Sample records for terahertz reflection spectroscopy

  1. Picosecond dynamics of hydrated water in biomolecular solution revealed by terahertz time-domain attenuated total reflection spectroscopy

    Microsoft Academic Search

    T. Arikawa; M. Nagai; K. Tanaka

    2007-01-01

    We propose a novel method to characterize hydration state in solution from dielectric responses in terahertz (THz) frequency region. Slower motion of hydrated water molecules than that of bulk water molecules results in the decrement in dielectric loss, which is detected using THz time-domain attenuated total reflection (TD-ATR) spectroscopy. By fitting experimental data with a dielectric function derived based on

  2. Terahertz time-domain spectroscopy of biological tissues

    SciTech Connect

    Nazarov, M M; Shkurinov, A P; Kuleshov, E A [M. V. Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation); Tuchin, V V [N. G. Chernyshevskii Saratov State University, Saratov (Russian Federation)

    2008-07-31

    Terahertz absorption spectra and dispersion of biologically important substances such as sugar, water, hemoglobin, lipids and tissues are studied. The characteristic absorption lines in the frequency range of a terahertz spectrometer (0.1-3.5 THz) are found. The refraction indices and absorption coefficients of human tooth enamel and dentine are measured. The method of terahertz phase reflection spectroscopy is developed for strongly absorbing substances. Simple and reliable methods of time-resolved terahertz spectroscopy are developed. (biophotonics)

  3. Nondestructive evaluation of sol–gels using terahertz time-domain reflectance spectroscopy to probe the effects of dendrimer incorporation and humidity on sol–gel aging

    Microsoft Academic Search

    Anita R. Taulbee-Combs; Matthew J. Bachus; Kamila M. Wiaderek; William H. Steinecker; Zechariah D. Sandlin; James A. Cox; Gilbert E. Pacey

    2010-01-01

    Terahertz (THz) time-domain reflectance spectroscopy is evaluated as a technique for nondestructive analysis of sol–gels over\\u000a the first week of aging without directly contacting or disturbing the sol–gels. In the sol–gels analyzed, tetramethyl orthosilicate\\u000a (TMOS) is the precursor and polyamidoamine (PAMAM) dendrimers are incorporated into each of two sol–gel sample groups; a third\\u000a control group contains no dendrimer. The study

  4. Terahertz Time-Domain Spectroscopy

    Microsoft Academic Search

    Jason D. Readle

    Terahertz time-domain spectroscopy (THz-TDS) is a technique in which the time-dependent electric field of a THz wave is measured after it interacts with a sample and compared to a reference measurement in which there is no sample. This technique, developed originally in the 1980's, has evolved into a powerful and versatile probing method because of the unique ways in which

  5. Medical diagnostics using terahertz pulsed spectroscopy

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Kudrin, Konstantin G.; Koroleva, Svetlana A.; Fokina, Irina N.; Volodarskaya, Svetlana I.; Novitskaya, Ekaterina V.; Perov, Artem N.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

    2014-03-01

    The paper contains recent results of studying the ability of human body disease diagnosis with terahertz time-domain spectroscopy. In vitro skin cancer samples (squamous cell carcinoma, epithelioid cell melanoma, infiltrating carcinoma) were studied experimentally with terahertz pulsed spectrometer. The parametrical in vitro images of skin cancers are presented. The ability to make early tooth cariosity diagnosis with terahertz time-domain spectroscopy was also shown experimentally. The results of studying the in vitro tooth samples are presented and discussed.

  6. Modulated orientation sensitive terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Singh, Rohit

    The energies of protein correlated motions lie in the far infrared or THz frequency range (lambda = 1 cm -- 50 mm, f = 0.03 -- 6 THz). The existence of correlated motions has been confirmed by neutron and inelastic x-ray scattering measurements. These techniques require large sample volumes and specialized facilities, limiting their application to systematic studies of changes in correlated motions with functional state and allosteric interactions. Standard terahertz time domain spectroscopy measurements have shown sensitivity to protein-ligand binding, oxidation state, conformation, temperature and hydration. However, the response is broad, in part from the large vibrational density of states and in part from the dielectric response contribution from surface water and side-chains. As an overall strategy to measure the correlated structural motions in protein, we use anisotropic and birefringent behavior of molecular crystals to develop a new technique called MOSTS (Modulated Orientation Sensitive Terahertz Spectroscopy). We achieve high sensitivity and mode separation, by using single molecular crystal such as sucrose and oxalic acid, and rapid modulation of the relative alignment of the terahertz polarization and the crystal axes by rotating the sample. By locking into the signal at the rotation frequency, we determine the polarization sensitive signal and map out the optically active vibrational resonances. To illustrate the technique, we compare our measured spectra with the calculated, and find a close agreement. We measure dielectric properties of oxalic acid, sucrose and protein crystals and polycarbonate sheet using standard terahertz time domain spectroscopy. We determine the absorbances in oxalic acid and sucrose crystals, using MOSTS technique. We compare the resonances in these two distinct methods. Then, we develop a protein model sample by sticking together two thin plates of sucrose and polycarbonate. We carry out standard THz-TDS and MOSTS measurements on the protein model sample. We show that we are able to isolate the vibrational modes from glassy background in protein model sample by using MOSTS.

  7. Terahertz spectroscopy of liver cirrhosis: investigating the origin of contrast

    NASA Astrophysics Data System (ADS)

    Sy, Stanley; Huang, Shengyang; Wang, Yi-Xiang J.; Yu, Jun; Ahuja, Anil T.; Zhang, Yuan-ting; Pickwell-MacPherson, Emma

    2010-12-01

    We have previously demonstrated that terahertz pulsed imaging is able to distinguish between rat tissues from different healthy organs. In this paper we report our measurements of healthy and cirrhotic liver tissues using terahertz reflection spectroscopy. The water content of the fresh tissue samples was also measured in order to investigate the correlations between the terahertz properties, water content, structural changes and cirrhosis. Finally, the samples were fixed in formalin to determine whether water was the sole source of image contrast in this study. We found that the cirrhotic tissue had a higher water content and absorption coefficient than the normal tissue and that even after formalin fixing there were significant differences between the normal and cirrhotic tissues' terahertz properties. Our results show that terahertz pulsed imaging can distinguish between healthy and diseased tissue due to differences in absorption originating from both water content and tissue structure.

  8. Characterization of burn injuries using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Arbab, M. Hassan; Dickey, Trevor C.; Winebrenner, Dale P.; Chen, Antao; Mourad, Pierre D.

    2011-03-01

    The accuracy rates of the clinical assessment techniques used in grading burn injuries remain significantly low for partial thickness burns. In this paper, we present experimental results from terahertz characterization of 2nd and 3rd degree burn wounds induced on a rat model. Reflection measurements were obtained from the surface of both burned and normal skin using pulsed terahertz spectroscopy. Signal processing techniques are described for interpretation of the acquired terahertz waveform and differentiation of burn wounds. Furthermore, the progression of burn injuries is shown by comparison between acute characterization and 72-hours survival studies. While the water content of healthy and desiccated skin has been considered as a source of terahertz signal contrast, it is demonstrated that other biological effects such as formation of post-burn interstitial edema as well as the density of the discrete scattering structures in the skin (such as hair follicles, sweat glands, etc.) play a significant role in the terahertz response of the burn wounds.

  9. Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures

    NASA Astrophysics Data System (ADS)

    Azad, Abul K.; Chen, Hou-Tong; Taylor, Antoinette J.; O'Hara, John F.; Han, Jiaguang; Lu, Xinchao; Zhang, Weili

    2009-02-01

    The fascinating properties of plasmonic structures have had significant impact on the development of next generation ultracompact photonic and optoelectronic components. We study two-dimensional plasmonic structures functioning at terahertz frequencies. Resonant terahertz response due to surface plasmons and dipole localized surface plasmons were investigated by the state-of-the-art terahertz time domain spectroscopy (THz-TDS) using both transmission and reflection configurations. Extraordinary terahertz transmission was demonstrated through the subwavelength metallic hole arrays made from good conducting metals as well as poor metals. Metallic arrays made from Pb, generally a poor metal, and having optically thin thicknesses less than one-third of a skin depth also contributed in enhanced THz transmission. A direct transition of a surface plasmon resonance from a photonic crystal minimum was observed in a photo-doped semiconductor array. Electrical controls of the surface plasmon resonances by hybridization of the Schottky diode between the metallic grating and the semiconductor substrate are investigated as a function of the applied reverse bias. In addition, we have demonstrated photo-induced creation and annihilation of surface plasmons with appropriate semiconductors at room temperature. According to the Fano model, the transmission properties are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Such plasmonic structures may find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, tunable filters, and integrated terahertz devices.

  10. Terahertz spectroscopy of two-dimensional subwavelength plasmonic structures

    SciTech Connect

    Azad, Abul K [Los Alamos National Laboratory; Chen, Houtong [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Han, Jiaguang [OSU; Lu, Xinchao [OSU; Zhang, Weili [OSU

    2009-01-01

    The fascinating properties of plasmonic structures have had significant impact on the development of next generation ultracompact photonic and optoelectronic components. We study two-dimensional plasmonic structures functioning at terahertz frequencies. Resonant terahertz response due to surface plasmons and dipole localized surface plasmons were investigated by the state-of-the-art terahertz time domain spectroscopy (THz-TDS) using both transmission and reflection configurations. Extraordinary terahertz transmission was demonstrated through the subwavelength metallic hole arrays made from good conducting metals as well as poor metals. Metallic arrays m!lde from Pb, generally a poor metal, and having optically thin thicknesses less than one-third of a skin depth also contributed in enhanced THz transmission. A direct transition of a surface plasmon resonance from a photonic crystal minimum was observed in a photo-doped semiconductor array. Electrical controls of the surface plasmon resonances by hybridization of the Schottkey diode between the metallic grating and the semiconductor substrate are investigated as a function of the applied reverse bias. In addition, we have demonstrated photo-induced creation and annihilation of surface plasmons with appropriate semiconductors at room temperature. According to the Fano model, the transmission properties are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Such plasmonic structures may find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, tunable filters, and integrated terahertz devices.

  11. Terahertz spectroscopy of DNA

    NASA Astrophysics Data System (ADS)

    Tsurkan, M. V.; Balbekin, N. S.; Sobakinskaya, E. A.; Panin, A. N.; Vaks, V. L.

    2013-06-01

    The spectra of the degraded DNA of herring are studied using two methods of THz spectroscopy that employ a femtosecond laser and a frequency synthesizer based on a BWO and a high-Q cavity. An interpretation of the experimental results is presented.

  12. Reflective terahertz imaging of porcine skin burns.

    PubMed

    Taylor, Z D; Singh, R S; Culjat, M O; Suen, J Y; Grundfest, W S; Lee, H; Brown, E R

    2008-06-01

    A reflective pulsed terahertz imaging system based on direct detection was developed and used to obtain high-resolution images of a porcine skin specimen with superficial partial-thickness (second-degree) burns. Images were also obtained of the sample through ten layers of dry medical (cotton) gauze with minimal image degradation. The burned and unburned regions of skin had large differences in terahertz reflectivity, displaying clear delineation [20 dB signal-to-noise ratio (SNR) difference signal] between both regions in the images. The terahertz images also exhibited a "halo" surrounding the burn areas that may correlate to the extent of burn injury. The system operated at a center frequency of 500 GHz with 125 GHz of 3 dB bandwidth and used whiskbroom scanning to generate images with a spatial resolution of 1.5 mm. Each pixel was acquired with a 16 ms integration time, resulting in a 40 dB postdetection SNR. The simplicity and high SNR of the reflective terahertz system are promising steps toward real-time terahertz medical imaging. PMID:18516193

  13. Terahertz spectroscopy techniques for explosives detection

    Microsoft Academic Search

    Megan R. Leahy-Hoppa; Michael J. Fitch; Robert Osiander

    2009-01-01

    Spectroscopy in the terahertz frequency range has demonstrated unique identification of both pure and military-grade explosives.\\u000a There is significant potential for wide applications of the technology for nondestructive and nonintrusive detection of explosives\\u000a and related devices. Terahertz radiation can penetrate most dielectrics, such as clothing materials, plastics, and cardboard.\\u000a This allows both screening of personnel and through-container screening. We review

  14. Metallic scattering lifetime measurements with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Lea, Graham Bryce

    The momentum scattering lifetime is a fundamental parameter of metallic conduction that can be measured with terahertz time-domain spectroscopy. This technique has an important strength over optical reflectance spectroscopy: it is capable of measuring both the phase and the amplitude of the probing radiation. This allows simultaneous, independent measurements of the scattering lifetime and resistivity. Broadly, it is the precision of the phase measurement that determines the precision of scattering lifetime measurements. This thesis describes milliradian-level phase measurement refinements in the experimental technique and measures the conductivity anisotropy in the correlated electron system CaRuO3. These phase measurement refinements translate to femtosecond-level refinements in scattering lifetime measurements of thin metallic films. Keywords: terahertz time-domain spectroscopy, calcium ruthenate, ruthenium oxides, correlated electrons, experimental technique.

  15. A promising diagnostic method: Terahertz pulsed imaging and spectroscopy

    PubMed Central

    Sun, Yiwen; Sy, Ming Yiu; Wang, Yi-Xiang J; Ahuja, Anil T; Zhang, Yuan-Ting; Pickwell-MacPherson, Emma

    2011-01-01

    The terahertz band lies between the microwave and infrared regions of the electromagnetic spectrum. This radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. It is strongly attenuated by water and very sensitive to water content. Unique absorption spectra due to intermolecular vibrations in this region have been found in different biological materials. These unique features make terahertz imaging very attractive for medical applications in order to provide complimentary information to existing imaging techniques. There has been an increasing interest in terahertz imaging and spectroscopy of biologically related applications within the last few years and more and more terahertz spectra are being reported. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques, and a number of applications such as molecular spectroscopy, tissue characterization and skin imaging are discussed. PMID:21512652

  16. Terahertz spectroscopy for quantifying refined oil mixtures.

    PubMed

    Li, Yi-nan; Li, Jian; Zeng, Zhou-mo; Li, Jie; Tian, Zhen; Wang, Wei-kui

    2012-08-20

    In this paper, the absorption coefficient spectra of samples prepared as mixtures of gasoline and diesel in different proportions are obtained by terahertz time-domain spectroscopy. To quantify the components of refined oil mixtures, a method is proposed to evaluate the best frequency band for regression analysis. With the data in this frequency band, dualistic linear regression fitting is used to determine the volume fraction of gasoline and diesel in the mixture based on the Beer-Lambert law. The minimum of regression fitting R-Square is 0.99967, and the mean error of fitted volume fraction of 97# gasoline is 4.3%. Results show that refined oil mixtures can be quantitatively analyzed through absorption coefficient spectra in terahertz frequency, which it has bright application prospects in the storage and transportation field for refined oil. PMID:22907017

  17. Signal restoration from atmospheric degradation in terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Kong, Seong G.; Wu, Dong H.

    2008-06-01

    This paper presents a method of restoring signals in terahertz spectroscopy by removing the distortion from the observed terahertz signals. The distortion is generated by the absorption and scattering of gas molecules and water vapor in the atmosphere during the transmission of terahertz beams through the air from the source to the spectrometer. Such atmospheric degradation causes spurious spectral dips and peaks in the terahertz spectrum, which often obscure the spectral peaks specific to the material of interest. This fact makes it challenging to measure the terahertz spectroscopic signatures of objects in a humid air environment, even at a short distance of approximately 1 m. A terahertz signal restoration filter based on a nonlinear artificial neural network model effectively removes noisy absorption peaks in terahertz spectra caused by atmospheric degradation.

  18. Science Experimenter: Reflectance Spectroscopy.

    ERIC Educational Resources Information Center

    Mims, Forrest M., III

    1991-01-01

    Provides construction details for a simple reflectometer that can be utilized for the observational technique known as reflectance spectroscopy. Includes background discussion, applications, calibrating techniques, and typical results. (JJK)

  19. Time-domain terahertz spectrometer for angular reflection measurements

    NASA Astrophysics Data System (ADS)

    Nóvoa, José Antonio; Ordoñez, Ismael; Rial, Carmen; Martín, Jorge; Gil, Álvaro; Ramón Salgueiro, José

    2015-04-01

    We describe a terahertz time-domain spectrometer developed to perform measurements by reflection under a wide range of angles. The different parts of the device are described as well as the process of frequency-scale calibration and signal linearity evaluation. Also the main parameters that characterize the system and account their performance are measured. Finally an example of application to the measurement of the bandgap of a photonic crystal designed for the terahertz band is presented.

  20. High power, high resolution terahertz spectroscopy technologies and its applications

    NASA Astrophysics Data System (ADS)

    Wu, Dong Ho; Graber, Benjamin; Kim, Christopher

    2015-03-01

    Since a large number of molecules' resonance frequencies lie within terahertz frequencies, terahertz spectroscopy is a highly useful tool for scientific investigation of various materials. At the same time one can use the same technology for the identification of hidden materials. Despite these potential applications presently terahertz spectroscopy is largely underutilized, and it is mostly being used in the laboratory environment. This is in part largely due to the fact that no portable, high power, high resolution spectrometer is currently available. So we have been developing a high power, wideband terahertz source. The terahertz source is capable to produce a relatively high power (>2 mW), wideband (0.1 - 3 THz) terahertz beam. In addition to the source we have optimized and calibrated an electro-optic (EO) detector, of which sensitivity is 10-13 W/(Hz)1/2. Recently, by utilizing these terahertz source and detector, we have constructed a high power, high resolution terahertz spectrometer, and carried out various experiments to understand resonance spectra of water vapor, chemicals and ionized air. Also we constructed a modified terahertz spectrometer for a stand-off detection applications. In this presentation I will discuss our experimental achievements and progresses. Supported by DTRA.

  1. A Comparison of Terahertz Pulsed Spectroscopy and Backward-Wave Oscillator Spectroscopy

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Gavdush, Arseniy A.; Chernomyrdin, Nikita V.; Kruchkov, Nikita P.; Kudrin, Konstantin G.; Nosov, Pavel A.; Karasik, Valeriy E.; Yurchenko, Stanislav O.

    2014-09-01

    This paper presents new experimental and theoretical results for the material parameter reconstruction utilizing the terahertz (THz) pulsed spectroscopy (TPS). The material parameter reconstruction algorithm was realized and experimentally implemented to study the test sample. The algorithm takes into account multiple reflections of THz pulse within the flat sample during the transmission mode measurements. Therefore the samples with small thickness or low refractive index could be studied utilizing the proposed method. In order to estimate the reconstruction accuracy, test sample material parameters, obtained with the TPS, were compared with the results of the same sample studying by the use of the backward-wave oscillator (BWO) spectroscopy. Thus, high reconstruction accuracy was demonstrated.

  2. Influence of noise on the characterization of materials by terahertz time-domain spectroscopy

    Microsoft Academic Search

    Lionel Duvillaret; Frédéric Garet; Jean-Louis Coutaz

    2000-01-01

    We analyze the contributions of various error sources to uncertainty in the far-infrared optical constants (re- fractive index and absorption coefficient) measured by terahertz (THz) time-domain spectroscopy. We focus our study on the influence of noise. This noise study is made with a thick slab of transparent material for which the THz transmitted signal exhibits temporal echoes owing to reflections

  3. Terahertz reflection response measurement using a phonon polariton wave

    NASA Astrophysics Data System (ADS)

    Inoue, Hayato; Katayama, Kenji; Shen, Qing; Toyoda, Taro; Nelson, Keith A.

    2009-03-01

    We developed a new technique for the measurement of terahertz reflection responses utilizing a propagating phonon polariton wave. Frequency tunable phonon polariton waves were generated by the recently developed continuously variable spatial frequency transient grating method [K. Katayama, H. Inoue, H. Sugiya, Q. Shen, T. Taro, and K. A. Nelson, Appl. Phys. Lett. 92, 031906 (2008)]. The phonon polariton wave traveled in a ferroelectric crystal in an in-plane direction with an inclined angle of 26°, and the wave reflected at the crystal edge where a sample was positioned. The reflected polariton wave was detected by the same method as that used for the generation of the polariton waves. By comparing the reflection intensities in the presence and absence of the sample, reflectivity of the polariton wave was calculated, and the refractive index and absorption in the terahertz region were obtained.

  4. Compressed sensing pulse-echo mode terahertz reflectance tomography

    E-print Network

    Compressed sensing pulse-echo mode terahertz reflectance tomography Kyung Hwan Jin,1 Youngchan Kim reconstruction is accomplished using a compressed sensing ap- proach. One of the main advantages of the proposed [1] and diffraction and/or computed tomography [2]. Recently, Chan et al. proposed a compressed sens

  5. Biological Sensing with Terahertz Circular Dichroism Spectroscopy

    NASA Astrophysics Data System (ADS)

    Xu, J.; Ramian, G.; Scopatz, A. M.; Allen, S. J.; Plaxco, K. W.

    2003-03-01

    Chirality is believed to be a general and unique trait of life. Since biopolymers absorb broadly in the terahertz regime, we expect circular dichroism to appear everywhere but with zero-crossings as a bio-polymer specific spectroscopic signature; terahertz circular dichroism (heretofore unexplored) may provide a universal and unambiguous signature of biological systems, regardless of their genesis. We are building a novel terahertz circular dichroism spectrometer. It is being tested with a 139 gigahertz Gunn source. But, we will explore terahertz circular dichroism over a very broad frequency range, in and out of aqueous solution using the intense and broadly tunable terahertz radiation from the free electron lasers at UCSB (0.12 to 4.75 THz). Preliminary experimental results will be presented as well as coupled harmonic oscillator models for the broad terahertz frequency circular dichroism expected for these disordered systems. Supported by NASA abd ARO

  6. Terahertz technology for imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Crowe, T. W.; Porterfield, D. W.; Hesler, J. L.; Bishop, W. L.; Kurtz, D. S.; Hui, K.

    2006-05-01

    The terahertz region of the electromagnetic spectrum has unique properties that make it especially useful for imaging and spectroscopic detection of concealed weapons, explosives and chemical and biological materials. However, terahertz energy is difficult to generate and detect, and this has led to a technology gap in this frequency band. Nonlinear diodes can be used to bridge this gap by translating the functionality achieved at microwave frequencies to the terahertz band. Basic building blocks include low-noise mixers, frequency multipliers, sideband generators and direct detectors. These terahertz components rely on planar Schottky diodes and recently developed integrated diode circuits make them easier to assemble and more robust. The new generation of terahertz sources and receivers requires no mechanical tuning, yet achieves high efficiency and broad bandwidth. This paper reviews the basic design of terahertz transmitters and receivers, with special emphasis on the recent development of systems that are compact, easy to use and have excellent performance.

  7. Ultrabroadband terahertz spectroscopies of biomolecules and water

    NASA Astrophysics Data System (ADS)

    Turton, David; Harwood, Thomas; Lapthorn, Adrian; Ellis, Elizabeth; Wynne, Klaas

    2013-03-01

    We describe the use of a range of modern spectroscopic techniques—from terahertz time-domain spectroscopy (THz- TDS) to high dynamic-range femtosecond optical Kerr-effect (OKE) spectroscopy—to study the interaction of proteins, peptides, and other biomolecules with the aqueous solvent. Chemical reactivity in proteins requires fast picosecond fluctuations to reach the transition state, to dissipate energy, and (possibly) to reduce the width and height of energy barriers along the reaction coordinate. Such motions are linked with the structure and dynamics of the aqueous solvent making hydration critical to function. These dynamics take place over a huge range of timescales: from the nanosecond timescale of diffusion of water molecules in the first solvation shell of proteins, picosecond motions of amino-acid side chains, and sub-picosecond librational and phonon-like motions of water. It is shown that a large range of frequencies from MHz to THz is accessible directly using OKE resulting in the reduced anisotropic Raman spectrum and by using a combination of techniques including THz-TDS resulting in the dielectric spectrum. Using these techniques, we can now observe very significant differences in the spectra of proteins in aqueous solvent in the 3-30 THz range and more subtle differences at lower frequencies (10 GHz-3 THz).

  8. Protein Conformational State Observed through Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chen, J. Y.; Whitmire, S. E.; Wolpert, D.; Markelz, A. G.; Hillebrecht, J. R.; Galan, J.; Birge, R. R.

    2003-03-01

    We present the first demonstration of the dependence of far infrared (FIR) absorption on protein conformational state using terahertz time domain spectroscopy. FIR spectral measurements of wild type (WT) and D96N mutant bacteriorhodopsin thin films have been carried out as a function of hydration, temperature and conformational state. The results are compared to calculated spectra generated via normal mode analyses using CHARMm. The FIR absorbance is slowly increasing with frequency and without strong narrow features over the range of 2-60 cm-1. The absorption shifts in frequency with decreasing temperature as expected with a strongly anharmonic potential. Decreasing hydration shifts the absorption to higher frequencies. Ground state FIR absorbances have nearly identical frequency dependence, with the mutant having less optical density than the wild type. We use photoexcitation and thermal capture to perform measurements as a function of the M intermediate state content. In the M state the FIR absorbance of the WT increases whereas there is no change for D96N. Support was provided by ARO DAAD19-02-1-0271 and DAAD19-99-1-0198 and NSF EIA-0129731.

  9. Terahertz vibrational absorption spectroscopy using microstrip-line waveguides

    NASA Astrophysics Data System (ADS)

    Byrne, M. B.; Cunningham, J.; Tych, K.; Burnett, A. D.; Stringer, M. R.; Wood, C. D.; Dazhang, L.; Lachab, M.; Linfield, E. H.; Davies, A. G.

    2008-11-01

    We demonstrate that terahertz microstrip-line waveguides can be used to measure absorption spectra of polycrystalline materials with a high frequency resolution (˜2 GHz) and with a spatial resolution that is determined by the microstrip-line dimensions, rather than the free-space wavelength. The evanescent terahertz-bandwidth electric field extending above the microstrip line interacts with, and is modified by, overlaid dielectric samples, thus enabling the characteristic vibrational absorption resonances in the sample to be probed. As an example, the terahertz absorption spectrum of polycrystalline lactose monohydrate was investigated; the lowest lying mode was observed at 534(±2) GHz, in excellent agreement with free-space measurements. This microstrip technique offers both a higher spatial and frequency resolution than free-space terahertz time-domain spectroscopy and requires no contact between the waveguide and sample.

  10. Terahertz time domain spectroscopy of phonon-depopulation based quantum cascade lasers

    E-print Network

    Boyer, Edmond

    1 Terahertz time domain spectroscopy of phonon-depopulation based quantum cascade lasers N. Jukam) 251108" #12;2 Abstract The gain and loss in a terahertz quantum cascade laser based on a longitudinal optical phonon depopulation scheme is studied using terahertz time domain spectroscopy. At laser threshold

  11. Bragg reflection of terahertz waves in plasmonic crystals.

    PubMed

    Lee, Eui Su; Kang, D H; Fernandez-Dominguez, A I; Garcia-Vidal, F J; Martin-Moreno, L; Kim, D S; Jeon, Tae-In

    2009-05-25

    We present experimental and theoretical studies on terahertz surface plasmon (TSP) propagation on slit and rectangular aperture arrays in an aluminum sheet. Terahertz waves are coupled onto the plasmonic structures via a parallel plate waveguide. Long-lasting oscillations are observed in the temporal pulse shape after propagating through the periodic structure, whose Fourier transformation into the frequency domain results in Bragg-resonance spectral features. We show that the interference between the incident wave and the radiation reflected from both the aperture array and the waveguide block is responsible for this Bragg-resonance behavior. The reflection coefficient for a single slit is deduced to be 0.017 +/- 0.002. PMID:19466171

  12. Time-resolved terahertz spectroscopy of black silicon

    Microsoft Academic Search

    H. P. Porte; D. Turchinovich; P. U. Jepsen; S. Persheyev; Y. Fan; M. J. Rose

    2010-01-01

    The ultrafast photoconductivity dynamics of black silicon is measured by time-resolved terahertz spectroscopy. Black silicon is produced by laser annealing of an a-Si:H film. We show that the decay time of the photoconductivity depends on the annealing method and fluence used in the production process.

  13. Squeezing terahertz light into nanovolumes: nanoantenna enhanced terahertz spectroscopy (NETS) of semiconductor quantum dots.

    PubMed

    Toma, Andrea; Tuccio, Salvatore; Prato, Mirko; De Donato, Francesco; Perucchi, Andrea; Di Pietro, Paola; Marras, Sergio; Liberale, Carlo; Proietti Zaccaria, Remo; De Angelis, Francesco; Manna, Liberato; Lupi, Stefano; Di Fabrizio, Enzo; Razzari, Luca

    2015-01-14

    Terahertz spectroscopy has vast potentialities in sensing a broad range of elementary excitations (e.g., collective vibrations of molecules, phonons, excitons, etc.). However, the large wavelength associated with terahertz radiation (about 300 ?m at 1 THz) severely hinders its interaction with nano-objects, such as nanoparticles, nanorods, nanotubes, and large molecules of biological relevance, practically limiting terahertz studies to macroscopic ensembles of these compounds, in the form of thick pellets of crystallized molecules or highly concentrated solutions of nanomaterials. Here we show that chains of terahertz dipole nanoantennas spaced by nanogaps of 20 nm allow retrieving the spectroscopic signature of a monolayer of cadmium selenide quantum dots, a significant portion of the signal arising from the dots located within the antenna nanocavities. A Fano-like interference between the fundamental antenna mode and the phonon resonance of the quantum dots is observed, accompanied by an absorption enhancement factor greater than one million. NETS can find immediate applications in terahertz spectroscopic studies of nanocrystals and molecules at extremely low concentrations. Furthermore, it shows a practicable route toward the characterization of individual nano-objects at these frequencies. PMID:25422163

  14. Conformational characteristics of ?-glucan in laminarin probed by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Shin, Hee Jun; Oh, Seung Jae; Kim, Sung In; Won Kim, Ha; Son, Joo-Hiuk

    2009-03-01

    We measured the binding-state-dependent power absorptions, refractive indices, and dielectric constants of triple-stranded helices (TSHs) and single-stranded helices (SSHs) ?-glucans in laminarin using terahertz time-domain spectroscopy (TDS). The SSH ?-glucan was obtained from a TSH ?-glucan laminarin by a chemical treatment with NaOH solution. The power absorption of TSH ?-glucan increased more rapidly than that of the SSH ?-glucan with the frequency increment. The refractive index and dielectric constants of TSH ?-glucan were also larger than those of the SSH ?-glucan. This result implies that terahertz-TDS is a very effective method in classifying the conformational state of ?-glucans.

  15. Identify paraffin-embedded brain glioma using terahertz pulsed spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Ze-ren; Meng, Kun; Chen, Tu-nan; Chen, Tao; Zhu, Li-guo; Liu, Qiao; Li, Zhao; Li, Fei; Zhong, Sen-cheng; Feng, Hua; Zhao, Jian-heng

    2015-01-01

    The refractive indices, absorption coefficients and complex dielectric constants spectra of paraffin-embedded brain glioma and normal brain tissues have been measured by a terahertz time domain spectroscopy (THz-TDS) system in the range of 0.2 - 2.0 THz. The spectral differences between glioma and normal brain tissues were obtained. Our results indicate that, compared with normal tissue, glioma had higher refractive index, absorption coefficient, and dielectric constant. Based on these results, the suitable frequency components for different methods of glioma imaging (intensity imaging, coherent imaging and terahertz pulsed imaging) are analyzed.

  16. Step-scan time-domain terahertz magneto-spectroscopy.

    PubMed

    Molter, D; Torosyan, G; Ballon, G; Drigo, L; Beigang, R; Léotin, J

    2012-03-12

    We present a novel approach for terahertz time-domain spectroscopy of magneto-optic phenomena. The setup used in this work combines a tabletop pulsed magnet and a standard terahertz time-domain spectroscopy system. The approach is based on repetitive operation of the pulsed magnet and step-wise increment of the delay time of the time-domain spectroscopy system. The method is demonstrated by plotting the magneto-transmission spectra of linearly polarized THz pulses through the hole gas of a Ge sample and the electron gas of GaAs, InSb and InAs samples. Cyclotron resonance spectra are displayed in the frequency range from 200 GHz to 2 THz and for a magnetic field up to 6 T. The GaAs spectra are analyzed in more detail using simulations based on the Drude model. PMID:22418476

  17. Terahertz spectroscopy of silicon micromachined three-dimensional photonic bandgap crystal

    SciTech Connect

    Oezbay, E.; Michel, E.; Tuttle, G.; Biswas, R.; Ho, K.M. [Iowa State Univ., Ames, IA (United States); Bostak, J.; Bloom, D.M. [Stanford Univ., CA (United States). Edward L. Ginzton Lab.

    1995-04-01

    Using micromachined silicon wafers, the authors have fabricated three-dimensional photonic bandgap crystals. Terahertz spectroscopy techniques have been used to measure bandgap frequencies over 500 GHz.

  18. Tablet Content Analysis Using Terahertz Transmission Spectroscopy

    Microsoft Academic Search

    John A. Spencer; Everett H. Jefferson; Ajaz S. Hussain; David Newnham; Thomas Lo

    2007-01-01

    A group of pressed tablets with acetaminophen content between 60 mg and 120 mg were scanned in the terahertz spectral region\\u000a (2 cm?1–120 cm?1) in transmission mode. Tablet acetaminophen content was determined by a standard HPLC method. Despite the lack of discernible\\u000a spectral features and the tablets being opaque above 45 cm?1, a working partial least squares model could be constructed. The results show the

  19. Ultrafast Coherent Terahertz Spectroscopy in High Magnetic Fields

    Microsoft Academic Search

    S. A. Crooker; A. J. Taylor

    2002-01-01

    With an aim towards measuring the high-frequency complex conductivity of correlated electron materials in the regime of low temperatures and high magnetic fields, we introduce a method for performing time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed-field magnets. Miniature, fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 5 K

  20. Terahertz spectroscopy properties of the selected engine oils

    NASA Astrophysics Data System (ADS)

    Zhu, Shouming; Zhao, Kun; Lu, Tian; Zhao, Songqing; Zhou, Qingli; Shi, Yulei; Zhao, Dongmei; Zhang, Cunlin

    2010-11-01

    Engine oil, most of which is extracted from petroleum, consist of complex mixtures of hydrocarbons of molecular weights in the range of 250-1000. Variable amounts of different additives are put into them to inhibit oxidation, improve the viscosity index, decrease the fluidity point and avoid foaming or settling of solid particles among others. Terahertz (THz) spectroscopy contains rich physical, chemical, and structural information of the materials. Most low-frequency vibrational and rotational spectra of many petrochemicals lie in this frequency range. In recent years, much attention has been paid to the THz spectroscopic studies of petroleum products. In this paper, the optical properties and spectroscopy of selected kinds of engine oil consisting of shell HELIX 10W-40, Mobilube GX 80W-90, GEELY ENGINE OIL SG 10W-30, SMA engine oil SG 5W-30, SMA engine oil SG 10W-30, SMA engine oil SG 75W-90 have been studied by the terahertz time-domain spectroscopy (THz-TDS) in the spectral range of 0.6-2.5 THz. Engine oil with different viscosities in the terahertz spectrum has certain regularity. In the THz-TDS, with the increase of viscosity, time delay is greater and with the increase of viscosity, refractive indexes also grow and their rank is extremely regular. The specific kinds of engine oil can be identified according to their different spectral features in the THz range. The THz-TDS technology has potentially significant impact on the engine oil analysis.

  1. TeraHertz Time-Domain Spectroscopy for Explosive Trace Detection

    Microsoft Academic Search

    Seong G. Kong; Dong H. Wu

    2006-01-01

    This paper presents Terahertz time-domain spectroscopy for stand-off detection of explosive traces. Despite several well-developed explosive detection techniques available, the detection of a small amount of explosive traces is still challenging. Terahertz spectroscopy demonstrates potential for explosive detection through unique absorption spectra pattern of various kinds of explosive materials. Terahertz waves show good penetration through many dielectric materials that are

  2. Application of superlattice multipliers for high-resolution terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Endres, C. P.; Lewen, F.; Giesen, T. F.; Schlemmer, S.; Paveliev, D. G.; Koschurinov, Y. I.; Ustinov, V. M.; Zhucov, A. E.

    2007-04-01

    Frequency multipliers based on superlattice (SL) devices as nonlinear elements have been developed as radiation sources for a terahertz (THz) laboratory spectrometer. Input frequencies of 100 and 250 GHz from backward wave oscillators have been multiplied up to the 11th harmonic, producing usable frequencies up to 2.7 THz. Even at these high frequencies the output power is sufficient for laboratory spectroscopy. Comparisons to conventional high-resolution microwave spectroscopy methods reveal several superior features of this new device such as very high line frequency accuracies, broadband tunability, high output power levels at odd harmonics of the input frequency up to high orders, and a robust applicability.

  3. High-Resolution Waveguide Terahertz Spectroscopy of Partially Oriented Organic Polycrystalline Films

    E-print Network

    the orientation of the polycrystalline TCNQ films on the PPWG surface and to qualitatively explain the differentHigh-Resolution Waveguide Terahertz Spectroscopy of Partially Oriented Organic Polycrystalline, 2007 We have characterized the terahertz (THz) vibrational spectroscopy of organic polycrystalline thin

  4. Ultrabroadband terahertz spectroscopy of chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Zalkovskij, Maksim; Zoffmann Bisgaard, Christer; Novitsky, Andrey; Malureanu, Radu; Savastru, Dan; Popescu, Aurelian; Uhd Jepsen, Peter; Lavrinenko, Andrei V.

    2012-01-01

    Chalcogenide glasses are receiving a lot of attention due to their unique optical properties. In this paper we study the optical properties of As2S3 and GaLaS glasses in a broad terahertz (THz) frequency range (0.2-18 THz). Complex dispersion behavior with drastic changes of refractive index and absorption coefficient is found for both glasses. We observe the breakdown of the universal power-law dependence of the absorption coefficient due to atomic vibrations observed at low THz frequencies in disordered materials, and see the transition to localized vibrational dynamics for the As2S3 compound at higher frequencies. In addition, As2S3 displays two transparency regions, at 7-8 THz and 12.2 THz, of potential interest for future nonlinear applications in the THz range.

