the background cosmological parameters and the foreground nuisance parameters to their best fit baseline values, we report that the best fit power law primordial power spectrum is consistent with the reconstructed form of the PPS at 2σ C.L. of the estimated errors (apart from the local features mentioned above). As a consistency test, we found the reconstructed primordial power spectrum from Planck temperature data can also substantially improve the fit to WMAP-9 angular power spectrum data (with respect to power-law form of the PPS) allowing an overall amplitude shift of ∼ 2.5%. In this context low-ℓ and 100 GHz spectrum from Planck which have proper overlap in the multipole range with WMAP data found to be completely consistent with WMAP-9 (allowing amplitude shift). As another important result of our analysis we do report the evidence of gravitational lensing through the reconstruction analysis. Finally we present two smooth form of the PPS containing only the important features. These smooth forms of PPS can provide significant improvements in fitting the data (with respect to the power law PPS) and can be helpful to give hints for inflationary model building.

  18. Clock shifts in a Fermi gas interacting with a minority component: A soluble model

    SciTech Connect

    Bruun, G. M.; Pethick, C. J.; Yu Zhenhua

    2010-03-15

    We consider the absorption spectrum of a Fermi gas mixed with a minority species when majority fermions are transferred to another internal state by an external probe. In the limit when the minority species is much more massive than the majority one, we show that the minority species may be treated as static impurities and the problem can be solved in closed form. The analytical results bring out the importance of vertex corrections, which change qualitatively the nature of the absorption spectrum. It is demonstrated that large line shifts are not associated with resonant interactions in general. We also show that the commonly used ladder approximation fails when the majority component is degenerate for large mass ratios between the minority and majority species and that bubble diagrams, which correspond to the creation of many particle-hole pairs, must be taken into account. We carry out detailed numerical calculations, which confirm the analytical insights, and we point out the connection to shadowing phenomena in nuclear physics.

  19. On the role of spatial position of bridged oxygen atoms as surface passivants on the ground-state gap and photo-absorption spectrum of silicon nano-crystals

    SciTech Connect

    Nazemi, Sanaz; Soleimani, Ebrahim Asl; Pourfath, Mahdi E-mail: pourfath@iue.tuwien.ac.at

    2015-11-28

    Silicon nano-crystals (NCs) are potential candidates for enhancing and tuning optical properties of silicon for optoelectronic and photo-voltaic applications. Due to the high surface-to-volume ratio, however, optical properties of NC result from the interplay of quantum confinement and surface effects. In this work, we show that both the spatial position of surface terminants and their relative positions have strong effects on NC properties as well. This is accomplished by investigating the ground-state HOMO-LUMO band-gap, the photo-absorption spectra, and the localization and overlap of HOMO and LUMO orbital densities for prototype ∼1.2 nm Si{sub 32–x}H{sub 42–2x}O{sub x} hydrogenated silicon NC with bridged oxygen atoms as surface terminations. It is demonstrated that the surface passivation geometry significantly alters the localization center and thus the overlap of frontier molecular orbitals, which correspondingly modifies the electronic and optical properties of NC.

  20. Solar Doppler shifts - Sources of continuous spectra

    NASA Technical Reports Server (NTRS)

    Duvall, T. L., Jr.; Harvey, J. W.

    1986-01-01

    Oscillation observations can be used to study nonoscillatory solar phenomena that exhibit Doppler shifts. The paper discusses several effects of these phenomena and their associated temporal and spatial power spectra: (1) they limit the signal-to-noise ratio and sometimes detectability of oscillation modes; (2) there is the potential for better understanding and/or detection of solar phenomena; (3) large-scale convection may spatially modulate oscillation modes, leading to a continuous background spectrum; and (4) in regions of the spectrum where the resolution to separate modes is lacking one can determine upper limits for the integrated effects of modes.

  1. Spectrum allocations above 40 GHz

    NASA Technical Reports Server (NTRS)

    Katzenstein, W. E.; Moore, R. P.; Kimball, H. G.

    1981-01-01

    The 1979 World Administrative Radio Conference (WARC-79) revised the International Table of Frequency Allocations to reflect increased interest and activity in the region of the EM spectrum above 40 GHz. The total width of the spectrum allocated (235 GHz) in the region above 40 GHz indicates the extent of this new spectrum resource, made accessible by advances in the state-of-the-art of telecommunications equipment. There are some striking differences between the approach to allocation above and below 40 GHz. For example, there are not bands allocated exclusively. This reflects the characteristics of propagation and the small antenna beamwidths achievable at these frequencies. Attention is given to atmospheric window and absorption band limits, allocations to satellite services, allocations to scientific services, allocations to terrestrial services, the future refinement of the radio regulations above 40 GHz, and allocations of WARC-79 and frequency management.

  2. Shifting scintillator neutron detector

    SciTech Connect

    Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

    2014-03-04

    Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

  3. Conduction-band electronic states of YbInCu{sub 4} studied by photoemission and soft x-ray absorption spectroscopies

    SciTech Connect

    Utsumi, Yuki; Kurihara, Hidenao; Maso, Hiroyuki; Tobimatsu, Komei; Sato, Hitoshi; Shimada, Kenya; Namatame, Hirofumi; Hiraoka, Koichi; Kojima, Kenichi; Ohkochi, Takuo; Fujimori, Shin-ichi; Takeda, Yukiharu; Saitoh, Yuji; Mimura, Kojiro; Ueda, Shigenori; Yamashita, Yoshiyuki; Yoshikawa, Hideki; Kobayashi, Keisuke; Oguchi, Tamio; Taniguchi, Masaki

    2011-09-15

    We have studied conduction-band (CB) electronic states of a typical valence-transition compound YbInCu{sub 4} by means of temperature-dependent hard x-ray photoemission spectroscopy (HX-PES) of the Cu 2p{sub 3/2} and In 3d{sub 5/2} core states taken at h{nu}=5.95 keV, soft x-ray absorption spectroscopy (XAS) of the Cu 2p{sub 3/2} core absorption region around h{nu}{approx}935 eV, and soft x-ray photoemission spectroscopy (SX-PES) of the valence band at the Cu 2p{sub 3/2} absorption edge of h{nu}=933.0 eV. With decreasing temperature below the valence transition at T{sub V}=42 K, we have found that (1) the Cu 2p{sub 3/2} and In 3d{sub 5/2} peaks in the HX-PES spectra exhibit the energy shift toward the lower binding-energy side by {approx}40 and {approx}30 meV, respectively, (2) an energy position of the Cu 2p{sub 3/2} main absorption peak in the XAS spectrum is shifted toward higher photon-energy side by {approx}100 meV, with an appearance of a shoulder structure below the Cu 2p{sub 3/2} main absorption peak, and (3) an intensity of the Cu L{sub 3}VV Auger spectrum is abruptly enhanced. These experimental results suggest that the Fermi level of the CB-derived density of states is shifted toward the lower binding-energy side. We have described the valence transition in YbInCu{sub 4} in terms of the charge transfer from the CB to Yb 4f states.

  4. Monopeptide versus Monopeptoid: Insights on Structure and Hydration of Aqueous Alanine and Sarcosine via X-ray Absorption Spectroscopy

    SciTech Connect

    Uejio, Janel S.; Schwartz, Craig P.; Duffin, Andrew M.; England, Alice; Prendergast, David; Saykally, Richard J.

    2009-11-19

    Despite the obvious significance, the aqueous interactions of peptides remain incompletely understood. Their synthetic analogues called peptoids (poly-N-substituted glycines), have recently emerged as a promising biomimetic material, particularly due to their robust secondary structure and resistance to denaturation. We describe comparative near-edge x-ray absorption fine structure (NEXAFS) spectroscopy studies of aqueous sarcosine, the simplest peptoid, and alanine, its peptide isomer, interpreted by density functional theory calculations. The sarcosine nitrogen K-edge spectrum is blue-shifted with respect to that of alanine, in agreement with our calculations; we conclude that this shift results primarily from the methyl group substitution on the nitrogen of sarcosine. Our calculations indicate that the nitrogen K-edge spectrum of alanine differs significantly between dehydrated and hydrated scenarios, while that of the sarcosine zwitterion is less affected by hydration. In contrast, the computed sarcosine spectrum is greatly impacted by conformational variations, while the alanine spectrum is not. This relates to a predicted solvent dependence for alanine, as compared to sarcosine. Additionally, we show the theoretical nitrogen K-edge spectra to be sensitive to the degree of hydration, indicating that experimental X-ray spectroscopy may be able to distinguish between bulk and partial hydration, such as found in confined environments near proteins and in reverse micelles.

  5. [Spectral Calibration of Space-born Imaging Spectrometers Using Spectrum-Matching Technique].

    PubMed

    Zhao, Min-jie; Si, Fu-qi; Lu, Yi-huai; Wang, Yu; Wang, Shi-mei; Jiang, Yu; Zhou, Hai-jin; Liu, Wen-qing

    2015-07-01

    Spectral calibration of space-born imaging spectrometers based on spectrum-matching technique is presented, which adopts atmospheric absorption lines as the matching lines, and chooses correlation coefficient method as the criteria. In order to simulation the onboard spectral calibration, the spectrum-matching technique is applied on the imaging spectrometers that after the vibration test. The vibration test is able to simulation the launching. The spectral resolution, center wavelength of two-dimensional pixel is determined during onboard spectral calibration. As the calibration results show, the spectral resolution of imaging spectrometers after the vibration test is 0.40 nm, it is the same comparing to the value before the vibration, the wavelength shifts 0.08 nm towards the long wave for the spectral pixels, and the spectral smile is determined for all spatial elements, which shifts towards the short wave direction, with the max smile value is 0.96 nm, the result is similar to that before the vibration. As a result, the spectrum-matching technique is tested and verified. PMID:26717777

  6. Temperature-dependent excitonic photoluminescence excited by two-photon absorption in perovskite CsPbBr3 quantum dots.

    PubMed

    Wei, Ke; Xu, Zhongjie; Chen, Runze; Zheng, Xin; Cheng, Xiangai; Jiang, Tian

    2016-08-15

    Recently, lead halide perovskite quantum dots have been reported with potential for photovoltaic and optoelectronic applications due to their excellent luminescent properties. Herein excitonic photoluminescence (PL) excited by two-photon absorption in perovskite CsPbBr3 quantum dots (QDs) has been studied at a broad temperature range, from 80 to 380 K. Two-photon absorption has been investigated and the absorption coefficient is up to 0.085 cm/GW at room temperature. Moreover, the PL spectrum excited by two-photon absorption shows a linear blue-shift (0.32 meV/K) below the temperature of 220 K. However, for higher temperatures, the PL peak approaches a roughly constant value and shows temperature-independent chromaticity up to 380 K. This behavior is distinct from the general red-shift for semiconductors and can be attributed to the result of thermal expansion, electron-phonon interaction and structural phase transition around 360 K. The strong nonlinear absorption and temperature-independent chromaticity of CsPbBr3 QDs observed in temperature range from 220 to 380 K will offer new opportunities in nonlinear photonics, light-harvesting, and light-emitting devices. PMID:27519098

  7. Solvent stark effects and spectral shifts. II

    SciTech Connect

    Nicol, M; Swain, J; Shum, Y Y; Merin, R; Chen, R H.H.

    1981-03-01

    Solvent shifts of the energies of the lowest /sup 1/L/sub a/ bands of the electronic absorption spectra of anthracene, chrysene, phenanthrene, and tetracene and of the lowest /sup 1/L/sub b/ bands of the electronic absorption spectra of naphthalene, phenanthrene, chrysene, and picene are reported. The origins of these shifts are analyzed in terms of theories developed by Baur and Nicol and by Abe. Satisfactory fits of the experimental data are obtained for theoretical expressions derived from both theories, but discrepancies are observed between the relative magnitudes assigned to the various contributions to the shifts by the two theories. The magnitudes of the parameters of the Baur and Nicol theory, relating solvent shifts to the dielectric constant and refractive index of the solvent, are found to be the same within experimental precision for the /sup 1/L/sub a/ transitions in all of the molecules studied; a similar regularity of the parameters for the /sup 1/L/sub b/ transitions also is observed.