  5. Grating-assisted coupling of terahertz waves into a dielectric waveguide studied by terahertz time-domain spectroscopy

    Microsoft Academic Search

    Jean-Francois Roux; Fabien Aquistapace; Frederic Garet; Lionel Duvillaret; Jean-Louis Coutaz

    2002-01-01

    We report on the efficient coupling of terahertz (THz) waves into a dielectric waveguide by means of a diffraction grating engraved at the top of the waveguide. The waveguide is made of a 201-mum-thick high-resistivity silicon wafer. The transmission of the device, measured versus frequency by terahertz time-domain spectroscopy, shows usual m lines when a frequency component of the THz

  6. Hydration state inside HeLa cell monolayer investigated with terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Shiraga, K.; Suzuki, T.; Kondo, N.; Tanaka, K.; Ogawa, Y.

    2015-06-01

    The hydration state in living cells is believed to be associated with various cellular activities. Nevertheless, in vivo characterization of intracellular hydration state under physiological condition has not been well documented to date. In this study, the hydration state of an intact HeLa cell monolayer was investigated by terahertz time-domain attenuated total reflection spectroscopy. Combined with the extended theory of Onsager, we found 23.8 ± 7.4% of HeLa intracellular water was hydrated to biomolecules (corresponding to 1.25 g H2O/g solute); exhibiting slower relaxation dynamics than bulk water.

  7. Terahertz spectral investigation of anhydrous and monohydrated glucose using terahertz spectroscopy and solid-state theory

    NASA Astrophysics Data System (ADS)

    Zheng, Zhuan-Ping; Fan, Wen-Hui; Li, Hui; Tang, Jie

    2014-02-01

    The terahertz absorption spectra of anhydrous and monohydrated glucose have been investigated and compared by using THz spectroscopy and solid-sate density functional theory. The unrevealed mechanism of THz spectral differences of both materials measured has been analyzed based on the crystalline structure. Solid-state calculations of the THz characteristic spectra using Perdew-Burke-Ernzerhof functional have provided the satisfactory spectral reproduction for these two materials. It is found that the characterized features of monohydrated glucose mainly come from the intermolecular modes of water-glucose and glucose-glucose molecules, while those of anhydrous glucose origin from the interactions of glucose molecules.

  8. High power time domain terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Graber, Benjamin

    Terahertz (THz) has become a strong area for scientific research and commercial application in recent years. This research group has redesigned and optimized a THz photoconductive antenna, which currently operates with approximately 10x the power of a commercial antenna. It has been determined by this research that the THz signal emitted from a photoconductive antenna consists of coherent and incoherent signals. In addition to the improvement of the THz photoconductive antenna, I have optimized an electro optic THz detection system by characterizing the field dependency of an electro optic crystal, which enabled me to estimate the THz electric field strength. The high power THz source and optimized detection system were combined into a high power, high resolution time domain THz spectrometer. This spectrometer was used to conduct original measurements of the THz spectrum of water vapor, ionized air, and various chemical vapor including explosives. Most of these measurements were only possible with our improved THz spectrometer. In order to understand ionized air, an additional study was carried out to explore the ionization of several gases (e.g. N2, O2, Ar, CO2, and water vapor) which were ionized by radioactive isotopes. This unique study found that in addition to dose rate, the gamma energy of the radioactive isotopes and the sequential ionization levels of gases affect the equilibrium ion densities of these gases. This effect was especially pronounced for argon gas. The study of ion dynamics in gases has lead to the development of a prototype for stand-off detection and identification of radioactive isotopes. This prototype, despite being simple in design, can detect isotopes faster and more cheaply than a conventional gamma ray spectrometer. Throughout this thesis research I have successfully developed a high power, high resolution terahertz spectrometer and demonstrated that with the spectrometer I could identify characteristic resonances of water vapor, some chemicals including explosives, and even ionized air produced by nuclear isotopes. From the characteristic resonance frequencies one can understand the underlying physics or chemistry of molecules or atoms.

  9. Terahertz time-domain spectroscopy of four hydroxycinnamic acid derivatives.

    PubMed

    Ge, Min; Zhao, Hongwei; Wang, Wenfeng; Zhang, Zengyan; Yu, Xiaohan; Li, Wenxin

    2006-11-01

    The well-resolved absorption spectra of the hydroxycinnamic acid (HCA) derivatives, caffeic acid, ferulic acid, sinapic acid and chlorogenic acid, were measured over the frequency region from 0.3 to 2.0 THz at 294 K with terahertz time-domain spectroscopy (THz-TDS). Theoretical calculation was applied to assist the analysis and assignment of the individual THz absorption spectra of the HCA derivatives with density functional theory (DFT). The distinctive spectral features were originated from the collective motion of molecules held together by hydrogen bonds. The real and imaginary parts of dielectric function of the four HCA derivatives were also obtained. PMID:19669446

  10. Terahertz electromodulation spectroscopy of electron transport in GaN

    NASA Astrophysics Data System (ADS)

    Engelbrecht, S. G.; Arend, T. R.; Zhu, T.; Kappers, M. J.; Kersting, R.

    2015-03-01

    Time-resolved terahertz (THz) electromodulation spectroscopy is applied to investigate the high-frequency transport of electrons in gallium nitride at different doping concentrations and densities of threading dislocations. At THz frequencies, all structures reveal Drude transport. The analysis of the spectral response provides the fundamental transport properties, such as the electron scattering time and the electrons' conductivity effective mass. We observe the expected impact of ionized-impurity scattering and that scattering at threading dislocations only marginally affects the high-frequency mobility.

  11. Two-dimensional Raman-terahertz spectroscopy of water

    PubMed Central

    Savolainen, Janne; Ahmed, Saima; Hamm, Peter

    2013-01-01

    Two-dimensional Raman-terahertz (THz) spectroscopy is presented as a multidimensional spectroscopy directly in the far-IR regime. The method is used to explore the dynamics of the collective intermolecular modes of liquid water at ambient temperatures that emerge from the hydrogen-bond networks water forming. Two-dimensional Raman-THz spectroscopy interrogates these modes twice and as such can elucidate couplings and inhomogeneities of the various degrees of freedoms. An echo in the 2D Raman-THz response is indeed identified, indicating that a heterogeneous distribution of hydrogen-bond networks exists, albeit only on a very short 100-fs timescale. This timescale appears to be too short to be compatible with more extended, persistent structures assumed within a two-state model of water. PMID:24297930

  12. Characterization of wheat varieties using terahertz time-domain spectroscopy.

    PubMed

    Ge, Hongyi; Jiang, Yuying; Lian, Feiyu; Zhang, Yuan; Xia, Shanhong

    2015-01-01

    Terahertz (THz) spectroscopy and multivariate data analysis were explored to discriminate eight wheat varieties. The absorption spectra were measured using THz time-domain spectroscopy from 0.2 to 2.0 THz. Using partial least squares (PLS), a regression model for discriminating wheat varieties was developed. The coefficient of correlation in cross validation (R) and root-mean-square error of cross validation (RMSECV) were 0.985 and 1.162, respectively. In addition, interval PLS was applied to optimize the models by selecting the most appropriate regions in the spectra, improving the prediction accuracy (R = 0.992 and RMSECV = 0.967). Results demonstrate that THz spectroscopy combined with multivariate analysis can provide rapid, nondestructive discrimination of wheat varieties. PMID:26024421

  13. Characterization of Wheat Varieties Using Terahertz Time-Domain Spectroscopy

    PubMed Central

    Ge, Hongyi; Jiang, Yuying; Lian, Feiyu; Zhang, Yuan; Xia, Shanhong

    2015-01-01

    Terahertz (THz) spectroscopy and multivariate data analysis were explored to discriminate eight wheat varieties. The absorption spectra were measured using THz time-domain spectroscopy from 0.2 to 2.0 THz. Using partial least squares (PLS), a regression model for discriminating wheat varieties was developed. The coefficient of correlation in cross validation (R) and root-mean-square error of cross validation (RMSECV) were 0.985 and 1.162, respectively. In addition, interval PLS was applied to optimize the models by selecting the most appropriate regions in the spectra, improving the prediction accuracy (R = 0.992 and RMSECV = 0.967). Results demonstrate that THz spectroscopy combined with multivariate analysis can provide rapid, nondestructive discrimination of wheat varieties. PMID:26024421

  14. Instrument independent diffuse reflectance spectroscopy

    PubMed Central

    Yu, Bing; Fu, Henry L.; Ramanujam, Nirmala

    2011-01-01

    Diffuse reflectance spectroscopy with a fiber optic probe is a powerful tool for quantitative tissue characterization and disease diagnosis. Significant systematic errors can arise in the measured reflectance spectra and thus in the derived tissue physiological and morphological parameters due to real-time instrument fluctuations. We demonstrate a novel fiber optic probe with real-time, self-calibration capability that can be used for UV-visible diffuse reflectance spectroscopy in biological tissue in clinical settings. The probe is tested in a number of synthetic liquid phantoms over a wide range of tissue optical properties for significant variations in source intensity fluctuations caused by instrument warm up and day-to-day drift. While the accuracy for extraction of absorber concentrations is comparable to that achieved with the traditional calibration (with a reflectance standard), the accuracy for extraction of reduced scattering coefficients is significantly improved with the self-calibration probe compared to traditional calibration. This technology could be used to achieve instrument-independent diffuse reflectance spectroscopy in vivo and obviate the need for instrument warm up and post?premeasurement calibration, thus saving up to an hour of precious clinical time. PMID:21280897

  15. Conductivity of ZnO Nanowires, Nanoparticles, and Thin Films Using Time-Resolved Terahertz Spectroscopy

    E-print Network

    Conductivity of ZnO Nanowires, Nanoparticles, and Thin Films Using Time-Resolved Terahertz of nanostructured ZnO have been determined using time-resolved terahertz spectroscopy, a noncontact optical probe. ZnO properties were measured directly for thin films and were extracted from measurements of nanowire

  16. Semiconductor Nonlinear Dynamics Study by Broadband Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ho, I.-Chen

    Semiconductor nonlinearity in the terahertz (THz) frequency range has been attracting considerable attention due to the recent development of high-power semiconductor-based nanodevices. However, the underlying physics concerning carrier dynamics in the presence of high-field THz transients is still obscure. This thesis introduces an ultrafast, time-resolved THz pump/THz probe approach to the study of semiconductor properties in the nonlinear regime. The carrier dynamics regarding two mechanisms, intervalley scattering and impact ionization, is observed for doped InAs on a sub-picosecond time scale. In addition, polaron modulation driven by intense THz pulses is experimentally and theoretically investigated. The observed polaron dynamics verifies the interaction between energetic electrons and a phonon field. In contrast to previous work which reports optical phonon responses, acoustic phonon modulations are addressed in this study. A further understanding of the intense field interacting with solid materials will accelerate the development of semiconductor devices. This thesis starts with the design and performance of a table-top THz spectrometer which has the advantages of ultra-broad bandwidth (one order higher bandwidth compared to a conventional ZnTe sensor) and high electric field strength (>100 kV/cm). Unlike the conventional THz time-domain spectroscopy, the spectrometer integrates a novel THz air-biased-coherent-detection (THz-ABCD) technique and utilizes selected gases as THz emitters and sensors. In comparison with commonly used electro-optic (EO) crystals or photoconductive (PC) dipole antennas, the gases have the benefits of no phonon absorption as existing in EO crystals and no carrier life time limitation as observed in PC dipole antennas. The newly development THz-ABCD spectrometer with a strong THz field strength capability provides a platform for various research topics especially on the nonlinear carrier dynamics of semiconductors. Two mechanisms, electron intervalley scattering and impact ionization of InAs crystals, are observed under the excitation of intense THz field on a sub-picosecond time scale. These two competing mechanisms are demonstrated by changing the impurity doping type of the semiconductors and varying the strength of the THz field. Another investigation of nonlinear carrier dynamics is the observation of coherent polaron oscillation in n-doped semiconductors excited by intense THz pulses. Through modulations of surface reflection with a THz pump/THz probe technique, this work experimentally verifies the interaction between energetic electrons and a phonon field, which has been theoretically predicted by previous publications, and shows that this interaction applies for the acoustic phonon modes. Usually, two transverse acoustic (2TA) phonon responses are inactive in infrared measurement, while they are detectable in second-order Raman spectroscopy. The study of polaron dynamics, with nonlinear THz spectroscopy (in the far-infrared range), provides a unique method to diagnose the overtones of 2TA phonon responses of semiconductors, and therefore incorporates the abilities of both infrared and Raman spectroscopy. This work presents a new milestone in wave-matter interaction and seeks to benefit the industrial applications in high power, small scale devices.

  17. Effect on influenza hemagglutinin protein binding with neutralizing antibody using terahertz spectroscopy technology

    NASA Astrophysics Data System (ADS)

    Sun, Yiwen; Zhong, Junlan; Zuo, Jian; Zhang, Cunlin

    2014-11-01

    Terahertz spectroscopy is sensitive to probe several aspects of biological systems. We have reported the terahertz dielectric spectrum is able to identify the type of the charges in the hydrogen-bonded antibodies' networks in our previous work. Recently we demonstrate a highly sensitive THz-TDS method to monitor binding interaction of influenza hemagglutinin (HA) against its target antibody F10. The terahertz dielectric properties of HA was strongly affected by the presence of a specific antibody. Protein solution concentration or even molecular binding interaction can also affect the terahertz signal. This enables us to detect the specificity and sensitivity of antibody-antigen binding under THz radiation.

  18. Nonlinear terahertz spectroscopy of every phase of matter

    NASA Astrophysics Data System (ADS)

    Nelson, Keith

    2014-03-01

    Tabletop generation of intense terahertz (THz) pulses with peak field amplitudes in the 0.1-1 MV/cm range and field enhancement up to 10 MV/cm and beyond has enabled nonlinear responses in solids, liquids, and gases to be driven by THz fields. This has enabled nonlinear THz spectroscopy and THz coherent control of a wide variety of samples. In semiconductors and other samples, acceleration of carriers to multi-eV energies by THz excitation pulses has resulted in strong changes in carrier mobility and, in some cases, impact ionization that can lead to dramatic changes in conductivity. Tunneling ionization has resulted in insulator-metal phase transitions with associated structural phase transitions. In liquids and gases, THz pulses have produced molecular alignment and orientation. Coherent control over molecular rotational motion involving multiple rotational levels has been demonstrated. Recent nonlinear THz spectroscopy and prospects for more extensive THz coherent control over molecules and materials will be discussed.

  19. Identification of biomolecules by terahertz spectroscopy and fuzzy pattern recognition

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Li, Zhi; Mo, Wei

    2013-04-01

    An approach for automatic identification of terahertz (THz) spectra of biomolecules is proposed based on principal component analysis (PCA) and fuzzy pattern recognition in this paper, and THz transmittance spectra of some typical amino acid and saccharide biomolecular samples are investigated to prove its feasibility. Firstly, PCA is applied to reduce the dimensionality of the original spectrum data and extract features of the data. Secondly, instead of the original spectrum variables, the selected principal component scores matrix is fed into the model of fuzzy pattern recognition, where a principle of fuzzy closeness based optimization is employed to identify those samples. Results demonstrate that THz spectroscopy combined with PCA and fuzzy pattern recognition can be efficiently utilized for automatic identification of biomolecules. The proposed approach provides a new effective method in the detection and identification of biomolecules using THz spectroscopy.

  20. The generation of high field terahertz radiation and its application in terahertz nonlinear spectroscopy

    E-print Network

    Yeh, Ka-Lo

    2009-01-01

    In this thesis research, I implemented a terahertz generation scheme that enables high-field near-single-cycle terahertz (THz) pulse generation via optical rectification in a LiNbO3 (LN) crystal. I also developed a method ...

  1. Total internal reflection Raman spectroscopy.

    PubMed

    Woods, David A; Bain, Colin D

    2012-01-01

    Total internal reflection (TIR) Raman spectroscopy is an experimentally straightforward, surface-sensitive technique for obtaining chemically specific spectroscopic information from a region within approximately 100-200 nm of a surface. While TIR Raman spectroscopy has long been overshadowed by surface-enhanced Raman scattering, with modern instrumentation TIR Raman spectra can be acquired from sub-nm thick films in only a few seconds. In this review, we describe the physical basis of TIR Raman spectroscopy and illustrate the performance of the technique in the diverse fields of surfactant adsorption, liquid crystals, lubrication, polymer films and biological interfaces, including both macroscopic structures such as the surfaces of leaves, and microscopic structures such as lipid bilayers. Progress, and challenges, in using TIR Raman to obtain depth profiles with sub-diffraction resolution are described. PMID:22003492

  2. Developments in time-resolved ultrafast imaging and spectroscopy at terahertz frequencies

    E-print Network

    Teo, Stephanie M

    2014-01-01

    Prior to the advent of high energy pulsed femtosecond lasers, the field of terahertz (THz) spectroscopy was stagnated by the lack of both high power THz sources and sensitive THz detectors. Over the past few years, it has ...

  3. Terahertz Spectroscopy of High K Methanol Transitions

    NASA Astrophysics Data System (ADS)

    Pearson, John C.; Yu, Shanshan; Gupta, Harshal; Drouin, Brian J.

    2011-06-01

    Methanol is one of the primary sources of line confusion in warm star-forming regions. Herschel has detected rotational transitions in v_t=0,1,2 with rotational quantum numbers to J>35. The Herschel observations are clearly beam diluted on the hottest regions. Since ALMA will not suffer from similar beam dilution it is likely that significantly more methanol states are quickly detected. Since the existing detections largely span the previously analyzed space of laboratory data, a program of THz measurements of methanol has been undertaken to identify higher K_a states and to connect the v_t=2 manifold more completely to the rest of the available data with microwave accuracy. During the course of this work it became possible to directly compare TuFIR, FTIR, Laser Sideband, Quantum Cascade Laser, and conventional millimeter-wave spectroscopy. It has also been possible to assess the strengths and weakness of the rho-axis method (RAM) Hamiltonian in extrapolation for methanol.

  4. Terahertz Time-Domain Spectroscopy of D2O

    NASA Astrophysics Data System (ADS)

    Torcedo, Jojit; Tom, Harry

    2010-03-01

    The dielectric spectrum of D2O between 15 GHz and 2 THz was measured using Terahertz Time-Domain Spectroscopy. The motivation of this work is to gain an understanding of liquid water dynamics on a molecular level. To achieve this, we use a correction to the dielectric response of polar molecules known as the reduced polarization. This correction allows us to relate the macroscopic quantity of the permittivity to the microscopic correlation function in a manner appropriate for polar liquids. Similar to previous studies on H2O, evidence is shown of correlated and anti-correlated dipole-dipole interactions in liquid D2O. More interestingly, the spectra also reveal dynamics that could be intimately related to the density anomaly of water.

  5. Ultrafast terahertz spectroscopy and control of collective modes in semiconductors

    NASA Astrophysics Data System (ADS)

    Seletskiy, Denis V.

    In this dissertation we applied methods of ultrafast terahertz (THz) spectroscopy to study several aspects of semiconductor physics and in particular of collective mode excitations in semiconductors. We detect and analyze THz radiation emitted by these collective modes to reveal the underlying physics of many-body interactions. We review a design, implementation and characterization of our ultrafast terahertz (THz) time-domain spectroscopy setup, with additional features of mid-infrared tunability and coherent as well as incoherent detection capabilities. Temperature characterization of the collective plasmon excitation in indium antimonide (InSb) is presented to reveal the importance of non-parabolicity corrections in quantitative description. We also obtain electronic mobility from the radiation signals, which, once corrected for ultrafast scattering mechanisms, is in good agreement with DC Hall mobility measurements. Exhibited sensitivity to non-parabolicity and electronic mobility is applicable to non-contact characterization of electronic transport in nanostructures. As a first goal of this work, we have addressed the possibility of an all-optical control of the electronic properties of condensed matter systems on an ultrafast time scale. Using femtosecond pulses we have demonstrated an ability to impose a nearly 20% blue-shift of the plasma frequency in InSb. Preliminary investigations of coherent control of the electron dynamics using third-order nonlinearity were also carried out in solid state and gaseous media. In particular, we have experimentally verified the THz coherent control in air-breakdown plasmas and have demonstrated the ability to induce quantum-interference current control in indium arsenide crystals. As a second focus of this dissertation, we have addressed manipulation of the plasmon modes in condensed matter systems. After development of the analytical model of radiation from spatially extended longitudinal modes, we have applied it to analysis of two experiments. In first, we established the ability to control plasmon modes in InSb by means of a plasmonic one dimensional cavity. By control of the cavity geometry, we shifted the plasmon mode into the regime where nonlocal electron-electron interaction is enforced. We observed the consequential Landau damping of the collective mode, in good agreement with the predictions made within the random-phase approximation. In the second experiment we have invoked plasmon confinement in all three dimensions via a nanowire geometry. We observed enhancement of terahertz emission which we attributed to leaky modes of the waveguide. We attributed this emission to the low-energy acoustic surface plasmon mode of the nanowire, which was also supported by our numerical modeling results and independent DC electronic measurements.

  6. Terahertz spectroscopy of concrete for evaluating the critical hydration level

    NASA Astrophysics Data System (ADS)

    Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Sasmal, Saptarshi; Pesala, Bala

    2014-03-01

    Concrete, a mixture of cement, coarse aggregate, sand and filler material (if any), is widely used in the construction industry. Cement, mainly composed of Tricalcium Silicate (C3S) and Dicalcium Silicate (C2S) reacts readily with water, a process known as hydration. The hydration process forms a solid material known as hardened cement paste which is mainly composed of Calcium Silicate Hydrate (C-S-H), Calcium Hydroxide and Calcium Carbonate. To quantify the critical hydration level, an accurate and fast technique is highly desired. However, in conventional XRD technique, the peaks of the constituents of anhydrated and hydrated cement cannot be resolved properly, where as Mid-infrared (MIR) spectroscopy has low penetration depth and hence cannot be used to determine the hydration level of thicker concrete samples easily. Further, MIR spectroscopy cannot be used to effectively track the formation of Calcium Hydroxide, a key by-product during the hydration process. This paper describes a promising approach to quantify the hydration dynamics of cement using Terahertz (THz) spectroscopy. This technique has been employed to track the time dependent reaction mechanism of the key constituents of cement that react with water and form the products in the hydrated cement, viz., C-S-H, Calcium Hydroxide and Calcium Carbonate. This study helps in providing an improved understanding on the hydration kinetics of cement and also to optimise the physio-mechanical characteristics of concrete.

  7. Coating and Density Distribution Analysis of Commercial Ciprofloxacin Hydrochloride Monohydrate Tablets by Terahertz Pulsed Spectroscopy and Imaging.

    PubMed

    Sakamoto, Tomoaki; Portieri, Alessia; Arnone, Donald D; Taday, Philip F; Kawanishi, Toru; Hiyama, Yukio

    2012-06-01

    Terahertz pulsed spectroscopy was used to qualitatively detect ciprofloxacin hydrochloride monohydrate (CPFX·HCl·H(2)O) in tablets, and terahertz pulsed imaging (TPI) was used to scrutinize not only the coating state but also the density distribution of tablets produced by several manufacturers. TPI was also used to evaluate distinguishability among these tablets. The same waveform, which is a unique terahertz absorption spectrum derived from pure CPFX·HCl·H(2)O, was observed in all of the crushed tablets and in pure CPFX·HCl·H(2)O. TPI can provide information about the physical states of coated tablets. Information about the uniformity of parameters such as a coating thickness and density can be obtained. In this study, the authors investigated the coating thickness distributions of film-coated CPFX·HCl·H(2)O from four different manufacturers. Unique terahertz images of the density distributions in these commercial tablets were obtained. Moreover, B-scan (depth) images show the status of the coating layer in each tablet and the density map inside the tablets. These features would reflect differences resulting from different tablet-manufacturing processes. PMID:22707994

  8. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    NASA Astrophysics Data System (ADS)

    Kojima, Seiji; Shibata, Tomohiko; Igawa, Hikaru; Mori, Tatsuya

    2014-03-01

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz.

  9. Quantitative analyses of tartaric acid based on terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Cao, Binghua; Fan, Mengbao

    2010-10-01

    Terahertz wave is the electromagnetic spectrum situated between microwave and infrared wave. Quantitative analysis based on terahertz spectroscopy is very important for the application of terahertz techniques. But how to realize it is still under study. L-tartaric acid is widely used as acidulant in beverage, and other food, such as soft drinks, wine, candy, bread and some colloidal sweetmeats. In this paper, terahertz time-domain spectroscopy is applied to quantify the tartaric acid. Two methods are employed to process the terahertz spectra of different samples with different content of tartaric acid. The first one is linear regression combining correlation analysis. The second is partial least square (PLS), in which the absorption spectra in the 0.8-1.4THz region are used to quantify the tartaric acid. To compare the performance of these two principles, the relative error of the two methods is analyzed. For this experiment, the first method does better than the second one. But the first method is suitable for the quantitative analysis of materials which has obvious terahertz absorption peaks, while for material which has no obvious terahertz absorption peaks, the second one is more appropriate.

  10. Optical fiber-coupled InGaAs-based terahertz time--domain spectroscopy system

    NASA Astrophysics Data System (ADS)

    Han, Sang-Pil; Ko, Hyunsung; Kim, Namje; Ryu, Han-Cheol; Lee, Chul Wook; Leem, Young Ahn; Lee, Donghun; Jeon, Min Yong; Noh, Sam Kyu; Chun, Hyang Sook; Park, Kyung Hyun

    2011-08-01

    The successful demonstration of an optical fiber-coupled terahertz time--domain spectroscopy (THz-TDS) system is described in this study. The terahertz output power of the emitter with two optical band rejection filters was 132nW, which is an improvement of 70% over the output power without any filters. This improvement is due to the suppression of an optical modulated signal that is reverse-generated when an alternating current bias exceeding a certain threshold is applied to the emitter. Under the optimal alignment conditions, the terahertz detector in a fiber-coupled THz-TDS system clearly measured water vapor dips in the free space.

  11. Accuracy of sample material parameters reconstruction using terahertz pulsed spectroscopy

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Gavdush, Arseniy A.; Karasik, Valeriy E.; Alekhnovich, Valentin I.; Nosov, Pavel A.; Lazarev, Vladimir A.; Reshetov, Igor V.; Yurchenko, Stanislav O.

    2014-05-01

    New experimental and theoretical results for the material parameter reconstruction using terahertz (THz) pulsed spectroscopy (TPS) are presented. The material parameter reconstruction algorithm was realized and experimentally implemented to study the test sample. In order to both verify the algorithm and to estimate the reconstruction accuracy, test sample material parameters obtained with the TPS were compared with the results of the same sample studying by the use of the backward-wave oscillator (BWO) spectroscopy. Thus, high reconstruction accuracy was demonstrated for the spectral range, corresponding to the BWO sensitivity and located between 0.2 and 1.2 THz. The numerical simulations were applied for determining the material parameter reconstruction stability in the presence of white Gaussian noise in TPS waveforms as well as fluctuations in the femtosecond (FS) optical pulse duration. We report a strong dependence of the inverse problem solution stability on these factors. We found that the instability of the FS optical pulse duration used for THz pulses generation and detection limits the material parameter reconstruction with TPS.

  12. Thin film characterization using terahertz differential time-domain spectroscopy and double modulation

    Microsoft Academic Search

    Samuel P. Mickan; Kwang-Su Lee; Toh-Ming Lu; Edward Barnat; Jesper Munch; Derek Abbott; Xi-Cheng Zhang

    2001-01-01

    Characterizing the optical and dielectric properties of thin films in the GHz to THz range is critical for the development of new technologies in integrated circuitry, photonics systems and micro-opto-electro-mechanical systems (MOEMS). Terahertz differential time-domain spectroscopy (DTDS) is a new technique that uses pulsed terahertz (THz) radiation to detect phase changes of less than 0.6 femtoseconds (fs) and absorption changes

  13. Laser Original Magneto-Optical Spectroscopy of Semiconductors Using Terahertz Quantum Cascade Lasers

    E-print Network

    Kono, Junichiro

    860 Laser Original Magneto-Optical Spectroscopy of Semiconductors Using Terahertz Quantum Cascade will be described. Key Words: Quantum cascade lasers, THz magneto-optical spectroscopy, Cyclotron resonance Lasers Junichiro KONO Department of Electrical and Computer Engineering, Rice University, Houston, Texas

  14. High-Q terahertz bandpass filters based on coherently interfering metasurface reflections.

    PubMed

    Born, Norman; Reuter, Marco; Koch, Martin; Scheller, Maik

    2013-03-15

    We present compact and easy-to-realize terahertz bandpass filters with Q values in the order of 500. The filters are based on coherently interfering reflections from two parallel metasurfaces applied to the boundaries of a semiconductor disk. By changing the thickness of the semiconductor disk and the dimensions of the metasurface structures, the filter can be optimized for various terahertz frequencies. Moreover, a precise tuning of the resonance frequency is possible via the temperature of the structure or its angle with respect to the propagation direction. PMID:23503256

  15. High-Q terahertz bandpass filters based on coherently interferingmetasurface reflections

    Microsoft Academic Search

    Norman Born; Marco Reuter; Martin Koch; Maik Scheller

    2013-01-01

    We present compact and easy-to-realize terahertz bandpass filters\\u000a\\u0009with Q values in the order of 500. The filters are based on coherently\\u000a\\u0009interfering reflections from two parallel metasurfaces applied to\\u000a\\u0009the boundaries of a semiconductor disk. By changing the thickness\\u000a\\u0009of the semiconductor disk and the dimensions of the metasurface structures,\\u000a\\u0009the filter can be optimized for various terahertz frequencies.

  16. Terahertz spectroscopy and detection of brain tumor in rat fresh-tissue samples

    NASA Astrophysics Data System (ADS)

    Yamaguchi, S.; Fukushi, Y.; Kubota, O.; Itsuji, T.; Yamamoto, S.; Ouchi, T.

    2015-03-01

    Terahertz (THz) spectroscopy and imaging of biomedical samples is expected to be an important application of THz analysis techniques. Identification and localization of tumor tissue, imaging of biological samples, and analysis of DNA by THz spectroscopy have been reported. THz time-domain spectroscopy (TDS) is useful for obtaining the refractive index over a broad frequency range. However, THz-TDS spectra of fresh tissue samples are sensitive to procedures such as sample preparation, and a standardized measurement protocol is required. Therefore, in this work, we establish a protocol for measurements of THz spectra of fresh tissue and demonstrate reliable detection of rat brain tumor tissue. We use a reflection THz-TDS system to measure the refractive index spectra of the samples mounted on a quartz plate. The tissue samples were measured immediately after sectioning to avoid sample denaturalization during storage. Special care was taken in THz data processing to eliminate parasitic reflections and reduce noise. The error level in our refractive index measurements was as low as 0.02 in the frequency range 0.8-1.5 THz. With increasing frequency, the refractive index in the tumor and normal regions monotonically decreased, similarly to water, and it was 0.02 higher in the tumor regions. The spectral data suggest that the tumor regions have higher water content. Hematoxylin-eosin stained images showed that increased cell density was also responsible for the observed spectral features. A set of samples from 10 rats showed consistent results. Our results suggest that reliable tumor detection in fresh tissue without pretreatment is possible with THz spectroscopy measurements. THz spectroscopy has the potential to become a real-time in vivo diagnostic method.

  17. Few-cycle terahertz generation and spectroscopy of nanostructures.

    PubMed

    Darmo, Juraj; Müller, Thomas; Parz, Wolfgang; Kröll, Josef; Strasser, Gottfried; Unterrainer, Karl

    2004-02-15

    We report on new schemes for terahertz (THz) generation. The THz efficiency of photoconducting antennas can be increased by using a cavity effect for the near-infrared pump beam. The cavity is formed by a molecular beam epitaxy grown semiconductor Bragg mirror below the photoconducting layer. The optical confinement is accompanied by an electrical confinement suppressing undesired leakage currents and providing a constant electric field in the active layers. The performance of this cavity-enhanced emitter is further improved by using a mobility optimized low-temperature GaAs layer. This emitter is successfully used in a femtosecond Ti:sapphire laser cavity for highly efficient intracavity THz generation, where the photoconductive layer serves also as a saturable absorber. The broadband THz pulses generated are used for time-resolved spectroscopy of nanostructures. We study the dynamics of intersubband transitions in semiconductor quantum wells. The relaxation of carriers excited by a near-infrared pump pulse is investigated by measuring the THz absorption between the different subbands with our THz pulses. For transition energies below the optical phonon energy we find relatively long relaxation times with a strong dependence on the excited carrier density. PMID:15306518

  18. An anti-reflection coating for silicon optics at terahertz frequencies

    Microsoft Academic Search

    A. J. Gatesman; J. Waldman; M. Ji; C. Musante; S. Yagvesson

    2000-01-01

    A method for reducing the reflections from silicon optics at terahertz frequencies has been investigated. In this study, we used thin films of parylene as an anti-reflection (AR) layer for silicon optics and show low-loss behavior well above 1 THz. Transmittance spectra are acquired on double-sided-parylene-coated, high-resistivity, single-crystal silicon etalons between 0.45 THz and 2.8 THz. Modeling the optical behavior

  19. Precise Determination of Thicknesses of Multilayer Polyethylene Composite Materials by Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Palka, Norbert; Krimi, Soufiene; Ospald, Frank; Miedzinska, Danuta; Gieleta, Roman; Malek, Marcin; Beigang, Rene

    2015-06-01

    The multilayer structure of an ultra-high molecular weight polyethylene (UHMWPE) composite material was investigated in the terahertz (THz) spectral range by means of time-domain spectroscopy (TDS) technique. Such structures consist of many alternating layers of fibers, each being perpendicular to the other and each having a thickness of about 50 ?m. Refractive indices of two composite samples and of a sample composed of four single layers (plies) having the same fiber orientation were determined for two orthogonal orientations of the electric field in a transmission TDS system. The birefringence of a single layer was measured, and the origin of this phenomenon is discussed. Using the TDS system in reflection, the formation of many pulses shifted in time was observed originating from reflections from interfaces of successive layers caused by the periodic modulation of the refractive index along the propagation of the THz radiation. This phenomenon is theoretically described and simulated by means of a transfer matrix method (TMM). A time-domain fitting procedure was used to determine thicknesses of all layers of the composite material. The reconstructed waveform based on the optimized thicknesses shows very good agreement with the measured waveform, with typical differences between measurements and simulations between 3 and 7 ?m (depending on the sample). As a result, we were able to determine the thicknesses of all layers of two multilayer (~200 plies) structures by means of the reflection TDS technology with high accuracy.

  20. Terahertz Circular Dichroism Spectroscopy of Biomolecules. , Jhenny Galanb

    E-print Network

    Xu, Jing

    dichroism. Terahertz circular dichroism (TCD) is potentially important as a biospecific sensor, unobscured scale "breathing" motions of the protein in order for the ligand to access the heme iron 1 . Countless

  1. Terahertz time-domain and Fourier-transform infrared spectroscopy of traditional Korean pigments

    NASA Astrophysics Data System (ADS)

    Hong, Taeyoon; Choi, Kyujin; Ha, Taewoo; Park, Byung Cheol; Sim, Kyung Ik; Kim, Jong Hyeon; Kim, Jae Hoon; Kwon, Jy Eun; Lee, Sanghyun; Kang, Dai Ill; Lee, Han Hyoung

    2014-03-01

    Representative traditional Korean pigments (oyster shell white [hobun], massicot [miltaseung], indigo [jjok], azurite [seokcheong], malachite [seokrok], and red lead [yeondan]) have been studied with terahertz time-domain spectroscopy (THz-TDS) and Fourier-transform infrared spectroscopy (FTIRS) over the spectral region of 0.1-7.5 THz. Both the refractive index n and the extinction coefficient k were simultaneously and independently determined in the terahertz region without a Kramers-Kronig analysis while the absoprtion coefficient spectra were acquired in the infrared region. All pigments studied in the present work exhibited a set of characteristic absorption peaks unique to the pigment species in addition to a background that increased with increasing frequency. Our study demonstrates that terahertz and infrared techniques can be useful identification and diagnostic tools for the traditional Korean pigments used in heritage buildings and artworks.

  2. Optical Properties of Laminarin Using Terahertz Time-Domain Spectroscopy (abstract)

    NASA Astrophysics Data System (ADS)

    Shin, Hee Jun; Maeng, Inhee; Oh, Seung Jae; Kim, Sung In; Kim, Ha Won; Son, Joo-Hiuk

    2009-04-01

    Terahertz spectroscopy is important in the study of biomolecular structure because the vibration and rotation energy of large molecules such as DNA, proteins, and polysaccharides are laid in terahertz regions. Terahertz time-domain spectroscopy (THz-TDS), using terahertz pulses generated and detected by femto-second pulses laser, has been used in the study of biomolecular dynamics, as well as carrier dynamics of semiconductors. Laminarin is a polysaccharide of glucose in brown algae. It is made up of ?(1-3)-glucan and ?(1-6)-glucan. ?-glucan is an anticancer material that activates the immune reaction of human cells and inhibits proliferation of cancer cells. ?-glucan with a single-strand structure has been reported to activate the immune reaction to a greater extent than ?-glucan with a triple-strand helix structure. We used THz-TDS to characterize the difference between single-strand and triple-strand ?-glucan. We obtained single-strand ?-glucan by chemical treatment of triple-strand ?-glucan. We measured the frequency dependent optical constants of Laminarin using THz-TDS. Power absorption of the triple-strand helix is larger than the single-strand helix in terahertz regions. The refractive index of the triple-strand helix is also larger than that of the single-strand helix.

  3. Terahertz spectroscopy of intrinsic biomarkers for non-melanoma skin Cecil S. Joseph1*

    E-print Network

    Massachusetts at Lowell, University of

    to the National Institute of Health (NIH), people with fairer skin have a higher risk of getting skin cancerTerahertz spectroscopy of intrinsic biomarkers for non-melanoma skin cancer. Cecil S. Joseph1 of human cancers. The aim of this study was to identify intrinsic biomarkers for non-melanoma skin cancer

  4. Application of terahertz spectroscopy and molecular modeling in isomers investigation: Glucose and fructose

    NASA Astrophysics Data System (ADS)

    Zheng, Zhuan-Ping; Fan, Wen-Hui; Liang, Yu-Qing; Yan, Hui

    2012-04-01

    Terahertz spectra of glucose and fructose have been measured by terahertz time-domain spectroscopy (THz-TDS) at room temperature. Because they have the same molecular formula, the differences of the THz spectra can be attributed to their molecular structures and the arrangement of molecules in unit cell. In this paper, gaseous-state theory has been employed to simulate the isolated molecule of these two isomers. The results indicate that experimental THz spectral features (0.5 - 4.0 THz) of glucose and fructose arise from the mixture of intramolecular and intermolecular modes, involving hydrogen bonds and covalent bonds, and with the intermolecular modes dominating.

  5. Analysis of drugs-of-abuse and explosives using terahertz time-domain and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Burnett, Andrew; Fan, Wenhui; Upadhya, Prashanth; Cunningham, John; Linfield, Edmund; Davies, Giles; Edwards, Howell; Munshi, Tasnim; O'Neil, Andrew

    2006-02-01

    We demonstrate that, through coherent measurement of the transmitted terahertz electric fields, broadband (0.3-8THz) time-domain spectroscopy can be used to measure far-infrared vibrational modes of a range of illegal drugs and high explosives that are of interest to the forensic and security services. Our results show that these absorption features are highly sensitive to the structural and spatial arrangement of the molecules. Terahertz frequency spectra are also compared with high-resolution low-frequency Raman spectra to assist in understanding the low frequency inter- and intra-molecular vibrational modes of the molecules.

  6. Terahertz spectroscopy and computational investigation of the flufenamic acid/nicotinamide cocrystal.

    PubMed

    Delaney, Sean P; Korter, Timothy M

    2015-04-01

    Terahertz spectroscopy probes the low-frequency vibrations that are sensitive to both the intermolecular and intramolecular interactions of molecules in the solid state. Thus, terahertz spectroscopy can be a useful tool in the investigation of crystalline pharmaceutical compounds, where slight changes in the packing arrangement can modify the overall effectiveness of a drug formulation. This is especially true for cases of polymorphic systems, hydrates/solvates, and cocrystals. In this work, the cocrystal of flufenamic acid with nicotinamide was investigated using terahertz spectroscopy and solid-state density functional theory. The solid-state simulations enable understanding of the low-frequency vibrations seen in the terahertz spectra, while also providing insight into the energetics involved in the formation of the cocrystal. The comparison of the cocrystal to the pure forms of the molecular components reveals that the cocrystal has better overall binding energy, driven by increased intermolecular hydrogen bond strength and greater London dispersion forces and that the trifluoromethyl torsional potential is significantly different between the studied solids. PMID:25787318

  7. Leaf water dynamics of Arabidopsis thaliana monitored in-vivo using terahertz time-domain spectroscopy

    PubMed Central

    Castro-Camus, E.; Palomar, M.; Covarrubias, A. A.

    2013-01-01

    The declining water availability for agriculture is becoming problematic for many countries. Therefore the study of plants under water restriction is acquiring extraordinary importance. Botanists currently follow the dehydration of plants comparing the fresh and dry weight of excised organs, or measuring their osmotic or water potentials; these are destructive methods inappropriate for in-vivo determination of plants' hydration dynamics. Water is opaque in the terahertz band, while dehydrated biological tissues are partially transparent. We used terahertz spectroscopy to study the water dynamics of Arabidopsis thaliana by comparing the dehydration kinetics of leaves from plants under well-irrigated and water deficit conditions. We also present measurements of the effect of dark-light cycles and abscisic acid on its water dynamics. The measurements we present provide a new perspective on the water dynamics of plants under different external stimuli and confirm that terahertz can be an excellent non-contact probe of in-vivo tissue hydration. PMID:24105302

  8. New experimental methods in Terahertz spectroscopy E. J. Slingerlanda, T. M. Goyettea, R. H. Gilesa and W. E. Nixonb

    E-print Network

    Massachusetts at Lowell, University of

    correspondence to E.J.S. at Elizabeth Slingerland@student.uml.edu #12;Figure 1 shows the spectral signatureNew experimental methods in Terahertz spectroscopy E. J. Slingerlanda, T. M. Goyettea, R. H. Gilesa

  9. Terahertz Spectroscopy and Imaging for Defense and Security Applications

    Microsoft Academic Search

    Hai-Bo Liu; Hua Zhong; Nicholas Karpowicz; Yunqing Chen; Xi-Cheng Zhang

    2007-01-01

    Terahertz (THz) radiation, which occupies a relatively unexplored portion of the electromagnetic spectrum between the mid-infrared and microwave bands, offers innovative sensing and imaging technologies that can provide information unavailable through conventional methods such as microwave and X-ray techniques. With the advancement of THz technologies, THz sensing and imaging will impact a broad range of interdisciplinary fields, including chemical and

  10. Terahertz time-domain spectroscopy and its applications

    NASA Astrophysics Data System (ADS)

    Shan, Jie

    Mode-locked lasers can now readily produce optical pulses of femtosecond duration. In this thesis, results are presented on new methods by which these laser pulses can be exploited to measure and control electric fields on an ultrafast time scale. In addition to the development of these techniques, the resulting capability is used for time-domain far-infrared spectroscopy measurements. With respect to approaches for the detection of electric fields on the femtosecond time scale, two new detection methods based on nonlinear optical interactions with femtosecond laser pulses have been developed. In one scheme, electro-optic sampling of ultrafast electrical transients is extended to permit the capture of a complete electric-field waveform with a single femtosecond laser pulse. This is achieved by using a multichannel detection scheme combined with an experimental geometry in which the femtosecond probe pulse experiences time skew across its wave front relative to the electric field being measured. This method eliminates the need for sampling and the associated scanning of a delay line. A further development involves application of the electric field- induced optical second-harmonic generation. This process is shown to permit the characterization of the magnitude and direction of electric fields in centrosymmetric materials, such as silicon, with high sensitivity, spatial and temporal resolution. With respect to the generation of ultrashort electromagnetic transients, results are presented on the enhancement of the emission efficiency of optically gated photoconductive emitters under application of an external magnetic field. The basic mechanism of the large observed enhancements is clarified within the context of a simple model incorporating a Lorentz-Drude description of carrier dynamics together with an appropriate treatment of the radiation process for the photo-induced current transients. One important application of these capabilities is the time-domain spectroscopy in the terahertz (THz) or far- infrared spectral region. In this approach one produces a controlled electric-field waveform and measures directly in the time domain the changes in this waveform induced by the sample. The method provides access to a spectral region that is difficult to reach by conventional means. It also offers unique capabilities for probing the non- equilibrium properties of rapidly changing systems. These capabilities have permitted the study of the nature and transport of photo-generated electrons in a condensed- phase system consisting of liquid hexane. A second application illustrates the utility of controlled single- cycle THz pulses for the elucidation of fundamental questions about electromagnetic waves and their interactions. In particular, the properties of circularly polarized electromagnetic pulses with a duration approaching that of one optical cycle are investigated experimentally. The results are found to agree well with a theoretical treatment that predicts that the orthogonal components of the electric field of circularly polarized radiation satisfy a Hilbert transform relation. This new analysis provides a completely general description of polarized electromagnetic radiation, one which extends beyond the conventional quasi-monochromatic limit.

  11. Characteristic responses of biological and nanoscale systems in the terahertz frequency range

    NASA Astrophysics Data System (ADS)

    Angeluts, A. A.; Balakin, A. V.; Evdokimov, M. G.; Esaulkov, M. N.; Nazarov, M. M.; Ozheredov, I. A.; Sapozhnikov, D. A.; Solyankin, P. M.; Cherkasova, O. P.; Shkurinov, A. P.

    2014-07-01

    This paper briefly examines methods for the generation of pulsed terahertz radiation and principles of pulsed terahertz spectroscopy, an advanced informative method for studies of complex biological and nanostructured systems. Some of its practical applications are described. Using a number of steroid hormones as examples, we demonstrate that terahertz spectroscopy in combination with molecular dynamics methods and computer simulation allows one to gain information about the structure of molecules in crystals. A 'terahertz colour vision' method is proposed for analysis of pulsed terahertz signals reflected from biological tissues and it is shown that this method can be effectively used to analyse the properties of biological tissues and for early skin cancer diagnosis.

  12. Total internal reflectance optoacoustic spectroscopy

    Microsoft Academic Search

    P. R. Muessig; G. J. Diebold

    1983-01-01

    When radiation undergoes total internal reflection at a solid–gas interface, an exponentially decaying wave, known as the evanescent wave, propagates into the gas. If the incident radiation is amplitude modulated and the gas has an absorption at the wavelength of the radiation, the optoacoustic effect can be produced by absorption of energy from the evanescent wave. Experiments with 10.6 ?

  13. Total internal reflectance optoacoustic spectroscopy

    Microsoft Academic Search

    P. R. Muessig; G. J. Diebold

    1983-01-01

    When radiation undergoes total internal reflection at a solid--gas interface, an exponentially decaying wave, known as the evanescent wave, propagates into the gas. If the incident radiation is amplitude modulated and the gas has an absorption at the wavelength of the radiation, the optoacoustic effect can be produced by absorption of energy from the evanescent wave. Experiments with 10.6 ..mu..

  14. Bidirectional reflectance spectroscopy. I - Theory

    Microsoft Academic Search

    Bruce Hapke

    1981-01-01

    An approximate analytic solution is derived for the radiative transfer equation describing particulate surface light scattering, taking into account multiple scattering and mutual shadowing. Analytical expressions for the following quantities are found: bidirectional reflectance, radiance coefficient and factor, the normal, Bond, hemispherical, and physical albedos, integral phase function and phase integral, and limb-darkening profile. Scattering functions for mixtures can be

  15. Terahertz Spectra of L-Ascorbic Acid and Thiamine Hydrochloride Studied by Terahertz Spectroscopy and Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Jiang, Ling; Li, Miao; Li, Chun; Sun, Haijun; Xu, Li; Jin, Biaobin; Liu, Yunfei

    2014-10-01

    We have investigated the terahertz spectra of L-ascorbic acid and thiamine hydrochloride measured by terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infrared spectroscopy (FTIR). The measured absorption spectra were demonstrated to be in good agreement with the results simulated by Density Functional Theory (DFT) using hybrid functional B3LYP with basis set of 6-31G (d), except with slight frequency shift and few peaks missing. We presented the comparison of measured spectra by the FTIR spectroscopy employing low temperature silicon bolometer as detector and the TDS system. The measured spectra of the L-ascorbic acid showed shoulder bands at 0.25, 1.1, 1.5, 1.82, 2.03, 2.30, 2.44, 2.67, 2.97, 3.12, and 3.40 THz, respectively. The spectra of the thiamine hydrochloride show shoulder bands at 0.48, 1.11, 1.57, 1.75, 1.92, 2.08, 2.31, 2.53, 2.69, 2.85, 3.12, 3.22, and 3.31 THz. Most absorption peaks of the two samples agree with the results simulated by Density Function Theory (DFT) method of Gaussian 09 software. In our work, more spectral peaks based on experimental and theoretical results were found in comparison to that of other groups, since we employed higher sensitive FTIR measurement system and considered the effect of number of molecule unit in simulation. The study suggests that the effect of intermolecular vibration is stronger than intramolecular interaction on the absorption bands in THz region.

  16. Total internal reflectance optoacoustic spectroscopy

    SciTech Connect

    Muessig, P.R.; Diebold, G.J.

    1983-08-01

    When radiation undergoes total internal reflection at a solid--gas interface, an exponentially decaying wave, known as the evanescent wave, propagates into the gas. If the incident radiation is amplitude modulated and the gas has an absorption at the wavelength of the radiation, the optoacoustic effect can be produced by absorption of energy from the evanescent wave. Experiments with 10.6 ..mu.. radiation internally reflected in an NaCl prism show the amplitude of the optoacoustic signal (in SF/sub 6/) to be linearly proportional to the product of the square of the electric field amplitude and the penetration depth of the evanescent wave as given by Fresnel's equations. The amplitude of the optoacoustic signal in a 100-..mu..l detection cell is found to increase linearly with the mole fraction of SF/sub 6/ in He over the range from 10/sup -5/ to 10/sup -2/.

  17. Measurement and analysis of the diffuse reflectance of powdered samples at terahertz frequencies using a quantum cascade laser

    Microsoft Academic Search

    P. Dean; A. D. Burnett; K. Tych; S. P. Khanna; M. Lachab; J. E. Cunningham; E. H. Linfield; A. G. Davies

    2011-01-01

    We report terahertz (THz) diffuse reflectance measurements of bulk powdered samples at a frequency of 2.83 THz using a narrowband quantum cascade laser. Samples studied comprise polydisperse powders with absorption coefficients extending over two orders of magnitude from ~3 cm-1 to >200 cm-1. Diffuse reflectance measurements are used to obtain the effective absorption coefficient of these samples from the backscattering

  18. Tuning photoinduced terahertz conductivity in monolayer graphene: Optical-pump terahertz-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Kar, Srabani; Mohapatra, Dipti R.; Freysz, Eric; Sood, A. K.

    2014-10-01

    Optical-pump terahertz-probe differential transmission measurements of as-prepared single layer graphene (AG) (unintentionally hole doped with Fermi energy EF at ˜-180meV), nitrogen doping compensated graphene (NDG) with EF˜-10 meV, and thermally annealed doped graphene (TAG) are examined quantitatively to understand the opposite signs of photoinduced dynamic terahertz conductivity ??. It is negative for AG and TAG but positive for NDG. We show that the recently proposed mechanism of multiple generations of secondary hot carriers due to Coulomb interaction of photoexcited carriers with the existing carriers together with the intraband scattering can explain the change of photoinduced conductivity sign and its magnitude. We give a quantitative estimate of ?? in terms of controlling parameters—the Fermi energy EF and momentum relaxation time ?. Furthermore, the cooling of photoexcited carriers is analyzed using a supercollision model which involves a defect mediated collision of the hot carriers with the acoustic phonons, thus giving an estimate of the deformation potential.

  19. Investigating the use of terahertz pulsed time domain reflection imaging for the study of fabric layers of an Egyptian mummy

    NASA Astrophysics Data System (ADS)

    Fukunaga, K.; Cortes, E.; Cosentino, A.; Stã¼nkel, I.; Leona, M.; Duling, N.; Mininberg, D. T.

    2011-08-01

    This paper reports the first use of terahertz time domain reflection imaging involving textiles on part of a complete human mummy, still in original wrapping. X-ray technique has been used extensively to investigate anatomical features, since X-ray pass through the wrapping. Terahertz waves, on the other hand, can penetrate into non-metallic materials and its reflection depends on the refractive index of materials at the interface, such as textiles and the air. The mummy of Kharushere (ca. 945-712 B.C.) was examined by using Terahertz time domain reflection imaging in the Egyptian galleries of The Metropolitan Museum of Art. Experimental results suggest that the Terahetz imaging is a promising technique for probing the fabric layers surrounding Egyptian mummies, although it is still very limited in its current state. In the future it could become a useful complement to CT scanning when materials with low radiographic density and contrast are being investigated

  20. Fabrication of anti-reflective micro-structure at terahertz frequency by using Chinese acupuncture needles.

    PubMed

    Li, YunZhou; Cai, Bin; Zhu, Yiming

    2015-06-15

    A terahertz (THz) anti-reflective structure on a polystyrene layer was fabricated by using a handmade metallic mold comprising a bunch of Chinese acupuncture needles. Polystyrene was spin-coated onto a silicon substrate and then deformed by the mold via a hot-embossing process. The deformed layer yielded gradient refractive index profiles on the substrate. Compared with a common single antireflective layer, we observed an increase of ?20% in the transmittance. We also observed broader bandwidth properties compared with the single layer structure. The process imposes no substrate limiting, i.e., it can be applied onto various THz device surfaces for antireflection purpose. PMID:26076295

  1. Terahertz Kerr and Reflectivity Measurements on the Topological Insulator Bi2Se3

    Microsoft Academic Search

    G. S. Jenkins; A. B. Sushkov; D. C. Schmadel; N. P. Butch; P. Syers; J. Paglione; H. D. Drew

    2010-01-01

    We report the first terahertz Kerr measurements on bulk crystals of the\\u000atopological insulator Bi2Se3. At T=10K and fields up to 8T, the real and\\u000aimaginary Kerr angle and reflectance measurements utilizing both linearly and\\u000acircularly polarized incident radiation were measured at a frequency of\\u000a5.24meV. A single fluid free carrier bulk response can not describe the\\u000aline-shape. Surface states

  2. Broadband terahertz spectroscopy: principles, fundamental research and potential for industrial applications

    NASA Astrophysics Data System (ADS)

    Zouaghi, W.; Thomson, M. D.; Rabia, K.; Hahn, R.; Blank, V.; Roskos, H. G.

    2013-11-01

    Terahertz radiation (also called T-rays) can be employed for spectroscopy and imaging, from the laboratory to industrial applications. In this paper we give an overview of how broadband optoelectronic THz techniques (i.e. using optical lasers to achieve THz generation and detection) can be implemented, and give examples of their unique use in solid-state physics, and in biological and industrial applications.

  3. Detection of pesticides residues in rapeseed oil by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Xiao-li, Zhao; Jiu-sheng, Li

    2011-02-01

    The absorption spectra of panax notoginseng and glycyrrhiza in the frequency range of 0.2~1.6THz has been measured with terahertz time-domin spectroscopy at room temperature. Simultaneously, the corresponding theoretical spectra were given by using density functional theory methods. It was found that the absorption peaks of the two molecules obtained by theoretical were in good agreement with the experimental results.

  4. Nondestructive measurement of carrier mobility in conductive polymer PEDOT:PSS using Terahertz and infrared spectroscopy

    Microsoft Academic Search

    Masatsugu Yamashita; Chiko Otani; Hidenori Okuzaki; Masahiro Shimizu

    2011-01-01

    Novel method to evaluate the density and mobility of carriers in conductive polymers is presented. The method utilizes the broadband spectral information of THz and infrared region. Terahertz-time domain spectroscopy revealed that the strong carrier scattering induced the weakly localized carrier behavior in conductive polymer poly(3, 4- ethylenedioxythiophene):poly(styrene sulfonate acid) (PEDOT:PSS) thin films. However, it is impossible to determine the

  5. Time domain terahertz spectroscopy of semiconductor bulk and multiple quantum wells structures

    Microsoft Academic Search

    Yue Chen

    1998-01-01

    A time-domain terahertz spectroscopic system with high source power (average power > 10 nW) and high signal-to- noise ratio (>104) was developed and used to study ultrafast electronic processes in semiconductor structures. The physics of the spectroscopy, the theoretical basis of the interferometry, the model of the electron-electromagnetic field interaction, and the principle of experimental data processing are presented. The

  6. Vortex dynamics in a NbN film studied by terahertz spectroscopy

    Microsoft Academic Search

    Y. Ikebe; R. Shimano; M. Ikeda; T. Fukumura; M. Kawasaki

    2009-01-01

    We have investigated the effect of vortex dynamics on high-frequency conductivity of a superconducting NbN film by using terahertz time-domain spectroscopy. The complex conductivity of the mixed state up to 7 T is determined without using Kramers-Kronig analysis. The experimentally obtained conductivity spectra are analyzed by considering the contribution from quasiparticles in vortices and also from the vortex dynamics. To

  7. Fiber-coupled antennas for ultrafast coherent terahertz spectroscopy in low temperatures and high magnetic fields

    Microsoft Academic Search

    S. A. Crooker

    2002-01-01

    For the purposes of measuring the high-frequency complex conductivity of correlated-electron materials at low temperatures and high magnetic fields, a method is introduced for performing coherent time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed magnets. Miniature fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 1.5 K and up to

  8. Spectrally interleaved, comb-mode-resolved spectroscopy using swept dual terahertz combs

    PubMed Central

    Hsieh, Yi-Da; Iyonaga, Yuki; Sakaguchi, Yoshiyuki; Yokoyama, Shuko; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Araki, Tsutomu; Yasui, Takeshi

    2014-01-01

    Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5?MHz and enhanced spectral accuracy of 8.39 × 10?7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy. PMID:24448604

  9. Soft tissue differentiation by diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zam, Azhar; Stelzle, Florian; Nkenke, Emeka; Tangermann-Gerk, Katja; Schmidt, Michael; Adler, Werner; Douplik, Alexandre

    2009-07-01

    Laser surgery gives the possibility to work remotely which leads to high precision, little trauma and high level sterility. However these advantages are coming with the lack of haptic feedback during the laser ablation of tissue. Therefore additional means are required to control tissue-specific ablation during laser surgery supporting the surgeon regardless of experience and skills. Diffuse Reflectance Spectroscopy provides a straightforward and simple approach for optical tissue differentiation. We measured diffuse reflectance from four various tissue types ex vivo. We applied Linear Discriminant Analysis (LDA) to differentiate the four tissue types and computed the area under the ROC curve (AUC). Special emphasis was taken on the identification of nerve as the most crucial tissue for maxillofacial surgery. The results show a promise for differentiating soft tissues as guidance for tissue-specific laser surgery by means of the diffuse reflectance.

  10. Thermal denaturation of protein studied by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Fu, Xiuhua; Li, Xiangjun; Liu, Jianjun; Du, Yong; Hong, Zhi

    2012-12-01

    In this study, the absorption spectra of native or thermal protein were measured in 0.2-1.4THz using terahertz time-domain spectroscopy (THz-TDS) system at room temperature, their absorption spectra and the refractive spectra were obtained. Experimental results indicate that protein both has strong absorption but their characteristics were not distinct in the THz region, and the absorption decreased during thermal denatured state. In order to prove protein had been denatured, we used Differential scanning calorimeter (DSC) measured their denatured temperature, from their DSC heating traces, collagen Td=101?, Bovine serum albumin Td=97?. While we also combined the Fourier transform infrared spectrometer (FTIR) to investigate their secondary and tertiary structure before and after denatuation, but the results did not have the distinct changes. We turned the absorption spectra and the refractive spectra to the dielectric spectra, and used the one-stage Debye model simulated the terahertz dielectric spectra of protein before and after denaturation. This research proved that the terahertz spectrum technology is feasible in testing protein that were affected by temperature or other factors which can provide theoretical foundation in the further study about the THz spectrum of protein and peptide temperature stability.

  11. [The error analysis and experimental verification of laser radar spectrum detection and terahertz time domain spectroscopy].

    PubMed

    Liu, Wen-Tao; Li, Jing-Wen; Sun, Zhi-Hui

    2010-03-01

    Terahertz waves (THz, T-ray) lie between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Many chemical agent explosives show characteristic spectral features in the terahertz. Compared with conventional methods of detecting a variety of threats, such as weapons and chemical agent, THz radiation is low frequency and non-ionizing, and does not give rise to safety concerns. The present paper summarizes the latest progress in the application of terahertz time domain spectroscopy (THz-TDS) to chemical agent explosives. A kind of device on laser radar detecting and real time spectrum measuring was designed which measures the laser spectrum on the bases of Fourier optics and optical signal processing. Wedge interferometer was used as the beam splitter to wipe off the background light and detect the laser and measure the spectrum. The result indicates that 10 ns laser radar pulse can be detected and many factors affecting experiments are also introduced. The combination of laser radar spectrum detecting, THz-TDS, modern pattern recognition and signal processing technology is the developing trend of remote detection for chemical agent explosives. PMID:20496663

  12. Reflectance and fluorescence spectroscopies in photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Finlay, Jarod C.

    In vivo fluorescence spectroscopy during photodynamic therapy (PDT) has the potential to provide information on the distribution and degradation of sensitizers, the formation of fluorescent photoproducts and changes in tissue autofluorescence induced by photodynamic treatment. Reflectance spectroscopy allows quantification of light absorption and scattering in tissue. We present the results of several related studies of fluorescence and reflectance spectroscopy and their applications to photodynamic dosimetry. First, we develop and test an empirical method for the correction of the distortions imposed on fluorescence spectra by absorption and scattering in turbid media. We characterize the irradiance dependence of the in vivo photobleaching of three sensitizers, protoporphyrin IX (PpIX), Photofrin and mTHPC, in a rat skin model. The photobleaching and photoproduct formation of PpIX exhibit irradiance dependence consistent with singlet oxygen (1O2)-mediated bleaching. The bleaching of mTHPC occurs in two phases, only one of which is consistent with a 1O 2-mediated mechanism. Photofrin's bleaching is independent of irradiance, although its photoproduct formation is not. This can be explained by a mixed-mechanism bleaching model. Second, we develop an algorithm for the determination of tissue optical properties using diffuse reflectance spectra measured at a single source-detector separation and demonstrate the recovery of the hemoglobin oxygen dissociation curve from tissue-simulating phantoms containing human erythrocytes. This method is then used to investigate the heterogeneity of oxygenation response in murine tumors induced by carbogen inhalation. We find that while the response varies among animals and within each tumor, the majority of tumors exhibit an increase in blood oxygenation during carbogen breathing. We present a forward-adjoint model of fluorescence propagation that uses the optical property information acquired from reflectance spectroscopy to obtain the undistorted fluorescence spectrum over a wide range of optical properties. Finally, we investigate the ability of the forward-adjoint theory to extract undistorted fluorescence and optical property information simultaneously from a single measured fluorescence spectrum. This method can recover the hemoglobin oxygen dissociation curve in tissue-simulating phantoms with an accuracy comparable to that of reflectance-based methods while correcting distortions in the fluorescence over a wide range of absorption and scattering coefficients.

  13. Subwavelength film sensing based on terahertz anti-resonant reflecting hollow waveguides.

    PubMed

    You, Borwen; Lu, Ja-Yu; Liou, Jia-Hong; Yu, Chin-Ping; Chen, Hao-Zai; Liu, Tze-An; Peng, Jin-Long

    2010-08-30

    A simple dielectric hollow-tube has been experimentally demonstrated at terahertz range for bio-molecular layer sensing based on the anti-resonant reflecting wave-guidance mechanism. We experimentally study the dependence of thin-film detection sensitivity on the optical geometrical parameters of tubes, different thicknesses and tube wall refractive indices, and on different resonant frequencies. A polypropylene hollow-tube with optimized sensitivity of 0.003 mm/?m is used to sense a subwavelength-thick (?/225) carboxypolymethylene molecular overlayer on the tube's inner surface, and the minimum detectable quantity of molecules could be down to 1.22 picomole/mm(2). A double-layered Fabry-Pérot model is proposed for calculating the overlayer thicknesses, which agrees well with the experimental results. PMID:20940830

  14. Elimination of Fresnel Reflection Boundary Effects and Beam Steering in Pulsed Terahertz Computed Tomography

    NASA Astrophysics Data System (ADS)

    Mukherjee, Suman; Federici, John; Lopes, Paulo; Cabral, Miguel

    2013-09-01

    For the past few decades there has been tremendous innovation and development of Terahertz (THz) science and imaging. In particular, the technique of 3-D computed tomography has been adapted from the X-Ray to the THz range. However, the finite refractive index of materials in the THz range can severally refract probing THz beams during the acquisition of tomography data. Due to Fresnel reflection power losses at the boundaries as well as steering of the THz beam through the sample, refractive effects lead to anomalously high local attenuation coefficients near the material boundaries of a reconstructed image. These boundary phenomena can dominate the reconstructed THz-CT images making it difficult to distinguish structural defect(s) inside the material. In this paper an algorithm has been developed to remove the effects of refraction in THz-CT reconstructed images. The algorithm is successfully implemented on cylindrical shaped objects.

  15. High-speed terahertz time-domain spectroscopy of cyclotron resonance in pulsed magnetic field.

    PubMed

    Molter, D; Ellrich, F; Weinland, T; George, S; Goiran, M; Keilmann, F; Beigang, R; Léotin, J

    2010-12-01

    We present time-resolved cyclotron resonance spectra of holes in p-Ge measured during single magnetic field pulses by using a rapid-scanning, fiber-coupled terahertz time-domain spectroscopy system. The key component of the system is a rotating monolithic delay line featuring four helicoid mirror surfaces. It allows measurements of THz spectra at up to 250 Hz repetition rate. Here we show results taken at 150 Hz. In a single 900 ms measurement 135 cyclotron resonance spectra were recorded that fully agree with what is expected from literature. PMID:21164965

  16. Label-free monitoring of interaction between DNA and oxaliplatin in aqueous solution by terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Wu, Xiaojun; E, Yiwen; Xu, Xinlong; Wang, Li

    2012-07-01

    We demonstrated the feasibility of applying terahertz time-domain spectroscopy (THz-TDS) to monitor the molecular reactions in aqueous solutions of anticancer drug oxaliplatin with ?-DNA and macrophages DNA. The reaction time dependent refractive index and absorption coefficient were extracted and analyzed. The reaction half-decaying time of about 4.0 h for ?-DNA and 12.9 h for M-DNA was established. The results suggest that the THz-TDS detection could be an effective label-free technique to sense the molecular reaction in aqueous solutions and could be very useful in biology, medicine, and pharmacy industry.

  17. Causality-based method for determining the time origin in terahertz emission spectroscopy.

    PubMed

    Unuma, Takeya; Ino, Yusuke; Peiponen, Kai-Erik; Vartiainen, Erik M; Kuwata-Gonokami, Makoto; Hirakawa, Kazuhiko

    2011-06-20

    We propose a method for determining the time origin on the basis of causality in terahertz (THz) emission spectroscopy. The method is formulated in terms of the singly subtractive Kramers-Kronig relation, which is useful for the situation where not only the amplitude spectrum but also partial phase information is available within the measurement frequency range. Numerical analysis of several simulated and observed THz emission data shows that the misplacement of the time origin in THz waveforms can be detected by the method with an accuracy that is an order of magnitude higher than the given temporal resolutions. PMID:21716518

  18. Application of terahertz spectroscopy to the characterization of biological samples using birefringence silicon grating

    NASA Astrophysics Data System (ADS)

    Saha, Shimul C.; Grant, James P.; Ma, Yong; Khalid, Ata; Hong, Feng; Cumming, David R. S.

    2012-06-01

    We present a device and method for performing vector transmission spectroscopy on biological specimens at terahertz (THz) frequencies. The device consists of artificial dielectric birefringence obtained from silicon microfluidic grating structures. The device can measure the complex dielectric function of a liquid, across a wide THz band of 2 to 5.5 THz, using a Fourier transform infrared spectrometer. Measurement data from a range of liquid specimens, including sucrose, salmon deoxyribonucleic acid (DNA), herring DNA, and bovine serum albumin protein solution in water are presented. The specimen handling is simple, using a microfluidic channel. The transmission through the device is improved significantly and thus the measurement accuracy and bandwidth are increased.

  19. Integrated injection seeded terahertz source and amplifier for time-domain spectroscopy.

    PubMed

    Maysonnave, J; Jukam, N; Ibrahim, M S M; Maussang, K; Madéo, J; Cavalié, P; Dean, P; Khanna, S P; Steenson, D P; Linfield, E H; Davies, A G; Tignon, J; Dhillon, S S

    2012-02-15

    We used a terahertz (THz) quantum cascade laser (QCL) as an integrated injection seeded source and amplifier for THz time-domain spectroscopy. A THz input pulse is generated inside a QCL by illuminating the laser facet with a near-IR pulse from a femtosecond laser and amplified using gain switching. The THz output from the QCL is found to saturate upon increasing the amplitude of the THz input power, which indicates that the QCL is operating in an injection seeded regime. PMID:22344163

  20. In-vitro terahertz spectroscopy of rat skin under the action of dehydrating agents

    NASA Astrophysics Data System (ADS)

    Kolesnikov, Aleksandr S.; Kolesnikova, Ekaterina A.; Tuchina, Daria K.; Terentyuk, Artem G.; Nazarov, Maxim; Skaptsov, Alexander A.; Shkurinov, Alexander P.; Tuchin, Valery V.

    2014-01-01

    In the paper we present the results of study of rat skin and rat subcutaneous tumor under the action of dehydrating agents in terahertz (THz) range (15-30 THz). Frustrated Total Internal Reflection (FTIR) spectra were obtained with infrared Fourier spectrometer Nicolet 6700 and then they were recalculated in the transmittance spectra with Omnic software. Experiments were carried out with healthy and xenografted tumor in skin tissue in vitro. As the dehydrating agents 100% glycerol, 40%-water glucose solution, PEG-600, and propylene glycol were used. To determine the effect of the optical clearing agent (OCA), the alterations of terahertz transmittance for the samples were analyzed. The results have shown that PEG-600 and 40%-glucose water solution are the most effective dehydrating agent. The transmittance of healthy skin after PEG-600 application increased approximately by 6% and the transmittance of tumor tissue after PEG- 600 and 40%-glucose water solution application increased approximately by 8%. Obtained data can be useful for further application of terahertz radiation for tumor diagnostics.

  1. Distinguishing of different kinds of gunpowder using various methods based on terahertz radiation

    NASA Astrophysics Data System (ADS)

    Gavenda, Tomáš; K?esálek, Vojt?ch

    2014-10-01

    This article provides information about using terahertz radiation based methods such as time-domain spectroscopy, ATR spectroscopy and terahertz reflection imaging for distinguishing of different kinds of gunpowder. The findings in this article prove that gunpowder does not have any sharp peaks in terahertz region of electromagnetic spectrum up to 2.5 THz, but also prove that distinguishing of different kinds of gunpowder is possible using different methods based on terahertz radiation. All presented results are connected to absorbance of gunpowder and other measured materials, because comparison of absorbance analysis is essential for distinguishing of gunpowder samples.

  2. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Anomalous behaviours of terahertz reflected waves transmitted from GaAs induced by optical pumping

    Microsoft Academic Search

    Yu-Lei Shi; Qing-Li Zhou; Dong-Mei Zhao; Cun-Lin Zhang

    2009-01-01

    Femtosecond pump-terahertz probe studies of carrier dynamics in semi-insulating GaAs have been investigated in detail for various pump powers. It is observed that, at high pump powers, the reflection peaks flip to the opposite polarity and dramatically enhance as the pump arrival time approaches the reflected wave of the terahertz pulse. The abnormal polarity-flip and enhancement can be interpreted by

  3. Terahertz polariton propagation in patterned materials.

    PubMed

    Stoyanov, Nikolay S; Ward, David W; Feurer, Thomas; Nelson, Keith A

    2002-10-01

    Generation and control of pulsed terahertz-frequency radiation have received extensive attention, with applications in terahertz spectroscopy, imaging and ultrahigh-bandwidth electro-optic signal processing. Terahertz 'polaritonics', in which terahertz lattice waves called phonon-polaritons are generated, manipulated and visualized with femtosecond optical pulses, offers prospects for an integrated solid-state platform for terahertz signal generation and guidance. Here, we extend terahertz polaritonics methods to patterned structures. We demonstrate femtosecond laser fabrication of polaritonic waveguide structures in lithium tantalate and lithium niobate crystals, and illustrate polariton focusing into, and propagation within, the fabricated waveguide structures. We also demonstrate a 90 degrees turn within a structure consisting of two waveguides and a reflecting face, as well as a structure consisting of splitting and recombining elements that can be used as a terahertz Mach-Zehnder interferometer. The structures permit integrated terahertz signal generation, propagation through waveguide-based devices, and readout within a single solid-state platform. PMID:12618821

  4. Terahertz time-domain spectroscopy and its applications

    Microsoft Academic Search

    Jie Shan

    2001-01-01

    Mode-locked lasers can now readily produce optical pulses of femtosecond duration. In this thesis, results are presented on new methods by which these laser pulses can be exploited to measure and control electric fields on an ultrafast time scale. In addition to the development of these techniques, the resulting capability is used for time-domain far-infrared spectroscopy measurements. With respect to

  5. Far-infrared optical and dielectric response of ZnS measured by terahertz time-domain spectroscopy

    E-print Network

    Far-infrared optical and dielectric response of ZnS measured by terahertz time-domain spectroscopy of ZnS in the frequency range extending from 0.3 to 3.5 THz. THz-TDS clearly reveals the low-frequency phonon resonance features in both the single- and polycrystalline ZnS. These phonons account

  6. Estimation of crystallinity of trehalose dihydrate microspheres by usage of terahertz time-domain spectroscopy.

    PubMed

    Takeuchi, Issei; Tomoda, Keishiro; Nakajima, Takehisa; Terada, Hiroshi; Kuroda, Hideki; Makino, Kimiko

    2012-09-01

    Crystalline state of pharmaceutical materials is of great importance in the preparation of pharmaceutics because their physicochemical properties affect bioavailability, quality of products, therapeutic level, and manufacturing process. In this study, we have estimated the crystallinity of trehalose dihydrate microspheres by measuring terahertz (THz) spectroscopy. The commercially available trehalose dihydrate takes in general a crystalline state, but trehalose dihydrate microspheres prepared by using spray-drying method are in an amorphous state. We have prepared amorphous anhydrous trehalose by using melt-quenched method from crystalline trehalose dihydrate. We have measured the absorbance of trehalose dihydrate containing amorphous anhydrous trehalose (0%, 25%, 50%, 75%, and 100%) using THz time-domain spectroscopy (THz-TDS) to prepare calibration curves. Using the calibration curves, we have estimated the crystallinity of trehalose dihydrate microspheres prepared by using spray-drying method. Our results suggest that THz-TDS is well suited to distinguish crystallinity differences in pharmaceutical compounds. PMID:22499332

  7. Frequency-Comb-Assisted Terahertz Quantum Cascade Laser Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bartalini, S.; Consolino, L.; Cancio, P.; De Natale, P.; Bartolini, P.; Taschin, A.; De Pas, M.; Beere, H.; Ritchie, D.; Vitiello, M. S.; Torre, R.

    2014-04-01

    We report a metrological-grade THz spectroscopy based on the combination of a THz frequency-comb synthesizer (FCS) and a THz quantum cascade laser (QCL). The QCL, emitting at 2.5 THz, is phase locked to the free-space THz FCS, and its frequency is swept across a methanol transition by tuning the comb-repetition rate, which is ultimately disciplined by the Cs primary frequency standard. The absolute frequency scale provides an uncertainty of a few parts in 10-11 on the laser frequency and 10-9 on the line-center determination, ranking this technique among the most precise ever developed in the THz range.