  8. Spectral shifting by dyes to enhance algae growth.

    PubMed

    Prokop, A; Quinn, M F; Fekri, M; Murad, M; Ahmed, S A

    1984-11-01

    The photosynthetic growth action spectrum of a green alga at three bands of visible light (blue, orange, and red) at fixed quanta input and under light-limiting conditions was measured in a batch cultivation system. Quantum efficiencies (biomass dry weight increment per quanta absorbed) were better in the yellow-red region than in the blue region. Results served as a basis for the design and optimization of a dye system that would shift the energy of solar radiation to the required wavelength range by absorbing ultraviolet to blue radiation and emitting in the yellow-red, thus enhancing algae growth. Direct incorporation of dyes into the growth medium, although theoretically expected to enhance growth, in fact resulted in dye decomposition, toxicity to algae and consequently in growth inhibition. Indirect application of dyes in a double tubular reactor (algae inside and dye solution outside) demonstrated growth enhancement for certain dyes with high quantum yields and stability, which had suitable absorption/emission spectra for artificial light sources used. The maximum indirect growth enhancement was obtained using rhodamine 6G at a concentration of 3x10(-5)M with tungsten filament lamp sources. PMID:18551655

  9. The first UV absorption band of l-tryptophan is not due to two simultaneous orthogonal electronic transitions differing in the dipole moment.

    PubMed

    Catalán, Javier

    2016-06-01

    Based on UV/Vis spectroscopic evidence obtained in this work, the first band in the absorption spectrum of l-tryptophan is largely due to a single electronic transition from the ground state to the (1)Lb excited state. However, emission spectra of this compound recorded at a variable temperature in ethanol, n-butanol and diethyl ether are structureless and considerably red-shifted at room temperature; also, lowering the temperature causes the emission to become structured and to undergo such a strong blue shift that it appears to be due to the (1)Lb state of the compound. Based on these findings, the formation (from the excited (1)Lb state) of the excited state responsible for the structureless, markedly red-shifted emission in l-tryptophan is strongly dependent not only on the viscosity of the medium, but also on its dipolarity. PMID:27197597

  10. Demonstrating Absorption Spectra Using Commercially Available Incandescent Light Bulbs

    NASA Astrophysics Data System (ADS)

    Birriel, Jennifer J.

    In introductory astronomy courses, I typically introduce the three types of spectra: continuous, absorption line, and emission line. It is standard practice to use an ordinary incandescent light bulb to demonstrate the production of a continuous spectrum, and gas discharge tubes to demonstrate the production of an emission line spectrum. The concept of an absorption spectrum is more difficult for students to grasp. A variety of commercially available light bulbs can be used to demonstrate absorption spectra. Here I discuss the use of specialty incandescent light bulbs to demonstrate the phenomenon of absorption of the continuous spectrum produced by a hot tungsten filament. The bulbs examined include the GE Reveal bulb, yellow anti-insect lights, colored party bulbs, and an incandescent "black light" bulb. The bulbs can be used in a lecture or laboratory setting.

  11. Our World: Fluid Shift

    NASA Video Gallery

    Learn about the circulatory system and how gravity aids blood flow in our bodies here on Earth. Find out how NASA flight surgeons help the astronauts deal with the fluid shift that happens during s...

  12. Shape-Shifting Plastic

    SciTech Connect

    2015-05-20

    A new plastic developed by ORNL and Washington State University transforms from its original shape through a series of temporary shapes and returns to its initial form. The shape-shifting process is controlled through changes in temperature

  13. Molecular Electronic Shift Registers

    NASA Technical Reports Server (NTRS)

    Beratan, David N.; Onuchic, Jose N.

    1990-01-01

    Molecular-scale shift registers eventually constructed as parts of high-density integrated memory circuits. In principle, variety of organic molecules makes possible large number of different configurations and modes of operation for such shift-register devices. Several classes of devices and implementations in some specific types of molecules proposed. All based on transfer of electrons or holes along chains of repeating molecular units.

  14. Computation of Mössbauer isomer shifts from first principles

    NASA Astrophysics Data System (ADS)

    Zwanziger, J. W.

    2009-05-01

    Computation of the observables of a Mössbauer spectrum, primarily the isomer shift, from a first-principles approach is described. The framework used is density functional theory using the projector augmented wave formalism (DFT PAW), which enables efficient computation even of many-electron solids such as SnCl2. The proper PAW version of the isomer shift is derived and shown to be correct through comparison of computed shifts and experiment in a variety of compounds based on tin, germanium and zinc. The effects of pressure are considered as well as motional effects including the Lamb-Mössbauer factor and the second-order Doppler shift.

  15. Effects of backlight structure on absorption experiments

    SciTech Connect

    Iglesias, C A

    2004-11-08

    The impact of spectral details in the backlight of absorption spectroscopy experiments is considered. It is shown that experimentally unresolved structure in the backlight spectrum can introduce significant errors in the inferred transmission. Furthermore, it is shown that a valuable experimental procedure previously used to test the accuracy of the data fails to reveal these errors.

  16. [A method for resolving spectra shift in the urban air quality monitoring system (DOAS)].

    PubMed

    Liu, Shi-Sheng; Wei, Qing-Nong; Feng, Wei-Wei; Zhan, Kai; Wang, Feng-Ping

    2009-06-01

    In the urban air quality monitoring system, there is spectra shift which is caused by environment factors on the optical part (temperature and optic fiber position), or by the self-change of Xe-lamp. Relative spectra shift will occur if the shift of lamp-spectrum and air-spectrum is inconsistent which has direct influences on the accuracy of the measurement results. So the match of wavelength between lamp-spectrum and air-spectrum should be considered when we retrieve pollutants concentration measurement of trace gas in the atmosphere through DOAS method. Based on the study of the unique structures for Xe-lamp emitting spectrum, a method for the calibration of two signal spectra using Xe-lamp emitting peak and least square fitting is given. The results show that, the impact of spectrum shift can be reduced by this method for retrieving results. PMID:19810506

  17. The HI absorption "Zoo"

    NASA Astrophysics Data System (ADS)

    Geréb, K.; Maccagni, F. M.; Morganti, R.; Oosterloo, T. A.

    2015-03-01

    We present an analysis of the H I 21 cm absorption in a sample of 101 flux-selected radio AGN (S1.4 GHz> 50 mJy) observed with the Westerbork Synthesis Radio Telescope (WSRT). We detect H I absorption in 32 objects (30% of the sample). In a previous paper, we performed a spectral stacking analysis on the radio sources, while here we characterize the absorption spectra of the individual detections using the recently presented busy function. The H I absorption spectra show a broad variety of widths, shapes, and kinematical properties. The full width half maximum (FWHM) of the busy function fits of the detected H I lines lies in the range 32 km s-1absorption (FW20) lies in the range 63 km s-1 200 km s-1). We study the kinematical and radio source properties of each group, with the goal of identifying different morphological structures of H I. Narrow lines mostly lie at the systemic velocity and are likely produced by regularly rotating H I disks or gas clouds. More H I disks can be present among galaxies with lines of intermediate widths; however, the H I in these sources is more unsettled. We study the asymmetry parameter and blueshift/redshift distribution of the lines as a function of their width. We find a trend for which narrow profiles are also symmetric, while broad lines are the most asymmetric. Among the broadest lines, more lines appear blueshifted than redshifted, similarly to what was found by previous studies. Interestingly, symmetric broad lines are absent from the sample. We argue that if a profile is broad, it is also asymmetric and shifted relative to the systemic velocity because it is tracing unsettled H I gas. In particular, besides three of the broadest (up to FW20 = 825 km s-1

  18. The bispectrum of the Lyman α forest at z~ 2-2.4 from a large sample of UVES QSO absorption spectra (LUQAS)

    NASA Astrophysics Data System (ADS)

    Viel, M.; Matarrese, S.; Heavens, A.; Haehnelt, M. G.; Kim, T.-S.; Springel, V.; Hernquist, L.

    2004-01-01

    We present a determination of the bispectrum of the flux in the Lyman α forest of quasi-stellar object (QSO) absorption spectra obtained from a large sample of Ultraviolet Echelle Spectrograph (UVES) QSO absorption spectra (LUQAS), which consists of spectra observed with the high-resolution UVES. Typical errors on the observed bispectrum as obtained from a jack-knife estimator are ~ 50 per cent. For wavenumbers in the range 0.03 < k < 0.1 s km-1 the observed bispectrum agrees within the errors with that of the synthetic absorption spectra obtained from numerical hydro-simulations of a ΛCDM model with and without feedback from star formation. Including galactic feedback changes the bispectrum by less than 10 per cent. At smaller wavenumbers, the associated metal absorption lines contribute about 50 per cent to the bispectrum and the observed bispectrum exceeds that of the simulations. At wavenumbers k < 0.03 s km-1, second-order perturbation theory applied to the flux spectrum gives a reasonable (errors smaller than 30 per cent) approximation to the bispectra of observed and simulated absorption spectra. The bispectrum of the observed absorption spectra also agrees, within the errors, with that of a randomized set of absorption spectra where a random shift in wavelength has been added to absorption lines identified with VPFIT. This suggests that for a sample of the size presented here, the errors on the bispectrum are too large to discriminate between models with very different 3D distribution of Lyman α absorption. If it were possible to substantially reduce these errors for larger samples of absorption spectra, the bispectrum might become an important statistical tool for probing the growth of gravitational structure in the Universe at redshift z>~ 2.

  19. Energy spectrum of C60 fullerene

    NASA Astrophysics Data System (ADS)

    Mironov, G. I.; Murzashev, A. I.

    2011-11-01

    The energy spectrum of the C60 fullerene has been calculated in terms of the Shubin-Vonsovskii-Hubbard model using an approximation of static fluctuations. Based on the spectrum, the optical absorption bands at 4.84, 5.88, and 6.30 eV observed experimentally have been successfully explained. It has been concluded that the model used is applicable for the calculation of the energy spectrum and the energy properties of other nanosystems, such as fullerenes of higher orders, carbon nanotubes, and grafen planes.

  20. Ultrafast Relaxation of the Poly(3-hexylthiophene) Emission Spectrum

    SciTech Connect

    Banerji, Natalie; Cowan, Sarah; Vauthey, Eric; Heeger, Alan J.

    2011-05-19

    The femtosecond-resolved evolution of the emission spectrum of the important conjugated polymer poly(3-hexylthiophene) (P3HT) is presented. Detailed fluorescence up-conversion spectroscopy was performed on P3HT solidstate films and on P3HT in chlorobenzene solution. Two excitation wavelengths and several emission wavelengths, covering the entire fluorescence spectrum, were used. The data were complemented by polarization-sensitive measurements. Our global analysis allowed a reconstruction of the time-resolved emission spectra with 200 fs temporal resolution, so that spectral changes due to the early relaxation processes following π π* interband absorption in the pristine polymer could be comprehensively characterized. Absorption occurs in isolated polymer chains in solution and in the solid state (including interchain interactions) for the film. In both cases, we find evidence of delocalization of the electrons and holes formed in the energy bands directly after photoexcitation with excess energy. This is followed by ultrafast (~100 fs) self-localization of the primary photoexcitation and by relatively slow exciton formation (~1 ps). Further relaxation occurs with time constants ranging from hundreds of femtoseconds to tens of picoseconds, due to exciton hopping to sites with lower energy and to a slow conformational planarization of the polymer backbone. Depolarization, a spectral red shift, and important changes in the vibronic structure are observed as a consequence of this relaxation. Finally, relaxed intrachain and interchain singlet excitons are formed in solution and film, respectively, on a 100 200 ps time scale. They decay with a ~500 ps time constant, by intersystem crossing in solution and by nonradiative recombination in the film. Our results are consistent with and strongly support the conclusions we obtained from a similar time-resolved fluorescence study of the polymer PCDTBT (J. Am. Chem. Soc. 2010, 132, 17459): ultrafast charge separation in

  1. Photocycles of bacteriorhodopsin in light- and dark-adapted purple membrane studied by time-resolved absorption spectroscopy.

    PubMed Central

    Hofrichter, J; Henry, E R; Lozier, R H

    1989-01-01

    Nanosecond time-resolved absorption spectra have been measured throughout the photocycle of bacteriorhodopsin in both light-adapted and dark-adapted purple membrane (PM). The data from dark-adapted samples are interpretable as the superposition of two photocycles arising independently from the all-trans and 13-cis retinal isomers that coexist in the dark-adapted state. The presence of a photocycle in dark-adapted PM which is indistinguishable from that observed for light-adapted PM under the same experimental conditions is demonstrated by the observation of the same five relaxation rates associated with essentially identical changes in the photoproduct spectra. This cycle is attributed to the all-trans component. The cycle of the 13-cis component is revealed by scaling the data measured for the light-adapted sample and subtracting it from the data on the dark-adapted mixture. At times less than 1 ms, the resulting difference spectra are nearly time-independent. The peak of the difference spectrum is near 600 nm, although there appears to be a slight (approximately 2 nm) blue-shift in the first few microseconds. Subsequently the amplitude of this spectrum decays and the peak of the difference spectrum shifts in two relaxations. Most of the amplitude of the photoproduct difference spectrum (approximately 80%) decays in a single relaxation having a time constant of approximately 35 ms. The difference spectrum remaining after this relaxation peaks at approximately 590 nm and is indistinguishable from the classical light-dark difference spectrum, which we find, in experiments performed on a much longer time scale, to peak at 588 nm. The decay of this remaining photo-product is not resolvable in the nanosecond kinetic experiments, but dark adaptation of a completely light-adapted sample is found to occur exponentially with a relaxation time of approximately 2,000 s under the conditions of our experiments. PMID:2819234

  2. Infra-red absorption lines by molecules in grain mantles

    NASA Astrophysics Data System (ADS)

    Hagen, W.; Allamandola, L. J.; Greenberg, J. M.