  8. Terahertz spectroscopy of shift currents resulting from asymmetric (110)-oriented GaAs/AlGaAs quantum wells

    SciTech Connect

    Priyadarshi, Shekhar; Leidinger, Markus; Pierz, Klaus; Racu, Ana M.; Siegner, Uwe; Bieler, Mark [Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig (Germany); Dawson, Philip [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)

    2009-10-12

    We report the observation and the study of an additional shift current tensor element in (110)-oriented GaAs quantum wells, which arises from an out-of-plane asymmetry of the quantum well structure. The current resulting from this tensor element is optically induced with 150 fs laser pulses and detected by measuring the simultaneously emitted terahertz radiation. This terahertz spectroscopy of shift currents is a powerful technique for symmetry investigations, which shows, for example, that our nominally symmetric (110)-oriented GaAs/AlGaAs quantum wells grown by molecular beam epitaxy are in reality asymmetric structures with different right and left interfaces.

  9. Optical Reflection Spectroscopy of GEO Objects

    NASA Technical Reports Server (NTRS)

    Seitzer, Patrick; Cardona, Tammaso; Lederer, Susan M.; Cowardin, Heather; Abercromby, Kira J.; Barker, Edwin S.; Bedard, Donald

    2013-01-01

    We report on optical reflection spectroscopy of geosynchronous (GEO) objects in the US Space Surveillance Network (SSN) catalog. These observations were obtained using imaging spectrographs on the 6.5-m Magellan telescopes at the Las Campanas Observatory in Chile. Our goal is to determine the composition of these objects by comparing these spectral observations with ground-based laboratory measurements of spacecraft materials. The observations are all low resolution (1 nm after smoothing) obtained through a 5 arcsecond wide slit and using a grism as the dispersing element. The spectral range covered was from 450 nm to 800 nm. All spectra were flux calibrated using observations of standard stars with the exact same instrumental setup. An effort was made to obtain all observations within a limited range of topocentric phase angle, although the solar incident angle is unknown due to the lack of any knowledge of the attitude of the observed surface at the time of observation.

  10. Using Terahertz Spectroscopy to Study Systems with Solar Energy Applications

    NASA Astrophysics Data System (ADS)

    Milot, Rebecca L.; Moore, Gary F.; Martini, Lauren A.; Brudvig, Gary W.; Crabtree, Robert H.; Schmuttenmaer, Charles A.

    2013-06-01

    Biomimetic solar water oxidation systems are being developed as renewable alternatives to fossil fuels. One possible design incorporates thin-film dye-sensitized nanoparticle photoanades to capture and convert visible light to charge carriers and catalysts to facilitate water oxidation. The physical properties of the dye are important due to its position as the light absorber and electron transfer initiator. Given the role that porphyrins play in photosynthesis and their synthetic tunability, they are promising components for these photoanodes. Time-Resolved THz Spectroscopy (TRTS), an optical pump/THz probe technique, is a non-contact electrical probe with proven usefulness for studying electron transfer and conductivity on a sub-picosecond timescale. Using TRTS, the efficiency and dynamics of electron injection from porphyrin dyes into metal oxide surfaces was found to be strongly influenced by the structure and photophysical properties of the dye.

  11. Label-free detection and characterization of the binding of hemagglutinin protein and broadly neutralizing monoclonal antibodies using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Sun, Yiwen; Zhong, Junlan; Zhang, Cunlin; Zuo, Jian; Pickwell-MacPherson, Emma

    2015-03-01

    Hemagglutinin (HA) is the main surface glycoprotein of the influenza A virus. The H9N2 subtype influenza A virus is recognized as the most possible pandemic strain as it has crossed the species barrier, infecting swine and humans. We use terahertz spectroscopy to study the hydration shell formation around H9 subtype influenza A virus's HA protein (H9 HA) as well as the detection of antigen binding of H9 HA with the broadly neutralizing monoclonal antibody. We observe a remarkable concentration dependent nonlinear response of the H9 HA, which reveals the formation process of the hydration shell around H9 HA molecules. Furthermore, we show that terahertz dielectric properties of the H9 HA are strongly affected by the presence of the monoclonal antibody F10 and that the terahertz dielectric loss tangent can be used to detect the antibody binding at lower concentrations than the standard ELISA test.

  12. Reflectance spectroscopy of organic compounds: 1. Alkanes

    USGS Publications Warehouse

    Clark, R.N.; Curchin, J.M.; Hoefen, T.M.; Swayze, G.A.

    2009-01-01

    Reflectance spectra of the organic compounds comprising the alkane series are presented from the ultraviolet to midinfrared, 0.35 to 15.5 /??m. Alkanes are hydrocarbon molecules containing only single carbon-carbon bonds, and are found naturally on the Earth and in the atmospheres of the giant planets and Saturn's moon, Titan. This paper presents the spectral properties of the alkanes as the first in a series of papers to build a spectral database of organic compounds for use in remote sensing studies. Applications range from mapping the environment on the Earth, to the search for organic molecules and life in the solar system and throughout the. universe. We show that the spectral reflectance properties of organic compounds are rich, with major diagnostic spectral features throughout the spectral range studied. Little to no spectral change was observed as a function of temperature and only small shifts and changes in the width of absorption bands were observed between liquids and solids, making remote detection of spectral properties throughout the solar system simpler. Some high molecular weight organic compounds contain single-bonded carbon chains and have spectra similar to alkanes even ' when they fall into other families. Small spectral differences are often present allowing discrimination among some compounds, further illustrating the need to catalog spectral properties for accurate remote sensing identification with spectroscopy.

  13. High spectral resolution reflectance spectroscopy of minerals

    USGS Publications Warehouse

    Clark, R.N.; King, T.V.V.; Klejwa, M.; Swayze, G.A.; Vergo, N.

    1990-01-01

    The reflectance spectra of minerals are studied as a function of spectral resolution in the range from 0.2 to 3.0 ??m. Selected absorption bands were studied at resolving powers (??/????) as high as 2240. At resolving powers of approximately 1000, many OH-bearing minerals show diagnostic sharp absorptions at the resolution limit. At low resolution, some minerals may not be distinguishable, but as the resolution is increased, most can be easily identified. As the resolution is increased, many minerals show fine structure, particularly in the OH-stretching overtone region near 1.4 ??m. The fine structure can enhance the ability to discriminate between minerals, and in some cases the fine structure can be used to determine elemental composition. The study shows that high-resolution reflectance spectroscopy of minerals may prove to be a very important tool in the laboratory, in the field using field-portable spectrometers, from aircraft, and from satellites looking at Earth or other planetary surfaces. -from Authors

  14. Detection and electrical characterization of hidden layers using time-domain analysis of terahertz reflections

    Microsoft Academic Search

    I. Geltner; D. Hashimshony; A. Zigler

    2002-01-01

    We use a time-domain analysis method to characterize the outer layer of a multilayer structure regardless of the inner ones, thus simplifying the characterization of all the layers. We combine this method with THz reflection spectroscopy to detect nondestructively a hidden aluminum oxide layer under opaque paint and to measure its conductivity and high-frequency dielectric constant in the THz range.

  15. Discrimination of Transgenic Rice containing the Cry1Ab Protein using Terahertz Spectroscopy and Chemometrics

    PubMed Central

    Xu, Wendao; Xie, Lijuan; Ye, Zunzhong; Gao, Weilu; Yao, Yang; Chen, Min; Qin, Jianyuan; Ying, Yibin

    2015-01-01

    Spectroscopic techniques combined with chemometrics methods have proven to be effective tools for the discrimination of objects with similar properties. In this work, terahertz time-domain spectroscopy (THz-TDS) combined with discriminate analysis (DA) and principal component analysis (PCA) with derivative pretreatments was performed to differentiate transgenic rice (Hua Hui 1, containing the Cry1Ab protein) from its parent (Ming Hui 63). Both rice samples and the Cry1Ab protein were ground and pressed into pellets for terahertz (THz) measurements. The resulting time-domain spectra were transformed into frequency-domain spectra, and then, the transmittances of the rice and Cry1Ab protein were calculated. By applying the first derivative of the THz spectra in conjunction with the DA model, the discrimination of transgenic from non-transgenic rice was possible with accuracies up to 89.4% and 85.0% for the calibration set and validation set, respectively. The results indicated that THz spectroscopic techniques and chemometrics methods could be new feasible ways to differentiate transgenic rice. PMID:26154950

  16. Conductivity of ZnO nanowires, nanoparticles, and thin films using time-resolved terahertz spectroscopy.

    PubMed

    Baxter, Jason B; Schmuttenmaer, Charles A

    2006-12-21

    The terahertz absorption coefficient, index of refraction, and conductivity of nanostructured ZnO have been determined using time-resolved terahertz spectroscopy, a noncontact optical probe. ZnO properties were measured directly for thin films and were extracted from measurements of nanowire arrays and mesoporous nanoparticle films by applying Bruggeman effective medium theory to the composite samples. Annealing significantly reduces the intrinsic carrier concentration in the ZnO films and nanowires, which were grown by chemical bath deposition. The complex-valued, frequency-dependent photoconductivities for all morphologies were found to be similar at short pump-probe delay times. Fits using the Drude-Smith model show that films have the highest mobility, followed by nanowires and then nanoparticles, and that annealing the ZnO increases its mobility. Time constants for decay of photoinjected electron density in films are twice as long as those in nanowires and more than 5 times those for nanoparticles due to increased electron interaction with interfaces and grain boundaries in the smaller-grained materials. Implications for electron transport in dye-sensitized solar cells are discussed. PMID:17165967

  17. Spectroscopy study of ephedrine hydrochloride and papaverine hydrochloride in terahertz range

    NASA Astrophysics Data System (ADS)

    Deng, Fusheng; Shen, Jingling; Wang, Guangqin; Liang, Meiyan

    2008-12-01

    The terahertz(THz) fingerprint spectra of Ephedrine Hydrochloride and Papaverine Hydrochloride have been measured using THz time-domain Spectroscopy (THz-TDS) system in the region of 0.2~2.6 THz. To explain the spectra, both gas-phase simulation methods and solid-state simulation methods were performed in the efforts to extract pictures of the molecular interior vibrational modes. By comparing the results of various gas-phase simulation methods, It was found that using the semi-empirical theory is more applicable than the density functional theory (DFT) for some chemical compounds. In the solid-state calculations, solid-state density functional theory (DFT) was employed to obtain the vibration frequencies and Difference-Dipole Method (DDM) was used to calculate the corresponding infrared (IR) intensity. In the process of calculating the IR intensity of Papaverine Hydrochloride in terahertz range, we found that the results by Hirshfeld partitioning method agree better with the experiments than the ones derived from Mulliken atomic charges. Moreover, the accuracy of simulation results depends on the basis sets and grid size being chosen.

  18. Terahertz transmission and reflection studies of the topological Kondo insulator candidate SmB6

    NASA Astrophysics Data System (ADS)

    Morris, Christopher M.; Laurita, N. J.; Koopayeh, S.; Cottingham, P.; Phelan, W. A.; Schoop, L.; McQueen, T. M.; Armitage, N. P.

    2015-03-01

    The Kondo insulator SmB6 has long been known to display anomalous transport behavior at low temperatures (T < 10 K) and high pressures. At low temperatures, a plateau is observed in the resistivity, contrary to the logarithmic divergence expected for a normal Kondo insulator. Recent theoretical calculations suggest that SmB6 may be the first topological Kondo insulator, a material with a Kondo insulating bulk, but topologically protected metallic surface states. Here, time domain terahertz spectroscopy (TDTS) is used to investigate the temperature dependent optical conductivity of single crystals of SmB6. A saturation of the transmission is observed associated with the resistance plateau as the bulk becomes insulating. A secondary bulk conduction mechanism remains down to the lowest measured temperature, 1.6 K. Additionally, FTIR measurements have been performed that show the Kondo gap of SmB6 opening at low temperatures. Work supported by The Institute of Quantum Matter under DOE Grant DE-FG02-08ER46544 and by the Gordon and Betty Moore Foundation.

  19. Low-Frequency Spectra of Amino Acids and Short-Chain Peptides Studied by Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ponseca, Carlito S.; Kambara, Ohki; Kawaguchi, Shintaro; Yamamoto, Kohji; Tominaga, Keisuke

    2010-07-01

    The low-frequency spectra of the amino acids l-alanine and glycine and their peptides were studied using terahertz (THz) time-domain spectroscopy (TDS) at room temperature. In a previous work (Yamamoto et al., Biophys. J. 89, L22-L24 (2005)), the low-frequency spectra of amino acids (glycine and l-alanine) and their polypeptides (polyglycine and poly- l-alanine) were studied by THz-TDS, and it was found that there is a clear difference in low-frequency dynamics between the amino acids and the polypeptides. In the present study, amino acids and short peptides were chosen in order to investigate the effect of polymerization on low-frequency spectra. We focus on two physical quantities to represent the spectral features: (1) the intensity of the reduced absorption cross section (RACS), which we define from the absorption coefficient and refractive index, and (2) the exponent in the power law behavior of the RACS. We found that the two physical quantities show different dependences on peptide chain length, suggesting that the two physical quantities reflect different dynamics and interactions. The change in RACS intensity may be due to intermolecular or intrachain motion. The validity of the assumption of constant IR activity in the investigated frequency region is critical to understanding the origin of the variation in the exponent with chain length.

  20. Materials for terahertz science and technology

    Microsoft Academic Search

    Bradley Ferguson; Xi-Cheng Zhang

    2002-01-01

    Terahertz spectroscopy systems use far-infrared radiation to extract molecular spectral information in an otherwise inaccessible portion of the electromagnetic spectrum. Materials research is an essential component of modern terahertz systems: novel, higher-power terahertz sources rely heavily on new materials such as quantum cascade structures. At the same time, terahertz spectroscopy and imaging provide a powerful tool for the characterization of

  1. Reflection optical two-dimensional Fourier-transform spectroscopy.

    PubMed

    Li, Hebin; Moody, Galan; Cundiff, Steven T

    2013-01-28

    We have developed a technique to perform optical two-dimensional Fourier-transform (2DFT) spectroscopy in a reflection geometry. Various reflection 2DFT spectra are obtained for an atomic vapor. The technique is useful for the cases where optical 2DFT spectroscopy cannot be performed in the transmission geometry. PMID:23389154

  2. Degradation diagnosis of ultrahigh-molecular weight polyethylene with terahertz-time-domain spectroscopy

    SciTech Connect

    Yamamoto, Kohji; Yamaguchi, Mariko; Tani, Masahiko; Hangyo, Masanori; Teramura, Satoshi; Isu, Toshiro; Tomita, Naohide [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka, 565-0871 (Japan); Graduate School of Material Science, Nara Institute of Science and Technology (NAIST), 8916-5, Takayama, Ikoma, Nara, 630-0101 (Japan); International Innovation Center, Kyoto University, Yoshida-Hon-machi, Sakyo-ku, Kyoto, 606-8501 (Japan)

    2004-11-29

    We investigated ultrahigh-molecular-weight-polyethylene (UHMWPE) samples prepared by various conditions with terahertz-time-domain spectroscopy (THz-TDS). Degradation of the virgin UHMWPE samples by {gamma} irradiation induced a drastic increase of the absorption ranging continuously over the THz region. The increase of the absorption continuum is interpreted to originate in the oxidation of the amorphous region within the sample. Only slight THz spectral changes induced by the {gamma} irradiation were, however, observed for the UHMWPE samples doped with 0.1 and 0.3 wt % vitamin E. This result agrees with the earlier indication that vitamin E has an antidegradation effect on UHMWPE. The present result shows that the THz-TDS can be used for the quality control of UHMWPE by monitoring the absorption continuum in the THz region.

  3. Compact fiber-coupled terahertz spectroscopy system pumped at 800 nm wavelength.

    PubMed

    Ellrich, Frank; Weinland, Tristan; Molter, Daniel; Jonuscheit, Joachim; Beigang, René

    2011-05-01

    Photonic terahertz (THz) technology using femtosecond (fs) lasers has a great potential in a wide range of applications, such as non-destructive testing of objects or spectroscopic identification of chemical substances. For industrial purposes, a THz system has to be compact and easily implementable into the particular application. Therefore, fiber-coupled THz systems are the key to a widespread use of THz technology. In order to have flexible THz emitters and detectors near infrared fs light pulses have to be sent through optical fibers of considerable length. As a consequence, the fiber's dispersion has to be compensated for and nonlinear effects in the fiber have to be minimized. A fiber-based THz time-domain spectroscopy system of high stability, flexibility, and portability is presented here. PMID:21639487

  4. Compact fiber-coupled terahertz spectroscopy system pumped at 800 nm wavelength

    NASA Astrophysics Data System (ADS)

    Ellrich, Frank; Weinland, Tristan; Molter, Daniel; Jonuscheit, Joachim; Beigang, René

    2011-05-01

    Photonic terahertz (THz) technology using femtosecond (fs) lasers has a great potential in a wide range of applications, such as non-destructive testing of objects or spectroscopic identification of chemical substances. For industrial purposes, a THz system has to be compact and easily implementable into the particular application. Therefore, fiber-coupled THz systems are the key to a widespread use of THz technology. In order to have flexible THz emitters and detectors near infrared fs light pulses have to be sent through optical fibers of considerable length. As a consequence, the fiber's dispersion has to be compensated for and nonlinear effects in the fiber have to be minimized. A fiber-based THz time-domain spectroscopy system of high stability, flexibility, and portability is presented here.

  5. Intrinsic carrier multiplication efficiency in bulk Si crystals evaluated by optical-pump/terahertz-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Yamashita, G.; Matsubara, E.; Nagai, M.; Kanemitsu, Y.; Ashida, M.

    2014-12-01

    We estimated the carrier multiplication efficiency in the most common solar-cell material, Si, by using optical-pump/terahertz-probe spectroscopy. Through close analysis of time-resolved data, we extracted the exact number of photoexcited carriers from the sheet carrier density 10 ps after photoexcitation, excluding the influences of spatial diffusion and surface recombination in the time domain. For incident photon energies greater than 4.0 eV, we observed enhanced internal quantum efficiency due to carrier multiplication. The evaluated value of internal quantum efficiency agrees well with the results of photocurrent measurements. This optical method allows us to estimate the carrier multiplication and surface recombination of carriers quantitatively, which are crucial for the design of the solar cells.

  6. Confined photocarrier transport in InAs pyramidal quantum dots via terahertz time-domain spectroscopy.

    PubMed

    Presto, Jorge Michael M; Prieto, Elizabeth Ann P; Omambac, Karim M; Afalla, Jessica Pauline C; Lumantas, Deborah Anne O; Salvador, Arnel A; Somintac, Armando S; Estacio, Elmer S; Yamamoto, Kohji; Tani, Masahiko

    2015-06-01

    We present experimental demonstration of photocarrier dynamics in InAs quantum dots (QDs) via terahertz (THz) time-domain spectroscopy (TDS) using two excitation wavelengths and observing the magnetic field polarity characteristics of the THz signal. The InAs QDs was grown using standard Stranski-Krastanow technique on semi-insulating GaAs substrate. Excitation pump at 800 nm- and 910 nm-wavelength were used to distinguish THz emission from the InAs/GaAs matrix and InAs respectively. THz-TDS at 800 nm pump revealed intense THz emission comparable to a bulk p-InAs. For 910 nm pump, the THz emission generally weakened and upon applying external magnetic field of opposite polarities, the THz time-domain plot exhibited anomalous phase-shifting. This was attributed to the possible current-surge associated with the permanent dipole in the QD. PMID:26072813

  7. Fiber-coupled Antennas for Ultrafast Coherent Terahertz Spectroscopy in Low Temperatures and High Magnetic Fields

    E-print Network

    Crooker, S A

    2002-01-01

    For the purposes of measuring the high-frequency complex conductivity of correlated-electron materials at low temperatures and high magnetic fields, a method is introduced for performing coherent time-domain terahertz spectroscopy directly in the cryogenic bore of existing dc and pulsed magnets. Miniature fiber-coupled THz emitters and receivers are constructed and are demonstrated to work down to 1.5 Kelvin and up to 17 Tesla, for eventual use in higher-field magnets. Maintaining the sub-micron alignment between fiber and antenna during thermal cycling, obtaining ultrafast (${optical gating pulses at the end of long optical fibers, and designing highly efficient devices that work well with low-power optical gating pulses constitute the major technical challenges of this project. Data on a YBCO superconducting thin film and a high mobility 2D electron gas is shown.

  8. Reflectance anisotropy spectroscopy of magnetite (110) surfaces

    NASA Astrophysics Data System (ADS)

    Fleischer, K.; Verre, R.; Mauit, O.; Sofin, R. G. S.; Farrell, L.; Byrne, C.; Smith, C. M.; McGilp, J. F.; Shvets, I. V.

    2014-05-01

    Reflectance anisotropy spectroscopy (RAS) has been used to measure the optical anisotropies of bulk and thin-film Fe3O4(110) surfaces. The spectra indicate that small shifts in energy of the optical transitions, associated with anisotropic strain or electric field gradients caused by the (110) surface termination or a native oxide layer, are responsible for the strong signal observed. The RAS response was then measured as a function of temperature. A distinct change in the RAS line-shape amplitude was observed in the spectral range from 0.8 to 1.6 eV for temperatures below the Verwey transition of the crystal. Finally, thin-film magnetite was grown by molecular beam epitaxy on MgO(110) substrates. Changes in the RAS spectra were found for different film thickness, suggesting that RAS can be used to monitor the growth of magnetite (110) films in situ. The thickness dependence of the RAS is discussed in terms of various models for the origin of the RAS signal.

  9. Specular Reflection and Diffuse Reflectance Spectroscopy of Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Studies on the occurrence and effects of specular reflection in mid-infrared spectra of soils have shown that distortions due to specular reflection occur for both organic (humic acid) and non-organic fractions (carbonates, silica, ashed fraction of soil). The results demonstrated explain why the s...

  10. Quantitative determination of cyfluthrin in n-hexane by terahertz time-domain spectroscopy with chemometrics methods

    Microsoft Academic Search

    Yuefang Hua; Hongjian Zhang; Hongliang Zhou

    2009-01-01

    Terahertz time-domain spectroscopy (THz-TDS) was used for the detection of cyfluthrin content in N-hexane solvent with the concentration range of 0.5-10 mug\\/mL. The absorbance of the solution form cyfluthrin was obtained in the frequency range between 0.5-1.5 THz. Two kinds of multivariate linear regression models were then built between the absorbance and the concentration of 15 samples, using partial least

  11. Pulsed terahertz spectroscopy of DNA, bovine serum albumin and collagen between 0.1 and 2.0 THz

    Microsoft Academic Search

    A. G. Markelz; A. Roitberg; E. J. Heilweil

    2000-01-01

    We report the first use of pulsed terahertz spectroscopy to examine low-frequency collective vibrational modes of biomolecules. Broadband absorption increasing with frequency was observed for lyophilized powder samples of calf thymus DNA, bovine serum albumin and collagen in the 0.06–2.00 THz (2–67 cm?1) frequency range, suggesting that a large number of the low-frequency collective modes for these systems are IR

  12. Two-dimensional photonic crystal slabs in parallel-plate metal waveguides studied with terahertz time-domain spectroscopy

    Microsoft Academic Search

    Zhongping Jian; Jeremy Pearce; Daniel M. Mittleman

    2005-01-01

    In this paper, we report our experimental study on two-dimensional photonic crystal slabs embedded inside parallel-plate metal waveguides, using terahertz time-domain spectroscopy. We observe that the temporal response of the photonic crystal slabs is significantly dispersed, indicative of strong dispersion near the edges of the photonic band gap. In the frequency domain, we observe several gaps whose sizes compare well

  13. Time-domain Terahertz spectroscopy as a diagnostic tool for the electrodynamic properties of high temperature superconductors

    Microsoft Academic Search

    I. Wilke; M. Khazan; C. T. Rieck; P. Kuzel; C. Jaekel; H. Kurz

    2000-01-01

    Time-domain Terahertz transmission spectroscopy (TDTTS) has proved to be a unique method for the experimental study of electromagnetic properties of high temperature superconducting thin-films at THz-frequencies in basic and applied research. We have improved the analysis of TDTTS-measurements by numerically extracting the complex index of refraction from the measured complex transmission of the superconducting thin film. Based on this other

  14. Energy-Gap Dynamics of Superconducting NbN Thin Films Studied by Time-Resolved Terahertz Spectroscopy

    Microsoft Academic Search

    M. Beck; M. Klammer; S. Lang; P. Leiderer; V. V. Kabanov; G. N. Gol'Tsman; J. Demsar

    2011-01-01

    Using time-domain terahertz spectroscopy we performed direct studies of the photoinduced suppression and recovery of the superconducting gap in a conventional BCS superconductor NbN. Both processes are found to be strongly temperature and excitation density dependent. The analysis of the data with the established phenomenological Rothwarf-Taylor model enabled us to determine the bare quasiparticle recombination rate, the Cooper pair-breaking rate

  15. Terahertz time domain spectroscopy allows contactless monitoring of grapevine water status

    PubMed Central

    Santesteban, Luis G.; Palacios, Inés; Miranda, Carlos; Iriarte, Juan C.; Royo, José B.; Gonzalo, Ramón

    2015-01-01

    Agriculture is the sector with the greatest water consumption, since food production is frequently based on crop irrigation. Proper irrigation management requires reliable information on plant water status, but all the plant-based methods to determine it suffer from several inconveniences, mainly caused by the necessity of destructive sampling or of alteration of the plant organ due to contact installation. The aim of this work is to test if terahertz (THz) time domain reflectance measurements made on the grapevine trunk allows contactless monitoring of plant status. The experiments were performed on a potted 14-years-old plant, using a general purpose THz emitter receiver head. Trunk THz time-domain reflection signal proved to be very sensitive to changes in plant water availability, as its pattern follows the trend of soil water content and trunk growth variations. Therefore, it could be used to contactless monitor plant water status. Apart from that, THz reflection signal was observed to respond to light conditions which, according to a specifically designed girdling experiment, was caused by changes in the phloem. This latter results opens a promising field of research for contactless monitoring of phloem activity. PMID:26082791

  16. Terahertz time domain spectroscopy allows contactless monitoring of grapevine water status.

    PubMed

    Santesteban, Luis G; Palacios, Inés; Miranda, Carlos; Iriarte, Juan C; Royo, José B; Gonzalo, Ramón

    2015-01-01

    Agriculture is the sector with the greatest water consumption, since food production is frequently based on crop irrigation. Proper irrigation management requires reliable information on plant water status, but all the plant-based methods to determine it suffer from several inconveniences, mainly caused by the necessity of destructive sampling or of alteration of the plant organ due to contact installation. The aim of this work is to test if terahertz (THz) time domain reflectance measurements made on the grapevine trunk allows contactless monitoring of plant status. The experiments were performed on a potted 14-years-old plant, using a general purpose THz emitter receiver head. Trunk THz time-domain reflection signal proved to be very sensitive to changes in plant water availability, as its pattern follows the trend of soil water content and trunk growth variations. Therefore, it could be used to contactless monitor plant water status. Apart from that, THz reflection signal was observed to respond to light conditions which, according to a specifically designed girdling experiment, was caused by changes in the phloem. This latter results opens a promising field of research for contactless monitoring of phloem activity. PMID:26082791

  17. Standoff Detection of Hidden Explosives and Cold and Fire Arms by Terahertz Time-Domain Spectroscopy and Active Spectral Imaging (Review)

    NASA Astrophysics Data System (ADS)

    Skvortsov, L. A.

    2014-11-01

    Terahertz time-domain spectroscopy and standoff spectral imaging for detection of explosives and cold and fire arms hidden, for example, under clothing, were reviewed. Special attention was paid to different schemes for practical implementation of these methods. Progress in this direction and existing problems and the prospects for their solution were discussed. Issues related to sources and receivers of terahertz radiation were briefly discussed. It was noted that interest in quantum-cascade lasers as compact sources of terahertz radiation and the potential of using them at room temperature were increasing.

  18. Qualitative and quantitative analysis of calcium-based microfillers using terahertz spectroscopy and imaging.

    PubMed

    Abina, Andreja; Puc, Uroš; Jegli?, Anton; Prah, Jana; Venckevi?ius, Rimvydas; Kašalynas, Irmantas; Valušis, Gintaras; Zidanšek, Aleksander

    2015-10-01

    In different industrial applications, several strictly defined parameters of calcium-based microfillers such as average particle size, particle size distribution, morphology, specific surface area, polymorphism and chemical purity, play a key role in the determination of its usefulness and effectiveness. Therefore, an analytical tool is required for rapid and non-destructive characterization of calcium-based microfillers during the synthesis process or before its use in a further manufacturing process. Since spectroscopic techniques are preferred over microscopy and thermogravimetry, particularly due to its non-destructive nature and short analysis time, we applied terahertz (THz) spectroscopy to analyse calcite microfillers concentration in polymer matrix, its granulation and chemical treatment. Based on the analysis of peak absorbance amplitude, peak frequency position, and the appearance of additional spectral features, quantitative and qualitative analysis was successfully achieved. In addition, THz imaging was also applied for both quantitative and qualitative analysis of calcium-based microfillers. By using spatial distribution map, the inhomogeneity in concentration of calcium carbonate in polymer matrix was characterized. Moreover, by THz spectroscopy and imaging different calcium compounds were detected in binary mixtures. Finally, we demonstrated that the applied spectroscopic technique offers valuable results and can be, in combination with other spectroscopic and microscopic techniques, converted to a powerful rapid analytical tool. PMID:26078145

  19. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers.

    PubMed

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-01-01

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

  20. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

    PubMed Central

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-01-01

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

  1. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    NASA Astrophysics Data System (ADS)

    Demming, Anna; Tonouchi, Masayoshi; Reno, John L.

    2013-05-01

    A useful synergy is being established between terahertz research and nanotechnology. High power sources [1-3] and detectors [4] in what was once considered the terahertz 'frequency gap' [5] in the electromagnetic spectrum have stimulated research with huge potential benefits in a range of industries including food, medicine and security, as well as fundamental physics and astrophysics. This special section, with guest editors Masayoshi Tonouchi and John Reno, gives a glimpse of the new horizons nanotechnology is broaching in terahertz research. While the wavelengths relevant to the terahertz domain range from hundreds of micrometres to millimetres, structures at the nanoscale reveal interesting low energy dynamics in this region. As a result terahertz spectroscopy techniques are becoming increasingly important in nanomaterial characterization, as demonstrated in this special section by colleagues at the University of Oxford in the UK and the Australian National University. They use terahertz spectroscopy to identify the best nanostructure parameters for specific applications [6]. The low energy dynamics in nanostructures also makes them valuable tools for terahertz detection [7]. In addition the much sought after terahertz detection over broadband frequency ranges has been demonstrated, providing versatility that has been greatly in demand, particularly in spectroscopy applications [8, 9]. Also in this special section, researchers in Germany and China tackle some of the coupling issues in terahertz time domain spectroscopy with an emitter specifically well suited for systems operated with an amplified fibre [3]. 'In medical imaging, the advantage of THz radiation is safety, because its energy is much lower than the ionization energy of biological molecules, in contrast to hazardous x-ray radiation,' explains Joo-Hiuk Son from the University of Seoul in Korea in his review [10]. As he also points out, the rotational and vibrational energies of water molecules are within the THz spectral region providing an additional benefit. His review describes the principle, characteristics, and applications of terahertz molecular imaging, where the use of nanoparticle probes allows dramatically enhanced sensitivity. Jiaguang Han and Weili Zhang and colleagues in China, Saudi Arabia, Japan and the US report exciting developments for optoelectronics [11]. They describe work on plasmon-induced transparency (PIT), an analogue of electromagnetically induced transparency (EIT) where interference leads to a sharp transparency window that may be useful for nonlinear and slow-light devices, optical switching, pulse delay, and storage for optical information processing. While PIT has advantages over the cumbersome experimental systems required for EIT, it has so far been constrained to very narrow band operation. Now Zhang and colleagues present the simulation, implementation, and measurement of a broadband PIT metamaterial functioning across a frequency range greater than 0.40 THz in the terahertz regime. 'We can foresee a historic breakthrough for science and technology through terahertz research,' concluded Masayoshi Tonouchi in his review over five years ago as momentum in the field was mounting [12]. He added, 'It is also noteworthy that THz research is built on many areas of science and the coordination of a range of disciplines is giving birth to a new science.' With the inherently multidisciplinary nature of nanotechnology research it is not so strange to see the marriage of the two fields form such a fruitful partnership, as this special section highlights. References [1] Williams B S, Kumar S, Hu Q and Reno J L 2006 High-power terahertz quantum-cascade lasers Electron. Lett. 42 89-91 [2] Köhler R et al 2002 Terahertz semiconductor-heterostructure laser Nature 417 156-9 [3] Mittendorff M, Xu M, Dietz R J B, K¨unzel H, Sartorius B, Schneider H, Helm M and Winnerl S 2013 Large area photoconductive THz emitter for 1.55 ?m excitation based on an InGaAs heterostructure Nanotechnology 24 214007 [4] Chen H-T, Padilla W J, Zide J M O, Gossa

  2. Dielectric characterization of [Fe(NH2-trz)3]Br2•H2O thermal spin crossover compound by terahertz time domain spectroscopy

    Microsoft Academic Search

    P. Mounaix; N. Lascoux; J. Degert; E. Freysz; A. Kobayashi; N. Daro; J.-F. Létard

    2005-01-01

    The complex optical index refraction of an iron (II) spin-crossover coordination polymer is measured in the Terahertz frequency range by Terahertz time-domain spectroscopy (THz-TDS). By scanning the temperature from 288 to 333 K, we have recorded the evolution of the THz spectrum within the low spin - high spin thermal hysteresis loop. We were able to simultaneously infer the refractive

  3. In vivo terahertz spectroscopy of pigmentary skin nevi: Pilot study of non-invasive early diagnosis of dysplasia

    NASA Astrophysics Data System (ADS)

    Zaytsev, Kirill I.; Kudrin, Konstantin G.; Karasik, Valeriy E.; Reshetov, Igor V.; Yurchenko, Stanislav O.

    2015-02-01

    In vivo terahertz (THz) spectroscopy of pigmentary skin nevi is performed. The in vivo THz dielectric characteristics of healthy skin and dysplastic and non-dysplastic skin nevi are reconstructed and analyzed. The dielectric permittivity curves of these samples in the THz range exhibit significant differences that could allow non-invasive early diagnosis of dysplastic nevi, which are melanoma precursors. An approach for differentiating dysplastic and non-dysplastic skin nevi using the THz dielectric permittivity is proposed. The results demonstrate that THz pulsed spectroscopy is potentially an effective tool for non-invasive early diagnosis of dysplastic nevi and melanomas of the skin.

  4. Monitoring the Polymerization of Two-Component Epoxy Adhesives Using a Terahertz Time Domain Reflection System

    NASA Astrophysics Data System (ADS)

    Probst, T.; Sommer, S.; Soltani, A.; Kraus, E.; Baudrit, B.; Town, G. E.; Koch, M.

    2015-06-01

    We report nondestructive measurements of the properties of two-component epoxy adhesives at THz wavelengths using a reflective time-domain spectroscopy system. We describe a simple method to determine the refractive index, layer thickness, and absorption coefficient using time-domain data applying a Fresnel-equation based approach. The results indicate that the adhesive's curing process may be monitored using a simple parameter extraction technique based on time-domain measurements for systems featuring small bandwidth, showing good agreement with data obtained with from transmission measurements.

  5. Development of grating light reflection spectroscopy for chemical sensing applications

    Microsoft Academic Search

    Sean Acie Smith

    2000-01-01

    Grating Light Reflection Spectroscopy (GLRS) exploits the interaction of light with a transmission diffraction grating in contact with a sample. With this technique, light reflected from the grating exhibits a redistribution of spectral intensity and phase dependent upon the bulk dielectric properties (refractive index and absorbance) of the sample. The use of a transmission diffraction grating makes GLRS unique within

  6. Estimating soil quality indicators with diffuse reflectance spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rapid estimation of soil quality is needed for determining and mapping soil variability in site-specific management. One technology that can fulfill this need is diffuse reflectance spectroscopy, which measures light reflected from the soil in the visible and near infrared wavelength bands. Reflecta...

  7. Does Spectral Format Matter in Diffuse Reflection Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near- and more recently, mid-infrared diffuse reflectance spectroscopy have come to be extensively used to determine the composition of products ranging from forages to drugs. In these methods, spectra are generally collected as (Reflectance or R) and transformed to log (1/R) according to the Beer-...

  8. Terahertz emission from black silicon

    Microsoft Academic Search

    P. Hoyer; M. Theuer; R. Beigang; E.-B. Kley

    2008-01-01

    We report on a terahertz emitter made out of black silicon. The black surface structure absorbs the whole optical pump power in the very surface. In contrast to expectations for indirect semiconductors, the black structure shows an emission in the terahertz range. The emitted radiation of the black silicon crystal is characterized for different parameters using terahertz time-domain spectroscopy.

  9. Simultaneous prediction of density and moisture content of wood by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Inagaki, Tetsuya; Ahmed, Belal; Hartley, Ian D.; Tsuchikawa, Satoru; Reid, Matthew

    2014-11-01

    In this study, demonstration of simultaneous prediction of solid wood density and moisture content, both of which are critical in manufacturing operations, of 4 species (Aspen, Birch, Hemlock and Maple) was accomplished using terahertz time-domain spectroscopy (THz-TDS). THz measurements of wood at various moisture contents were taken for two orientations of the THz field (parallel and perpendicular) with respect to the visible grain. The real and imaginary parts of the dielectric function averaged over the frequency range of 0.1 to 0.2 THz had strong correlation with density and moisture content of the wood. We extend a model that has been applied previously to oven-dry wood to include the effects of moisture below the fiber saturation point by combining two effective medium models, which allows the dielectric function of water, air and oven-dry cell wall material to be modeled to give an effective dielectric function for the wood. A strong correlation between measured and predicted values for density and moisture content were observed.

  10. Feasibility of terahertz time-domain spectroscopy to detect tetracyclines hydrochloride in infant milk powder.

    PubMed

    Qin, Jianyuan; Xie, Lijuan; Ying, Yibin

    2014-12-01

    We report the use of terahertz time-domain spectroscopy (THz-TDS) to detect tetracyclines hydrochloride (TCsH) in infant milk powder for the first time. Four kinds of TCsH exhibited their unique spectral features in the region of 0.3-1.8 THz. The main spectral features of these TCsH were still detectable when mixed with infant milk powder with concentrations at 1%-50%, even in the ternary mixtures. The results from chemometrics analysis showed that qualitative and quantitative detection of TCsH in infant milk powder could be successfully achieved. The residual predictive deviation (RPD) values of all these TCsH models were all higher than 2, indicating these models were considered good and could be used in screening purposes. The RPD values of TCH, DTCH, and CTCH models were higher than 3, which were considered excellent for prediction purposes. These preliminary results indicated that THz-TDS combined with chemometrics analysis was suitable for detecting the presence of TCsH residues in a food matrix. PMID:25348376

  11. Observing the Temperature Dependent Transition of the GP2 Peptide Using Terahertz Spectroscopy

    PubMed Central

    Sun, Yiwen; Zhu, Zexuan; Chen, Siping; Balakrishnan, Jega; Abbott, Derek; Ahuja, Anil T.; Pickwell-MacPherson, Emma

    2012-01-01

    The GP2 peptide is derived from the Human Epidermal growth factor Receptor 2 (HER2/nue), a marker protein for breast cancer present in saliva. In this paper we study the temperature dependent behavior of hydrated GP2 at terahertz frequencies and find that the peptide undergoes a dynamic transition between 200 and 220 K. By fitting suitable molecular models to the frequency response we determine the molecular processes involved above and below the transition temperature (TD). In particular, we show that below TD the dynamic transition is dominated by a simple harmonic vibration with a slow and temperature dependent relaxation time constant and that above TD, the dynamic behavior is governed by two oscillators, one of which has a fast and temperature independent relaxation time constant and the other of which is a heavily damped oscillator with a slow and temperature dependent time constant. Furthermore a red shifting of the characteristic frequency of the damped oscillator was observed, confirming the presence of a non-harmonic vibration potential. Our measurements and modeling of GP2 highlight the unique capabilities of THz spectroscopy for protein characterization. PMID:23209703

  12. Determination of soluble solids content in apple products by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Hao, Guohui; Liu, Jianjun; Hong, Zhi

    2011-08-01

    Soluble solids content is an important index for fruit quality. One of the traditional methods in determining soluble solids content of fruits is refractometry which measures the refractive index in visible or near infrared. Here we reported the use of terahertz time-domain transmission spectroscopy (THz-TDTS) technique for the determination of soluble solids content in apple products. Not only the refractive index, but also the absorption coefficient is used in regression model. In method one, sucrose solutions were for the calibration set , root mean square of validation set (RMSEP) was 0.168% for absorption coefficient model, 0.741% for refractive index model. In method two, apple products were for the calibration set, RMSEP was 0.143% for absorption coefficient model, 0.648% for refractive index model. Less absolute error of 0.2% between predicted and refractometer value has been both obtained from two methods with absorption coefficient model. This result proved the THz-TDS technique is quite potential for nondestructive detection on food quality.

  13. Monitoring Plant Drought Stress Response Using Terahertz Time-Domain Spectroscopy[C][W

    PubMed Central

    Born, Norman; Behringer, David; Liepelt, Sascha; Beyer, Sarah; Schwerdtfeger, Michael; Ziegenhagen, Birgit; Koch, Martin

    2014-01-01

    We present a novel measurement setup for monitoring changes in leaf water status using nondestructive terahertz time-domain spectroscopy (THz-TDS). Previous studies on a variety of plants showed the principal applicability of THz-TDS. In such setups, decreasing leaf water content directly correlates with increasing THz transmission. Our new system allows for continuous, nondestructive monitoring of the water status of multiple individual plants each at the same constant leaf position. It overcomes previous drawbacks, which were mainly due to the necessity of relocating the plants. Using needles of silver fir (Abies alba) seedlings as test subjects, we show that the transmission varies along the main axis of a single needle due to a variation in thickness. Therefore, the relocation of plants during the measuring period, which was necessary in the previous THz-TDS setups, should be avoided. Furthermore, we show a highly significant correlation between gravimetric water content and respective THz transmission. By monitoring the relative change in transmission, we were able to narrow down the permanent wilting point of the seedlings. Thus, we established groups of plants with well-defined levels of water stress that could not be detected visually. This opens up the possibility for a broad range of genetic and physiological experiments. PMID:24501000

  14. Monitoring plant drought stress response using terahertz time-domain spectroscopy.

    PubMed

    Born, Norman; Behringer, David; Liepelt, Sascha; Beyer, Sarah; Schwerdtfeger, Michael; Ziegenhagen, Birgit; Koch, Martin

    2014-04-01

    We present a novel measurement setup for monitoring changes in leaf water status using nondestructive terahertz time-domain spectroscopy (THz-TDS). Previous studies on a variety of plants showed the principal applicability of THz-TDS. In such setups, decreasing leaf water content directly correlates with increasing THz transmission. Our new system allows for continuous, nondestructive monitoring of the water status of multiple individual plants each at the same constant leaf position. It overcomes previous drawbacks, which were mainly due to the necessity of relocating the plants. Using needles of silver fir (Abies alba) seedlings as test subjects, we show that the transmission varies along the main axis of a single needle due to a variation in thickness. Therefore, the relocation of plants during the measuring period, which was necessary in the previous THz-TDS setups, should be avoided. Furthermore, we show a highly significant correlation between gravimetric water content and respective THz transmission. By monitoring the relative change in transmission, we were able to narrow down the permanent wilting point of the seedlings. Thus, we established groups of plants with well-defined levels of water stress that could not be detected visually. This opens up the possibility for a broad range of genetic and physiological experiments. PMID:24501000

  15. Distinguishing Gasoline Engine Oils of Different Viscosities Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Adbul-Munaim, Ali Mazin; Reuter, Marco; Koch, Martin; Watson, Dennis G.

    2015-07-01

    Terahertz-time-domain spectroscopy (THz-TDS) in the range of 0.5-2.0 THz was evaluated for distinguishing among gasoline engine oils of three different grades (SAE 5W-20, 10W-40, and 20W-50) from the same manufacturer. Absorption coefficient showed limited potential and only distinguished ( p < 0.05) the 20W-50 grade from the other two grades in the 1.7-2.0-THz range. Refractive index data demonstrated relatively flat and consistently spaced curves for the three oil grades. ANOVA results confirmed a highly significant difference ( p < 0.0001) in refractive index among each of the three oils across the 0.5-2.0-THz range. Linear regression was applied to refractive index data at 0.25-THz intervals from 0.5 to 2.0 THz to predict kinematic viscosity. All seven linear regression models, intercepts, and refractive index coefficients were highly significant ( p < 0.0001). All models had a similar fit with R 2 ranging from 0.9773 to 0.9827 and RMSE ranging from 6.33 to 7.75. The refractive indices at 1.25 THz produced the best fit. The refractive indices of these oil samples were promising for identification and distinction of oil grades.

  16. Time-domain terahertz spectroscopy and applications on drugs and explosives

    NASA Astrophysics Data System (ADS)

    Fan, W. H.; Zhao, W.; Cheng, G. H.; Burnett, A. D.; Upadhya, P. C.; Cunningham, J. E.; Linfield, E. H.; Davies, A. G.

    2008-03-01

    Many materials of interest to the forensic and security services, such as explosives, drugs and biological agents, exhibit characteristic spectral features in the terahertz (THz) frequency range. These spectral features originate from inter-molecular interactions, involving collective motions of molecules. Broadband THz time-domain spectroscopy (THz-TDS) system have been used to analyze a number of drugs-of-abuse and explosives that are of interest to the forensic and security services. These samples ranged from crystalline powders, pressed into pellets, to thin sheets of plastic explosives, and all being measured in transmission geometry in the frequency range 0.1 - 8 THz. To well understand the nature of the observed spectral features and the effects of thermal broadening on these far-infrared signatures, temperature-dependent THz-TDS measurements have also been performed at temperatures as low as 4 K, especially for two types of cocaine. Well-resolved low-frequency absorption peaks were observed in the frequency range 0.1 - 3 THz with high resolution. Some of absorption peaks were found clearly to become more intense and shift to higher frequencies as the temperature was reduced. The results confirm that the low-frequency collective modes are highly sensitive to the structural and spatial arrangement of molecules. Furthermore, a number of common postal packaging materials made from paper, cardboard, even several types of plastic, have been tested with drug sample to assess the ability of THz-TDS in a hostile detection environment.

  17. Reflectance spectroscopy for evaluating hair follicle cycle

    NASA Astrophysics Data System (ADS)

    Liu, Caihua; Guan, Yue; Wang, Jianru; Zhu, Dan

    2014-02-01

    Hair follicle, as a mini-organ with perpetually cycling of telogen, anagen and catagen, provides a valuable experimental model for studying hair and organ regeneration. The transition of hair follicle from telogen to anagen is a significant sign for successful regeneration. So far discrimination of the hair follicle stage is mostly based on canonical histological examination and empirical speculation based on skin color. Hardly a method has been proposed to quantitatively evaluate the hair follicle stage. In this work, a commercial optical fiber spectrometer was applied to monitor diffuse reflectance of mouse skin with hair follicle cycling, and then the change of reflectance was obtained. Histological examination was used to verify the hair follicle stage. In comparison with the histological examination, the skin diffuse reflectance was relatively high for mouse with telogen hair follicles; it decreased once hair follicles transited to anagen stage; then it increased reversely at catagen stage. This study provided a new method to quantitatively evaluate the hair follicle stage, and should be valuable for the basic and therapeutic investigations on hair regeneration.

  18. Reflectance spectroscopy of interplanetary dust particles

    NASA Astrophysics Data System (ADS)

    Bradley, J. P.; Keller, L. P.; Brownlee, D. E.; Thomas, K. L.

    1996-05-01

    Reflectance spectra were collected from chondritic interplanetary dust particles (IDPs), a polar micrometeorite, Allende (CV3) meteorite matrix, and mineral standards using a microscope spectrophotometer. Data were acquired over the 380-1100 nm wavelength range in darkfield mode using a halogen light source, particle aperturing diaphrams, and photomultiplier tube (PMT) detectors. Spectra collected from titanium oxide (Ti4O7), magnetite (Fe3O4), and Allende matrix establish that it is possible to measure indigenous reflectivities of micrometer-sized (>5 ?m in diameter) particles over the visible (VIS) wavelength range 450-800 nm. Below 450 nm, small particle effects cause a fall-off in signal into the ultraviolet (UV). Near-infrared (IR) spectra collected from olivine and pyroxene standards suggest that the ˜1 ?m absorption features of Fe-bearing silicates in IDPs can be detected using microscope spectrophotometry. Chondritic IDPs are dark objects (<15% reflectivity) over the VIS 450-800 nm range. Large (>1 ?m in diameter) embedded and adhering single mineral grains make IDPs significantly brighter, while surficial magnetite formed by frictional heating during atmospheric entry makes them darker. Most chondritic smooth (CS) IDPs, dominated by hydrated layer silicates, exhibit generally flat spectra with slight fall-off towards 800 nm, which is similar to type CI and CM meteorites and main-belt C-type asteroids. Most chondritic porous (CP) IDPs, dominated by anhydrous silicates (pyroxene and olivine), exhibit generally flat spectra with a slight rise towards 800 nm, which is similar to outer P and D asteroids. The most C-rich CP IDPs rise steeply towards 800 nm with a redness comparable to that of the outer asteroid object Pholus (Binzel, 1992). Chondritic porous IDPs are the first identified class of meteoritic materials exhibiting spectral reflectivities (between 450 and 800 nm) similar to those of P and D asteroids. Although large mineral grains, secondary magnetite, and small particle effects complicate interpretation of IDP reflectance spectra, microscope spectrophotometry appears to offer a rapid, nondestructive technique for probing the mineralogy of IDPs, comparing them with meteorites, investigating their parent body origins, and identifying IDPs that may have been strongly heated during atmospheric entry.

  19. Ultrafast insulator–metal phase transition in vanadium dioxide studied using optical pump–terahertz probe spectroscopy.

    PubMed

    Liu, H W; Wong, L M; Wang, S J; Tang, S H; Zhang, X H

    2012-10-17

    We studied the ultrafast dynamic behavior of the photoinduced insulator–metal phase transition in VO2 thin film using optical pump–terahertz probe spectroscopy with different excitation fluences and at different temperatures. We observed two processes in the insulator–metal phase transition in VO2: a fast process and a slow process. The fast process is a nonthermal process, which is ascribed to the nucleation of the metal phase, while the slow process is strongly affected by temperature and is ascribed to the thermally driven growth and coalescence of metal domains in VO2. The transient complex conductivity spectra at different delay times are also investigated. PMID:23014464

  20. Probing many-body quantum states in single InAs quantum dots: Terahertz and tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Shibata, K.; Nagai, N.; Ndebeka-Bandou, C.; Bastard, G.; Hirakawa, K.

    2015-06-01

    We have investigated the many-body quantum states in single InAs quantum dots (QDs) by simultaneously obtaining the terahertz (THz) intersublevel transition and single electron tunneling spectra. It is found that the intersublevel transition energies measured in the few-electron region are systematically larger than the excited state (ES) energies determined from the transport measurements. We show that tunneling and THz spectroscopy probe the same many-body excited states in the QDs, but their sensitivities depend on their selection rules. In the many-electron region, we observe THz peaks whose energies coincide with the tunneling ESs.

  1. Nonlinear terahertz spectroscopy of electronic and vibrational responses in condensed matter systems

    E-print Network

    Hwang, Harold Young

    2012-01-01

    In this work, I describe experiments utilizing high-field terahertz (THz) pulses to initiate nonlinear responses in several classes of materials. We have developed several methods for interrogating the nonlinear THz response ...

  2. Terahertz time domain spectroscopy for the analysis of cultural heritage related materials

    Microsoft Academic Search

    J.-M. Manceau; A. Nevin; C. Fotakis; S. Tzortzakis

    2008-01-01

    A powerful broadband femtosecond laser-driven terahertz source was built and used to analyze cultural heritage and art-related\\u000a materials in the terahertz region of the electromagnetic spectrum. The high signal-to-noise ratio available in our system\\u000a revealed details in the absorption spectra which are inaccessible with traditional FTIR spectrometers. Clear spectral signatures\\u000a were recorded from organic binding media thus demonstrating the potential

  3. Observation of water trees using terahertz spectroscopy and time-domain imaging

    Microsoft Academic Search

    Ryo Sato; Marina Komatsu; Yoshimichi Ohki; Norikazu Fuse; Yoshinobu Nakamichi; Maya Mizuno; Kaori Fukunaga

    2011-01-01

    Terahertz measurements were carried out to detect water trees grown in low-density polyethylene sheets. Water absorbs light at terahertz frequencies, fairly strongly at about 5.0 THz and rather weakly from 0.1 to 1.0 THz. Using the absorption at these frequencies, observation of water trees was tried according to the following procedures. First, we made a model sample, consisting of a

  4. Diffuse reflectance spectroscopy of fibrous proteins.

    PubMed

    Millington, Keith R

    2012-09-01

    UV-visible diffuse reflectance (DR) spectra of the fibrous proteins wool and feather keratin, silk fibroin and bovine skin collagen are presented. Natural wool contains much higher levels of visible chromophores across the whole visible range (700-400 nm) than the other proteins and only those above 450 nm are effectively removed by bleaching. Both oxidative and reductive bleaching are inefficient for removing yellow chromophores (450-400 nm absorbers) from wool. The DR spectra of the four UV-absorbing amino acids tryptophan, tyrosine, cystine and phenylalanine were recorded as finely ground powders. In contrast to their UV-visible spectra in aqueous solution where tryptophan and tyrosine are the major UV absorbing species, surprisingly the disulphide chromophore of solid cystine has the strongest UV absorbance measured using the DR remission function F(R)(?). The DR spectra of unpigmented feather and wool keratin appear to be dominated by cystine absorption near 290 nm, whereas silk fibroin appears similar to tyrosine. Because cystine has a flat reflectance spectrum in the visible region from 700 to 400 nm and the powder therefore appears white, cystine absorption does not contribute to the cream colour of wool despite the high concentration of cystine residues near the cuticle surface. The disulphide absorption of solid L: -cystine in the DR spectrum at 290 nm is significantly red shifted by ~40 nm relative to its wavelength in solution, whereas homocystine and lipoic acid showed smaller red shifts of 20 nm. The large red shift observed for cystine and the large difference in intensity of absorption in its UV-visible and DR spectra may be due to differences in the dihedral angle between the crystalline solid and the solvated molecules in solution. PMID:22218994

  5. Diffuse reflecting material for integrating cavity spectroscopy, including ring-down spectroscopy.

    PubMed

    Cone, Michael T; Musser, Joseph A; Figueroa, Eleonora; Mason, John D; Fry, Edward S

    2015-01-10

    We report the development of a diffuse reflecting material with measured reflectivity values as high as 0.99919 at 532 nm and 0.99686 at 266 nm. This material is a high-purity fumed silica, or quartz powder, with particle sizes on the order of 40 nm. We demonstrate that this material can be used to produce surfaces with nearly Lambertian behavior, which in turn can be used to form the inner walls of high-reflectivity integrating cavities. Light reflecting off such a surface penetrates into the material. This means there will be an effective "wall time" for each reflection off the walls in an integrating cavity. We measure this wall time and show that it can be on the order of several picoseconds. Finally, we introduce a technique for absorption spectroscopy in an integrating cavity based on cavity ring-down spectroscopy. We call this technique integrating cavity ring-down spectroscopy. PMID:25967634

  6. Ultrawideband MgB2 Mixer for High-Resolution Terahertz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Karasik, Boris

    Terahertz high-resolution spectroscopy of interstellar molecular clouds greatly relies on the hot-electron superconducting bolometric (HEB) mixers. A frequency independent mechanism of absorption of radiation inherent in such mixers makes them the detector of choice for heterodyne receivers from 1.5 THz to 4.7 THz. The current state-of-the-art receivers use mixer devices made from an ultrathin (~ 5 nm) film of NbN with a critical temperature ~ 9-11 K. Such mixers have been deployed on a number of ground based, suborbital, and orbital platform including the HIFI instrument on the Hershel Space Observatory. Despite its popularity, good sensitivity, and well established fabrication process, the NbN HEB mixer suffers from a relatively narrow intermediate frequency (IF) bandwidth ~ 2-4 GHz which is insufficient for the spectroscopy of the Galactic center and for extragalactic line observations. As the THz heterodyne receivers are now trending upwards the “high THz” frequencies, the need in a larger IF bandwidth becomes more pressing since the same velocity resolution for a Doppler shifted line at 5 THz requires a 5-tmes greater IF bandwidth than at 1 THz. We propose to develop an HEB mixer with the IF bandwidth ~ 20 GHz or even greater using an ultrathin superconducting film of MgB2. This high critical temperature (40 K) material was discovered 11 year ago and thin films suitable for HEB device fabrication are becoming available now. Compared to NbN, the intrinsic electron-phonon relaxation time in this material is much shorter (estimated to 2-3 ps). Also, MgB2 can be fabricated on MgO buffers, which provide a perfect acoustic match between the film and the substrate that is critical for realization of the fast thermal relaxation in a mixer device. The outcome of this works will be a state-of-the-art heterodyne sensor applicable throughout the 1.5-4.7 THz frequency range with the noise temperature < 1000 K and the IF bandwidth > 10 GHz and operating at ~ 20 K. Beside the bulk substrate (c-sapphire, MgO) we will build mixer devices on MgO buffered silicon-on-insulator (SOI) wafers which are instrumental for integration of HEB mixers into micromachined waveguide array receivers. The near term application of this mixer would be on SOFIA and suborbital balloons. The higher operating temperature will be a very important factor for the future space applications as the required cryocooling can be be provided at much lower cost.

  7. Research on heavy metal ions detection in soil with terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Bin; Wang, Mao-hua; Cao, Wei; Zhang, Zhen-wei

    2011-08-01

    Nowadays, heavy metals pollution is becoming a serious problem in agriculture. This paper reports a preliminary work on a feasibility study of applying terahertz (THz) technology for heavy metal ions detection in soil. This study was first conducted at Oklahoma State University, and then carried out at China Agricultural University and Capital Normal University. Pure soil was collected in an experimental field, which contains nearly no heavy metal ions from standard detection; in the experiment, heavy metal ions were mainly Pb2+, Cr3+, Zn2+ and Cu2+ from chemical compounds. Based on the National Standard for Heavy Metals Pollution, a set of soil samples with different polluted levels were prepared in the lab. The metal ions concentration levels were selected as 50ppm, 300ppm and 700ppm. Each soil sample was pre-processed by collecting, weighing, mixing, drying, grinding and labeling before measurements. The thickness of soil samples was selected as 1.5mm and 3mm. The absorption spectra for the soil samples with different heavy metal ions were collected using THz time-domain spectroscopy (THz-TDS) equipments separately at Oklahoma State University and Capital Normal University. The test results showed that soil samples with Pb2+, Cr3+, Zn2+ and Cu2+ had different absorption characteristics within the bandwidth of 0.1-1.1THz. A narrow bandwidth only up to 1.1THz was got because the soil particles showed much absorption and scattering properties to the THz spectroscopy. Different soil samples with different concentration of heavy metal ions also showed much difference and it could be used to predict the heavy metal concentration in the future. The results from the preliminary study show a potential of THz technology applied for heavy metal ions detection in agricultural fields environment. However, since the high scattering features of samples and high cost of equipments, the measurement methods and practical issues needs to be further investigated and improved to make the THz technology a feasible tool for soil heavy metal ions detection.

  8. Skin cancer detection by oblique-incidence diffuse reflectance spectroscopy 

    E-print Network

    Smith, Elizabeth Brooks

    2009-05-15

    Skin cancer is the most common form of cancer and it is on the rise. If skin cancer is diagnosed early enough, the survival rate is close to 90%. Oblique-incidence diffuse reflectance (OIR) spectroscopy offers a technology that may be used...

  9. Instrumentation for Reflectance Spectroscopy and Microspectroscopy with Application to Astrobiology

    NASA Technical Reports Server (NTRS)

    Mouroulis, Pantazis; Blaney, Diana L.; Green, Robert O.

    2008-01-01

    We present instrument concepts for in-situ reflectance spectroscopy over a spatial resolution range from several meters to tens of micrometers. These have been adapted to the low mass and power requirements of rover or similar platforms. Described are a miniaturized imaging spectrometer for rover mast, a combined mast and arm point spectrometer, and an imaging microspectrometer for the rover arm.

  10. Reflection Electron Microscopy and Spectroscopy for Surface Analysis

    E-print Network

    Wang, Zhong L.

    -losses. Accurate structure analysis is possible using the purely elastically scattered electrons, the scattering the surface structure. There are several techniques, such as weak-beam dark-field and surface profile imaging1 Reflection Electron Microscopy and Spectroscopy for Surface Analysis by Zhong Lin Wang

  11. Abstract--Terahertz (THz) time domain spectroscopy is used to investigate the gain and losses of a THz quantum cascade laser

    E-print Network

    Paris-Sud XI, Université de

    1 Abstract--Terahertz (THz) time domain spectroscopy is used to investigate the gain and losses of a THz quantum cascade laser (QCL) operating at 2.86THz. This measurement technique allows access, gain measurement. I. INTRODUCTION ERAHERTZ (THz) quantum cascade lasers (QCL) have shown considerable

  12. Using terahertz pulse spectroscopy to study the crystalline structure of a drug: A case study of the polymorphs of ranitidine hydrochloride

    Microsoft Academic Search

    P. F. Taday; I. V. Bradley; D. D. Arnone; M. Pepper

    2003-01-01

    We describe the application of Terahertz pulse spectroscopy to polymorph identification. The particular compounds investigated were the different crystalline Forms 1 and 2 of ranitidine hydrochloride, both in the pure form and also obtained as a marketed pharmaceutical product. Identification was clear. The technique has advant- ages that excitation is not via a powerful laser source, as used in Raman

  13. Pulsed Terahertz Signal Reconstruction

    NASA Astrophysics Data System (ADS)

    Fletcher, J. R.; Swift, G. P.; Dai, DeChang; Chamberlain, J. M.; Upadhya, P. C.

    2007-12-01

    A procedure is outlined which can be used to determine the response of an experimental sample to a single, simple broadband frequency pulse in terahertz frequency time domain spectroscopy (TDS). The advantage that accrues from this approach is that oscillations and spurious signals (arising from a variety of sources in the TDS system or from ambient water vapor) can be suppressed. In consequence, small signals (arising from the interaction of the radiation with the sample) can be more readily observed in the presence of noise. Procedures for choosing key parameters and methods for eliminating further artifacts are described. In particular, the use of input functions which are based on the binomial distribution is described. These binomial functions are used to unscramble the sample response to a simple pulse: they have sufficient flexibility to allow for variations in the spectra of different terahertz sources, some of which have low frequency as well as high frequency cutoffs. The signal processing procedure is validated by simple reflection and transmission experiments using a gap between polytetrafluoroethylene (PTFE) plates to mimic a void within a larger material. It is shown that a resolution of 100?m is easily achievable in reflection geometry after signal processing.

  14. Apollo 17 Soil Characterization for Reflectance Spectroscopy

    NASA Technical Reports Server (NTRS)

    Taylor, L. A.; Pieters, C.; Patchen, A.; Morris, R. V.; Keller, L. P.; Wentworth, S.; McKay, D. S.

    1999-01-01

    It is the fine fractions that dominate the observed spectral signatures of bulk lunar soil, and the next to the smallest size fractions are the most similar to the overall properties of the bulk soil. Thus, our Lunar Soil Characterization Consortium has concentrated on understanding the inter-relations of compositional, mineralogical, and optical properties of the <45-micron size fraction and its component sizes (20-44 micron, 10-20 micron, and <10 micron size fractions). To be able to generalize our results beyond the particular sample set studied, it is necessary to quantitatively identify the observed effects of space weathering and evaluate the processes involved. For this, it is necessary to know the chemistry of each size fraction, modal abundances of each phase, average compositions of the minerals and glasses, I(sub s)/FeO values, reflectance spectra, and the physical makeup of the individual particles and their patinas. This characterization includes the important dissection of the pyroxene minerals into four separate populations, with data on both modes and average chemical compositions. Armed with such data, it should be possible to effectively isolate spectral effects of space weathering from spectral properties related to mineral and glass chemistry. Four mare soils from the Apollo 17 site were selected for characterization based upon similarities in bulk composition and their contrasting maturities, ranging from immature to submature to mature. The methodology of our characterization has been discussed previously. Results of the Apollo 17 mare soils, outlined herein, are being prepared for publication in MAPS. As shown, with decreasing grain size, the agglutinitic (impact) glass content profoundly increases. This is the most impressive change for the mare soils. In several soils we have examined, there is an over two-fold increase in the agglutinitic glass contents between the 90-150- micron and the 10-20-micron size fractions. Accompanying this increase in agglutinitic glass is a definite decrease in pyroxenes and to lesser extents, the oxides (ilmenite), volcanic glass, and olivine. Unexpectedly, however, the absolute plagioclase abundances stay relatively constant throughout the different grain sizes, although the abundance of plagioclase relative to the mafic minerals increases with decreasing particle size. These soils were chosen for study based upon their similarities in FeO and Ti02 content, allowing for direct comparisons between evolutions of chemistry between size fractions and among different maturities of soils. The bulk chemistry of these fractions was determined by EMP analyses of fused glass beads. In contrast to the systematic variations in bulk chemistry discussed below, the relatively uniform composition of agglutinitic glass with grain size and soil maturity is illustrated. The composition of the bulk fraction of each size fraction becomes more feldspathic with increasing maturity, with the effect being most pronounced for the finest fractions. The composition of the agglutinitic glass, however, is relatively invariant and more feldspathic (i.e., rich in Al2O3) than even the <10-micron fraction. This relation not only strengthens the "fusion of the finest fraction" (F(sup 3)) hypothesis, but also highlights the important role of plagioclase in the formation of agglutinitic glass. With decreasing grain size, FeO, MgO, and TiO2 contents decrease, whereas CaO, Na2O, and Al2O3 (plag components) increase for all soils. These chemical variations would appear to be coupled with the significant increase in agglutinitic glass and decrease in oxide (ilmenite),pyroxene, and volcanic glass. These changes in chemistry do not appear to be due to distinct changes in the compositions of individual phases but to their abundances. Values of I(sub s)/FeO increase with decreasing grain size, even though the bulk FeO contents decrease. That is, the percentage of the total Fe that is present as nanophase Fe(sup O) has increased substantially in the smaller size fraction. Note that the incre

  15. Characteristics of chiral and racemic ketoprofen drugs using terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, Yong; Liu, Jianjun; Hong, Zhi

    2013-08-01

    Absorption spectra of chiral S-(+)- and racemic RS-ketoprofen pharmaceutical molecules in crystalline form were recorded in the terahertz region between 6 and 66 cm-1 (0.2 ~ 2.0 THz) by using time-domain terahertz spectroscopic (THz-TDS) measurement. Different distinctive absorption features were observed which are strikingly sensitive to the change of subtle conformational structures within such isostructural crystal molecules. The results suggest that the THz-TDS technique can be definitely used for distinguishing between chiral and racemic compounds in pharmaceutical and biological fields.

  16. Polarization orientation dependence of the far infrared spectra of oriented single crystals of 1,3,5,-trinitro-s-triazine (RDX) using terahertz-time-domain spectroscopy

    SciTech Connect

    Whitley, Von H [Los Alamos National Laboratory; Hooks, Dan E [Los Alamos National Laboratory; Ramos, Kyle J [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Azad, A K [Los Alamos National Laboratory; Taylor, A J [Los Alamos National Laboratory; Barber, J [NON LANL; Averitt, R D [BOSTON UNIV

    2008-01-01

    The far infrared spectra of (100), (010), and (001)-oriented RDX single crystals were measured as the crystal was rotated about the axis perpendicular to the polarization plane of the incident radiation. Absorption measurements were taken at temperatures of both 20 K and 295 K for all rotations using terahertz time-domain spectroscopy. A number of discrete absorptions were found ranging from 10-100 cm(-1) (0.3-3 THz). The absorptions are highly dependent on the orientation of the terahertz polarization with respect to crystallographic axes.

  17. Optical Fiber Sensing Based on Reflection Laser Spectroscopy

    PubMed Central

    Gagliardi, Gianluca; Salza, Mario; Ferraro, Pietro; Chehura, Edmond; Tatam, Ralph P.; Gangopadhyay, Tarun K.; Ballard, Nicholas; Paz-Soldan, Daniel; Barnes, Jack A.; Loock, Hans-Peter; Lam, Timothy T.-Y.; Chow, Jong H.; De Natale, Paolo

    2010-01-01

    An overview on high-resolution and fast interrogation of optical-fiber sensors relying on laser reflection spectroscopy is given. Fiber Bragg-gratings (FBGs) and FBG resonators built in fibers of different types are used for strain, temperature and acceleration measurements using heterodyne-detection and optical frequency-locking techniques. Silica fiber-ring cavities are used for chemical sensing based on evanescent-wave spectroscopy. Various arrangements for signal recovery and noise reduction, as an extension of most typical spectroscopic techniques, are illustrated and results on detection performances are presented. PMID:22294902

  18. Far-Infrared Characteristics of ZnS Nanoparticles Measured by Terahertz Time-Domain Spectroscopy

    E-print Network

    ARTICLES Far-Infrared Characteristics of ZnS Nanoparticles Measured by Terahertz Time Form: December 3, 2005 The optical and dielectric properties of ZnS nanoparticles are studied by use.6 ( 0.2 THz. Meanwhile, the low-frequency phonon resonance of ZnS nanoparticles is compared

  19. Investigation of spectral gain narrowing in quantum cascade lasers using terahertz time domain spectroscopy

    E-print Network

    Paris-Sud XI, Université de

    -infrared QCLs. For these measurements, electro-luminescence from a non-lasing cavity is coupled into an adjacent cavity that shows laser action.5 However, in the terahertz regime such electro-luminescence based studies are difficult, because of the reduced spontaneous emission at longer wavelengths. Electro-luminescence from

  20. Photoexcited GaAs surfaces studied by transient terahertz time-domain spectroscopy

    Microsoft Academic Search

    Michael Schall; Peter Uhd Jepsen

    2000-01-01

    The transmission characteristics of an air - GaAs interface and the transient absorption and index spectra of the thin, photoexcited surface layer are investigated subsequent to excitation by a femtosecond laser pulse. We find that the total phase change and transmission of a terahertz (THz) probe pulse are dominated by interface effects. This observation has important implications in the interpretation

  1. Terahertz spectroscopy with a holographic Fourier transform spectrometer plus array detector using coherent synchrotron radiation

    SciTech Connect

    Nikolay I. Agladz, John Klopf, Gwyn Williams, Albert J. Sievers

    2010-06-01

    By use of coherent terahertz synchrotron radiation, we experimentally tested a holographic Fourier transform spectrometer coupled to an array detector to determine its viability as a spectral device. Somewhat surprisingly, the overall performance strongly depends on the absorptivity of the birefringent lithium tantalate pixels in the array detector.

  2. Technical Report: Final project report for Terahertz Spectroscopy of Complex Matter

    Microsoft Academic Search

    R. A. Cheville; D. R. Grischkowsky

    2007-01-01

    This project designed characterization techniques for thin films of complex matter and other materials in the terahertz spectral region extending from approximately 100 GHz to 4000 GHz (4 THz) midway between radio waves and light. THz has traditionally been a difficult region of the spectrum in which to conduct spectroscopic measurements. The THz gap arises from the nature of the

  3. Optoelectronic characterization of transmission lines and waveguides by terahertz time-domain spectroscopy

    Microsoft Academic Search

    Daniel R. Grischkowsky

    2000-01-01

    An overview is presented of an experimental search for an ultrawide-band transmission channel with low dispersion and loss. Such a terahertz (THz) interconnect will soon be required by the insatiable demand for higher speed devices and wider bandwidth communication. Starting with the early optoelectronic generation and detection of single-mode, subpicosecond electrical pulses on coplanar transmission lines, their complete characterization by

  4. Probing the conformational changes of proteins in liquid water by dielectric terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Charkhesht, Ali; George, Deepu; Vinh, Nguyen

    2015-03-01

    Proteins solvated in their biological milieu are expected to exhibit strong absorption in the terahertz range that contain information on their global and sub-global collective vibrational modes (conformational dynamics) and global dynamical correlations among solvent water molecules and proteins. Measurements in this region, however, are challenging due to the strong absorption of water and often severe interference artifacts. In response, we have developed a highly sensitive dielectric terahertz frequency-domain system and a terahertz-time domain system for probing the collective dynamics in aqueous solution. Using these techniques we explore the complex dielectric response from 5 GHz up to 3 THz that directly probes such questions as the hydration level around proteins and the large scale vibrational modes of biological polymers. We make a direct comparison to the existing molecular dynamic simulations and normal mode calculations and investigate the dependence of the terahertz frequency dynamics on protein concentration. Our measurements shed light on the macromolecular motions in a biologically relevant water environment.

  5. Broadband microwave and time-domain terahertz spectroscopy of chemical vapor deposition grown graphene

    E-print Network

    graphene W. Liu, R. Valdés Aguilar, Yufeng Hao, R. S. Ruoff, and N. P. Armitage Citation: J. Appl. Phys. Related Articles Edge surface modes in magnetically biased chemically doped graphene strips Appl. Phys. Lett. 99, 231902 (2011) Terahertz coherent acoustic experiments with semiconductor superlattices Appl

  6. Attenuated total reflectance spectroscopy with chirped-pulse upconversion.

    PubMed

    Shirai, Hideto; Duchesne, Constance; Furutani, Yuji; Fuji, Takao

    2014-12-01

    Chirped-pulse upconversion technique has been applied to attenuated total reflectance (ATR) infrared spectroscopy. An extremely broadband infrared pulse was sent to an ATR diamond prism and the reflected pulse was converted to the visible by using four-wave mixing in krypton gas. Absorption spectra of liquids in the range from 200 to 5500 cm(-1) were measured with a visible spectrometer on a single-shot basis. The system was applied to observe the dynamics of exchanging process of two solvents, water and acetone, which give clear vibrational spectral contrast. We observed that the exchange was finished within ? 10 ms. PMID:25606893

  7. In situ characterization of soil properties using visible near-infrared diffuse reflectance spectroscopy 

    E-print Network

    Waiser, Travis Heath

    2007-09-17

    Diffuse reflectance spectroscopy (DRS) is a rapid proximal-sensing method that is being used more and more in laboratory settings to measure soil properties. Diffuse reflectance spectroscopy research that has been completed in laboratories shows...

  8. Point contact Andreev reflection spectroscopy for measuring spin polarization

    Microsoft Academic Search

    Muhammad Muzummal Faiz

    2009-01-01

    The Co-Pt systems have been extensively studied because of their potential applications in spintronic devices. We have experimentally measured transport spin polarization (PC) using Point Contact Andreev Reflection (PCAR) spectroscopy and magnetic properties of Co1-xPt x alloys. All films with x varying from 0 to 100% and a thickness of ˜1000 A were grown on Si substrates covered with ˜250

  9. Magnetic circular dichroism in reflection electron energy loss spectroscopy?

    SciTech Connect

    Harp, G.R. [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States)] [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States); Farrow, R.F.; Marks, R.F. [IBM Research Division, Almaden Research Center, San Jose, California 95120-6099 (United States)] [IBM Research Division, Almaden Research Center, San Jose, California 95120-6099 (United States)

    1996-07-01

    We evaluate the possibility of using dichroic electron energy loss spectroscopy (DEELS) as an alternative to x-ray magnetic circular dichroism (XMCD). It is well known that electron energy loss spectroscopy and x-ray absorption spectroscopy provide similar information. A simple semiclassical model suggests that reflection DEELS might have a magnetic sensitivity similar to that of XMCD. This sensitivity will be reduced, however, by multiple scattering of the probe electron before and after the energy loss event. Thus, it is difficult to predict the magnitude of the DEELS effect. Experiments were performed at the {ital L} edges of polycrystalline Fe, Co, and Ni thin-film samples prepared {ital in} {ital situ} with a uniaxial magnetic bias. Even in these most favorable cases, the DEELS effect is limited to less than one-tenth of related effects in XMCD. {copyright} {ital 1996 American Vacuum Society}

  10. Superconducting states study in electron-overdoped BaFe1.8Co0.2As2 using terahertz and far-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahmad, D.; Min, B. H.; Seo, Y. I.; Choi, W. J.; Kimura, Shin-Ichi; Seo, Jungpil; Kwon, Yong Seung

    2015-07-01

    Terahertz and far-infrared spectroscopy in the temperature range, 4–300 K were used to study the normal and superconducting states of superconductor BaFe1.8Co0.2As2 with Tc = 22.5 K. At T < Tc, the vanishing of optical conductivity caused by the unity approach and flat behavior in reflectivity were observed below 45 cm?1. This feature indicates the formation of a superconducting energy gap due to the formation of Cooper pairs. The introduction of the two Drudes model well reproduced the normal state optical conductivity, indicating the multiband nature of this superconductor. Two superconducting energy gaps were estimated as {{? }1} = 2.90 meV and {{? }2} = 6.75 meV by the BCS model. Using the sum rule and dielectric function, the superconducting plasma frequency ({{? }p,s}) can be estimated as 5170 ± 270 cm?1, yielding that the magnetic penetration depth (?) is 3090 ± 160 Å. This material was observed to fall on the universal scaling line, Nc ? 4.4 {{? }dc}{{T}c}.