    1980-06-01

    The laboratory spectrum of a solid mixture of H2O, CO, CH3OH, and NH3 at a temperature of 10 K reproduces the shape and peak positions of interstellar features. It is shown that the broad absorption features evident in the MIR spectra of some astronomical objects associated with interstellar dust can be explained by absorptions of molecules in grain mantles.

  3. Two-dimensional probe absorption in coupled quantum dots

    NASA Astrophysics Data System (ADS)

    Liu, Ningwu; Zhang, Yan; Kang, Chengxian; Wang, Zhiping; Yu, Benli

    2016-07-01

    We investigate the two-dimensional (2D) probe absorption in coupled quantum dots. It is found that, due to the position-dependent quantum interference effect, the 2D optical absorption spectrum can be easily controlled via adjusting the system parameters. Thus, our scheme may provide some technological applications in solid-state quantum communication.

  4. Predicting catastrophic shifts.

    PubMed

    Weissmann, Haim; Shnerb, Nadav M

    2016-05-21

    Catastrophic shifts are known to pose a serious threat to ecology, and a reliable set of early warning indicators is desperately needed. However, the tools suggested so far have two problems. First, they cannot discriminate between a smooth transition and an imminent irreversible shift. Second, they aimed at predicting the tipping point where a state loses its stability, but in noisy spatial system the actual transition occurs when an alternative state invades. Here we suggest a cluster tracking technique that solves both problems, distinguishing between smooth and catastrophic transitions and to identify an imminent shift in both cases. Our method may allow for the prediction, and thus hopefully the prevention of such transitions, avoiding their destructive outcomes. PMID:26970446

  5. Isotope shift in chromium

    NASA Astrophysics Data System (ADS)

    Furmann, B.; Jarosz, A.; Stefańska, D.; Dembczyński, J.; Stachowska, E.

    2005-01-01

    Thirty-three spectral lines of chromium atom in the blue-violet region (425-465 nm) have been investigated with the method of laser-induced resonance fluorescence on an atomic beam. For all the lines, the isotope shifts for every pair of chromium isotopes have been determined. The lines can be divided into six groups, according to the configuration of the upper and lower levels. Electronic factors of the field shift and the specific mass shift ( Fik and MikSMS, respectively) have been evaluated and the values for each pure configuration involved have been determined. Comparison of the values Fik and MikSMS to the ab initio calculations results has been performed. The presence of crossed second order (CSO) effects has been observed.

  6. Quantum theory of the mazer. III. Spectrum

    NASA Astrophysics Data System (ADS)

    Schröder, Michael; Vogel, Karl; Schleich, Wolfgang P.; Scully, Marlan O.; Walther, Herbert

    1997-11-01

    We calculate the spectrum of the micromaser with quantized motion of the pump atoms [M. O. Scully, G. M. Meyer, and H. Walther, Phys. Rev. Lett. 76, 4144 (1996)] in different velocity regimes. We show that when the kinetic energy of the pump atoms is comparable to the atom-field interaction energy the spectrum of the cavity field is no longer centered at the cavity frequency. In the case of very slow atoms huge broadenings and shifts occur in the vicinity of the mazer resonances. We present approximate analytical results for the spectrum that allow a comparison with the exact numerical calculations.

  7. Differential phase shift of partially reflected radio waves.

    NASA Technical Reports Server (NTRS)

    Connolly, D. J.

    1971-01-01

    The addition of phase difference measurements to differential absorption experiments is shown to be both feasible and desirable. The phase information can provide a more sensitive measurement of electron density above about 75 km. The differential phase shift is only weakly dependent on collision frequency in this range, and so an accurate collision frequency profile is not a prerequisite. The differential phase shift and differential absorption measurements taken together can provide both electron density and collision frequency data from about 70 to 90 km.

  8. Autism Spectrum Disorder

    MedlinePlus

    ... Awards Enhancing Diversity Find People About NINDS NINDS Autism Spectrum Disorder Information Page Condensed from Autism Spectrum ... en Español Additional resources from MedlinePlus What is Autism Spectrum Disorder? Autistic disorder (sometimes called autism or ...

  9. Spectral analysis on origination of the bands at 437 nm and 475.5 nm of chlorophyll fluorescence excitation spectrum in Arabidopsis chloroplasts.

    PubMed

    Zeng, Lizhang; Wang, Yongqiang; Zhou, Jun

    2016-05-01

    Chlorophyll fluorescence has been often used as an intrinsic optical molecular probe to study photosynthesis. In this study, the origin of bands at 437 and 475.5 nm in the chlorophyll fluorescence excitation spectrum for emission at 685 nm in Arabidopsis chloroplasts was investigated using various optical analysis methods. The results revealed that this fluorescence excitation spectrum was related to the absorption characteristics of pigment molecules in PSII complexes. Moreover, the excitation band centred at 475.5 nm had a blue shift, but the excitation band at 437 nm changed relatively less due to induction of non-photochemical quenching (NPQ). Furthermore, fluorescence emission spectra showed that this blue shift occurred when excitation energy transfer from both chlorophyll b (Chl b) and carotenoids (Cars) to chlorophyll a (Chl a) was blocked. These results demonstrate that the excitation band at 437 nm was mainly contributed by Chl a, while the excitation band at 475.5 nm was mainly contributed by Chl b and Cars. The chlorophyll fluorescence excitation spectrum, therefore, could serve as a useful tool to describe specific characteristics of light absorption and energy transfer between light-harvesting pigments. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26358732

  10. Broad spectrum bioactive sunscreens.

    PubMed

    Velasco, Maria Valéria Robles; Sarruf, Fernanda Daud; Salgado-Santos, Idalina Maria Nunes; Haroutiounian-Filho, Carlos Alberto; Kaneko, Telma Mary; Baby, André Rolim

    2008-11-01

    The development of sunscreens containing reduced concentration of chemical UV filters, even though, possessing broad spectrum effectiveness with the use of natural raw materials that improve and infer UV absorption is of great interest. Due to the structural similarities between polyphenolic compounds and organic UV filters, they might exert photoprotection activity. The objective of the present research work was to develop bioactive sunscreen delivery systems containing rutin, Passiflora incarnata L. and Plantago lanceolata extracts associated or not with organic and inorganic UV filters. UV transmission of the sunscreen delivery system films was performed by using diffuse transmittance measurements coupling to an integrating sphere. In vitro photoprotection efficacy was evaluated according to the following parameters: estimated sun protection factor (SPF); Boot's Star Rating category; UVA/UVB ratio; and critical wavelength (lambda(c)). Sunscreen delivery systems obtained SPF values ranging from 0.972+/-0.004 to 28.064+/-2.429 and bioactive compounds interacted with the UV filters positive and negatively. This behavior may be attributed to: the composition of the delivery system; the presence of inorganic UV filter and quantitative composition of the organic UV filters; and the phytochemical composition of the P. incarnata L. and P. lanceolata extracts. Among all associations of bioactive compounds and UV filters, we found that the broad spectrum sunscreen was accomplished when 1.68% (w/w) P. incarnata L. dry extract was in the presence of 7.0% (w/w) ethylhexyl methoxycinnamate, 2.0% (w/w) benzophenone-3 and 2.0% (w/w) TiO(2). It was demonstrated that this association generated estimated SPF of 20.072+/-0.906 and it has improved the protective defense against UVA radiation accompanying augmentation of the UVA/UVB ratio from 0.49 to 0.52 and lambda(c) from 364 to 368.6nm. PMID:18662760

  11. The structure of the aggregate form of bacteriochlorophyll c showing the Q y absorption above 740 nm: a 1H-NMR study

    NASA Astrophysics Data System (ADS)

    Mizoguchi, Tadashi; Matsuura, Katsumi; Shimada, Keizo; Koyama, Yasushi

    1996-09-01

    Bacteriochlorophyll c (3 1S, 8-isobutyl-12-ethyl, farnesyl) was dissolved in a mixture of methylene chloride and carbon tetrachloride (1 : 3), and changes in the 1H-NMR spectrum caused by the titration of methanol were traced. On the basis of the changes in chemical shift due to the ring-current effect of the neighboring macrocycles and in peak intensity (broadening) due to their stacking, the structure of the aggregate form showing the Q y absorption band above 740 nm is proposed: the macrocycles are stacked to form a one-dimensional inclined column, the y axis of each macrocycle being parallel to the long axis of the column.

  12. Deimos: A featureless asteroid-like spectrum

    NASA Technical Reports Server (NTRS)

    Grundy, W. M.; Fink, Uwe

    1991-01-01

    High quality CCD spectra were obtained of Deimos from 0.5 to 1.0 micron at a spectral resolution of 15A at the time of the 1988 Mars opposition. The data acquisition and reduction methods allowed the quantitative prevention of scattered light from Mars contaminating the spectra. Solar analog stars BS560, BS2007, and BS8931 were observed the same night to allow removal of telluric absorptions. The ratio spectrum of Deimos has a red slope, increasing in reflectance by a factor of approx. 50 pct. over the one octave wavelength interval observed. Other than this slope, the spectrum is remarkably featureless. The absence of absorption bands in the spectrum of Deimos is in marked contrast with the spectra of Martian surface materials. No trace of the Fe(2+) charge transfer absorption band around 1 micron is observed, which rules out the presence of significant quantities of minerals such as the pyroxenes or olivine at the surface of Deimos. The featureless red spectrum of Deimos appears to be consistent with a surface composition of fine grained carbonaceous chondrite type material. An analysis is presented of the spectrum of Deimos which makes use of the Hapke scattering surface model.

  13. Shifting Up a Gear.

    ERIC Educational Resources Information Center

    Palmer, Martin

    1997-01-01

    Shift workers are often excluded from educational opportunities on and off the job. General education and leisure learning needs are addressed less than job-specific training needs. Providers should consider open/distance learning, creative marketing, targeted funding, and consortia of employer-developed programs. (SK)

  14. Eluding catastrophic shifts

    PubMed Central

    Villa Martín, Paula; Bonachela, Juan A.; Levin, Simon A.; Muñoz, Miguel A.

    2015-01-01

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences. PMID:25825772

  15. Eluding catastrophic shifts.

    PubMed

    Villa Martín, Paula; Bonachela, Juan A; Levin, Simon A; Muñoz, Miguel A

    2015-04-14

    Transitions between regimes with radically different properties are ubiquitous in nature. Such transitions can occur either smoothly or in an abrupt and catastrophic fashion. Important examples of the latter can be found in ecology, climate sciences, and economics, to name a few, where regime shifts have catastrophic consequences that are mostly irreversible (e.g., desertification, coral reef collapses, and market crashes). Predicting and preventing these abrupt transitions remains a challenging and important task. Usually, simple deterministic equations are used to model and rationalize these complex situations. However, stochastic effects might have a profound effect. Here we use 1D and 2D spatially explicit models to show that intrinsic (demographic) stochasticity can alter deterministic predictions dramatically, especially in the presence of other realistic features such as limited mobility or spatial heterogeneity. In particular, these ingredients can alter the possibility of catastrophic shifts by giving rise to much smoother and easily reversible continuous ones. The ideas presented here can help further understand catastrophic shifts and contribute to the discussion about the possibility of preventing such shifts to minimize their disruptive ecological, economic, and societal consequences. PMID:25825772

  16. Trophic shift, not collapse

    USGS Publications Warehouse

    Madenjian, Charles P.; Rutherford, Edward S.; Stow, Craig A.; Roseman, Edward F.; He, Ji X.

    2013-01-01

    scientists who are closely monitoring Lake Huron’s food web, we believe that the ongoing changes are more accurately characterized as a trophic shift in which benthic pathways have become more prominent. While decreases in abundance have occurred for some species, others are experiencing improved reproduction resulting in the restoration of several important native species.

  17. IR absorption and reflectometric interference spectroscopy (RIfS) combined to a new sensing approach for gas analytes absorbed into thin polymer films.