  11. Screening mail for powders using terahertz technology

    NASA Astrophysics Data System (ADS)

    Kemp, Mike

    2011-11-01

    Following the 2001 Anthrax letter attacks in the USA, there has been a continuing interest in techniques that can detect or identify so-called 'white powder' concealed in envelopes. Electromagnetic waves (wavelengths 100-500 ?m) in the terahertz frequency range penetrate paper and have short enough wavelengths to provide good resolution images; some materials also have spectroscopic signatures in the terahertz region. We report on an experimental study into the use of terahertz imaging and spectroscopy for mail screening. Spectroscopic signatures of target powders were measured and, using a specially designed test rig, a number of imaging methods based on reflection, transmission and scattering were investigated. It was found that, contrary to some previous reports, bacterial spores do not appear to have any strong spectroscopic signatures which would enable them to be identified. Imaging techniques based on reflection imaging and scattering are ineffective in this application, due to the similarities in optical properties between powders of interest and paper. However, transmission imaging using time-of-flight of terahertz pulses was found to be a very simple and sensitive method of detecting small quantities (25 mg) of powder, even in quite thick envelopes. An initial feasibility study indicates that this method could be used as the basis of a practical mail screening system.

  12. Reflective mesoscopic spectroscopy for noninvasive detection of reflective index alternations at nano-scale

    NASA Astrophysics Data System (ADS)

    Tao, Yuanhao; Ding, Zhihua

    2011-01-01

    Cancer has been one of the most serious threats to human life. However, there is no substantial improvement in overall treatment of cancer patients. One of the key reasons is the unavailability of convenient method to detect cellular alterations in ultra-early stage of carcinogenesis processes, where genetic aberrations at nano-scale have not yet resulted in histological changes. In this paper, we described an optical method based on reflective mesoscopic spectroscopy for ultra-early cancer detection. According to mesoscopic light transport theory, photons propagating in one dimension (1D) within a weakly disordered medium have the non-self-averaging effect. Reflected signal after 1D propagating is sensitive to any length scale of refractive index fluctuations due to multiple interferences of light waves travelling along 1D trajectory. The principle of mesoscopic spectroscopy for perceiving reflective index fluctuations at length scale of nanometers is introduced. A system for the measurement of reflective mesoscopic spectroscopy based on spatial-incoherence broadband source and spectrometer is established. Simulations on light propagation in cell-emulating model with controlled refractive index distribution are done by finite-difference time-domain (FDTD) approach.

  13. Glass transition dynamics of anti-inflammatory ketoprofen studied by Raman scattering and terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Shibata, Tomohiko; Igawa, Hikaru; Kim, Tae Hyun; Mori, Tatsuya; Kojima, Seiji

    2014-03-01

    A liquid-glass transition and a crystalline state of pharmaceutical racemic ketoprofen were studied by Raman scattering and the broadband terahertz time-domain spectroscopy (THz-TDS) in the frequency range from 9 to 260 cm-1. The low-frequency Raman scattering spectra clearly shows the remarkable change related to a liquid-glass transition at about Tg = 267 K. After melt-quenching at liquid nitrogen temperature, a boson peak appears at about 16.5 cm-1 near and below Tg and the intensity of quasi-elastic scattering related to structural relaxation increases markedly on heating. The crystalline racemic ketoprofen of "conformer A" shows the noncoincidence effect of mode frequencies below 200 cm-1 between Raman scattering spectra and dielectric spectra observed by THz-TDS.

  14. Softening of infrared-active mode of perovskite BaZrO3 proved by terahertz time-domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Helal, M. A.; Mori, T.; Kojima, S.

    2015-05-01

    The low-frequency infrared-active optical modes were studied in a barium zirconate, BaZrO3, single crystal with the perovskite structure using terahertz (THz) time-domain spectroscopy (TDS). The real and imaginary parts of the dielectric constants were accurately determined in the frequency range between 0.2 and 2.7 THz. Upon cooling from room temperature to 8 K, the lowest-frequency TO1 mode at 2.32 THz showed a pronounced softening to 1.94 THz. The real part of the dielectric constant at 0.5 THz determined by THz-TDS obeys Barrett's relation, and the existence of a plateau confirms that the quantum effects lead to saturation of the soft mode frequencies of the TO1 and TO2 modes below ?20 K. This is reminiscent of incipient ferroelectrics with the perovskite structure such as CaTiO3.

  15. Investigation of coherent acoustic phonons in terahertz quantum cascade laser structures using femtosecond pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Bruchhausen, Axel; Lloyd-Hughes, James; Hettich, Mike; Gebs, Raphael; Grossmann, Martin; Ristow, Oliver; Bartels, Albrecht; Fischer, Milan; Beck, Mattias; Scalari, Giacomo; Faist, Jérôme; Rudra, Alok; Gallo, Pascal; Kapon, Eli; Dekorsy, Thomas

    2012-08-01

    The dynamics of acoustic vibrations in terahertz quantum cascade laser structures (THz-QCLs) is studied by means of femtosecond pump-probe spectroscopy. The phonon modes are characterized by the folding of the acoustic dispersion into an effective reduced Brillouin zone. An accurate identification of this dispersion allows the sample structure and periodicity to be determined with high precision on the order of 0.1%. By temperature tuning the energy of the electronic levels of the system and performing wavelength dependent measurements, we are able to study the impulsive resonant generation and detection of coherent acoustic phonon modes. These results are supported by simulations of the electronic system that well explain the experimental observations. The effects of interface (IF) roughness on coherent acoustic phonon spectra are clearly observed for equal nominal THz-QCL structures but with different interface qualities.

  16. Focus: Phase-resolved nonlinear terahertz spectroscopy-From charge dynamics in solids to molecular excitations in liquids.

    PubMed

    Elsaesser, Thomas; Reimann, Klaus; Woerner, Michael

    2015-06-01

    Intense terahertz (THz) electric field transients with amplitudes up to several megavolts/centimeter and novel multidimensional techniques are the key ingredients of nonlinear THz spectroscopy, a new area of basic research. Both nonlinear light-matter interactions including the non-perturbative regime and THz driven charge transport give new insight into the character and dynamics of low-energy excitations of condensed matter and into quantum kinetic phenomena. This article provides an overview of recent progress in this field, combining an account of technological developments with selected prototype results for liquids and solids. The potential of nonlinear THz methods for future studies of low-frequency excitations of condensed-phase molecular systems is discussed as well. PMID:26049419

  17. Focus: Phase-resolved nonlinear terahertz spectroscopy—From charge dynamics in solids to molecular excitations in liquids

    NASA Astrophysics Data System (ADS)

    Elsaesser, Thomas; Reimann, Klaus; Woerner, Michael

    2015-06-01

    Intense terahertz (THz) electric field transients with amplitudes up to several megavolts/centimeter and novel multidimensional techniques are the key ingredients of nonlinear THz spectroscopy, a new area of basic research. Both nonlinear light-matter interactions including the non-perturbative regime and THz driven charge transport give new insight into the character and dynamics of low-energy excitations of condensed matter and into quantum kinetic phenomena. This article provides an overview of recent progress in this field, combining an account of technological developments with selected prototype results for liquids and solids. The potential of nonlinear THz methods for future studies of low-frequency excitations of condensed-phase molecular systems is discussed as well.

  18. New insights into the diverse electronic phases of a novel vanadium dioxide polymorph: a terahertz spectroscopy study.

    PubMed

    Lourembam, James; Srivastava, Amar; La-o-vorakiat, Chan; Rotella, H; Venkatesan, T; Chia, Elbert E M

    2015-01-01

    A remarkable feature of vanadium dioxide is that it can be synthesized in a number of polymorphs. The conductivity mechanism in the metastable layered polymorph VO2(B) thin films has been investigated by terahertz time-domain spectroscopy (THz-TDS). In VO2(B), a critical temperature of 240 K marks the appearance of a non-zero Drude term in the observed complex conductivity, indicating the evolution from a pure insulating state towards a metallic state. In contrast, the THz conductivity of the well-known VO2(M1) is well fitted only by a modification of the Drude model to include backscattering. We also identified two different THz conductivity regimes separated by temperature in these two polymorphs. The electronic phase diagram is constructed, revealing that the width and onset of the metal-insulator transition in the B phase develop differently from the M1 phase. PMID:25777320

  19. Determination of the time origin by the maximum entropy method in time-domain terahertz emission spectroscopy.

    PubMed

    Unuma, Takeya; Ino, Yusuke; Kuwata-Gonokami, Makoto; Vartiainen, Erik M; Peiponen, Kai-Erik; Hirakawa, Kazuhiko

    2010-07-19

    We have developed a scheme for determining the time origin by the maximum entropy method (MEM) in time-domain terahertz (THz) emission spectroscopy. By applying the MEM to trial damped sinusoidal waveforms, we confirmed that the MEM gives true phase shifts across the resonance features and that its inherent uncertainty in determining the time origin is +/-15 fs for 100-fs-class excitation/sampling optical pulses. Furthermore, when the MEM was applied to a THz waveform recorded experimentally with a finite sampling interval for the Bloch oscillation in a semiconductor superlattice, a misplacement of the time origin was indeed detected with an accuracy limited by the worse of the MEM inherent uncertainty and the sampling interval. PMID:20720967

  20. Nonresonant ionization of oxygen molecules by femtosecond pulses: Plasma dynamics studied by time-resolved terahertz spectroscopy

    SciTech Connect

    Mics, Zoltan; Kadlec, Filip; Kuzel, Petr; Jungwirth, Pavel; Bradforth, Stephen E.; Apkarian, V. Ara [Institute of Physics, Academy of Sciences of the Czech Republic, and Center for Biomolecules and Complex Molecular Systems, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic (Czech Republic); Center for Biomolecules and Complex Molecular Systems, Flemingovo nam. 2, 166 10 Prague 6 (Czech Republic); Department of Chemistry, University of Southern California, Los Angeles, California 90089 (United States); Department of Chemistry, University of California, Irvine, California 92697 (United States)

    2005-09-08

    We show that optical pump-terahertz probe spectroscopy is a direct experimental tool for exploring laser-induced ionization and plasma formation in gases. Plasma was produced in gaseous oxygen by focused amplified femtosecond pulses. The ionization mechanisms at 400- and 800-nm excitation wavelengths differ significantly being primarily of a multiphoton character in the former case and a strong-field process in the latter case. The generation of the plasma in the focal volume of the laser and its expansion on subnanosecond time scale is directly monitored through its density-dependent susceptibility. A Drude model used to evaluate the plasma densities and electron-scattering rates successfully captures the observations for a wide range of pump intensities. In addition, rotational fingerprints of molecular and ionic species were also observed in the spectra.

  1. New Insights into the Diverse Electronic Phases of a Novel Vanadium Dioxide Polymorph: A Terahertz Spectroscopy Study

    PubMed Central

    Lourembam, James; Srivastava, Amar; La-o-vorakiat, Chan; Rotella, H.; Venkatesan, T.; Chia, Elbert E. M.

    2015-01-01

    A remarkable feature of vanadium dioxide is that it can be synthesized in a number of polymorphs. The conductivity mechanism in the metastable layered polymorph VO2(B) thin films has been investigated by terahertz time-domain spectroscopy (THz-TDS). In VO2(B), a critical temperature of 240?K marks the appearance of a non-zero Drude term in the observed complex conductivity, indicating the evolution from a pure insulating state towards a metallic state. In contrast, the THz conductivity of the well-known VO2(M1) is well fitted only by a modification of the Drude model to include backscattering. We also identified two different THz conductivity regimes separated by temperature in these two polymorphs. The electronic phase diagram is constructed, revealing that the width and onset of the metal-insulator transition in the B phase develop differently from the M1 phase. PMID:25777320

  2. EXPERIMENT #3 REFLECTANCE SPECTROSCOPY We will use the reflectance attachment and fiber optics OceanOptics spectrophotometer to

    E-print Network

    Nazarenko, Alexander

    EXPERIMENT #3 REFLECTANCE SPECTROSCOPY We will use the reflectance attachment and fiber optics OceanOptics spectrophotometer to measure the reflectance spectrum of several paint samples and a powdered solid. A. Calibration of Spectrophotometer in Reflectance mode. Turn on the computer and the power

  3. Propagation through terahertz waveguides with photonic crystal boundaries

    Microsoft Academic Search

    Adam L. Bingham

    2007-01-01

    Scope and method of study. The research presented in this dissertation investigates the integration of photonic crystal lattices into parallel plate waveguides at terahertz frequencies. The experimental data was obtained by measuring the terahertz pulses through the photonic crystal waveguides in a standard terahertz time-domain spectroscopy system. The terahertz pulses were generated and detected via optoelectronic means utilizing lithographically fabricated

  4. TOPICAL REVIEW: Pulsed terahertz tomography

    Microsoft Academic Search

    S. Wang; X.-C. Zhang

    2004-01-01

    Terahertz time-domain spectroscopy (THz-TDS) is a coherent measurement technology. Using THz-TDS, the phase and amplitude of the THz pulse at each frequency can be determined. Like radar, THz-TDS also provides time information that allows us to develop various three-dimensional THz tomographic imaging modalities. The three-dimensional THz tomographic imagings we investigated are: terahertz diffraction tomography (THz DT), terahertz computed tomography (THz

  5. Preliminary study on quality evaluation of pecans with terahertz time-domain spectroscopy

    Microsoft Academic Search

    Bin Li; Wei Cao; Sunil Mathanker; Weili Zhang; Ning Wang

    2010-01-01

    This paper reports a preliminary work on a feasibility study of applying terahertz (THz) technology for pecan quality evaluation. A set of native pecan nuts collected in 2009 were used during the experiment. Each pecan nutmeat was manually sliced at a thickness of about 1mm, 2mm, and 3mm and a size of about 2cm (length) ×1cm (width). Pecan shell and

  6. Time-Resolved Terahertz Spectroscopy of Free Carrier Nonlinear Dynamics in Semiconductors

    Microsoft Academic Search

    G. Sharma; L. Razzari; F. H. Su; F. Blanchard; A. Ayesheshim; T. L. Cocker; L. V. Titova; H. C. Bandulet; T. Ozaki; J.-C. Kieffer; R. Morandotti; M. Reid; F. A. Hegmann

    2010-01-01

    Nonlinear dynamics of free carriers in direct bandgap semiconductors at terahertz (THz) frequencies is studied using the intense few-cycle source available at the Advanced Laser Light Source (ALLS). Techniques such as Z-scan and optical-pump\\/THz-probe are employed to explore nonlinear interactions in an n-doped InGaAs thin film and a photoexcited GaAs sample, respectively. The physical mechanism that gives rise to such

  7. Conductivity of nanoporous InP membranes investigated using terahertz spectroscopy

    Microsoft Academic Search

    S. K. E. Merchant; J. Lloyd-Hughes; L. Sirbu; I. M. Tiginyanu; P. Parkinson; L. M. Herz; M. B. Johnston

    2008-01-01

    We have investigated the terahertz conductivity of extrinsic and photoexcited electrons in nanoporous indium phosphide (InP) at different pore densities and orientations. The form of electronic transport in the film was found to differ significantly from that for bulk InP. While photo-generated electrons showed Drude-like transport, the behaviour for extrinsic electrons deviated significantly from the Drude model. Time-resolved photoconductivity measurements

  8. Determination of carrier concentration dependent electron effective mass and scattering time of n-ZnO thin film by terahertz time domain spectroscopy

    SciTech Connect

    Tang, J.; Tay, C. B. [Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); NUSNNI-Nanocore, National University of Singapore, Singapore 117576 (Singapore); Deng, L. Y. [Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Zhang, X. H.; Chai, J. W. [Institute of Materials and Research Engineering, Agency for Science, Technology and Research, 3 Research Link, Singapore 117602 (Singapore); Qin, H. [Department of Chemical and Bioengineering, National University of Singapore, Singapore 117542 (Singapore); Liu, H. W. [Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Venkatesan, T. [NUSNNI-Nanocore, National University of Singapore, Singapore 117576 (Singapore); Chua, S. J., E-mail: elecsj@nus.edu.sg [Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); NUSNNI-Nanocore, National University of Singapore, Singapore 117576 (Singapore); Institute of Materials and Research Engineering, Agency for Science, Technology and Research, 3 Research Link, Singapore 117602 (Singapore)

    2014-01-21

    We demonstrated a novel and widely accessible method for determining the electron effective mass and scattering time of ZnO films with different carrier concentrations by combining terahertz time-domain spectroscopy with Hall measurement. The terahertz time domain spectroscopy (THz-TDS) transmission spectra (0.1–2THz) were well described by Drude model. It is found that electron effective mass varied from 0.23m{sub 0} to 0.26m{sub 0} as the electron concentration changes from 5.9?×?10{sup 17}?cm{sup ?3} to 4.0?×?10{sup 19}?cm{sup ?3}. The carrier concentration dependent characteristic is ascribed to the non-parabolicity of conduction band. Free carrier localization mechanism explained the discrepancy in mobilities obtained from THz-TDS and Hall measurements.

  9. Diffuse Reflectance Spectroscopy for High-Resolution Soil Sensing

    Microsoft Academic Search

    B. Stenberg; R. A. Viscarra Rossel

    \\u000a Diffuse reflectance spectroscopy in the visible–near-infrared (vis–NIR) and mid-infrared (mid-IR) is a practical analytical\\u000a technique that can be used for both laboratory and in situ soil analysis. The techniques are sensitive to both organic and\\u000a mineral soil composition. They are particularly well suited to situations where the primary (conventional) analytical method\\u000a is laborious and costly or where a large number

  10. Experimental characterization of hexaferrite ceramics from 100 GHz to 1 THz using vector network analysis and terahertz-time domain spectroscopy

    Microsoft Academic Search

    Bin Yang; Xinke Wang; Yan Zhang; Robert S. Donnan

    2011-01-01

    Gyrotropic, magnetically-hard hexaferrite ceramics, are a very promising material for deployment as quasioptical nonreciprocal devices at high frequencies (>>90 GHz). In this paper, a quasioptical measurement bench driven by a vector-network analyzer and a terahertz (THz) time domain spectroscopy measurement system are used in conjunction to characterize a thin (2.02 mm thickness) hexaferrite plate for two orthogonal states of beam

  11. Diffuse reflectance spectroscopy for in vivo pediatric brain tumor detection

    NASA Astrophysics Data System (ADS)

    Lin, Wei-Chiang; Sandberg, David I.; Bhatia, Sanjiv; Johnson, Mahlon; Oh, Sanghoon; Ragheb, John

    2010-11-01

    The concept of using diffuse reflectance spectroscopy to distinguish intraoperatively between pediatric brain tumors and normal brain parenchyma at the edge of resection cavities is evaluated using an in vivo human study. Diffuse reflectance spectra are acquired from normal and tumorous brain areas of 12 pediatric patients during their tumor resection procedures, using a spectroscopic system with a handheld optical probe. A total of 400 spectra are acquired at the rate of 33 Hz from a single investigated site, from which the mean spectrum and the standard deviation are calculated. The mean diffuse reflectance spectra collected are divided into the normal and the tumorous categories in accordance with their corresponding results of histological analysis. Statistical methods are used to identify those spectral features that effectively separated the two tissue categories, and to quantify the spectral variations induced by the motion of the handheld probe during a single spectral acquisition procedure. The results show that diffuse reflectance spectral intensities between 600 and 800 nm are effective in terms of differentiating normal cortex from brain tumors. Furthermore, probe movements induce large variations in spectral intensities (i.e., larger standard deviation) between 400 and 600 nm.

  12. Birefringence of wood at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Todoruk, Tara M.; Schneider, Jon; Hartley, Ian D.; Reid, Matthew

    2008-06-01

    Fibre content of solid wood plays an important role in the wood products industry in terms of value. Additionally, fibre structure in composite wood products such as Oriented Strand Board (OSB) and paper products plays an important role in terms of strength properties. The effect of moisture content on wood properties is important in the manufacturing process and final product performance, and therefore its effect on the birefringence is of considerable interest. Since solid wood exhibits strong birefringence at terahertz frequencies, there may be potential applications of terahertz spectroscopy to fibre content and structure sensing. There are two potential sources for this strong birefringence: (i) form birefringence resulting from the porous structure of solid wood and (ii) intrinsic birefringence resulting from the dielectric properties of the material itself. In this report, the variability of birefringence within and between species, the dependence of the birefringence on moisture content and the relative contributions from form and intrinsic birefringence are examined. In order to clarify the role of these contributions to the measured birefringence, polarized terahertz reflection spectroscopy is examined and compared to the results obtained in a transmission geometry. Comparison of the birefringence measured in transmission and reflection geometries suggests that form birefringence may dominate.

  13. Terahertz gas-phase spectroscopy: chemometrics for security and medical applications.

    PubMed

    Neumaier, P F-X; Schmalz, K; Borngräber, J; Wylde, R; Hübers, H-W

    2015-01-01

    We describe a spectrometer consisting of a vector network analyzer, a gas absorption cell, and a quasi-optical bench that acquires terahertz spectra of gaseous substances and mixtures. We tested volatile organic compounds that are medical biomarkers or chemicals which can be found on the US Environment Protection Agency list of harmful substances. Absorption spectra at gas pressures between 10 Pa and 5000 Pa were recorded. A subsequent multivariate data analysis demonstrated excellent qualitative and quantitative identification of pure substances and complex mixtures. The applied multivariate algorithms are principal components analysis, partial least square regression and soft independent modelling of class analogy. PMID:25406969

  14. High-speed terahertz reflection three-dimensional imaging for nondestructive

    E-print Network

    ) imaging based on electronically controlled optical sampling (ECOPS). ECOPS enables scanning of an axial is obtained, which is made of glass fiber reinforced polymer composite material and has defects such as delamination and inclusion, and is compared with an ultrasonic reflection 3D image of the sample. ©2012 Optical

  15. Assessing human skin with diffuse reflectance spectroscopy and colorimetry

    NASA Astrophysics Data System (ADS)

    Seo, InSeok; Liu, Yang; Bargo, Paulo R.; Kollias, Nikiforos

    2012-02-01

    Colorimetry has been used as an objective measure of perceived skin color by human eye to document and score physiological responses of the skin from external insults. CIE color space values (L*, a* and b*) are the most commonly used parameters to correlate visually perceived color attributes such as L* for pigment, a* for erythema, and b* for sallowness of the skin. In this study, we investigated the relation of Lab color scale to the amount of major skin chromophores (oxy-, deoxyhemoglobin and melanin) calculated from diffuse reflectance spectroscopy. Thirty two healthy human subjects with ages from 20 to 70 years old, skin types I-VI, were recruited for the study. DRS and colorimetry measurements were taken from the left and right cheeks, and on the right upper inner arm. The melanin content calculated from 630-700 nm range of DRS measurements was shown to correlate with the lightness of skin (L*) for most skin types. For subjects with medium-to-light complexion, melanin measured at the blue part spectrum and hemoglobin interfered on the relation of lightness of the skin color to the melanin content. The sallowness of the skin that is quantified by the melanin contribution at the blue part spectrum of DRS was found to be related to b* scale. This study demonstrates the importance of documenting skin color by assessing individual skin chromophores with diffuse reflectance spectroscopy, in comparison to colorimetry assessment.

  16. Near-infrared reflectance spectroscopy for noninvasive monitoring of metabolites.

    PubMed

    Heise, H M; Bittner, A; Marbach, R

    2000-02-01

    An important class of substances in clinical chemistry are metabolites in body fluids, which are accessible by near-infrared spectroscopy without sample treatment using reagentless, fast and readily automated in vitro assays. Furthermore, noninvasive sensing systems are under development for the determination of blood glucose, especially for diabetic patients or for monitoring in intensive care and surgery. Near-infrared diffuse reflectance spectrometry of skin was employed allowing a certain tissue volume to be integrally probed. For calibration, the partial least-squares (PLS) algorithm was used either based on wide spectral intervals or using special spectral variable selection. Capillary blood glucose reference concentrations were obtained by finger pricking and an automated laboratory method (hexokinase/G6P-DH). Clear evidence is provided for the physical effect, as manifested by the spectral glucose absorptivities, underlying the individual single-person calibration models, which still require improvements in the methodology in the normo- and hypoglycemic concentration range. In extending the potential of noninvasive blood assays by infrared spectroscopy, a novel technique is presented for probing the intravascular fluid space by using fast spectral near-infrared measurements of skin tissue. The pulsatile blood spectrum can be derived from reflectance spectra of oral mucosa by Fourier analysis (near-infrared plethysmography). Future applications and prospects for noninvasive blood assays are discussed. PMID:10834401

  17. Properties of planar electric metamaterials for novel terahertz applications John F. O'Hara,1,

    E-print Network

    . Furthermore, these resonant phenom- ena can be adjusted to occur at nearly any sub-optical (at present) region metamaterials are experimentally studied in transmission and reflection utilizing terahertz time-domain spectroscopy. Electrically resonant behavior is observed and provides an estimate of the frequency

  18. Double-modulation reflection-type terahertz ellipsometer for measuring the thickness of a thin paint coating.

    PubMed

    Iwata, Tetsuo; Uemura, Hiroaki; Mizutani, Yasuhiro; Yasui, Takeshi

    2014-08-25

    We constructed a double-modulation, reflection-type terahertz (THz) ellipsometer for precise measurement of the thickness of a paint film which is coated on a metal surface and which is not transparent to visible or mid-infrared light. The double-modulation technique enabled us to directly obtain two ellipsometric parameters, ?(?) and ?(?), as a function of angular frequency, ?, with a single measurement while reducing flicker noise due to a pump laser. The bias voltage of a photoconductive antenna (PCA) used as a THz pulse emitter was modulated at 100 kHz, and a first lock-in amplifier (LA1) was connected to the output of an electro-optic (EO) signal-sampling unit. In addition, a wire-grid polarizer (WGP) was rotated at 100 Hz to conduct polarization modulation with a frequency of 200 Hz. The output signal from LA1 was fed into a second lock-in amplifier (LA2) that worked in synchronization with the rotating WGP (RWGP). By operating LA2 in a quadrature phase-detection mode, we were able to obtain in-phase and out-of-phase signals simultaneously, from which the two ellipsometric parameters for an isotropic sample could be derived at the same time while cancelling common-mode noise. The lower detection limit of the thickness measurement and the relative standard deviation (RSD) of a black paint film coated on an aluminum substrate were 4.3 µm and 1.4%, respectively. The possibility of determining all elements of the Jones matrix for an anisotropic material is also discussed. PMID:25321264

  19. Terahertz wave spectrum analysis of microstrip structure

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2012-03-01

    Terahertz wave is a kind of electromagnetic wave ranging from 0.1~10THz, between microwave and infrared, which occupies a special place in the electromagnetic spectrum. Terahertz radiation has a strong penetration for many media materials and nonpolar substance, for example, dielectric material, plastic, paper carton and cloth. In recent years, researchers around the world have paid great attention on terahertz technology, such as safety inspection, chemical biology, medical diagnosis and terahertz wave imaging, etc. Transmission properties of two-dimensional metal microstrip structures in the terahertz regime are presented and tested. Resonant terahertz transmission was demonstrated in four different arrays of subwavelength microstrip structure patterned on semiconductor. The effects of microstrip microstrip structure shape were investigated by using terahertz time-domain spectroscopy system. The resonant terahertz transmission has center frequency of 2.05 THz, transmission of 70%.

  20. Terahertz wave spectrum analysis of microstrip structure

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2011-11-01

    Terahertz wave is a kind of electromagnetic wave ranging from 0.1~10THz, between microwave and infrared, which occupies a special place in the electromagnetic spectrum. Terahertz radiation has a strong penetration for many media materials and nonpolar substance, for example, dielectric material, plastic, paper carton and cloth. In recent years, researchers around the world have paid great attention on terahertz technology, such as safety inspection, chemical biology, medical diagnosis and terahertz wave imaging, etc. Transmission properties of two-dimensional metal microstrip structures in the terahertz regime are presented and tested. Resonant terahertz transmission was demonstrated in four different arrays of subwavelength microstrip structure patterned on semiconductor. The effects of microstrip microstrip structure shape were investigated by using terahertz time-domain spectroscopy system. The resonant terahertz transmission has center frequency of 2.05 THz, transmission of 70%.

  1. Terahertz time-domain spectroscopy combined with fuzzy rule-building expert system and fuzzy optimal associative memory applied to diagnosis of cervical carcinoma.

    PubMed

    Qi, Na; Zhang, Zhuoyong; Xiang, Yuhong; Yang, Yuping; Harrington, Peter de B

    2015-01-01

    Combined with terahertz time-domain spectroscopy, the feasibility of fast and reliable diagnosis of cervical carcinoma by a fuzzy rule-building expert system (FuRES) and a fuzzy optimal associative memory (FOAM) had been studied. The terahertz spectra of 52 specimens of cervix were collected in the work. The original data of samples were preprocessed by Savitzky-Golay first derivative (?derivative), principal component orthogonal signal correction (PC-OSC) and emphatic orthogonal signal correction to improve the performance of FuRES and FOAM models. The effect of the different pretreating methods to improve prediction accuracy was evaluated. The FuRES and FOAM models were validated using bootstrapped Latin-partition method. The obtained results showed that the FuRES and FOAM model optimized with the combination S-G first derivative and PC-OSC method had the better predictive ability with classification rates of 92.9 ± 0.4 and 92.5 ± 0.4 %, respectively. The proposed procedure proved that terahertz spectroscopy combined with fuzzy classifiers could supply a technology which has potential for diagnosis of cancerous tissue. PMID:25433946

  2. Terahertz Spectroscopy of Molecules, Radicals and Ions Using Evenson-Type Tunable FIR Spectrometer

    NASA Astrophysics Data System (ADS)

    Matsushima, Fusakazu

    2012-06-01

    Frequencies of pure rotational transitions of neutral molecules, free radicals, and ionic molecules in the terahertz region have been measured precisely by using a frequency tunable far-infrared spectrometer in Toyama for more than 2 decades. The spectrometer (sometimes called as TuFIR in short) was developed by K.M. Evenson about 30 years ago. The terahertz light source is generated by synthesizing difference frequency of two mid-infrared CO_2 laser lines using a MIM diode as a photo mixer. A microwave radiation is added so that the tunable sidebands are obtained. The molecules and ions investigated up to now in Toyama are; 1) neutral molecules or radicals ( LiH, KH, 18OH, NH, N18O, NH_3), 2) molecule with internal rotation (CH_3OH including transitions between different torsional states), 3) water molecules (H_2 16O including v_2=1 excited state, H_2 17O, H_2 18O, D_2O), 4) molecular cation ( protonated rare gas atoms such as HeH^+, NeH^+, ArH^+, KrH^+, XeH^+ including their isotopic species, H_2D^+, N_2H^+, H_2F^+), 5) molecular anion (OH^-, OD^-). The following topics are picked up in the talk. 1) principle and properties of TuFIR spectrometer with its history of developments, 2) some efforts to extend the properties of the spectrometer, 3) extended negative glow discharge cell: its property and recent application to investigate molecular ions. K.M. Evenson, D.A. Jennings, and F.R. Peterson, Appl. Phys. Lett. 44, 576 (1984) I.G. Nolt et al., J. Mol. Spectrosc., 125, 274 (1987)

  3. Near and Mid-Infrared Diffuse Reflectance Spectroscopy for Measuring Soil Metal Content

    Microsoft Academic Search

    Grzegorz Siebielec; Gregory W. McCarty; Tomasz I. Stuczynski; James B. Reeves

    2004-01-01

    purposes in diffuse reflectance applications: near-infra- red (NIR, 400-2500 nm) and mid-infrared (MIDIR, 2500- Rapidandnondestructivemethodssuchasdiffusereflectanceinfra- 25 000nm).BothNIRSandDRIFTSarenondestructive red spectroscopy provide potentially useful alternatives to time-con- suming chemical methods of soil metal analysis. To assess the utility rapid analyses that under common application require no of near-infrared reflectance spectroscopy (NIRS) and diffuse mid- sampletreatment exceptforgrindingand mixing.Applica- infrared reflectance spectroscopy (DRIFTS) for

  4. Quantification of tissue oxygenation levels using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    B. S., Suresh Anand; N., Sujatha

    2011-08-01

    Tumor growth is characterized by increased metabolic activity. The light absorption profile of hemoglobin in dysplastic tissue is different from a normal tissue. Neovascularization is a hallmark of many diseases and can serve as a predictive biomarker for the detection of cancers. Spectroscopic techniques can provide information about the metabolic and morphological changes related to the progression of neoplasia. Diffuse reflectance spectroscopy (DRS) measures the absorption and scattering properties of a biological tissue and this method can provide clinically useful information for the early diagnosis of epithelial precancers. We used tissue simulating phantoms with absorbing and scattering molecules for the determination of total hemoglobin concentration, hemoglobin oxygen saturation and intensity difference between the deoxy and oxy hemoglobin bands. The results show promising approach for the differentiating normal and malignant states of a tissue.

  5. Quantification of tissue oxygenation levels using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    B. S., Suresh Anand; N., Sujatha

    2010-12-01

    Tumor growth is characterized by increased metabolic activity. The light absorption profile of hemoglobin in dysplastic tissue is different from a normal tissue. Neovascularization is a hallmark of many diseases and can serve as a predictive biomarker for the detection of cancers. Spectroscopic techniques can provide information about the metabolic and morphological changes related to the progression of neoplasia. Diffuse reflectance spectroscopy (DRS) measures the absorption and scattering properties of a biological tissue and this method can provide clinically useful information for the early diagnosis of epithelial precancers. We used tissue simulating phantoms with absorbing and scattering molecules for the determination of total hemoglobin concentration, hemoglobin oxygen saturation and intensity difference between the deoxy and oxy hemoglobin bands. The results show promising approach for the differentiating normal and malignant states of a tissue.

  6. Dielectric characterization of [Fe(NH2-trz)3]Br2•H2O thermal spin crossover compound by terahertz time domain spectroscopy

    NASA Astrophysics Data System (ADS)

    Mounaix, P.; Lascoux, N.; Degert, J.; Freysz, E.; Kobayashi, A.; Daro, N.; Létard, J.-F.

    2005-12-01

    The complex optical index refraction of an iron (II) spin-crossover coordination polymer is measured in the Terahertz frequency range by Terahertz time-domain spectroscopy (THz-TDS). By scanning the temperature from 288 to 333 K, we have recorded the evolution of the THz spectrum within the low spin - high spin thermal hysteresis loop. We were able to simultaneously infer the refractive index and absorption variations. The low spin-high spin transition has a marked spectral signature in the millimeter wavelength. In the 0.1-0.6 THz frequency range, the variation of real and imaginary part of the index of refraction is 6% and 20%, respectively. A marked absorption is observed above 500 GHz. The THz-TDS provides a clear direct fingerprint of this class of materials, which are interestingly potential candidates for optical data storage and processing devices.

  7. Sensor applications of attenuated total reflection infrared spectroscopy.

    PubMed

    Vigano, C; Ruysschaert, Jean-Marie; Goormaghtigh, Erik

    2005-03-15

    Attenuated total reflection Fourier transform infrared spectroscopy is one of the most powerful methods for recording infrared spectra of biological materials in general, and of biological membranes in particular. It is fast, yields a strong signal with only a few micrograms of sample and recent ATR devices allow the recording of nanogram quantities. Importantly, it allows information about the orientation of various parts of the molecules under study to be evaluated in an oriented system. While mid-infrared radiation has been most used for fundamental research on molecular structure, it is becoming an interesting alternative for sensor research. In addition to the usual sensor response, one of its advantages is its sensitivity to molecular conformation. In turn, the binding of a drug onto a receptor may be monitored as for other detection methods but in addition the evaluation of the structural response of the receptor to this binding is likely to bring invaluable information on the mechanism of action of the drug. The present review focuses only on the ATR-mid IR spectroscopy with a special interest for proteins and biological membranes. PMID:18969923

  8. Andreev Reflection Spectroscopy on Bismuth- Chalcogenide Topological Insulators

    NASA Astrophysics Data System (ADS)

    Granstrom, C. R.; Fridman, I.; Wei, J. Y. T.; Lei, H.; Petrovic, C.; Liang, R. X.

    2015-03-01

    Andreev reflection (AR) is the basic mechanism underlying the superconducting proximity effect which, at the interface between a topological insulator (TI) and a spin-singlet superconductor, can give rise to Majorana-like states. Despite this basic importance, little is known about how AR is affected by the unique attributes of a three-dimensional TI, namely the linear dispersion and spin-momentum locking of its surface states. In this study, we use both s-wave and d-wave superconducting tips to perform AR spectroscopy on variously flux-grown Bi2Se3andBi2Te3 single crystals. The AR measurements are complemented by in-situ scanning tunneling spectroscopy, down to 300 mK and up to 9 T, in order to determine the doping level and characterize both the sample surface and tip condition. Our data are analyzed in terms of the characteristic band structure of Bi-chalcogenides, to elucidate how it affects the AR process. Work supported by NSERC, CFI-OIT, CIFAR, and the Center for Emergent Superconductivity, an Energy Frontier Research Center funded by the U.S. DOE, Office for Basic Energy Science.