    PubMed

    Leopold, Nicolae; Busche, Stefan; Gauglitz, Günter; Lendl, Bernhard

    2009-06-01

    Hydrophobic polymer layers (3 microm) were spin-coated on Si or Ge plates and placed in a flow through gas chamber. FTIR reflection spectra of the layers were recorded showing the characteristic IR absorption bands of the polymer and the interference pattern generated by layered structure of the polymer film. Upon exposure of the polymer layer to gaseous analytes enrichment in the polymer film occurred. This was evidenced by the appearance of analyte specific absorption particular in the mid-IR part of the spectrum, as well as by a shift in the interference pattern across the whole spectrum. Qualitative information concerning the analyte was accessible in the mid-IR part of the spectrum, whereas quantitative assessment was obtained from the interference pattern. Polyetherurethane, polydimethylsiloxane, Makrolon and polyisobutylene polymer layers were tested for such IR-RIfS measurements, whereas toluene, o-dichlorobenzene, m-xylene, ethyl acetate and cyclohexane were employed as analytes. There was no influence of water vapour neither on the IR absorptions nor the interference pattern as hydrophobic polymers were used. PMID:19233714

  18. IR absorption and reflectometric interference spectroscopy (RIfS) combined to a new sensing approach for gas analytes absorbed into thin polymer films

    NASA Astrophysics Data System (ADS)

    Leopold, Nicolae; Busche, Stefan; Gauglitz, Günter; Lendl, Bernhard

    2009-06-01

    Hydrophobic polymer layers (3 μm) were spin-coated on Si or Ge plates and placed in a flow through gas chamber. FTIR reflection spectra of the layers were recorded showing the characteristic IR absorption bands of the polymer and the interference pattern generated by layered structure of the polymer film. Upon exposure of the polymer layer to gaseous analytes enrichment in the polymer film occurred. This was evidenced by the appearance of analyte specific absorption particular in the mid-IR part of the spectrum, as well as by a shift in the interference pattern across the whole spectrum. Qualitative information concerning the analyte was accessible in the mid-IR part of the spectrum, whereas quantitative assessment was obtained from the interference pattern. Polyetherurethane, polydimethylsiloxane, Makrolon ® and polyisobutylene polymer layers were tested for such IR-RIfS measurements, whereas toluene, o-dichlorobenzene, m-xylene, ethyl acetate and cyclohexane were employed as analytes. There was no influence of water vapour neither on the IR absorptions nor the interference pattern as hydrophobic polymers were used.

  19. Absorption of waves by large-scale winds in stratified turbulence.

    PubMed

    Clark di Leoni, P; Mininni, P D

    2015-03-01

    The atmosphere is a nonlinear stratified fluid in which internal gravity waves are present. These waves interact with the flow, resulting in wave turbulence that displays important differences with the turbulence observed in isotropic and homogeneous flows. We study numerically the role of these waves and their interaction with the large-scale flow, consisting of vertically sheared horizontal winds. We calculate their space- and time-resolved energy spectrum (a four-dimensional spectrum) and show that most of the energy is concentrated along a dispersion relation that is Doppler shifted by the horizontal winds. We also observe that when uniform winds are let to develop in each horizontal layer of the flow, waves whose phase velocity is equal to the horizontal wind speed have negligible energy. This indicates a nonlocal transfer of their energy to the mean flow. Both phenomena, the Doppler shift and the absorption of waves traveling with the wind speed, are not accounted for in current theories of stratified wave turbulence. PMID:25871210

  20. Estimation of molar absorptivities and pigment sizes for eumelanin and pheomelanin using femtosecond transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Piletic, Ivan R.; Matthews, Thomas E.; Warren, Warren S.

    2009-11-01

    Fundamental optical and structural properties of melanins are not well understood due to their poor solubility characteristics and the chemical disorder present during biomolecular synthesis. We apply nonlinear transient absorption spectroscopy to quantify molar absorptivities for eumelanin and pheomelanin and thereby get an estimate for their average pigment sizes. We determine that pheomelanin exhibits a larger molar absorptivity at near IR wavelengths (750nm), which may be extended to shorter wavelengths. Using the molar absorptivities, we estimate that melanin pigments contain ˜46 and 28 monomer units for eumelanin and pheomelanin, respectively. This is considerably larger than the oligomeric species that have been recently proposed to account for the absorption spectrum of eumelanin and illustrates that larger pigments comprise a significant fraction of the pigment distribution.

  1. Design and synthesis of liquid crystals with controlled absorption properties in the midwave infrared region

    NASA Astrophysics Data System (ADS)

    Tripathi, Suvagata

    The infrared region of electromagnetic radiation is attractive for communication applications as the scattering is lower compared to that in the visible spectrum. Infrared lasers are widely used in bar-code scanners, laser rangefinders and topology mapping applications. Typically, the direction of a laser beam is altered by mechanically moving a mirror or a lens. But this process can impose severe limitations on critical performance parameters (longevity, precision, response time etc.) of the device. Thus, electro-optic control of the direction of the beam is highly desired. Commercial liquid crystals (LCs) are less than ideal for this purpose because they almost invariably have several absorption bands in the infrared region. For example, several absorption bands exist in the mid-infrared region (3-5 mum) due to common structure features found in LCs such as CH, CH 2, CH3 and CN. In the off-resonance regions, the baseline absorption coefficient can take very high value (up to alpha ~10/cm). This absorption loss becomes especially significant if the optical path is long. As the molecular vibration frequency (o) depends upon the spring constant (kappa) and the effective mass (m) of a diatomic group by the equation = √(kappa/m), replacement of hydrogen atoms in a molecule with heavier atoms can shift the absorptions to the far infrared region, thus making the midwave infrared region more transparent. Another strategy has been to develop high birefringence LCs so that lower liquid crystal cell gap can be used, thus minimizing the absorption loss due to the LC layer. But most of these materials have problems with UV stability. In the scope of this thesis, several strategies are investigated to mitigate the absorption loss in the midwave infrared region. The ultimate goal of this thesis is to develop LCs that will have both high birefringence and low absorption properties in the midwave-infrared region. Another goal of the thesis is to develop materials for

  2. Onset of the Electronic Absorption Spectra of Isolated and π-Stacked Oligomers of 5,6-Dihydroxyindole: An Ab Initio Study of the Building Blocks of Eumelanin.

    PubMed

    Tuna, Deniz; Udvarhelyi, Anikó; Sobolewski, Andrzej L; Domcke, Wolfgang; Domratcheva, Tatiana

    2016-04-14

    Eumelanin is a naturally occurring skin pigment which is responsible for developing a suntan. The complex structure of eumelanin consists of π-stacked oligomers of various indole derivatives, such as the monomeric building block 5,6-dihydroxyindole (DHI). In this work, we present an ab initio wave-function study of the absorption behavior of DHI oligomers and of doubly and triply π-stacked species of these oligomers. We have simulated the onset of the electronic absorption spectra by employing the MP2 and the linear-response CC2 methods. Our results demonstrate the effect of an increasing degree of oligomerization of DHI and of an increasing degree of π-stacking of DHI oligomers on the onset of the absorption spectra and on the degree of red-shift toward the visible region of the spectrum. We find that π-stacking of DHI and its oligomers substantially red-shifts the onset of the absorption spectra. Our results also suggest that the optical properties of biological eumelanin cannot be simulated by considering the DHI building blocks alone, but instead the building blocks indole-semiquinone and indole-quinone have to be considered as well. This study contributes to advancing the understanding of the complex photophysics of the eumelanin biopolymer. PMID:27005558

  3. Simulating One-Photon Absorption and Resonance Raman Scattering Spectra Using Analytical Excited State Energy Gradients within Time-Dependent Density Functional Theory

    SciTech Connect

    Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus J. J.; Jensen, Lasse

    2013-12-10

    A parallel implementation of analytical time-dependent density functional theory gradients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids, and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G, and a molecular host–guest complex (TTFcCBPQT4+). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host–guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experimental data for most exchange-correlation functionals. Finally, however, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.

  4. D-xylose absorption

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003606.htm D-xylose absorption To use the sharing features on this page, please enable JavaScript. D-xylose absorption is a laboratory test to determine ...

  5. Nitrogen-Pressure Shifts in the v3 Band of Methane Measured at Several Temperatures between 300 and 90 K

    NASA Technical Reports Server (NTRS)

    Tumuhimbise, Anthony T.; Hurtmans, Daniel; Mantz, Arlan W.; Mondelain, Didier

    2008-01-01

    Remote sensing of the Earth's atmosphere requires accurate knowledge of spectroscopic line parameters for the molecules investigated. Knowledge of the temperature dependence of these parameters is also essential if agreement, at the noise level, between calculated and experimental data is to be achieved. The authors recently published results of nitrogen broadening measurements in the v3 band of 12CH4 using the 5.37 m long absorption path length all-copper Herriott cell. The temperature dependent line parameters determined in the laboratory were applied to fit a portion of the atmospheric spectrum recorded with a balloon-borne remote sensing FTIR instrument, called the Limb Profile Monitor of the Atmosphere, and operating in absorption against the sun. Since the authors had a relatively complete series of data for the P(9) transition in the v3 band of 12CH4, the A2 1 as well as the F2 1, F1 1 and A1 1 lines recorded at different pressures and at four temperatures between 300 and 90 K, we reanalyzed the data to derive pressure shift information at different temperatures. The temperatures for which data were collected and analyzed are 298, 140 and 90K. The high precision pressure shift data obtained here over a large range of temperature demonstrate the ability of our experimental arrangement to address specific questions on a given spectral window like in the balloon experiment or in a satellite project, for example.

  6. Derivation of water vapour absorption cross-sections in the red region

    NASA Technical Reports Server (NTRS)

    Lal, M.; Chakrabarty, D. K.

    1994-01-01

    Absorption spectrum in 436 to 448 nm wavelength region gives NO2 and O3 column densities. This spectrum can also give H2O column density. The spectrum in the range of 655 to 667 nm contains absorption due to NO3 and H2O. Combining the absorption spectra in the wavelength ranges of 436 to 448 and 655 to 667 nm, water vapor absorption cross-sections in this range comes out to be of the order of 2.0 x 10(exp -24) cm(exp -2).

  7. Ambiguous red shifts

    NASA Astrophysics Data System (ADS)

    Wulfman, Carl E.

    2010-12-01

    A one-parameter conformal invariance of Maxwell's equations allows the wavelengths of electromagnetic waves to change as they propagate, and do so even in otherwise field-free space. This produces an ambiguity in interpretations of stellar red shifts. Experiments that will determine the value of the group parameter, and thereby remove the ambiguity, are proposed. They are based on an analysis of the anomalous frequency shifts uncovered in the Pioneer 10 and 11 spacecraft studies, and physical interpretation of an isomorphism discovered by E.L. Hill. If the group parameter is found to be non-zero, Hubble's relations will have to be reinterpreted and space-time metrics will have to be altered. The cosmological consequences of the transformations are even more extensive because, though they change frequencies they do not alter the energy and momentum conservation laws of classical and quantum-electrodynamical fields established by Cunningham and by Białynicki-Birula.

  8. Shifts that divide population

    NASA Astrophysics Data System (ADS)

    Muneepeerakul, Rachata; Qubbaj, Murad; Aggarwal, Rimjhim; Anderies, John M.; Janssen, Marco

    2014-05-01

    How does a population of organisms in an ecosystem or of people in a society respond to rapid shifts in the environment? Answers to this question are critical to our ability to anticipate and cope with a changing ecohydrological system. We have developed a generic model of adaptation mechanisms, based on replicator dynamics, in which we derive a simple and insightful threshold condition that separates two important types of responses: 'cohesive transition' in which the whole population changes gradually together, and 'population-dividing transition' in which the population splits into two groups with one eventually dominating the other. The threshold depends on the magnitude of the shift and the shape of the fitness landscape. Division in populations can fundamentally alter the functioning of and induce subsequent feedbacks within the system; knowing the condition that gives rise to such division is thus fundamentally important.

  9. The shifted penalty method

    NASA Astrophysics Data System (ADS)

    Zavarise, Giorgio

    2015-07-01

    The method presented here is a variation of the classical penalty one, suited to reduce penetration of the contacting surfaces. The slight but crucial modification concerns the introduction of a shift parameter that moves the minimum point of the constrained potential toward the exact value, without any penalty increase. With respect to the classical augmentation procedures, the solution improvement is embedded within the original penalty contribution. The problem is almost consistently linearized, and the shift is updated before each Newton's iteration. However, adding few iterations, with respect to the original penalty method, a reduction of the penetration of several orders of magnitude can be achieved. The numerical tests have shown very attractive characteristics and very stable solution paths. This permits to foresee a wide area of applications, not only in contact mechanics, but for any problem, like e.g. incompressible materials, where a penalty contribution is required.

  10. Cathodoluminescence Spectrum Imaging Software

    2011-04-07

    The software developed for spectrum imaging is applied to the analysis of the spectrum series generated by our cathodoluminescence instrumentation. This software provides advanced processing capabilities s such: reconstruction of photon intensity (resolved in energy) and photon energy maps, extraction of the spectrum from selected areas, quantitative imaging mode, pixel-to-pixel correlation spectrum line scans, ASCII, output, filling routines, drift correction, etc.

  11. Giant Goos-Hänchen shift via spontaneous generated coherence

    NASA Astrophysics Data System (ADS)

    Ziauddin

    2015-11-01

    The influence of spontaneous generated coherence (SGC) on the Goos-Hänchen (GH) shift in the reflected light is presented. A weak probe light is incident on a cavity containing three-level gaseous atomic medium consist of 85Rb atoms. The atom-field interaction follows electromagnetically induced transparency configuration, and the SGC modifies the dispersion and absorption properties of a system [Y. Niu and S. Gong, Phys. Rev. A 73, 053811 (2006)]. The SGC enhances the Kerr nonlinearity which leads to giant negative and positive GH shifts in the reflected light. Further, the control of negative and positive GH shifts is achieved via manipulation of probe field detuning.

  12. Nonlinear acoustic enhancement in photoacoustic imaging with wideband absorptive nanoemulsion beads

    NASA Astrophysics Data System (ADS)

    Wei, Chen-wei; Lombardo, Michael; Xia, Jinjun; Pelivanov, Ivan; Perez, Camilo; Larson-Smith, Kjersta; Matula, Thomas J.; Pozzo, Danilo; O'Donnell, Matthew

    2014-03-01

    A nanoemulsion contrast agent with a perfluorohexane core and optically absorptive gold nanospheres (GNSs) assembled on the surface, is presented to improve the specificity of photoacoustic (PA) molecular imaging in differentiating targeted cells or aberrant regions from heterogeneous background signals. Compared to distributed GNSs, clustered GNSs at the emulsion oil-water interface produce a red-shifted and broadened absorption spectrum, exhibiting fairly high absorption in the near-infrared region commonly used for deep tissue imaging. Above a certain laser irradiation fluence threshold, a phase transition creating a microbubble in the emulsion core leads to more than 10 times stronger PA signals compared with conventional thermal-expansion-induced PA signals. These signals are also strongly non-linear, as verified by a differential scheme using recorded PA images at different laser fluences. Assuming a linear relation between laser fluence and the PA signal amplitude, differential processing results in nearly perfect suppression of linear sources, but retains a significant residue for the non-linear nanoemulsion with more than 35 dB enhancement. This result demonstrates that contrast specificity can be improved using the nanoemulsion as a targeting agent in PA molecular imaging by suppressing all background signals related to a linear PA response. Furthermore, combined with a system providing simultaneous laser/ultrasound excitation, cavitation-generated bubbles have the potential to be a highly specific contrast agent for ultrasound molecular imaging and harmonic imaging, as well as a targeted means for noninvasive ultrasound-based therapies.

  13. Experimental determination of terahertz atmospheric absorption parameters

    NASA Astrophysics Data System (ADS)

    Slocum, David M.; Goyette, Thomas M.; Giles, Robert H.; Nixon, William E.

    2015-05-01

    The terahertz frequency regime is often used as the `chemical fingerprint' region of the electromagnetic spectrum since many molecules exhibit a dense selection of rotational and vibrational transitions. Water is a major component of the atmosphere and since it has a large dipole moment the propagation of terahertz radiation will be dominated by atmospheric effects. This study will present the results of high-­-resolution broadband measurements of the terahertz atmospheric absorption and detail the technique for directly measuring the pressure broadening coefficients, absolute absorption coefficients, line positions, and continuum effects. Differences between these measured parameters and those tabulated in HITRAN will be discussed. Once the water vapor absorption was characterized, the same technique was used to measure the line parameters for methanol, a trace gas of interest within Earth's atmosphere. Methanol has a dense absorption spectrum in the terahertz frequency region and is an important molecule in fields such as environmental monitoring, security, and astrophysics. The data obtained in the present study will be of immediate use for the remote sensing community, as it is uncommon to measure this many independent parameters as well as to measure the absolute absorption of the transitions. Current models rely on tabulated databases of calculated values for the line parameters measured in this study. Differences between the measured data and those in the databases will be highlighted and discussed.

  14. The vibrational spectrum of H2O3: An ab initio investigation

    NASA Technical Reports Server (NTRS)

    Jackels, Charles F.

    1991-01-01

    Theoretically determined frequencies and absorption intensities are reported for the vibrational spectrum of the covalent HOOOH and hydrogen bonded HO---HOO intermediates that may form in the reaction of the hydroxyl and hydroperoxyl radicals. Basis sets of DZP quality, augmented by diffuse and second sets of polarization functions have been used with CASSCF wave functions. The calculated harmonic vibrational frequencies of HOOOH have been corrected with empirical factors and presented in the form of a 'stick' spectrum. The oxygen backbone vibrations, predicted to occur at 519, 760, and 870 cm(exp -1), are well separated from most interferences, and may be the most useful for the species' identification. In the case of the hydrogen bonded isomer, emphasis has been placed upon prediction of the shifts in the intramolecular vibrational frequencies that take place upon formation of the complex. In particular, the HO stretch and HOO bend of HO2 are predicted to have shifts of -59 and 53 cm(exp -1), respectively, which should facilitate their identification. It is also noted that the antisymmetric stretching frequency of the oxygen backbone in HOOOH exhibits a strong sensitivity to the degree of electron correlation, such as has been previously observed for the same mode in ozone.

  15. Infrared absorption, Raman, and SERS investigations in conjunction with theoretical simulations on a phenothiazine derivative

    NASA Astrophysics Data System (ADS)

    Bolboaca, M.; Iliescu, T.; Kiefer, W.

    2004-03-01

    The vibrational characterization of the most stable conformer of 10-isopentyl-10H-phenothiazine-5,5-dioxide (10-I-10H-P-5,5-D) was performed by means of infrared absorption, Raman and surface-enhanced Raman spectroscopy (SERS). Hartree-Fock and density functional theory calculations were carried out to find the optimised structures and the computed vibrational wavenumbers of the title compound. The comparison of SER spectra obtained only in activated silver colloid with the corresponding Raman spectrum reveals small shifts and changes in the relative intensities proving the partial chemisorption of the molecules on the silver surface. The electromagnetic mechanism represents the main mechanism of the overall SERS enhancement. The changes observed in the SER spectra at different pH values were explained by considering the reorientation of the adsorbed molecule with respect to the metal surface.

  16. Visible-ultraviolet absorption cross sections for NO2 as a function of temperature

    NASA Technical Reports Server (NTRS)

    Davidson, J. A.; Cantrell, C. A.; Mcdaniel, A. H.; Shetter, R. E.; Madronich, S.

    1988-01-01

    A redetermination of the temperature dependence of the absorption cross-section (sigma) of NO2 in the visible-ultraviolet region was made in order to provide a more reliable data base for the calculation of NO2 photolysis rates in the atmosphere. Experiments over a wide range of temperatures and NO2 concentrations were conducted. The integral of a plot of sigma versus the inverse of the wavelength was essentially independent of temperature. Increasing temperature produced a shift of the spectrum toward longer wavelengths, resulting in a small negative temperature dependence of sigma over the 264-400 nm range and a small positive dependence over the 450-649 nm range. Increasing temperature produced broadening of individual spectral features, resulting in a systematic lowering of peaks and filling of valleys. Recommended cross sections are presented for use in tropospheric NO2 photolysis rate calculations.

  17. Linear and nonlinear optical absorption coefficients of spherical dome shells

    NASA Astrophysics Data System (ADS)

    Guo, Kangxian; Liu, Guanghui; Huang, Lu; Zheng, Xianyi

    2015-08-01

    Linear and nonlinear optical absorption coefficients of spherical dome shells are theoretically investigated within analytical wave functions and numerical quantized energy levels. Our results show that the inner radius, the outer radius and the cut-off angle of spherical dome shells have great influences on linear and nonlinear optical absorption coefficients as well as the total optical absorption coefficients. It is found that with the increase of the inner radius and the outer radius, linear and nonlinear optical absorption coefficients exhibit a blueshift and a redshift, respectively. However, with the increase of the cut-off angle, linear and nonlinear optical absorption coefficients do not shift. Besides, the resonant peaks of linear and nonlinear optical absorption coefficients climb up and then decrease with increasing the cut-off angle. The influences of the incident optical intensity on the total optical absorption coefficients are studied. It is found that the bleaching effect occurs at higher incident optical intensity.

  18. A High Signal-To-Noise Ultraviolet Spectrum of NGC 7469: New Support for Reprocessing of Continuum Radiation

    NASA Technical Reports Server (NTRS)

    Kriss, Gerard A.; Peterson, Bradley M.; Crenshaw, D. Michael; Zheng, Wei

    2000-01-01

    From 1996 June 10 to 1996 July 29, the International AGN Watch monitored the Seyfert 1 galaxy NGC 7469 using the International Ultraviolet Explorer, the Rossi X-Ray Timing Explorer, and a network of ground-based observatories. On 1996 June 18, in the midst of this intensive monitoring period, we obtained a high signal-to-noise snapshot of the UV spectrum from 1150 to 3300 A, using the Faint Object Spectrograph (FOS) on the Hubble Space Telescope. This spectrum allows us to disentangle the UV continuum more accurately from the broad wings of the emission lines, to identify clean continuum windows free of contaminating emission and absorption, and to deblend line complexes such as Ly(alpha) + N V, C IV + He II + O III], Si III] + C III], and Mg II + Fe II. Using the FOS spectrum as a template, we have fitted and extracted line and continuum fluxes from the IUE monitoring data. The cleaner continuum extractions c o n h the discovery of time delays between the different UV continuum bands by Wanders et al. Our new measurements show delays increasing with wavelength for continuum bands centered at 1485, 1740, and 1825 A, relative to 1315 A with delays of 0.09, 0.28, and 0.36 days, respectively. Like many other Seyfert I galaxies, the UV spectrum of NGC 7469 shows intrinsic, blue-shifted absorption in Ly(alpha), N V, and C IV. Soft X-ray absorption is also visible in archival ASCA X-ray spectra. The strength of the UV absorption, however, is not compatible with a single-zone model in which the same material absorbs both the UV and X-ray light. Similar to other Seyfert galaxies, such as NGC 3516, the UV-absorbing gas in NGC 7469 has a lower ionization parameter and column density than the X-ray-absorbing material. While the UV and X-ray absorption does not arise in the same material, the frequent occurrence of both associated UV absorption and X-ray warm absorbers in the same galaxies suggests that the gas supply for each has a common origin.

  19. Shape-shifting colloids via stimulated dewetting

    NASA Astrophysics Data System (ADS)

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-07-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly.

  20. Shape-shifting colloids via stimulated dewetting.

    PubMed

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-01-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly. PMID:27426418

  1. Shape-shifting colloids via stimulated dewetting

    PubMed Central

    Youssef, Mena; Hueckel, Theodore; Yi, Gi-Ra; Sacanna, Stefano

    2016-01-01

    The ability to reconfigure elementary building blocks from one structure to another is key to many biological systems. Bringing the intrinsic adaptability of biological systems to traditional synthetic materials is currently one of the biggest scientific challenges in material engineering. Here we introduce a new design concept for the experimental realization of self-assembling systems with built-in shape-shifting elements. We demonstrate that dewetting forces between an oil phase and solid colloidal substrates can be exploited to engineer shape-shifting particles whose geometry can be changed on demand by a chemical or optical signal. We find this approach to be quite general and applicable to a broad spectrum of materials, including polymers, semiconductors and magnetic materials. This synthetic methodology can be further adopted as a new experimental platform for designing and rapidly prototyping functional colloids, such as reconfigurable micro swimmers, colloidal surfactants and switchable building blocks for self-assembly. PMID:27426418

  2. Comparison of red-shifted firefly luciferase Ppy RE9 and conventional Luc2 as bioluminescence imaging reporter genes for in vivo imaging of stem cells

    NASA Astrophysics Data System (ADS)

    Liang, Yajie; Walczak, Piotr; Bulte, Jeff W. M.

    2012-01-01

    One critical issue for noninvasive imaging of transplanted bioluminescent cells is the large amount of light absorption in tissue when emission wavelengths below 600 nm are used. Luciferase with a red-shifted spectrum can potentially bypass this limitation. We assessed and compared a mutant of firefly luciferase (Ppy RE9, PRE9) against the yellow luciferase luc2 gene for use in cell transplantation studies. C17.2 neural stem cells expressing PRE9-Venus and luc2-Venus were sorted by flow cytometry and assessed for bioluminescence in vitro in culture and in vivo after transplantation into the brain of immunodeficient Rag2-/- mice. We found that the luminescence from PRE9 was stable, with a peak emission at 620 nm, shifted to the red compared to that of luc2. The emission peak for PRE9 was pH-independent, in contrast to luc2, and much less affected by tissue absorbance compared to that of luc2. However, the total emitted light radiance from PRE9 was substantially lower than that of luc2, both in vitro and in vivo. We conclude that PRE9 has favorable properties as compared to luc2 in terms of pH independence, red-shifted spectrum, tissue light penetration, and signal quantification, justifying further optimization of protein expression and enzymatic activity.