  9. Andreev reflection spectroscopy of iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Chien, C. L.

    2009-03-01

    After a reign of over two decades by the cuprate superconductors, several new families of iron-based high-temperature superconductors have recently been discovered. Essential to a superconductor is the nature of the superconducting gap, its value, its structure, and its temperature dependence. Point contact Andreev reflection (PCAR) spectroscopy operating in the ballistic limit is one of few techniques that can quantitatively measure the gap of these new Fe-based superconductors and its temperature dependence. In SmFeAsO1-xFx (0.15 <= x <= 0.30), we have determined a single gap 2?/kBTC 3.5-3.6 close to the BCS s-wave prediction and with a BCS-like temperature dependence.ootnotetextT. Y. Chen, Z. Tesanovic, R. H. Liu, X. H. Chen, and C. L. Chien, Nature, 453, 1224 (2008) These results will be compared with various theoretical possibilities and those obtained by other measurements, such as ARPES and penetration depth. While the principles of the PCAR spectroscopy are well established, poor contact control and ballistic heating might lead to the appearance of spurious gaps and pseudogaps in PCAR measurements. In collaboration with T. Y. Chen, S. X. Huang and Z. Tesanovic at JHU and R. H. Liu and X. H. Chen at USTC.

  10. Quantification of residual crystallinity in ball milled commercially sourced lactose monohydrate by thermo-analytical techniques and terahertz spectroscopy.

    PubMed

    Smith, Geoff; Hussain, Amjad; Bukhari, Nadeem Irfan; Ermolina, Irina

    2015-05-01

    The quantification of crystallinity is necessary in order to be able to control the milling process. The use of thermal analysis for this assessment presents certain challenges, particularly in the case of crystal hydrates. In this study, the residual crystallinity on ball milling of lactose monohydrate (LMH), for periods up to 90min, was evaluated by thermo-analytical techniques (TGA, DSC) and terahertz spectroscopy (THz). In general, the results from one of the DSC analysis and the THz measurements agree showing a monotonous decrease in relative residual crystallinity with milling time (?80% reduction after 60min milling) and a slight increase at the 90min time point. However, the estimates from TGA and two other methods of analyzing DSC curve do not agree with the former techniques and show variability with significantly higher estimates for crystallinity. It was concluded that, the thermal techniques require more complex treatment of the data in the evaluation of changes in crystallinity of a milled material (in particular to account for the de-vitrification and mutarotation of the material that inevitably occurs during the measurement cycle) while the analysis of THz data is more straightforward, with the measurement having no impact on the native state of the material. PMID:25784570

  11. Transient terahertz spectroscopy of excitons and unbound carriers in quasi two-dimensional electron-hole gases

    SciTech Connect

    Kaindl, Robert A.; Hagele, D.; Carnahan, M.A.; Chemla, D.S.

    2008-09-11

    We report a comprehensive experimental study and detailed model analysis of the terahertz (THz) dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued THz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the THz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the THz response exhibits both intra-excitonic and Drude features. Utilizing a two-component dielectric function, we derive the underlying exciton and unbound pair densities. In the ionized state, excellent agreement is found with the Saha thermodynamic equilibrium, which provides experimental verification of the two-component analysis and density scaling. During exciton formation, in turn, the pair kinetics is quantitatively described by a Saha equilibrium that follows the carrier cooling dynamics. The THz-derived kinetics is, moreover, consistent with time-resolved luminescence measured for comparison. Our study establishes a basis for tracking pair densities via transient THz spectroscopy of photoexcited quasi-2D electron-hole gases.

  12. Terahertz spectroscopy of two-dimensional electron-hole pairs: probing Mott physics of magneto-excitons

    NASA Astrophysics Data System (ADS)

    Zhang, Qi; Gao, Weilu; Watson, John; Manfra, Michael; Kono, Junichiro

    2015-03-01

    Density-dependent Coulomb interactions can drive electron-hole (e - h) pairs in semiconductors through an excitonic Mott transition from an excitonic gas into an e - h plasma. Theoretical studies suggest that these interactions can be strongly modified by an external magnetic field, including the absence of inter-exciton interactions in the high magnetic field limit in two dimensions, due to an e - h charge symmetry, which results in ultrastable magneto-excitons. Here, we present a systematic experimental study of e - h pairs in photo-excited undoped GaAs quantum wells in magnetic fields with ultrafast terahertz spectroscopy. We simultaneously monitored the dynamics of the intraexcitonic 1 s-2 p transition (which splits into 1 s-2p+ and 1 s-2p- transitions in a magnetic field) and the cyclotron resonance of unbound electrons and holes up to 10 Tesla. We found that the 1 s-2p- absorption feature is robust at high magnetic fields even under high excitation fluences, indicating magnetically enhanced stability of excitons. We will discuss the Mott physics of magneto-excitons as a function of temperature, e - h pair density, optical pump delay time, as well as magnetic field, and also compare two-dimensional excitons in GaAs quantum wells with three-dimensional excitons in bulk GaAs.

  13. Polarization-dependent terahertz spectroscopy of macroscopic films of aligned single-wall and multiwall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    He, Xiaowei; Robinson, John; Gao, Weilu; Zurbair, Ahmed; Alvarez, Noe; Hauge, Robvert H.; Kono, Junichiro

    2015-03-01

    The light absorption properties of carbon nanotubes are strongly anisotropic, especially in the terahertz (THz) region of the electromagnetic spectrum due to their inherently one-dimensional intraband carrier dynamics. Macroscopic films of aligned carbon nanotubes are thus ideal for developing high-performance, low-cost THz polarizers. Here, we present results of polarization-dependent time-domain THz spectroscopy studies of large-area films of aligned single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs) in a frequency range of 0.15-1 THz by varying the polarization of the incident beam with respect to the carbon nanotube alignment direction. The nematic order parameter (S), the extinction ratio (ER), and the degree of polarization (DOP) were calculated to establish the performance of the films as polarizers. We found the S of the SWCNT film to be 0.96. The ER of the SWCNT was found to be -12 dB. The measured value of the S for the MWCNT was 0.77, with an ER of -11 dB.

  14. Prediction of iron oxide contents using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Marques, José, Jr.; Arantes Camargo, Livia

    2015-04-01

    Determining soil iron oxides using conventional analysis is relatively unfeasible when large areas are mapped, with the aim of characterizing spatial variability. Diffuse reflectance spectroscopy (DRS) is rapid, less expensive, non-destructive and sometimes more accurate than conventional analysis. Furthermore, this technique allows the simultaneous characterization of many soil attributes with agronomic and environmental relevance. This study aims to assess the DRS capability to predict iron oxides content -hematite and goethite - , characterizing their spatial variability in soils of Brazil. Soil samples collected from an 800-hectare area were scanned in the visible and near-infrared spectral range. Moreover, chemometric calibration was obtained through partial least-squares regression (PLSR). Then, spatial distribution maps of the attributes were constructed using predicted values from calibrated models through geostatistical methods. The studied area presented soils with varied contents of iron oxides as examples for the Oxisols and Entisols. In the spectra of each soil is observed that the reflectance decreases with the content of iron oxides present in the soil. In soils with a high content of iron oxides can be observed more pronounced concavities between 380 and 1100 nm which are characteristic of the presence of these oxides. In soils with higher reflectance it were observed concavity characteristics due to the presence of kaolinite, in agreement with the low iron contents of those soils. The best accuracy of prediction models [residual prediction deviation (RPD) = 1.7] was obtained for goethite within the visible region (380-800 nm), and for hematite (RPD = 2.0) within the visible near infrared (380-2300 nm). The maps of goethite and hematite predicted showed the spatial distribution pattern similar to the maps of clay and iron extracted by dithionite-citrate-bicarbonate, being consistent with the iron oxide contents of soils present in the study area. These results confirm the value of DRS in the mapping of iron oxides in large areas at detailed scale.

  15. Qualitative Analysis of Collective Mode Frequency Shifts in L-alanine using Terahertz Spectroscopy

    PubMed Central

    Taulbee, Anita R.; Heuser, Justin A.; Spendel, Wolfgang U.; Pacey, Gilbert E.

    2009-01-01

    We have observed collective mode frequency shifts in the phonon absorbance spectra of deuterium-substituted L-alanine isotopologues. Terahertz (THz) absorbance spectra were acquired at room temperature in the spectral range of 66–90 cm?1, or 2.0–2.7 THz, for L-alanine (L-Ala) and four L-Ala compounds in which hydrogen atoms (atomic mass = 1 amu) were substituted with deuterium atoms (atomic mass = 2 amu): L-Ala-2-d, L-Ala-3,3,3-d3, L-Ala-2,3,3,3-d4 and L-Ala-d7. The absorbance maxima of two L-Ala collective modes in this spectral range were recorded for multiple spectral measurements of each compound, and the magnitude of each collective mode frequency shift due to increased mass of these specific atoms was evaluated for statistical significance. Calculations were performed which predict the THz absorbance frequencies based on the estimated reduced mass of the modes. The shifts in absorbance maxima were correlated with the location(s) of the substituted deuterium atom(s) in the L-alanine molecule, and the atoms contributing to the absorbing delocalized mode in the crystal structure were deduced using statistics described herein. The statistical analyses presented also indicate that the precision of the method allows reproducible frequency shifts as small as 1 cm?1, or 0.03 THz to be observed, and that these shifts are not random error in the measurement. PMID:19331431

  16. Physics and capabilities of terahertz spectroscopy to study the water-biomolecule interaction

    NASA Astrophysics Data System (ADS)

    Vezzoli, G. C.

    2007-09-01

    We have conducted the first study of the use of terahertz radiation to precisely identify pre-melting, melting, polymerization, depolymerization and the influence of polar water in sulfur by scanning frequency as a parametric function of temperature, and including identifying precursor and intermediate states. This spectroscopic study has also identified the orthorhombic-monoclinic phase transformation, and the melting of the superheated orthorhombic phase. This work also reports detection of a water absorption indicating a perturbation of the water molecules, associated with solvation spheres of the inter-chain dynamics, as a precursor to a transition, and supporting our earlier results showing the transducing capabilities of conglomerates of water molecules. Through a study of the fine structure of the water absorption, we are able to determine information about local polarization effects which contribute to the transducing properties of water relative to a ligand. The above inorganic polymer study is applied to the understanding of the response of biomolecules to thermal and chemical influences, and data are included giving optical, electrical, and pH properties of the DNA-water system, showing a major conformational transition at ~43°C, and various forms of reconformation of DNA macromolecule due to chemical perturbation. Our results include findings aimed at complementing existing inhibitors that are intended to prevent retrovirus/phage invasion of the host cell DNA.

  17. Imaging of ex vivo nonmelanoma skin cancers in the optical and terahertz spectral regions optical and terahertz skin cancers imaging.

    PubMed

    Joseph, Cecil S; Patel, Rakesh; Neel, Victor A; Giles, Robert H; Yaroslavsky, Anna N

    2014-05-01

    We tested the hypothesis that polarization sensitive optical and terahertz imaging may be combined for accurate nonmelanoma skin cancer (NMSC) delineation. Nine NMSC specimens were imaged. 513 ?m and 440 nm wavelengths were used for terahertz and optical imaging, respectively. Histopathology was processed for evaluation. Terahertz reflectance of NMSC was quantified. Our results demonstrate that cross-polarized terahertz images correctly identified location of the tumours, whereas cross-polarized and polarization difference optical images accurately presented morphological features. Cross-polarized terahertz images exhibited lower reflectivity values in cancer as compared to normal tissue. Combination of optical and terahertz imaging shows promise for intraoperative delineation of NMSC. PMID:22987857

  18. Noninvasive express diagnostics of pulmonary diseases based on control of patient's gas emission using methods of IR and terahertz laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Starikova, M. K.; Bulanova, A. A.; Bukreeva, E. B.; Karapuzikov, A. A.; Karapuzikov, A. I.; Kistenev, Y. V.; Klementyev, V. M.; Kolker, D. B.; Kuzmin, D. A.; Nikiforova, O. Y.; Ponomarev, Yu. N.; Sherstov, I. V.; Boyko, A. A.

    2013-11-01

    Pulmonary diseases diagnostics always occupies one of the key positions in medicine practices. A large variety of high technology methods are used today, but none of them cannot be used for early screening of pulmonary diseases. We discuss abilities of methods of IR and terahertz laser spectroscopy for noninvasive express diagnostics of pulmonary diseases on a base of analysis of absorption spectra of patient's gas emission, in particular, exhaled air. Experience in the field of approaches to experimental data analysis and hard-ware realization of gas analyzers for medical applications is also discussed.

  19. Intramyocardial oxygen transport by quantitative diffuse reflectance spectroscopy in calves

    NASA Astrophysics Data System (ADS)

    Lindbergh, Tobias; Larsson, Marcus; Szabó, Zoltán; Casimir-Ahn, Henrik; Strömberg, Tomas

    2010-03-01

    Intramyocardial oxygen transport was assessed during open-chest surgery in calves by diffuse reflectance spectroscopy using a small intramuscular fiber-optic probe. The sum of hemo- and myoglobin tissue fraction and oxygen saturation, the tissue fraction and oxidation of cytochrome aa3, and the tissue fraction of methemoglobin were estimated using a calibrated empirical light transport model. Increasing the oxygen content in the inhaled gas, 21%-50%-100%, in five calves (group A) gave an increasing oxygen saturation of 19+/-4%, 24+/-5%, and 28+/-8% (p<0.001, ANOVA repeated measures design) and mean tissue fractions of 1.6% (cytochrome aa3) and 1.1% (hemo- and myoglobin). Cardiac arrest in two calves gave an oxygen saturation lower than 5%. In two calves (group B), a left ventricular assistive device (LVAD pump) was implanted. Oxygen saturation in group B animals increased with LVAD pump speed (p<0.001, ANOVA) and with oxygen content in inhaled gas (p<0.001, ANOVA). The cytochrome aa3 oxidation level was above 96% in both group A and group B calves, including the two cases involving cardiac arrest. In conclusion, the estimated tissue fractions and oxygenation/oxidation levels of the myocardial chromophores during respiratory and hemodynamic provocations were in agreement with previously presented results, demonstrating the potential of the method.

  20. Terahertz Spectroscopy and Solid-State Density Functional Theory Calculations of Cyanobenzaldehyde Isomers.

    PubMed

    Dash, Jyotirmayee; Ray, Shaumik; Nallappan, Kathirvel; Kaware, Vaibhav; Basutkar, Nitin; Gonnade, Rajesh G; Ambade, Ashootosh V; Joshi, Kavita; Pesala, Bala

    2015-07-23

    Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of the molecules. These resonances are highly sensitive to the relative position of atoms in a molecule as well as the crystal packing arrangement. To understand the variation of THz resonances, THz spectra (2-10 THz) of three structural isomers: 2-, 3-, and 4-cyanobenzaldehyde have been studied. THz spectra obtained from Fourier transform infrared (FTIR) spectrometry of these isomers show that the resonances are distinctly different especially below 5 THz. For understanding the intermolecular interactions due to hydrogen bonds, four molecule cluster simulations of each of the isomers have been carried out using the B3LYP density functional with the 6-31G(d,p) basis set in Gaussian09 software and the compliance constants are obtained. However, to understand the exact reason behind the observed resonances, simulation of each isomer considering the full crystal structure is essential. The crystal structure of each isomer has been determined using X-ray diffraction (XRD) analysis for carrying out crystal structure simulations. Density functional theory (DFT) simulations using CRYSTAL14 software, utilizing the hybrid density functional B3LYP, have been carried out to understand the vibrational modes. The bond lengths and bond angles from the optimized structures are compared with the XRD results in terms of root-mean-square-deviation (RMSD) values. Very low RMSD values confirm the overall accuracy of the results. The simulations are able to predict most of the spectral features exhibited by the isomers. The results show that low frequency modes (<3 THz) are mediated through hydrogen bonds and are dominated by intermolecular vibrations. PMID:26114877

  1. Sub-terahertz frequency-domain spectroscopy reveals single-grain mobility and scatter influence of large-area graphene.

    PubMed

    Cervetti, Christian; Heintze, Eric; Gorshunov, Boris; Zhukova, Elena; Lobanov, Svyatoslav; Hoyer, Alexander; Burghard, Marko; Kern, Klaus; Dressel, Martin; Bogani, Lapo

    2015-04-01

    The response of individual domains in wafer-sized chemical vapor deposition graphene is measured by contactless sub-terahertz interferometry, observing the intrinsic optical conductance and reaching very high mobility values. It is shown that charged scatterers limit the mobility, validating previous theoretical predictions, and sub-terahertz quality assessment is demonstrated, as necessary for large-scale applications in touchscreens, as well as wearable and optoelectronic devices. PMID:25787669

  2. Phase-sensitive time-domain terahertz reflection spectroscopy A. Pashkin,a)

    E-print Network

    Ku?el, Petr

    silicon and for ferroelectric SrBi2Ta2O9 bulk ceramics as well as thin film on sapphire substrates thus yielding the complex transmittance of the sample. Finally, the com- plex refractive index equations for the transmittance.2 Let us emphasize the importance of the reference measurement: it ensures

  3. The effect of anisotropic reflectance on imaging spectroscopy of snow properties

    E-print Network

    California at Santa Barbara, University of

    The effect of anisotropic reflectance on imaging spectroscopy of snow properties Thomas H. Paintera directional reflectance affect the mapping of snow properties from imaging spectrometer data? This sensitivity­directional reflectance factor (HDRF) with prescribed snow-covered area and snow grain size. The MEMSCAG model determines

  4. Diffuse Reflectance Spectroscopy for Total Carbon Analysis of Hawaiian Soils

    NASA Astrophysics Data System (ADS)

    McDowell, M. L.; Bruland, G. L.; Deenik, J. L.; Grunwald, S.; Uchida, R.

    2010-12-01

    Accurate assessment of total carbon (Ct) content is important for fertility and nutrient management of soils, as well as for carbon sequestration studies. The non-destructive analysis of soils by diffuse reflectance spectroscopy (DRS) is a potential supplement or alternative to the traditional time-consuming and costly combustion method of Ct analysis, especially in spatial or temporal studies where sample numbers are large. We investigate the use of the visible to near-infrared (VNIR) and mid-infrared (MIR) spectra of soils coupled with chemometric analysis to determine their Ct content. Our specific focus is on Hawaiian soils of agricultural importance. Though this technique has been introduced to the soil community, it has yet to be fully tested and used in practical applications for all soil types, and this is especially true for Hawaii. In short, DRS characterizes and differentiates materials based on the variation of the light reflected by a material at certain wavelengths. This spectrum is dependent on the material’s composition, structure, and physical state. Multivariate chemometric analysis unravels the information in a set of spectra that can help predict a property such as Ct. This study benefits from the remarkably diverse soils of Hawaii. Our sample set includes 216 soil samples from 145 pedons from the main Hawaiian Islands archived at the National Soil Survey Center in Lincoln, NE, along with more than 50 newly-collected samples from Kauai, Oahu, Molokai, and Maui. In total, over 90 series from 10 of the 12 soil orders are represented. The Ct values of these samples range from < 1% - 55%. We anticipate that the diverse nature of our sample set will ensure a model with applicability to a wide variety of soils, both in Hawaii and globally. We have measured the VNIR and MIR spectra of these samples and obtained their Ct values by dry combustion. Our initial analyses are conducted using only samples obtained from the Lincoln archive. In this preliminary case, we use Partial Least Squares (PLS) regression with cross validation to develop a prediction model for soils of unknown carbon content given only their spectral signature. We find R2 values of greater than 0.93 for the MIR spectra and 0.87 for the VNIR spectra, indicating a strong ability to correlate a soil’s spectrum with its Ct content. We build on these encouraging results by continuing chemometric analyses using the full data set, different data subsets, separate model calibration and validation groups, combined VNIR and MIR spectra, and exploring different data pretreatment options and variations to the PLS parameters.

  5. Point contact Andreev reflection spectroscopy for measuring spin polarization

    NASA Astrophysics Data System (ADS)

    Faiz, Muhammad Muzummal

    The Co-Pt systems have been extensively studied because of their potential applications in spintronic devices. We have experimentally measured transport spin polarization (PC) using Point Contact Andreev Reflection (PCAR) spectroscopy and magnetic properties of Co1-xPt x alloys. All films with x varying from 0 to 100% and a thickness of ˜1000 A were grown on Si substrates covered with ˜250 A of SiO 2 by magnetron sputtering (Ref. [1]). We have also performed band-structure calculations of the spin polarization in the same Co-Pt system. We have demonstrated that the experimental and theoretical results are in reasonably good agreement. We have compared the PCAR results with the tunneling spin polarization (TSP) values recently reported by Kaiser et al. (Ref. [1]) and showed that the overall trend of PCAR spin polarization is almost the same as for TSP with Al 2O3 barrier, but it is very different from the TSP with ALN barrier. We have performed X-ray Diffraction (XRD) experiments on these alloys and found that they, in general, exhibited face centered cubic crystallographic structure. Furthermore, our results renounce the idea of a direct relationship between the spin polarization and the magnetic moment for these alloys. We were surprised to find that pure Pt films showed obvious magnetic signatures both from PCAR spectroscopy and magnetization measurements, while TSP was found to be zero for pure Pt electrodes (Ref. [1]). The Co-based Heusler alloys are also of special interest for possible spintronic applications due to their high Curie temperatures and high magnetic moment per unit cell. Co2FeSi is especially promising as a candidate half-metal as it has a Curie temperature of approximately 1100 K and the integer magnetic moment of 6 muB per unit cell (Ref. [2]). The samples have been prepared by arc melting of stoichiometric quantities of pure metals in argon atmosphere followed by annealing in sealed quartz tubes at 1300 K. We have experimentally measured PC in Co2FeSi and Co2Mn0.5Fe0.5Si using PCAR spectroscopy. We found that spin polarization for these two alloys was significantly lower than that predicted by theoretical studies. We have attributed this reduction in spin polarization to the defects and disorder in the crystallographic structure within the Heusler alloys. Moreover, we have also experimentally demonstrated that doping with Mn in Co2FeSi did not improve spin polarization for this alloy. Spin diffusion length (Lsf) is of fundamental importance for spin dependent transport and spintronic devices. So far, most of the measurements of Lsf in nonmagnetic metals have been done in the lateral non-local geometry, with the chemical potential difference characterizing the spin imbalance. We have experimentally demonstrated spin transport studies in Heusler/Au bilayers using PCAR spectroscopy. Variable thickness Au films were deposited on top of the Heusler alloys and the PCAR spectroscopy was then used to probe PC on the Au side. In our approach Lsf was measured directly with PCAR spectroscopy. A spin polarized current was injected from a ferromagnetic electrode, Co2Mn0.5Fe0.5Si Heusler alloy, into Au films of variable thickness. The spin current, which gradually decays with the increased thickness of the film, was measured with a superconducting Nb tip. We developed a phenomenological theory which allowed us to determine Lsf in such a system. We found L sf in Au to be on the order of 312+/-36 nm at 4 K, comparable to the results obtained by other techniques using conventional ferromagnetic spin injectors. Similar results were obtained with a Gd single crystal. One of the potential advantages of this new technique, however, is the ability to do the point contact measurements on the side of the normal electrode, which should allow one to do the complete measurement of spin diffusion length by consequentially measuring the spin polarization in a normal metal as a function of thickness in a single sample. This experimental demonstration may be considered as the first step in this direction. (Abstract shortened b

  6. Highly tunable optical activity in planar achiral terahertz metamaterials.

    PubMed

    Singh, Ranjan; Plum, Eric; Zhang, Weili; Zheludev, Nikolay I

    2010-06-21

    Using terahertz time domain spectroscopy we demonstrate tunable polarization rotation and circular dichroism in intrinsically non-chiral planar terahertz metamaterials without twofold rotational symmetry. The observed effect is due to extrinsic chirality arising from the mutual orientation of the metamaterial plane and the propagation direction of the incident terahertz wave. PMID:20588473

  7. Portable terahertz scanner for imaging and spectroscopy using InP-related devices

    NASA Astrophysics Data System (ADS)

    Park, Kyung Hyun; Kim, Namje; Lee, Il-Min; Moon, Kiwon; Lee, Eui Su; Ko, Hyunsung; Lee, Won-Hui; Han, Sang-Pil

    2015-03-01

    Our recent studies in regards of developing portable THz scanner for imaging and spectroscopy systems are presented. In the course, high power tunable continuous wave (CW) THz emitter and high sensitivity THz receiver platforms are presented. Those platforms can be realized with tunable optical beating source, broadband photomixer, arrayed photomixer and Schottky barrier diode, evanescently-coupled photodiodes with high saturation current, and semiconductor optical amplifier (SOA) integrated optical beating source. On the system level, our recent THz thickness measurement systems and the THz line scanner imaging system are presented.

  8. Infrared/Terahertz double resonance spectroscopy of CH3F and CH3Cl at atmospheric pressure

    E-print Network

    Dane J. Phillips; Elizabeth A. Tanner; Frank C. De Lucia; Henry O. Everitt

    2012-05-12

    A new method for highly selective remote sensing of atmospheric trace polar molecular gases is described. Based on infrared/terahertz double resonance spectroscopic techniques, the molecule- specific coincidence between the lines of a CO2 laser and rotational-vibrational molecular absorption transitions provide two dimensions of recognition specificity: infrared coincidence frequency and the corresponding terahertz frequency whose absorption strength is modulated by the laser. Atmospheric pressure broadening expands the molecular recognition "specificity matrix" by simultaneously relaxing the infrared coincidence requirement and strengthening the corresponding terahertz signature. Representative double resonance spectra are calculated for prototypical molecules CH3F and CH3Cl and their principal isotopomers, from which a heuristic model is developed to estimate the specificity matrix and double resonance signature strength for any polar molecule.

  9. Determination of plant silicon content with near infrared reflectance spectroscopy

    PubMed Central

    Smis, Adriaan; Ancin Murguzur, Francisco Javier; Struyf, Eric; Soininen, Eeva M.; Herranz Jusdado, Juan G.; Meire, Patrick; Bråthen, Kari Anne

    2014-01-01

    Silicon (Si) is one of the most common elements in the earth bedrock, and its continental cycle is strongly biologically controlled. Yet, research on the biogeochemical cycle of Si in ecosystems is hampered by the time and cost associated with the currently used chemical analysis methods. Here, we assessed the suitability of Near Infrared Reflectance Spectroscopy (NIRS) for measuring Si content in plant tissues. NIR spectra depend on the characteristics of the present bonds between H and N, C and O, which can be calibrated against concentrations of various compounds. Because Si in plants always occurs as hydrated condensates of orthosilicic acid (Si(OH)4), linked to organic biomolecules, we hypothesized that NIRS is suitable for measuring Si content in plants across a range of plant species. We based our testing on 442 samples of 29 plant species belonging to a range of growth forms. We calibrated the NIRS method against a well-established plant Si analysis method by using partial least-squares regression. Si concentrations ranged from detection limit (0.24 ppmSi) to 7.8% Si on dry weight and were well predicted by NIRS. The model fit with validation data was good across all plant species (n = 141, R2 = 0.90, RMSEP = 0.24), but improved when only graminoids were modeled (n = 66, R2 = 0.95, RMSEP = 0.10). A species specific model for the grass Deschampsia cespitosa showed even slightly better results than the model for all graminoids (n = 16, R2 = 0.93, RMSEP = 0.015). We show for the first time that NIRS is applicable for determining plant Si concentration across a range of plant species and growth forms, and represents a time- and cost-effective alternative to the chemical Si analysis methods. As NIRS can be applied concurrently to a range of plant organic constituents, it opens up unprecedented research possibilities for studying interrelations between Si and other plant compounds in vegetation, and for addressing the role of Si in ecosystems across a range of Si research domains. PMID:25309567

  10. Determination of plant silicon content with near infrared reflectance spectroscopy.

    PubMed

    Smis, Adriaan; Ancin Murguzur, Francisco Javier; Struyf, Eric; Soininen, Eeva M; Herranz Jusdado, Juan G; Meire, Patrick; Bråthen, Kari Anne

    2014-01-01

    Silicon (Si) is one of the most common elements in the earth bedrock, and its continental cycle is strongly biologically controlled. Yet, research on the biogeochemical cycle of Si in ecosystems is hampered by the time and cost associated with the currently used chemical analysis methods. Here, we assessed the suitability of Near Infrared Reflectance Spectroscopy (NIRS) for measuring Si content in plant tissues. NIR spectra depend on the characteristics of the present bonds between H and N, C and O, which can be calibrated against concentrations of various compounds. Because Si in plants always occurs as hydrated condensates of orthosilicic acid (Si(OH)4), linked to organic biomolecules, we hypothesized that NIRS is suitable for measuring Si content in plants across a range of plant species. We based our testing on 442 samples of 29 plant species belonging to a range of growth forms. We calibrated the NIRS method against a well-established plant Si analysis method by using partial least-squares regression. Si concentrations ranged from detection limit (0.24 ppmSi) to 7.8% Si on dry weight and were well predicted by NIRS. The model fit with validation data was good across all plant species (n = 141, R (2) = 0.90, RMSEP = 0.24), but improved when only graminoids were modeled (n = 66, R (2) = 0.95, RMSEP = 0.10). A species specific model for the grass Deschampsia cespitosa showed even slightly better results than the model for all graminoids (n = 16, R (2) = 0.93, RMSEP = 0.015). We show for the first time that NIRS is applicable for determining plant Si concentration across a range of plant species and growth forms, and represents a time- and cost-effective alternative to the chemical Si analysis methods. As NIRS can be applied concurrently to a range of plant organic constituents, it opens up unprecedented research possibilities for studying interrelations between Si and other plant compounds in vegetation, and for addressing the role of Si in ecosystems across a range of Si research domains. PMID:25309567

  11. Characterization of Soil Shrink-Swell Potential Using the Texas VNIR Diffuse Reflectance Spectroscopy Library 

    E-print Network

    Hallmark, C.T.; Morgan, C.L.; Hutchison, K.M.

    2011-08-04

    evapotranspiration rates exceed those of precipitation creating optimal conditions for soil wetting and drying cycles. This study was conducted to determine if visible near infrared diffuse reflectance spectroscopy (VNIR-DRS) can be used to predict the coefficient...

  12. The use of near infrared reflectance spectroscopy to predict protein fractions in free-ranging cattle 

    E-print Network

    Whitley, Evan Micah

    1996-01-01

    Research was conducted to assess the feasibility of using near infrared reflectance spectroscopy (NIRS) technology to predict fractional protein utilization in cattle on forage based diets. Forage samples were obtained from esophageal and ruminal...

  13. Terahertz technology in biology and medicine

    Microsoft Academic Search

    Peter H. Siegel

    2004-01-01

    Terahertz irradiation and sensing is being applied for the first time to a wide range of fields outside the traditional niches of space science, molecular line spectroscopy, and plasma diagnostics. This paper surveys some of the terahertz measurements and applications of interest in the biological and medical sciences.

  14. Study of paraffin-embedded colon cancer tissue using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Wahaia, Faustino; Kasalynas, Irmantas; Seliuta, Dalius; Molis, Gediminas; Urbanowicz, Andrzej; Carvalho Silva, Catia D.; Carneiro, Fatima; Valusis, Gintaras; Granja, Pedro L.

    2015-01-01

    In this work, samples of non-neoplastic and adenocarcinoma-affected human colon tissue samples were analyzed using multipoint transmission time-domain THz spectroscopy (THz-TDS) to sort out the contrast-contributing factors other than water, the main contrast mechanism factor in in-vivo or in freshly excised bio-tissue. Solving the electromagnetic inverse problem through THz-TDS and, analyzing the transmittance spectra that yielded the frequency-dependent absorption coefficient ? and refractive index n of non-neoplastic and neoplastic tissues, we show that it is possible to distinguish between non-neoplastic and neoplastic regions in paraffin-embedded dehydrated. Results and discussion are presented.

  15. RAPID PREDICTION OF ENERGY, DERIVED FROM FAT, IN CEREAL FOODS BY NEAR-INFRARED REFLECTANCE SPECTROSCOPY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Previous work established NIR reflectance spectroscopy as an accurate method for the determination of gross energy and available energy in diverse cereal food products.* The current study investigates the potential of NIR spectroscopy for the evaluation of energy derived from fat*. Using NIR refle...

  16. Reflectance spectroscopy: quantitative analysis techniques for remote sensing applications.

    USGS Publications Warehouse

    Clark, R.N.; Roush, T.L.

    1984-01-01

    Several methods for the analysis of remotely sensed reflectance data are compared, including empirical methods and scattering theories, both of which are important for solving remote sensing problems. The concept of the photon mean path length and the implications for use in modeling reflectance spectra are presented.-from Authors

  17. Reflectance Spectroscopy: Quantitative Analysis Techniques for Remote Sensing Applications

    Microsoft Academic Search

    Roger N. Clark; Ted L. Roush

    1984-01-01

    Several methods for the analysis of remotely sensed reflectance data are compared, including empirical methods and scattering theories, both of which are important for solving remote sensing problems. The concept of the photon mean optical path length and the implications for use in modeling reflectance spectra are presented. It is shown that the mean optical path length in a particulate

  18. Detection of Soil Surface Contaminants by Infrared Reflection Spectroscopy

    SciTech Connect

    Blake, Thomas A. (BATTELLE (PACIFIC NW LAB)); Gassman, Paul L. (BATTELLE (PACIFIC NW LAB)); S.D. Christensen, A.J. Sedlacek

    2002-01-01

    A benchtop Fourier transform infrared spectrometer and specular reflection accessory has been used to record reflection spectra of several chemical compounds coating a loamy, psamment soil. Unpolarized reflection spectra were recorded between 4600 and 500 cm-1 with a resolution of 4 cm-1 for the compounds dimethyl methylphosphonate, trimethyl phosphate, methylphosphonic acid, 2,2'-thiodiethanol, diazinon, diesel fuel, and ammonium nitrate mixed separately into soil samples with concentrations of 10, 5, and 1 mg of analyte per gram of soil. The soil reflection spectra are compared to liquid or solid transmission spectra of the pure compound and frequency shifts and relative intensity changes for the absorption features are noted. As an example of detection sensitivity, we have estimated that we can detect one of the C - H stretch modes of dimethyl methylphosphonate with a signal-to-noise (peak-to-peak) of 3 for 300 nanograms of analyte on the surface layer of soil in the focal spot of the reflectance accessory. We also estimate that the flux of infrared photons reaching the soil is 1018/sec. We have recorded polarization resolved reflection spectra of the uncoated soil and coarse and fine grained sands as a function of angle of incidence and reflection and have determined the degree of polarization for light reflected off of these materials at frequencies associated with volume scattering and surface scattering features. As might be expected, the volume scattering features show a significant depolarization of the light--degree of polarization after reflection is < 20%--and the surface scattering features retain a much higher degree of polarization upon reflection, > 75%. We have also recorded polarization resolved spectra of tributyl phosphate on the soil and found significant differences between the s- and p-polarized spectra. This fact could be used to employ polarization modulation detection to improve detection sensitivity.

  19. Carrier dynamics in bulk ZnO. II. Transient photoconductivity measured by time-resolved terahertz spectroscopy

    E-print Network

    Carrier dynamics in bulk ZnO. II. Transient photoconductivity measured by time-resolved terahertz in bulk ZnO at temperatures below 100 K. Carrier density and mobility are extracted by fitting the Drude. INTRODUCTION ZnO is a wide band-gap semiconductor Eg=3.37 eV with large exciton binding energy 60 me

  20. Terahertz spectroscopy of N18O and isotopic invariant fit of several nitric oxide isotopologs

    NASA Astrophysics Data System (ADS)

    Müller, Holger S. P.; Kobayashi, Kaori; Takahashi, Kazumasa; Tomaru, Kazuko; Matsushima, Fusakazu

    2015-04-01

    A tunable far-infrared laser sideband spectrometer was used to investigate a nitric oxide sample enriched in 18O between 0.99 and 4.75 THz. Regular, electric dipole transitions were recorded between 0.99 and 2.52 THz, while magnetic dipole transitions between the 2?1/2 and 2?3/2 spin-ladders were recorded between 3.71 and 4.75 THz. These data were combined with lower frequency data of N18 O (unlabeled atoms refer to 14 N and 16 O, respectively), with rotational data of NO, 15 NO, N17 O, and 15 N18 O, and with heterodyne infrared data of NO to be subjected to one isotopic invariant fit. Rotational, fine and hyperfine structure parameters were determined along with vibrational, rotational, and Born-Oppenheimer breakdown corrections. The resulting spectroscopic parameters permit prediction of rotational spectra suitable for the identification of various nitric oxide isotopologs especially in the interstellar medium by means of rotational spectroscopy.

  1. Terahertz time-domain reflectometry of multilayered systems

    NASA Astrophysics Data System (ADS)

    Jackson, J. Bianca

    Presented in this work are applications of terahertz pulse ranging, spectroscopy and imaging to the nondestructive evaluation of three disparate multilayer systems for the detection and measurement of hidden layers, as well as the extraction of system information that will aid in its maintenance, repair or replacement. Thermal protection systems for turbine engine components were investigated. Thermal barrier coatings (TBC) and thermally-grown oxide (TGO) thicknesses were determined with 10 micron resolution using time-of-flight and refractive index calculations. Two alternative methods of monitoring TGO growth using reflection amplitudes and spectral shifts were proposed for the prediction of TBC failure. Laser-machined defects as narrow as 50 microns were resolved in one- and two-dimensional images. The light and dark rings of trees, which reflect the changes in tree growth density over the course of a year, are measurable using pulsed terahertz beams. Tree-rings of bare and painted wood specimen were laterally and axially tomographically imaged in order to facilitate the dendrochronological cross-dating of artifacts. Comparisons were made between photographs and terahertz images to demonstrate the reliability of the technique. Historically, numerous unique artworks have been lost through the act of being covered over time. Samples of paintings, drawings and mosaics were imaged beneath layers of paint and plaster using pulsed-terahertz techniques to demonstrate the efficacy of the technique for art history and restoration. Sketch materials and pigments were measured, between 0.05 and 1.0 THz, to help identify colors in spectroscopic images. Other computational and processing methods were used to optimize the distinction between color domains. Additional time-domain terahertz applications for the examination of artwork and other artifacts were proposed.