  3. Validation of method for enhanced production of red-shifted bioluminescent photons in vivo

    NASA Astrophysics Data System (ADS)

    Dragavon, Joe; Blazquez, Samantha; Rogers, Kelly L.; Samson, Chelsea; Tournebize, Régis; Shorte, Spencer

    2011-02-01

    Bioluminescence Imaging (BLI) is an increasingly useful and applicable technique that allows for the non-invasive observation of biological events in intact living organisms, ranging from single cells to small rodents. Though the photon production occurs within the host, significant exposure times can be necessary due to the low photon flux compared to fluorescence imaging. The optical absorption spectrum of haemoglobin strongly overlaps most bioluminescent emission spectra, greatly attenuating the total detectable photons in animal models. We have developed and validated a technique that is able to red-shift the bioluminescent photons to the more desirable optical region of > 650 nm, a region of minimal absorbance by hemoglobin. This red-shift occurs by using bioluminescence as an internal light source capable of exciting a fluorophore, such as a fluorescent protein or a quantum dot, that emits in the red. Interestingly, in the absence of an absorber, this excitation can occur over substantial distances (microns to centimeters), far exceeding distances associated to, and thereby precluding, resonance energy transfer phenomena. We show this novel technique yields a substantial increase in the number of red photons for in vitro and ex vivo conditions, suggesting eventually utility for in vivo studies on, for example, intact living mice.

  4. CO2 pressure broadening and shift coefficients for the 2-0 band of 12C16O

    NASA Astrophysics Data System (ADS)

    Hashemi, R.; Predoi-Cross, A.; Dudaryonok, A. S.; Lavrentieva, N. N.; Vandaele, A. C.; Vander Auwera, J.

    2016-08-01

    Fourier transform absorption spectra of the 2-0 band of 12C16O mixed with CO2 have been recorded at total pressures from 156 to 1212 hPa and at 4 different temperatures between 240 K and 283 K. CO2 pressure-induced line broadening and line shift coefficients, and the temperature dependence of the former have been measured including line mixing using a multi-spectrum non-linear least squares fitting technique. Different line shape models have been considered to take into account the Dicke narrowing or speed dependence effects. Measured line-shape parameters were compared with theoretical values, calculated for individual temperatures using a semi-empirical method and the Exponential Power Gap (EPG) law.

  5. The CI pressure shift and gravitational redshift of the cool DBQA5 white dwarf LDS678A

    NASA Technical Reports Server (NTRS)

    Sion, E. M.; Vauclair, G.; Oswalt, T. D.; Hammond, G.; Liebert, J.; Koester, D.; Wegner, G.; Marcum, P.

    1990-01-01

    A high resolution ultraviolet spectrum of the helium rich degenerate LDS 678A, obtained with the International Ultraviolet Explorer (IUE) satellite is presented. LDS 678A is the coolest metallic line generate (DQ or DZ) yet observed with the IUE scale. These observations provide a detailed line profile of the strong C I 2479 absorption line with equivalent width (W sub 2479 = 2.35 plus or minus 0.06 angstroms) from which theoretical line profile fits yield a C abundance (log C/He = 6.4). The presence of carbon in a helium rich atmosphere lends credence to the notion that LDS 678A is a transitional case between the DB white dwarfs with nearly pure helium atmospheres and the helium rich DQ white dwarfs which exhibit carbon bands. Corrected for an inferred pressure shift for the C I line, a gravitational redshift is deduced from which a most probable mass of 0.55 solar mass is derived.

  6. VizieR Online Data Catalog: Optical spectrum of Cyg OB2 No. 12 (Klochkova+, 2004)

    NASA Astrophysics Data System (ADS)

    Klochkova, V. G.; Chentsov, E. L.

    2006-04-01

    We have obtained the first high spectral-resolution (R=15000 and 60000) optical spectra for the extremely luminous star No.12, identified with the IR-source IRAS 20308+4104 in the Cyg OB2 association. We have identified about 200 spectral features at 4552-7939{AA}, including interstellar NaI, KI and numerous DIBs, which are in the strongest absorptions in the spectrum, along with the HeI, CII, SiII lines. A two-dimensional spectral classification indicates that the star's spectral type is B5+/-0.5 Ia+. Our analyses of the radial velocities pattern shows the presence of a radial velocity gradient in the stellar atmosphere due to the infall of matter onto the star. The strong H(alpha) emission line displays broad Thompson wings and time-variable core absorption, providing evidence that the stellar wind is inhomogeneous and slightly blue-shifted P Cygni absorption profile. We conclude that the wind is time-variable. (1 data file).

  7. Angular spectrum detection instrument for label-free photonic crystal sensors.

    PubMed

    Liu, Longju; Xu, Zhen; Dong, Liang; Lu, Meng

    2014-05-01

    An angular spectrum analysis system was demonstrated to monitor the optical resonant mode of a photonic crystal (PC) sensor comprised of a one-dimensional grating structure. Exposed to solutions with different refractive indices or adsorbed with biomaterials, the PC sensor exhibited changes of the optical resonant modes. The developed detection system utilized a focused laser beam to detect shifts of the resonant angle, and thereby allowed a kinetic analysis of chemical absorption. Such a detection apparatus offers an adjustable angular resolution and a tunable detection range for a wide variety of refractometric sensing applications. A limit of detection of 6.57×10(-5) refractive index unit has been observed. The instrument also offers an imaging capability of rapidly characterizing low-contrast samples deposited on the PC surface with a spatial resolution of 10 μm. PMID:24784094

  8. Dipolar relaxation within the protein matrix of the green fluorescent protein: a red edge excitation shift study.

    PubMed

    Haldar, Sourav; Chattopadhyay, Amitabha

    2007-12-27

    The fluorophore in green fluorescent protein (GFP) is localized in a highly constrained environment, protected from the bulk solvent by the barrel-shaped protein matrix. We have used the wavelength-selective fluorescence approach (red edge excitation shift, REES) to monitor solvent (environment) dynamics around the fluorophore in enhanced green fluorescent protein (EGFP) under various conditions. Our results show that EGFP displays REES in buffer and glycerol, i.e., the fluorescence emission maxima exhibit a progressive shift toward the red edge, as the excitation wavelength is shifted toward the red edge of the absorption spectrum. Interestingly, EGFP displays REES when incorporated in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), independent of the hydration state. We interpret the observed REES to the constrained environment experienced by the EGFP fluorophore in the rigid protein matrix, rather than to the dynamics of the bulk solvent. These results are supported by the temperature dependence of REES and characteristic wavelength-dependent changes in fluorescence anisotropy. PMID:18052368

  9. Shifted genus expanded W ∞ algebra and shifted Hurwitz numbers

    NASA Astrophysics Data System (ADS)

    Zheng, Quan

    2016-05-01

    We construct the shifted genus expanded W ∞ algebra, which is isomorphic to the central subalgebra A ∞ of infinite symmetric group algebra and to the shifted Schur symmetrical function algebra Λ* defined by Okounkov and Olshanskii. As an application, we get some differential equations for the generating functions of the shifted Hurwitz numbers; thus, we can express the generating functions in terms of the shifted genus expanded cut-and-join operators.

  10. Transmission shift control assembly

    SciTech Connect

    Dzioba, D.L.

    1989-04-18

    This patent describes a transmission shift control assembly mounted on a steering column having a longitudinal axis comprising: bracket means secured to the steering column; transmission shift cable means having a portion secured to the bracket means and a portion linearly movable relative to the secured portion; mounting means on the bracket cable drive arm means having an axis and being rotatably mounted on the rotary axis on the mounting means oblique to the longitudinal axis and including a cable connecting portion secured to the movable portion of the cable means and lever mounting means adjacent the mounting means; operator control means including lever means, pin means for pivotally mounting the lever means on the lever mounting means on an axis substantially perpendicular to the rotary axis and positioning arm means formed on the lever means and extending from the pin means; and detent gate means disposed on the bracket means in position to abut the positioning arm means for limiting the extent of pivotal movement of the lever means.

  11. Shifted nondiffractive Bessel beams

    NASA Astrophysics Data System (ADS)

    Kovalev, Alexey A.; Kotlyar, Victor V.; Porfirev, Alexey A.

    2015-05-01

    Nondiffractive Bessel beams are well known to have infinite energy and infinite orbital angular momentum (OAM). However, when normalized to unity of energy, their OAM is finite. In this work, we derive an analytical relationship for calculating the normalized OAM of the superposition of off-axis Bessel beams characterized by the same topological charge. We show that if the constituent beams of the superposition have real-valued weight coefficients, the total OAM of the superposition of the Bessel beams equals that of an individual nonshifted Bessel beam. This property enables generating nondiffractive beams with different intensity distributions but identical OAM. The superposition of a set of identical Bessel beams centered on an arbitrary-radius circle is shown to be equivalent to an individual constituent Bessel beam put in the circle center. As a result of a complex shift of the Bessel beam, the transverse intensity distribution and OAM of the beam are also shown to change. We show that, in the superposition of two or more complex-shifted Bessel beams, the OAM may remain unchanged, while the intensity distribution is changed. Numerical simulation is in good agreement with theory.

  12. Exciton-Like Behavior in Low-Energy Absorption Spectra of Simple Alloys

    NASA Astrophysics Data System (ADS)

    Bakshi, Mira Hemendraray

    The valence excitation (ns('2) (--->) nsnp) spectra of Mg, Zn, and Ca impurities at various concentrations in Li have been measured. Polarization modulation ellipsometry was used to determine the impurity-induced changes in real and imaginary parts of the dielectric function simultaneously, together with the differential reflectivity, in the energy range 1.5 - 4.5 eV. The most important result at sufficiently dilute alloy compositions, is that the system investigated display a distinct absorption peak above the Drude background. The height of this peak varies linearly with impurity content. The impurity-specific character of these spectral features points to exciton-like behavior at low-energy, arising from atomic-like excitations in which the electron and the hole linger together at the impurity site. Existing theories of alloy spectra do not explain these effects, because they do not include the Coulomb correlations between the interacting quasiparticles created in the optical event, or the way in which the interacting pair is confined to the impurity site by the mutual field. A remarkable added result of this research is that the exciton-like behavior can be followed with increasing impurity content, all the way to the pure Mg response, when it becomes the interband transition. This has led Kunz and Flynn to reformulate the theory of optical absorption including excited state interactions; and to apply the theory to the spectrum of pure Mg. The Coulomb interaction causes striking effects which are in generally good agreement with experiment. Zn-Li alloys behave differently. At an alloy composition for which Zn-Zn interactions become prevalent, the local, impurity-specific character of the spectrum disappears, leaving only a featureless Drude-like absorption. These results have provoked cluster calculations by Boisvert and Kunz, which predict the spectral shifts, and exhibit qualitatively similar persistence for Mg-Li, and broadening for Zn-Li.

  13. Infrared Atlas of the Arcturus Spectrum, 0.9-5.3 microns

    NASA Astrophysics Data System (ADS)

    Hinkle, Kenneth; Wallace, Lloyd; Livingston, William

    1995-11-01

    A spectral atlas of the infrared spectrum of the bright K 2 giant Arcturus has been completed using the 4 meter Mayall telescope and FTS. The 0.9-5.3 micron spectrum of Arcturus was observed at high signal-to-noise with a resolution of 100,000. Telluric lines were removed by using telluric transmission spectra generated from McMath-Pierce solar spectra or 4 meter lunar spectra. The spectrum of Arcturus was observed on two different dates selected to give large opposite heliocentric shifts. The spectra observed on the different dates have been independently corrected for telluric absorption with the result that the telluric spectrum has been effectively removed from all but the most obscure wavelengths of the Arcturus spectrum. We attempted to identify lines with central depths stronger than a few percent. Identifications seem well in hand with the unidentified lines apparantly atmoic in origin. The atlas is available either on an AAS CD-ROM or as an ASP monograph. (c) Astronomical Society of the Pacific Bergeron, et al., PHOTOMETRIC CALIBRATION OF HYDROGEN- AND HELIUM-RICH WHITE DWARF MODELS Bolometric corrections and color indices on various photometric systems are provided for an extensive grid of hydrogen- and helium-rich white dwarf model atmospheres. Absolute visual magnitudes, masses, and ages are also obtained for each model from detailed evolutionary cooling sequences appropriate for these stars. The results of our calculations are briefly compared with published observational material. These calculations can easily be extended to any given photometric system. (SECTION: Stars)

  14. A spectrum of an extrasolar planet.

    PubMed

    Richardson, L Jeremy; Deming, Drake; Horning, Karen; Seager, Sara; Harrington, Joseph

    2007-02-22

    Of the over 200 known extrasolar planets, 14 exhibit transits in front of their parent stars as seen from Earth. Spectroscopic observations of the transiting planets can probe the physical conditions of their atmospheres. One such technique can be used to derive the planetary spectrum by subtracting the stellar spectrum measured during eclipse (planet hidden behind star) from the combined-light spectrum measured outside eclipse (star + planet). Although several attempts have been made from Earth-based observatories, no spectrum has yet been measured for any of the established extrasolar planets. Here we report a measurement of the infrared spectrum (7.5-13.2 microm) of the transiting extrasolar planet HD 209458b. Our observations reveal a hot thermal continuum for the planetary spectrum, with an approximately constant ratio to the stellar flux over this wavelength range. Superposed on this continuum is a broad emission peak centred near 9.65 microm that we attribute to emission by silicate clouds. We also find a narrow, unidentified emission feature at 7.78 microm. Models of these 'hot Jupiter' planets predict a flux peak near 10 microm, where thermal emission from the deep atmosphere emerges relatively unimpeded by water absorption, but models dominated by water fit the observed spectrum poorly. PMID:17314975

  15. Autism Spectrum Disorder

    MedlinePlus

    Autism spectrum disorder (ASD) is a neurological and developmental disorder that begins early in childhood and lasts throughout a ... and pervasive developmental disorders. It is called a "spectrum" disorder because people with ASD can have a ...

  16. Autism Spectrum Disorder (ASD)

    MedlinePlus

    ... spectrum disorder (ASD) is a group of developmental disabilities that can cause significant social, communication and behavioral ... for autism spectrum disorder (ASD) and other developmental disabilities. More E-mail Your Friends "Children with autism ...

  17. The spectrum of (136199) Eris between 350 and 2350 nm: results with X-Shooter

    NASA Astrophysics Data System (ADS)

    Alvarez-Candal, A.; Pinilla-Alonso, N.; Licandro, J.; Cook, J.; Mason, E.; Roush, T.; Cruikshank, D.; Gourgeot, F.; Dotto, E.; Perna, D.

    2011-08-01

    Context. X-Shooter is the first second-generation instrument for the ESO-Very Large Telescope. It is a spectrograph covering the entire 300-2480 nm spectral range at once with a high resolving power. These properties enticed us to observe the well-known trans-Neptunian object (136199) Eris during the science verification of the instrument. The target has numerous absorption features in the optical and near-infrared domain that have been observed by different authors, showing differences in these features' positions and strengths. Aims: Besides testing the capabilities of X-Shooter to observe minor bodies, we attempt to constrain the existence of super-volatiles, e.g., CH4, CO and N2, and in particular we try to understand the physical-chemical state of the ices on Eris' surface. Methods: We observed Eris in the 300 - 2480 nm range and compared the newly obtained spectra with those available in the literature. We identified several absorption features, measured their positions and depth, and compare them with those of the reflectance of pure methane ice obtained from the optical constants of this ice at 30 K to study shifts in these features' positions and find a possible explanation for their origin. Results: We identify several absorption bands in the spectrum that are all consistent with the presence of CH4 ice. We do not identify bands related to N2 or CO. We measured the central wavelengths of the bands and compared to those measured in the spectrum of pure CH4 at 30 K finding variable spectral shifts. Conclusions: Based on these wavelength shifts, we confirm the presence of a dilution of CH4 in other ice on the surface of Eris and the presence of pure CH4 that is spatially segregated. The comparison of the centers and shapes of these bands with previous works suggests that the surface is heterogeneous. The absence of the 2160 nm band of N2 can be explained if the surface temperature is below 35.6 K, the transition temperature between the alpha and beta phases

  18. X-ray absorption spectroscopy of xanthine oxidase. The molybdenum centres of the functional and the desulpho forms.

    PubMed Central

    Bordas, J; Bray, R C; Garner, C D; Gutteridge, S; Hasnain, S S

    1980-01-01

    X-ray absorption spectra have been recorded for the molybdenum K-edge region of xanthine oxidase. Both the absorption edge and the extended fine structure (e.x.a.f.s.) regions were investigated. Spectra were obtained for samples of the desulpho enzyme as well as for mixtures of this with the active enzyme. The spectrum of the pure active form was then obtained by difference. The desulpho enzyme shows a pronounced step in the absorption edge, of a type previously associated terminal oxygen ligands. In the active enzyme this step has decreased markedly. Satisfactory simulations of the e.x.a.f.s. spectrum of the desulpho enzyme could be obtained by assuming the molybdenum to be bonded to two terminal oxygen atoms (Mo = O about .175 nm), two sulphur atoms (presumably from cysteine residues, Mo-S about .0250 nm) and one sulphur atom (presumably from a methionine residue, Mo-S about 0.290 nm). E.x.a.f.s. of the active enzyme differed appreciably from this. In keeping with earlier proposals [Gutteridge, Tanner & Bray (1978) Biochem. J. 175, 887-897], the spectrum of the active enzyme could be simulated if a sulphur atom at about 0.225 nm (i.e. presumably a terminal sulphur atom) replaced one of the terminal oxygen atoms of the desulpho from, with small changes in the other bond distances. Validity of the interpretative procedures, which involved phase shift and amplitude calculations ab initio, was demonstrated by using low molecular weight compounds of known structure. PMID:6894537

  19. Shifting epidemiology of Flaviviridae.

    PubMed

    Petersen, Lyle R; Marfin, Anthony A

    2005-04-01

    The dengue, West Nile, Japanese encephalitis and yellow fever viruses are important mosquito-borne viruses whose epidemiology is shifting in response to changing societal factors, such as increasing commerce, urbanization of rural areas, and population growth. All four viruses are expanding geographically, as exemplified by the emergence of West Nile virus in the Americas and Japanese encephalitis virus in Australasia. The large, recent global outbreaks of severe neurological disease caused by West Nile virus, the increasing frequency of dengue hemorrhagic fever outbreaks in the Americas, and the emergence of yellow fever virus vaccination-associated viscerotropic disease, are new clinical epidemiologic trends. These worrisome epidemiologic trends will probably continue in coming decades, as a reversal of their societal and biological drivers is not in sight. Nevertheless, the substantial reductions in Japanese encephalitis virus incidence resulting from vaccination programs and economic development in some Asian countries provide some encouragement within this overall guarded outlook. PMID:16225801

  20. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, Gary E.

    1996-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  1. Phase shifting interferometer

    DOEpatents

    Sommargren, G.E.

    1999-08-03

    An interferometer is disclosed which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 11 figs.

  2. Phase shifting interferometer

    DOEpatents

    Sommargren, Gary E.

    1999-01-01

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of .lambda./1000 where .lambda. is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about .lambda./50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. Whereas current interferometers illuminate the optic to be tested with an aberrated wavefront which also limits the accuracy of the measurement, this interferometer uses an essentially perfect spherical measurement wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms.

  3. Phase shifting diffraction interferometer

    DOEpatents

    Sommargren, G.E.

    1996-08-29

    An interferometer which has the capability of measuring optical elements and systems with an accuracy of {lambda}/1000 where {lambda} is the wavelength of visible light. Whereas current interferometers employ a reference surface, which inherently limits the accuracy of the measurement to about {lambda}/50, this interferometer uses an essentially perfect spherical reference wavefront generated by the fundamental process of diffraction. This interferometer is adjustable to give unity fringe visibility, which maximizes the signal-to-noise, and has the means to introduce a controlled prescribed relative phase shift between the reference wavefront and the wavefront from the optics under test, which permits analysis of the interference fringe pattern using standard phase extraction algorithms. 8 figs.

  4. A Rapid Method for Estimating NMR Shifts for Protons Attached to Carbon.

    ERIC Educational Resources Information Center

    Jeffreys, J. A. D.

    1979-01-01

    Presented are lists of deshielding constants chosen to be easy to remember and to given estimates close enough to measured shifts to allow interpretation of the spectrum of a compound of known structure. (BT)

  5. Infrared Absorption in Acetanilide by Solitons

    NASA Astrophysics Data System (ADS)

    Careri, G.; Buontempo, U.; Carta, F.; Gratton, E.; Scott, A. C.

    1983-07-01

    The infrared spectrum of acetanilide shows a new band that is red shifted from the main amide-I maximum by about 15 cm-1, the intensity of which increases at low temperature. It is suggested that this band may arise from the creation of amide-I solitons that are similar (but not identical) to those proposed by Davydov for the alpha helix in proteins.

  6. UV nebular absorption in Eta Car and Weigelt D

    NASA Astrophysics Data System (ADS)

    Nielsen, K. E.; Vieira, G. L.; Gull, T. R.; Lindler, D. J.; Eta Car HST Treasury Team

    2003-12-01

    The high angular and high spectral resolution of the HST/STIS MAMA echelle mode, provide an unique means to distinguish the physical structures surrounding Eta Car. Observations are parts of the HST treasury program (K. Davidson P.I.) for monitoring variations over Eta Car's spectroscopic minimum. Nebular emission is present above and below the stellar spectrum which is about 0.03'' wide. We have extracted the nebular part of the central source spectrum and compared it with the spectrum of Weigelt D, located approximately 0.2'' Northwest of the central source. The spectra show significant similarities and our conclusions are two-fold. First, the radiation from the Wiegelt blobs give an unwanted contribution to the spectrum of the central source, which emphasizes the importance of using an extracted spectrum in a spectral analysis. Second, the Weigelt blobs have so far been assumed to produce a pure emission line spectrum. However, this comparison shows the presence of similar absorption structures previously observed in the spectrum of the central star (Gull et al., 2003, submitted ApJL). Two velocity structures at approximately -50 and -500 km/s, respectively, have been observed in the Weigelt D spectrum. We present identifications of the absorption structures to supplement the emission line work performed by T. Zethson (2000, PhD Thesis) and provide additional information regarding the geometry of the inner parts of the Eta Car nebula. The -50 km/s velocity component is similar to the absorption structure at -146 km/s observed in the spectrum of the central object. If these velocity systems are related, this implies that the absorption component is located close to the central parts of the nebular system.

  7. In-vivo absorption properties of algal pigments

    NASA Astrophysics Data System (ADS)

    Bidigare, Robert R.; Ondrusek, Michael E.; Morrow, John H.; Kiefer, Dale A.

    1990-09-01

    Estimates of the in vivo specific absorption coefficients (m2 mg'; 400-750 nm, 2 nm intervals) for the major algal pigment groups (chlorophylls, carotenoids and phycobilins) are presented. "Unpackaged" absorption coefficients were initially obtained by measuring the absorption properties of pure pigment standards spectrophotometrically and "shifting" their absorption maxima to match in vivo positions. Two approaches for estimating the phytoplankton absorption coefficient (spectral reconstruction and spectral decomposition) are compared by linear regression analysis, incorporating concurrent measurements of particulate absorption and pigmentation performed in the Sargasso Sea. Results suggest that "pigment package" effects are minimal for natural assemblages of open-oceanic phytoplankton and that accessory pigments do not always co-vary with chlorophyll a over depth and time.

  8. Absorption and emission in defective cholesteric liquid crystal cells

    NASA Astrophysics Data System (ADS)

    Gevorgyan, A. H.; Harutyunyan, M. Z.; Matinyan, G. K.; Oganesyan, K. B.; Rostovtsev, Yu V.; Kurizki, G.; Scully, M. O.

    2016-04-01

    We investigated peculiarities of absorption, emission and photonic density of states of a cholesteric liquid crystal with an isotropic defect layer inside. The influence of the defect layer position on absorption and emission in the system was studied. It was shown that for non-diffracting circularly polarized incident light absorption/emission is maximum if the defect is in the centre of the system; and for diffracting circularly polarized incident light absorption/emission is maximum if the defect is shifted from the centre of the system to its left border from where light is incident. We also investigated influence of the defect layer thickness and those parameters which characterize loss and gain on absorption and emission. The influence of anisotropic absorption in the cholesteric liquid crystal layer on photonic density states was investigated, too.

  9. Basic Modeling of the Solar Atmosphere and Spectrum

    NASA Technical Reports Server (NTRS)

    Avrett, Eugene; Wagner, William J. (Technical Monitor)

    2003-01-01

    This grant supported the research and publication of a major 26-page paper in The Astrophysical Journal, by Fontenla, Avrett, & Loeser (2002): 'Energy Balance in the Solar Transition Region. IV. Hydrogen and Helium Mass Flows with Diffusion.' This paper extended our previous modeling of the chromosphere-corona transition region to include cases with particle and mass flows. Inflows and outflows were shown to produce striking changes in the profiles of hydrogen and helium lines. An important conclusion is that line shifts are much less significant than the changes in line intensity and central reversal due to the influence of flows on the excitation and ionization of atoms in the solar atmosphere. This modeling effort at SAO is the only current one being undertaken anywhere to simulate in detail the full range of non-LTE absorption, emission, and scattering processes in the solar atmosphere to account for the entire solar spectrum from radio waves to X-rays. This effort is being continued with internal SAO funding at a relatively slow pace. Further NASA support in the future would yield results of great value for the interpretation of solar observations from NASA spacecraft.

  10. Tetrasulfur, S4: rotational spectrum, interchange tunneling, and geometrical structure.

    PubMed

    McCarthy, M C; Thorwirth, S; Gottlieb, C A; Thaddeus, P

    2004-07-01

    The rotational spectrum of S4 has been observed for the first time in an electrical discharge through sulfur vapor. Two techniques have been used: Fourier transform microwave spectroscopy and long-path millimeter-wave absorption spectroscopy. Small, but systematic shifts of the measured transition frequencies of the normal isotopic species indicate that S4 has C2v symmetry but with a low-lying transition state of D2h symmetry, yielding interchange tunneling at 14.1(2) kHz in its ground vibrational state. From the rotational constants of the normal and the single 34S isotopic species, an experimental (r0) structure has been derived: S4 is a singlet planar trapezoid with a terminal bond length of 1.899(7) A, a central bond of 2.173(32) A, and an S-S-S angle of 103.9(8) degrees. Like thiozone (S3), S4 is a candidate for detection in the atmosphere of the Jovian moon Io and in other astronomical sources. PMID:15260588

  11. Percutaneous absorption in diseased skin: an overview.

    PubMed

    Chiang, Audris; Tudela, Emilie; Maibach, Howard I

    2012-08-01

    The stratum corneum's (SC) functions include protection from external hazardous environments, prevention of water loss and regulation of body temperature. While intact skin absorption studies are abundant, studies on compromised skin permeability are less common, although products are often used to treat affected skin. We reviewed literature on percutaneous absorption through abnormal skin models. Tape stripping is used to disrupt water barrier function. Studies demonstrated that physicochemical properties influence the stripping effect: water-soluble drugs are more affected. Abrasion did not affect absorption as much. Freezing is commonly used to preserve skin. It does not seem to modify water absorption, but still increases the penetration of compounds. Comparatively, heating the skin consistently increased percutaneous absorption. Removing SC lipids may increase percutaneous absorption of drugs. Many organic solvents are employed to delipidize. Delipidization with chloroform-methanol increased hydrophilic compound permeability, but not lipophilic. Acetone pre-treatment enhanced hydrophilic compound penetration. More data is needed to determine influence on highly lipophilic compound penetration. Sodium lauryl sulfate (SLS) induces irritant dermatitis and is frequently used as a model. Studies revealed that SLS increases hydrophilic compound absorption, but not lipophilic. However, skin irritation with other chemicals increases lipophilic penetration as much as hydrophilic. Animal studies show that UV exposure increases percutaneous absorption whereas human studies do not. Human studies show increased penetration in psoriatic and atopic dermatitis skin. The data summarized here begin to characterize flux alteration associated with damaged skin. Understanding the degree of alteration requires interpretation of involved conditions and the enlarging of our database to a more complete physicochemical spectrum. PMID:22912973

  12. An isotropic chemical shift-chemical shift anisotropic correlation experiment using discrete magic angle turning.

    PubMed

    Hu, Jian Zhi; Sears, Jesse A; Kwak, Ja Hun; Hoyt, David W; Wang, Yong; Peden, Charles H F

    2009-05-01

    An isotropic-anisotropic shift 2D correlation spectroscopy is introduced that combines the advantages of both magic angle turning (MAT) and magic angle hopping (MAH) technologies. In this new approach, denoted DMAT for "discrete magic angle turning", the sample rotates clockwise followed by an anticlockwise rotation of exactly the same amount with each rotation less or equal than 360 degrees but greater than 240 degrees , with the rotation speed being constant only for times related to the evolution dimension. This back and forth rotation is repeated and synchronized with a special radio frequency (RF) pulse sequence to produce an isotropic-anisotropic shift 2D correlation spectrum. For any spin-interaction of rank-2 such as chemical shift anisotropy, isotropic magnetic susceptibility interaction, and residual homo-nuclear dipolar interaction in biological fluid samples, the projection along the isotropic dimension is a high resolution spectrum. Since a less than 360 degrees sample rotation is involved, the design potentially allows for in situ control over physical parameters such as pressure, flow conditions, feed compositions, and temperature so that true in situ NMR investigations can be carried out. PMID:19246221

  13. An improved Q estimation approach: the weighted centroid frequency shift method

    NASA Astrophysics Data System (ADS)

    Li, Jingnan; Wang, Shangxu; Yang, Dengfeng; Dong, Chunhui; Tao, Yonghui; Zhou, Yatao

    2016-06-01

    Seismic wave propagation in subsurface media suffers from absorption, which can be quantified by the quality factor Q. Accurate estimation of the Q factor is of great importance for the resolution enhancement of seismic data, precise imaging and interpretation, and reservoir prediction and characterization. The centroid frequency shift method (CFS) is currently one of the most commonly used Q estimation methods. However, for seismic data that contain noise, the accuracy and stability of Q extracted using CFS depend on the choice of frequency band. In order to reduce the influence of frequency band choices and obtain Q with greater precision and robustness, we present an improved CFS Q measurement approach—the weighted CFS method (WCFS), which incorporates a Gaussian weighting coefficient into the calculation procedure of the conventional CFS. The basic idea is to enhance the proportion of advantageous frequencies in the amplitude spectrum and reduce the weight of disadvantageous frequencies. In this novel method, we first construct a Gauss function using the centroid frequency and variance of the reference wavelet. Then we employ it as the weighting coefficient for the amplitude spectrum of the original signal. Finally, the conventional CFS is adopted for the weighted amplitude spectrum to extract the Q factor. Numerical tests of noise-free synthetic data demonstrate that the WCFS is feasible and efficient, and produces more accurate results than the conventional CFS. Tests for noisy synthetic data indicate that the new method has better anti-noise capability than the CFS. The application to field vertical seismic profile (VSP) data further demonstrates its validity5.

  14. Exploring the use of Generalized Indirect Covariance to reconstruct pure shift NMR spectra: Current Pros and Cons

    NASA Astrophysics Data System (ADS)

    Fredi, André; Nolis, Pau; Cobas, Carlos; Martin, Gary E.; Parella, Teodor

    2016-05-01

    The current Pros and Cons of a processing protocol to generate pure chemical shift NMR spectra using Generalized Indirect Covariance are presented and discussed. The transformation of any standard 2D homonuclear and heteronuclear spectrum to its pure shift counterpart by using a reference DIAG spectrum is described. Reconstructed pure shift NMR spectra of NOESY, HSQC, HSQC-TOCSY and HSQMBC experiments are reported for the target molecule strychnine.

  15. Direct and quantitative broadband absorptance spectroscopy with multilayer cantilever probes

    SciTech Connect

    Hsu, Wei-Chun; Tong, Jonathan Kien-Kwok; Liao, Bolin; Chen, Gang

    2015-04-21

    A system for measuring the absorption spectrum of a sample is provided that includes a broadband light source that produces broadband light defined within a range of an absorptance spectrum. An interferometer modulates the intensity of the broadband light source for a range of modulation frequencies. A bi-layer cantilever probe arm is thermally connected to a sample arm having at most two layers of materials. The broadband light modulated by the interferometer is directed towards the sample and absorbed by the sample and converted into heat, which causes a temperature rise and bending of the bi-layer cantilever probe arm. A detector mechanism measures and records the deflection of the probe arm so as to obtain the absorptance spectrum of the sample.

  16. Hydraulically actuated well shifting tool

    SciTech Connect

    Roth, B.A.

    1992-10-20

    This patent describes a hydraulically actuated shifting tool for actuating a sliding member in a well tool. It comprises: a housing having a hydraulic fluid bore therein; shifting dog means positioned on the housing for movement away and toward the housing; locking dog means positioned on the housing for movement away and toward the body; shifting dog hydraulic actuating means in fluid communication with the bore for causing engagement of the shifting dogs with the sliding member; locking dog hydraulic actuating means in communication with the bore for causing engagement of the locking dogs with the locking means; and hydraulic shifting means in communication with the bore for causing relative movement between the shifting dog means and the locking dog means for shifting the sliding sleeve.

  17. Quantized beam shifts in graphene

    NASA Astrophysics Data System (ADS)

    Kort-Kamp, Wilton; Sinitsyn, Nikolai; Dalvit, Diego

    We show that the magneto-optical response of a graphene-on-substrate system in the presence of an external magnetic field strongly affects light beam shifts. In the quantum Hall regime, we predict quantized Imbert-Fedorov, Goos-Hänchen, and photonic spin Hall shifts. The Imbert-Fedorov and photonic spin Hall shifts are given in integer multiples of the fine structure constant α, while the Goos-Hänchen ones in discrete multiples of α2. Due to time-reversal symmetry breaking the IF shifts change sign when the direction of the applied magnetic field is reversed, while the other shifts remain unchanged. We investigate the influence on these shifts of magnetic field, temperature, and material dispersion and dissipation. An experimental demonstration of quantized beam shifts could be achieved at terahertz frequencies for moderate values of the magnetic field. We acknowledge the LANL LDRD program for financial support.

  18. Solar absorption surface panel

    DOEpatents

    Santala, Teuvo J.

    1978-01-01

    A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

  19. Tissue type characterization using photoacoustic power spectrum, a feasibility study

    NASA Astrophysics Data System (ADS)

    Tavakoli, Behnoosh; Goldstein, Seth D.; Kang, Jin U.; Choti, Michaal; Boctor, Emad M.

    2015-03-01

    The development of technologies capable of non-invasive characterization of tissue has the potential to significantly improve diagnostic and therapeutic medical interventions. In this study we investigated the feasibility of a noninvasive photoacoustic (PA) approach for characterizing biological tissues. The measurement was performed in the transmission mode with a wideband hydrophone while a tunable Q-switched Nd:YAG pulsed laser was used for illumination. The power spectrum of photoacoustic signal induced by a pulsed laser light from tissue was analyzed and features were extracted to study their correlation with tissue biomechanical properties. For a controlled study, tissue mimicking gelatin phantoms with different densities and equivalent optical absorptions were used as targets. The correlation between gelatin concentration of such phantoms and their mechanical properties were validated independently with a dynamic mechanical analyzer capable of calculating complex loss and storage moduli between two compression plates. It was shown that PA spectrums were shifted towards higher frequencies by increasing gelatin concentration. In order to quantify this effect, signal energy in two intervals of low and high frequency ranges were calculated. Gelatin concentration was correlated with PA energy in high frequency range with R2=0.94. Subsequently, PA signals generated from freshly resected human thyroid specimens were measured and analyzed in a similar fashion. We found that in aggregate, malignant thyroid tissue contains approximately 1.6 times lower energy in the high frequency range in comparison to normal thyroid tissue (p<0.01). This ratio increased with increasing illumination wavelength from 700 nm to 900nm. In summary, this study demonstrated the feasibility of using photoacoustic technique for characterizing tissue on the basis of viscoelastic properties of the tissue.

  20. Toward absorption contrast imaging of biological tissues in vivo by using photothermal optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Makita, Shuichi; Hong, Young-Joo; Yasuno, Yoshiaki

    2014-03-01

    Optical coherence tomography has been proven in the last two decades its clinical value by providing 3D non-invasive in vivo biopsy of the biological samples. In addition to structural information given by the backscattered intensity, the optical absorption will also provide another powerful contrast. Optical absorbers in biological tissues exhibits important role such as hemoglobin and melanin. However, current methods of absorption contrast take long time and not suitable for in vivo imaging. Toward in vivo absorption contrast imaging, we developed photothermal OCT system by combining swept-source OCT system and excitation laser. A swept-source OCT system is used with a wavelength swept laser at 1310 nm with a scanning rate and range of 47 kHz and of 100 nm, respectively. Photocurrents from balanced photoreceivers are sampled by a high-speed digitizer by using k-clock from the source to sample optical spectrum in k-linear domain. The sensitivity of 107 dB for two polarization channels is achieved. At the sample arm, the OCT probe beam and an excitation laser are combined by a dielectric mirror. The fiber-coupled laser diode of 406 nm wavelength is used for excitation since the absorption of hemoglobin has peak around this wavelength. In order to evaluate the ability of this system, phase stability of the system was measured. The standard deviation of the phase shift is measured as 0.0028 radians, where the signal-to-noise-limited value is approximately 0.001. Several issues for in vivo case, motion, blood flow, thermal damage, and etc. will be addressed here.