  2. Reversible Immobilization of Peptides: Surface Modification and In Situ Detection by Attenuated Total Reflection FTIR Spectroscopy

    Microsoft Academic Search

    Per Rigler; Wolf-Peter Ulrich; Patrik Hoffmann; Michael Mayer; Horst Vogel

    2003-01-01

    A generic method is described for the reversible immobilization of polyhistidine-bearing polypeptides and proteins on attenuated total reflecting (ATR) sensor surfaces for the detection of biomo- lecular interactions by FTIR spectroscopy. Nitrilotriacetic acid (NTA) groups are covalently attached to self-assembled monolayers of either thioalkanes on gold films or mercaptosilanes on silicon dioxide films deposited on germanium internal reflection elements. Complex

  3. NEAR-INFRARED TRANSMISSION AND REFLECTANCE SPECTROSCOPY FOR DETERMINATION OF DIETARY FIBER IN BARLEY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near-infrared (NIR) transmission and reflectance spectroscopy were investigated as rapid screening tools to evaluate the total dietary fiber content of barley. The Foss Grainspec Rice Analyzer and the NIR Systems 6500 monochromator were used to obtain transmission and reflectance spectra, respectiv...

  4. Hydration kinetics of cement composites with varying water-cement ratio using terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Ray, Shaumik; Dash, Jyotirmayee; Devi, Nirmala; Sasmal, Saptarshi; Pesala, Bala

    2015-03-01

    Cement is mixed with water in an optimum ratio to form concrete with desirable mechanical strength and durability. The ability to track the consumption of major cement constituents, viz., Tri- and Dicalcium Silicates (C3S, C2S) reacting with water along with the formation of key hydration products, viz., Calcium-Silicate-Hydrate (C-S-H) which gives the overall strength to the concrete and Calcium Hydroxide (Ca(OH)2), a hydration product which reduces the strength and durability, using an efficient technique is highly desirable. Optimizing the amount of water to be mixed with cement is one of the main parameters which determine the strength of concrete. In this work, THz spectroscopy has been employed to track the variation in hydration kinetics for concrete samples with different water-cement ratios, viz., 0.3, 0.4, 0.5 and 0.6. Results show that for the sample with water-cement ratio of 0.3, significant amount of the C3S and C2S remain unreacted even after the initial hydration period of 28 days while for the cement with water-cement ratio of 0.6, most of the constituents get consumed during this stage. Analysis of the formation of Ca(OH)2 has been done which shows that the concrete sample with water-cement ratio of 0.6 produces the highest amount of Ca(OH)2 due to higher consumption of C3S/C2S in presence of excess water which is not desirable. Samples with water-cement ratio of 0.4 and 0.5 show more controlled reaction during the hydration which can imply formation of an optimized level of desired hydration products resulting in a more mechanically strong and durable concrete.

  5. Laboratory Studies of Organic Compounds With Reflectance Spectroscopy

    Microsoft Academic Search

    J. M. Curchin; R. N. Clark; T. M. Hoefen

    2007-01-01

    In order to properly interpret reflectance spectra of any solar system surface from the earth to the Oort cloud, laboratory spectra of candidate materials for comparative analysis are needed. Although the common cosmochemical species (H2O, CO2, CO, NH3, and CH4) are well represented in the spectroscopic literature, comparatively little reflectance work has been done on organics from room to cryogenic

  6. Mid-Infrared and Near-Infrared Diffuse Reflectance Spectroscopy for Soil Carbon Measurement

    Microsoft Academic Search

    G. W. McCarty; J. B. Reeves III; V. B. Reeves; R. F. Follett; J. M. Kimble

    2002-01-01

    Diffuse reflectance spectroscopy offers a nondestruc- tive means for measurement of C in soils based on the The ability to inventory soil C on landscapes is limited by the reflectance spectra of illuminated soil. Both the NIR ability to rapidly measure soil C. Diffuse reflectance spectroscopic (400-2500 nm) and MIR (2500-25 000 nm) region have analysis in the near-infrared (NIR,

  7. [Application of near infrared reflectance spectroscopy to predict meat chemical compositions: a review].

    PubMed

    Tao, Lin-Li; Yang, Xiu-Juan; Deng, Jun-Ming; Zhang, Xi

    2013-11-01

    In contrast to conventional methods for the determination of meat chemical composition, near infrared reflectance spectroscopy enables rapid, simple, secure and simultaneous assessment of numerous meat properties. The present review focuses on the use of near infrared reflectance spectroscopy to predict meat chemical compositions. The potential of near infrared reflectance spectroscopy to predict crude protein, intramuscular fat, fatty acid, moisture, ash, myoglobin and collagen of beef, pork, chicken and lamb is reviewed. This paper discusses existing questions and reasons in the current research. According to the published results, although published results vary considerably, they suggest that near-infrared reflectance spectroscopy shows a great potential to replace the expensive and time-consuming chemical analysis of meat composition. In particular, under commercial conditions where simultaneous measurements of different chemical components are required, near infrared reflectance spectroscopy is expected to be the method of choice. The majority of studies selected feature-related wavelengths using principal components regression, developed the calibration model using partial least squares and modified partial least squares, and estimated the prediction accuracy by means of cross-validation using the same sample set previously used for the calibration. Meat fatty acid composition predicted by near-infrared spectroscopy and non-destructive prediction and visualization of chemical composition in meat using near-infrared hyperspectral imaging and multivariate regression are the hot studying field now. On the other hand, near infrared reflectance spectroscopy shows great difference for predicting different attributes of meat quality which are closely related to the selection of calibration sample set, preprocessing of near-infrared spectroscopy and modeling approach. Sample preparation also has an important effect on the reliability of NIR prediction; in particular, lack of homogeneity of the meat samples influenced the accuracy of estimation of chemical components. In general the predicting results of intramuscular fat, fatty acid and moisture are best, the predicting results of crude protein and myoglobin are better, while the predicting results of ash and collagen are less accurate. PMID:24555369

  8. Inferring sedimentary chlorophyll concentrations with reflectance spectroscopy: a novel approach

    E-print Network

    Wolfe, Alexander P.

    to reconstructing historical changes in the trophic status of mountain lakes Biplob Das, Rolf D. Vinebrooke, Arturo lake trophic status. Résumé : La spectroscopie de réflectance permet de déterminer rapidement et sans important applications of paleolimnol- ogy is the reconstruction of historical changes in lake trophic

  9. Efficient terahertz emission from InAs nanowires

    NASA Astrophysics Data System (ADS)

    Seletskiy, Denis V.; Hasselbeck, Michael P.; Cederberg, Jeffrey G.; Katzenmeyer, Aaron; Toimil-Molares, Maria E.; Léonard, François; Talin, A. Alec; Sheik-Bahae, Mansoor

    2011-09-01

    We observe intense pulses of far-infrared electromagnetic radiation emitted from arrays of InAs nanowires. The terahertz radiation power efficiency of these structures is ˜15 times higher than a planar InAs substrate. This is explained by the preferential orientation of coherent plasma motion to the wire surface, which overcomes radiation trapping by total-internal reflection. We present evidence that this radiation originates from a low-energy acoustic surface plasmon mode of the nanowire. This is supported by independent measurements of electronic transport on individual nanowires, ultrafast terahertz spectroscopy, and theoretical analysis. Our combined experiments and analysis further indicate that these plasmon modes are specific to high aspect ratio geometries.

  10. Terahertz pulsed imaging in vivo

    NASA Astrophysics Data System (ADS)

    Pickwell-MacPherson, E.

    2011-03-01

    Terahertz (1012 Hz) pulsed imaging is a totally non-destructive and non-ionising imaging modality and thus potential applications in medicine are being investigated. In this paper we present results using our hand-held terahertz probe that has been designed for in vivo use. In particular, we use the terahertz probe to perform reflection geometry in vivo measurements of human skin. The hand-held terahertz probe gives more flexibility than a typical flat-bed imaging system, but it also results in noisier data and requires existing processing methods to be improved. We describe the requirements and limitations of system geometry, data acquisition rate, image resolution and penetration depth and explain how various factors are dependent on each other. We show how some of the physical limitations can be overcome using novel data processing methods.

  11. High-precision gigahertz-to-terahertz spectroscopy of aqueous salt solutions as a probe of the femtosecond-to-picosecond dynamics of liquid water

    E-print Network

    Vinh, N Q; Allen, S James; George, D K; Rahmani, A J; Plaxco, Kevin W

    2015-01-01

    Because it is sensitive to fluctuations occurring over femtoseconds to picoseconds, gigahertz-to-terahertz dielectric relaxation spectroscopy can provide a valuable window into water's most rapid intermolecular motions. In response, we have built a vector network analyzer dielectric spectrometer capable of measuring absorbance and index of refraction in this frequency regime with unprecedented precision. Using this to determine the complex dielectric response of water and aqueous salt solutions from 5.9 GHz to 1.12 THz (which we provide in the SI), we have obtained strong new constraints on theories of water's collective dynamics. For example, while the salt-dependencies we observe for water's two slower relaxations (8 and 1 ps) are easily reconciled with suggestions that they arise due to rotations of fully and partially hydrogen bonded molecules, respectively, the salt-dependence of the fastest relaxation (180 fs) appears difficult to reconcile with its prior assignment to liberations of single hydrogen bon...

  12. Photoinduced insulator-metal phase transition and the metallic phase propagation in VO2 films investigated by time-resolved terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Xue, Xin; Jiang, Meng; Li, Gaofang; Lin, Xian; Ma, Guohong; Jin, Ping

    2013-11-01

    The particle size and film thickness dependence of the photoinduced insulator-metal phase transition in VO2 films has been studied systematically by time-resolved terahertz spectroscopy at room temperature. It is found that the dynamical photoinduced phase transition from insulator to metal consists of two processes: a 1.7 ps fast process and a slow process with a typical time constant of 40 ps. Both of the two processes show particle size independence. The 40 ps slow process is revealed to arise from the longitudinal propagation of the metallic phase from the photoexcited surface to the interior of the VO2 film. A phase boundary propagation speed with a magnitude of ˜2400 m/s is obtained, which is close to the velocity of sound in solid materials and coincides with the prediction of diffusionless phase transformation. Our experimental results clearly establish the entire procedure of photoinduced phase change in the VO2 film.

  13. Temperature and carrier-density dependence of electron-hole scattering in silicon investigated by optical-pump terahertz-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Terashige, T.; Yada, H.; Matsui, Y.; Miyamoto, T.; Kida, N.; Okamoto, H.

    2015-06-01

    We measured the optical conductivity ? ˜(? ) spectra of photodoped silicon by optical-pump terahertz-probe spectroscopy and analyzed them with a two-carrier Drude model. Taking into account the values of electron (hole)-phonon scattering rates previously reported in chemically doped silicon, we evaluated the electron-hole scattering rates ?e -h. From 293 to 90 K , the magnitudes and temperature dependence of ?e -h were successfully reproduced by a theoretical model including the effects of Rutherford scattering, Coulomb screening, and Pauli exclusion. This suggests that these three factors dominate electron-hole scattering processes in silicon. Below 90 K , ?e -h becomes larger than that of the theoretical curve, which is attributable to a prolongation of the relaxation time of hot carriers.

  14. Interfacial and bulk polaron masses in Zn1-xMgxO/ZnO heterostructures examined by terahertz time-domain cyclotron spectroscopy

    NASA Astrophysics Data System (ADS)

    Lloyd-Hughes, J.; Failla, M.; Ye, J.; Jones, S. P. P.; Teo, K. L.; Jagadish, C.

    2015-05-01

    The cyclotron resonance of polarons in Zn1-xMgxO/ZnO heterostructures (with 0.15 < x < 0.22 ) was studied by terahertz time-domain spectroscopy. Low-temperature magnetoconductivity spectra of the 2D electron gas at the Zn1-xMgxO/ZnO interface determined the polaron density, mass, and scattering rate. The cyclotron mass of 2D polarons was found to increase significantly with magnetic field B from 0.24 me at B = 2 T to 0.37 me at B = 7.5 T. A nonlinear cyclotron frequency with B was also observed for 3D polarons in ZnO. The findings are discussed in the context of polaron mass renormalization driven by the electron-LO-phonon and electron-acoustic phonon interactions.

  15. Midinfrared spectroscopy of synthetic olivines: Thermal emission, specular and diffuse reflectance, and attenuated total reflectance

    E-print Network

    Glotch, Timothy D.

    , and attenuated total reflectance studies of forsterite to fayalite Melissa D. Lane,1 Timothy D. Glotch,2 M. Darby] Synthetic olivine samples ranging in composition from forsterite to fayalite are analyzed in the midinfrared is identified of a specific emissivity maximum/reflectivity minimum (the flection position). From forsterite

  16. Global soil characterization with VNIR diffuse reflectance spectroscopy

    Microsoft Academic Search

    David J. Brown; Keith D. Shepherd; Markus G. Walsh; M. Dewayne Mays; Thomas G. Reinsch

    2006-01-01

    There has been growing interest in the use of diffuse infrared reflectance as a quick, inexpensive tool for soil characterization. In studies reported to date, calibration and validation samples have been collected at either a local or regional scale. For this study, we selected 3768 samples from all 50 U.S. states and two tropical territories and an additional 416 samples

  17. Carrier dynamics in bulk ZnO. I. Intrinsic conductivity measured by terahertz time-domain spectroscopy

    E-print Network

    Carrier dynamics in bulk ZnO. I. Intrinsic conductivity measured by terahertz time 12 August 2009; published 30 December 2009 Far-infrared absorption and refractive index of a ZnORevB.80.235205 PACS number s : 72.20. i, 72.80.Ey, 78.20.Ci, 71.55.Gs I. INTRODUCTION ZnO is a wide band

  18. Frequency selective terahertz retroreflectors

    NASA Astrophysics Data System (ADS)

    Williams, Richard James

    The use of novel optical structures operating at terahertz frequencies in industrial and military applications continues to grow. Some of these novel structures include gratings, frequency selective surfaces, metamaterials and metasurfaces, and retroreflectors. A retroreflector is a device that exhibits enhanced backscatter by concentrating the reflected wave in the direction of the source. Retroreflectors have applications in a variety of diverse fields such as aviation, radar systems, antenna technology, communications, navigation, passive identification, and metrology due to their large acceptance angles and frequency bandwidth. This thesis describes the design, fabrication, and characterization of a retroreflector designed for terahertz frequencies and the incorporation of a frequency selective surface in order to endow the retroreflector with narrow-band frequency performance. The radar cross section of several spherical lens reflectors operating at terahertz frequencies was investigated. Spherical lens reflectors with diameters ranging from 2 mm to 8 mm were fabricated from fused silica ball lenses and their radar cross section was measured at 100 GHz, 160 GHz, and 350 GHz. Crossed-dipole frequency selective surfaces exhibiting band-pass characteristics at 350 GHz fabricated from 12 um-thick Nickel screens were applied to the apertures of the spherical lens reflectors. The radar cross section of the frequency selective retroreflectors was measured at 160 GHz and 350 GHz to demonstrate proof-of-concept of narrow-band terahertz performance.

  19. Cavity enhanced terahertz modulation

    SciTech Connect

    Born, N., E-mail: norman.born@physik.uni-marburg.de [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States); Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany); Scheller, M.; Moloney, J. V. [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States)] [College of Optical Sciences, University of Arizona, 1630 E University Boulevard, Tucson, Arizona 85721 (United States); Koch, M. [Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany)] [Faculty of Physics and Material Sciences Center, Philipps-Universität Marburg, Renthof 5, 35032 Marburg (Germany)

    2014-03-10

    We present a versatile concept for all optical terahertz (THz) amplitude modulators based on a Fabry-Pérot semiconductor cavity design. Employing the high reflectivity of two parallel meta-surfaces allows for trapping selected THz photons within the cavity and thus only a weak optical modulation of the semiconductor absorbance is required to significantly damp the field within the cavity. The optical switching yields to modulation depths of more than 90% with insertion efficiencies of 80%.

  20. Far infrared (terahertz) spectroscopy of a series of polycyclic aromatic hydrocarbons and application to structure interpretation of asphaltenes and related compounds.

    PubMed

    Cataldo, Franco; Angelini, Giancarlo; García-Hernández, D Aníbal; Manchado, Arturo

    2013-07-01

    A series of 33 different polycyclic aromatic hydrocarbons (PAHs) were studied by far infrared spectroscopy (terahertz spectroscopy) in the spectral range comprised between 600 and 50 cm(-1). In addition to common PAHs like naphthalene, anthracene, phenanthrene, fluoranthene, picene, pyrene, benzo[?]pyrene, and perylene, also quite unusual PAHs were studied like tetracene, pentacene, acenaphtene, acenaphtylene, triphenylene, and decacyclene. A series of alkylated naphthalenes and anthracenes were studied as well as methypyrene. Partially or totally hydrogenated PAHs were also object of the present investigation, ranging from tetrahydronaphthalene (tetralin) to decahydronaphthalene (decalin), 9,10-dihydroanthracene, 9,10-dihydrophenanthrene, hexahydropyrene, and dodecahydrotriphenylene. Finally, the large and quite rare PAHs coronene, quaterrylene, hexabenzocoronene, and dicoronylene were studied by far infrared spectroscopy. The resulting reference spectra were used in the interpretation of the chemical structure of asphaltenes (as extracted from a heavy petroleum fraction and from bitumen), the chemical structures of other petroleum fractions known as DAE (distillate aromatic extract) and RAE (residual aromatic extract), and a possible interpretation of components of the chemical structure of anthracite coal. Asphaltenes, heavy petroleum fractions, and coal were proposed as model compounds for the interpretation of the emission spectra of certain proto-planetary nebulae (PPNe) with a good matching in the mid infrared between the band pattern of the PPNe emission spectra and the spectra of these oil fractions or coal. Although this study was finalized in an astrochemical context, it may find application also in the petroleum and coal chemistry. PMID:23603577

  1. Atmospheric absorption of terahertz radiation and water vapor continuum effects

    E-print Network

    Massachusetts at Lowell, University of

    Atmospheric absorption of terahertz radiation and water vapor continuum effects David M. Slocum a April 2013 Keywords: Water vapor Absorption Continuum Terahertz Spectroscopy a b s t r a c t The water vapor continuum absorption spectrum was investigated using Fourier Trans- form Spectroscopy

  2. Terahertz radiation study on FRP composite solid laminates

    NASA Astrophysics Data System (ADS)

    Im, Kwang-Hee; Hsu, David K.; Chiou, Chien-Ping; Barnard, Daniel J.; Yang, In-Young; Park, Je-Woong

    2012-05-01

    Investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied as a nondestructive evaluation technique. Here carbon fiber-reinforced plastics (CFRP) derived their excellent mechanical strength, stiffness and electrical conductivity from carbon fibers. Especially, the electrical conductivity of CFRP composites depends on the direction of unidirectional fibers since carbon fibers are electrically conducting while the epoxy matrix is not. The THz TDS can be considered as a useful tool using general non-conducting materials; however it is quite limited to conducting materials. In order to solve various material properties, the index of refraction (n) is derived by using the terahertz time domain spectroscopy. Also, for a 48-ply thermoplastic PPS(poly-phenylene sulfide)-based CFRP solid laminate, the terahertz scanning images were made at the angles ranged from 0° to 180° with respect to the nominal fiber axis. So, the images were mapped out based on the electrical field (E-field) direction in the CFRP solid laminates.

  3. [Application of near-infrared diffuse reflectance spectroscopy to the detection and identification of transgenic corn].

    PubMed

    Rui, Yu-kui; Luo, Yun-bo; Huang, Kun-lun; Wang, Wei-min; Zhang, Lu-da

    2005-10-01

    With the rapid development of the GMO, more and more GMO food has been pouring into the market. Much attention has been paid to GMO labeling under the controversy of GMO safety. Transgenic corns and their parents were scanned by continuous wave of near infrared diffuse reflectance spectroscopy range of 12000-4000 cm(-1); the resolution was 4 cm(-1); scanning was carried out for 64 times; BP algorithm was applied for data processing. The GMO food was easily resolved. Near-infrared diffuse reflectance spectroscopy is unpolluted and inexpensive compared with PCR and ELISA, so it is a very promising detection method for GMO food. PMID:16395887

  4. In vivo soft tissue differentiation by diffuse reflectance spectroscopy: preliminary results

    NASA Astrophysics Data System (ADS)

    Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Neukam, Friedrich Wilhelm; Schmidt, Michael; Douplik, Alexandre

    Remote laser surgery does not provide haptic feedback to operate layer by layer and preserve vulnerable anatomical structures like nerve tissue or blood vessels. The aim of this study is identification of soft tissue in vivo by diffuse reflectance spectroscopy to set the base for a feedback control system to enhance nerve preservation in oral and maxillofacial laser surgery. Various soft tissues can be identified by diffuse reflectance spectroscopy in vivo. The results may set the base for a feedback system to prevent nerve damage during oral and maxillofacial laser surgery.

  5. The effect of anisotropic reflectance on imaging spectroscopy of snow properties

    Microsoft Academic Search

    Thomas H. Painter; Jeff Dozier

    2004-01-01

    How does snow's anisotropic directional reflectance affect the mapping of snow properties from imaging spectrometer data? This sensitivity study applies two spectroscopy models to synthetic images of the spectral hemispherical–directional reflectance factor (HDRF) with prescribed snow-covered area and snow grain size. The MEMSCAG model determines both sub-pixel snow-covered area and the grain size of the fractional snow cover. The Nolin\\/Dozier

  6. Measurement of chemical composition in wet whole maize silage by visible and near infrared reflectance spectroscopy

    Microsoft Academic Search

    D. Cozzolino; A. Fassio; E. Fernández; E. Restaino; A. La Manna

    2006-01-01

    Visible (Vis) and near infrared reflectance (NIR) spectroscopy were used to predict dry matter (DM), acid and neutral detergent fibre (ADFom and aNDFom), ash, crude protein (CP) and pH in wet whole maize (WWM) silage samples. Samples were analysed by reference methods and spectra collected using a NIR spectrophotometer in reflectance (400–2500nm). Predictive equations were developed using modified partial least

  7. Bidirectional reflectance spectroscopy. [for Moon, asteroid, Europa, and Oberon

    NASA Technical Reports Server (NTRS)

    Hapke, Bruce

    1987-01-01

    An analytical model is developed for the opposition effects (heiligenshein) in the case of light scattering from a semi-infinite, particulate medium with particles that are large relative to the wavelength. The effect is common for natural materials, and comprises a bright surge in light diffusively reflected from a surface at near zero phase. A generalized expression is devised for the extinction coefficient of a particulate medium. Models are developed for step function and hyperbolic tangent distributions of light scattered from a stratified medium and exhibiting the opposition effect. A maximum brightness amplitude increase of 0.753 is projected for the effect. Greater values must have other causes. To illustrate the theory it is fitted to observations of the Moon, an asteroid, and a satellite of Uranus; Europa is also discussed.

  8. Reflectance and Thermal Infrared Spectroscopy of Mars: Relationship Between ISM and TES for Compositional Determinations

    NASA Technical Reports Server (NTRS)

    Boyce, Joseph (Technical Monitor); Mustard, John

    2004-01-01

    Reflectance spectroscopy has demonstrated that high albedo surfaces on Mars contain heavily altered materials with some component of hematite, poorly crystalline ferric oxides, and an undefined silicate matrix. The spectral properties of many low albedo regions indicate crystalline basalts containing both low and high calcium pyroxene, a mineralogy consistent with the basaltic SNC meteorites. The Thermal Emission Spectrometer (TES) experiment on the Mars Geochemical Surveyor has acquired critical new data relevant to surface composition and mineralogy, but in a wavelength region that is complementary to reflectance spectroscopy. The essence of the completed research was to analyze TES data in the context of reflectance data obtained by the French ISM imaging spectrometer experiment in 1989. This approach increased our understanding of the complementary nature of these wavelength regions for mineralogic determinations using actual observations of the martian surface. The research effort focused on three regions of scientific importance: Syrtis Major-Isidis Basin, Oxia Palus-Arabia, and Valles Marineris. In each region distinct spatial variations related to reflectance, and in derived mineralogic information and interpreted compositional units were analyzed. In addition, specific science questions related to the composition of volcanics and crustal evolution, soil compositions and pedogenic processes, and the relationship between pristine lithologies and weathering provided an overall science-driven framework for the work. The detailed work plan involved colocation of TES and ISM data, extraction of reflectance and emissivity spectra from areas of known reflectance variability, and quantitative analysis using factor analysis and statistical techniques to determine the degree of correspondence between these different wavelength regions. Identified coherent variations in TES spectroscopy were assessed against known atmospheric effects to validate that the variations are due to surface properties. With this new understanding of reflectance and emission spectroscopy, mineralogic interpretations were derived and applied to the science objectives of the three regions.

  9. Probing near-normally propagating bulk acoustic waves using pseudo-reflection geometry Brillouin spectroscopy

    NASA Astrophysics Data System (ADS)

    Parsons, L. C.; Andrews, G. T.

    2012-09-01

    Pseudo-reflection geometry Brillouin spectroscopy can be used to probe acoustic wave dispersion approximately along the surface normal of a material system while avoiding the difficulties associated with specularly reflected light encountered in an ideal reflection configuration. As an example of its application, we show analytically that it can be used to determine both the refractive index and bulk acoustic mode velocities of optically-isotropic non-metallic materials and confirm the utility of the approach via a series of experiments on fused quartz, gallium phosphide, water, and porous silicon films.

  10. Mars surface composition from reflectance spectroscopy - A summary

    NASA Technical Reports Server (NTRS)

    Singer, R. B.; Clark, R. N.; Mccord, T. B.; Adams, J. B.; Huguenin, R. L.

    1979-01-01

    Visible and near-infrared reflectance spectra and multispectral maps of the Martian surface are discussed, and implications of the data for the composition of the Martian surface are considered. Spacecraft and earth-based telescopic observations have confirmed the generally bimodal albedo distribution of the planet, dividing the surface into bright and dark regions. Mars spectra are characterized by the presence of strong Fe(+3) absorption, which is attributed to various ferric oxide minerals. Interpretations of the spectra from the dark regions indicate a basaltic or ultramafic source rock. Evidence for water ice or a highly desiccated metal hydrate has been obtained, along with evidence for CO2-ice only in the south polar cap. Mariner 9 observations of Martian dust suggest the presence of rather acidic rock or mineral particles, or a montmorillonite-type clay. Prospects for the future study of Martian surface composition include continuing earth-based spectrophotometric studies, and high-spectral-resolution mapping of a significant portion of the surface by the Galileo spacecraft and the next Mars mission.

  11. Percutaneous Penetration Enhancement in Vivo Measured by Attenuated Total Reflectance Infrared Spectroscopy

    Microsoft Academic Search

    Vivien H. W. Mak; Russell O. Potts; Richard H. Guy

    1990-01-01

    A novel application of attenuated total reflectance IR Spectroscopy (ATR-IR) was used to monitor the outer several microns of the stratum corneum (SC) and, thereby, demonstrate enhanced percutaneous absorption in vivo in man. 4-Cyanophenol (CP) as a model permeant yielded a unique IR signal, distinct from those of the stratum corneum and the vehicle components. CP was administered for 1,

  12. Fast determination of total ginsenosides content in ginseng powder by near infrared reflectance spectroscopy

    Microsoft Academic Search

    Hua-cai Chen; Xing-dan Chen; Yong-jun Lu; Zhi-qiang Cao

    2006-01-01

    Near infrared (NIR) reflectance spectroscopy was used to develop a fast determination method for total ginsenosides in Ginseng (Panax Ginseng) powder. The spectra were analyzed with multiplicative signal correction (MSC) correlation method. The best correlative spectra region with the total ginsenosides content was 1660 nm~1880 nm and 2230nm~2380 nm. The NIR calibration models of ginsenosides were built with multiple linear

  13. Near-infrared transmission and reflectance spectroscopy for the measurement of dietary fiber in barley

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near-infrared (NIR) transmission and reflectance spectroscopy were investigated as rapid screening tools to evaluate the total dietary fiber content of barley (Hordeum vulgare L.) cultivars. A Foss Grainspec Rice Analyzer and an NIR Systems 6500 spectrometer were used to obtain transmission and ref...

  14. Analysis of Total Oil and Fatty Acids Composition by Near Infrared Reflectance Spectroscopy in Edible Nuts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near Infrared (NIR) Reflectance spectroscopy has established itself as an important tool in quantifying water and oil present in various food materials. It is rapid and nondestructive, easier to use, and does not require processing the samples with corrosive chemicals that would render them non-edib...

  15. INVESTIGATING ULTRASONIC DIFFRACTION GRATING SPECTROSCOPY AND REFLECTION TECHNIQUES FOR CHARACTERIZING SLURRY PROPERTIES

    EPA Science Inventory

    The objectives of the project are to investigate the use of (1) ultrasonic diffraction grating spectroscopy (UDGS) for measuring the particle size of a slurry and (2) shear wave reflection techniques to measure the viscosity of a slurry. For the first topic, the basic principle...

  16. Total Internal Reflection with Fluorescence Correlation Spectroscopy: Combined Surface Reaction and Solution Diffusion

    Microsoft Academic Search

    Tammy E. Starr; Nancy L. Thompson

    2001-01-01

    Total internal reflection with fluorescence correlation spectroscopy (TIR-FCS) is a method for measuring the surface association\\/dissociation rates and absolute densities of fluorescent molecules at the interface of solution and a planar substrate. This method can also report the apparent diffusion coefficient and absolute concentration of fluorescent molecules very close to the surface. An expression for the fluorescence fluctuation autocorrelation function

  17. Fluorescence spectroscopy in combination with reflectance measurements in human skin examination: what for and how

    Microsoft Academic Search

    Sergei R. Utz; Yuri P. Sinichkin; Igor V. Meglinsky; Helena A. Pilipenko

    1995-01-01

    Reflectance and fluorescence spectroscopy are successfully used for skin disease diagnostics. Human skin optical parameters are defined by its turbid, scattering properties with nonuniform absorption and fluorescence chromophores distribution, its multilayered structure, and variability under different physiological and pathological conditions. Theoretical modeling of light propagation in skin could improve the understanding of these conditions and may be useful in the

  18. Absorption and Scattering Coefficients: A Biophysical-Chemistry Experiment Using Reflectance Spectroscopy

    ERIC Educational Resources Information Center

    Cordon, Gabriela B.; Lagorio, M. Gabriela

    2007-01-01

    A biophysical-chemistry experiment, based on the reflectance spectroscopy for calculating the absorption and scattering coefficients of leaves is described. The results show that different plants species exhibit different values for both the coefficients because of their different pigment composition.

  19. FAECAL NEAR INFRARED REFLECTANCE SPECTROSCOPY TO PREDICT DIET QUALITY FOR SHEEP

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Faecal near infrared reflectance spectroscopy (NIRS) is a non-invasive method to determine diet quality in herbivores, but has not been reported for sheep (Ovis aries) in the US. A diet reference chemistry:faecal near infrared spectra calibration (n = 78) was developed to determine if faecal NIRS c...

  20. Mid-infrared diffuse reflectance spectroscopy for the rapid analysis of plant root composition

    Microsoft Academic Search

    Kathryn E. White; James B. Reeves; Frank J. Coale

    2011-01-01

    Roots are an important contributor of recalcitrant organic carbon compounds for soil organic matter formation, but little is known about the composition of many species. There is a need for techniques capable of rapidly assessing significant, but often overlooked, carbon sinks such as roots. Diffuse reflectance mid-infrared spectroscopy (DRIFTS) has great potential for the analysis and characterization of plant root

  1. Assessment of estuarine sediment and sedimentary organic matter properties by infrared reflectance spectroscopy

    Microsoft Academic Search

    Ghita Alaoui; Marc N. Léger; Jean-Pierre Gagné; Luc Tremblay

    2011-01-01

    The goal of this work was to evaluate the capability of mid-infrared diffuse reflectance (DRIFT) spectroscopy, coupled with multivariate chemometric analysis, to rapidly provide valuable information on sediment composition and organic geochemistry. A large (150) and heterogeneous set of estuarine sediments was analyzed in their natural matrix by DRIFT. Principal component analysis (PCA) of DRIFT spectra clearly discriminated sediments from

  2. Prediction of olive quality using FT-NIR spectroscopy in reflectance and transmittance modes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to use FT-NIR spectroscopy to predict the firmness, oil content and color of two olive (Olea europaea L) varieties (‘Ayvalik’ and ‘Gemlik’). Spectral measurements were performed on the intact olives for the wavelengths of 780-2500 nm in reflectance and for 800-1725...

  3. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Transient surface photoconductivity of GaAs emitter studied by terahertz pump-emission spectroscopy

    Microsoft Academic Search

    Yu-Lei Shi; Qing-Li Zhou; Cun-Lin Zhang

    2009-01-01

    This paper investigates the ultrafast carrier dynamics and surface photoconductivity of unbiased semi-insulating GaAs in detail by using a terahertz pump-emission technique. Based on theoretical modelling, it finds that transient photoconductivity plays a very important role in the temporal waveform of terahertz radiation pulse. Anomalous enhancement in both terahertz radiation and transient photoconductivity is observed after the excitation of pump

  4. In vivo detection of epileptic brain tissue using static fluorescence and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Yadav, Nitin; Bhatia, Sanjiv; Ragheb, John; Mehta, Rupal; Jayakar, Prasanna; Yong, William; Lin, Wei-Chiang

    2013-02-01

    Diffuse reflectance and fluorescence spectroscopy are used to detect histopathological abnormalities of an epileptic brain in a human subject study. Static diffuse reflectance and fluorescence spectra are acquired from normal and epileptic brain areas, defined by electrocorticography (ECoG), from pediatric patients undergoing epilepsy surgery. Biopsy specimens are taken from the investigated sites within an abnormal brain. Spectral analysis reveals significant differences in diffuse reflectance spectra and the ratio of fluorescence and diffuse reflectance spectra from normal and epileptic brain areas defined by ECoG and histology. Using these spectral differences, tissue classification models with accuracy above 80% are developed based on linear discriminant analysis. The differences between the diffuse reflectance spectra from the normal and epileptic brain areas observed in this study are attributed to alterations in the static hemodynamic characteristics of an epileptic brain, suggesting a unique association between the histopathological and the hemodynamic abnormalities in an epileptic brain.

  5. Reflectance spectroscopy of palagonite and iron-rich montmorillonite clay mixtures: Implications for the surface composition of Mars

    NASA Technical Reports Server (NTRS)

    Orenberg, J. B.; Handy, J.

    1991-01-01

    Because of the power of remote sensing reflectance spectroscopy in determining mineralogy, it was used as the major method of identifying possible mineral analogs of the Martian surface. A summary of proposed Martian surface compositions from reflectance spectroscopy before 1979 was presented. Since that time, iron-rich montmorillonite clay, nanocrystalline or nanophase hematite, and palagonite were suggested as Mars soil analog materials.

  6. /II sifu reflection electron energy loss spectroscopy measurements of low temperature surface cleaning for Si molecular beam epitaxy

    E-print Network

    Atwater, Harry

    /II sifu reflection electron energy loss spectroscopy measurements of low temperature surface cleaning for Si molecular beam epitaxy Shouleh Nikzad, Selmer S. Wong, Channing C. Ahn, Aimee L. Smith molecular beam epitaxy system, using reflection electron energy loss spectroscopy, in conjunction

  7. Influence of terahertz waves on the fiber direction of CFRP composite laminates

    NASA Astrophysics Data System (ADS)

    Im, Kwang-Hee; Hsu, David K.; Chiou, Chien-Ping; Barnard, Daniel J.; Yang, In-Young; Park, Je-Woong

    2013-01-01

    The importance of Carbon-fiber reinforced plastics (CFRP) are widely utilized due to more high performance in engineering structures. It was well known that a nondestructive technique would be very beneficial. A new terahertz radiation has been recognized for their importance in technological applications. Recently, T-ray (terahertz ray) advances of technology and instrumentation has provided a probing field on the electromagnetic spectrum. The THz-TDS can be considered as a useful tool using general non-conducting materials; however it is quite limited to conducting materials. In order to solve various material properties, the index of refraction (n) and the absorption coefficient (?) are derived in reflective and transmission configuration using the terahertz time domain spectroscopy. However, the T-ray is limited in order to penetrate a conducting material to some degree. Here, the T-ray would not go through easily the CFRP composite laminates since carbon fibers are electrically conducting while the epoxy matrix is not. So, investigation of terahertz time domain spectroscopy (THz TDS) was made and reflection and transmission configurations were studied for a 48-ply thermoplastic PPS (poly-phenylene sulfide)-based CFRP solid laminate. It is found that the electrical conductivity of CFRP composites depends on the direction of unidirectional fibers. Also, the T-ray could penetrate a CFRP composite laminate a few ply based on the E-filed (Electrical field) of carbon fibers. The terahertz scanning images were made at the angles ranged from 0° to 180° with respect to the nominal fiber axis. So, the images were mapped out based on the electrical field (E-field) direction in the CFRP solid laminates. Also, using two-dimensional spatial Fourier transform, interface C-scan images were transformed into quantitatively angular distribution plots to show the fiber orientation information therein and to predict the orientation of the ply.

  8. Terahertz technology: a boon to tablet analysis.

    PubMed

    Wagh, M P; Sonawane, Y H; Joshi, O U

    2009-05-01

    The terahertz gap has a frequency ranges from approximately 0.3 THz to approximately 10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets. PMID:20490288

  9. Terahertz Technology: A Boon to Tablet Analysis

    PubMed Central

    Wagh, M. P.; Sonawane, Y. H.; Joshi, O. U.

    2009-01-01

    The terahertz gap has a frequency ranges from ?0.3 THz to ?10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets. PMID:20490288

  10. [The research progress in determining lignocellulosic content by near infrared reflectance spectroscopy technology].

    PubMed

    Du, Juan; An, Dong; Xia, Tian; Huang, Yan-Hua; Li, Hong-Chao; Zhang, Yun-Wei

    2013-12-01

    Near infrared reflectance spectroscopy technology, as a new analytic method, can be used to determine the content of lignin, cellulose and hemi-cellulose which is faster, effective, easier to operate, and more accurate than the traditional wet chemical methods. Nowadays it has been widely used in measuring the composition of lignocelluloses in woody plant and herbaceous plant. The domestic and foreign research progress in determining the lignin, cellulose and hemi-cellulose content in woody plant ( wood and bamboo used as papermaking raw materials and wood served as potential biomass energy) and herbaceous plant (forage grass and energy grass) by near infrared reflectance spectroscopy technology is comprehensively summarized and the advances in method studies of measuring the composition of lignocelluloses by near infrared reflectance spectroscopy technology are summed up in three aspects, sample preparation, spectral data pretreatment and wavelength selection methods, and chemometric analysis respectively. Four outlooks are proposed combining the development statues of wood, forage grass and energy grass industry. First of all, the authors need to establish more feasible and applicable models for a variety of uses which can be used for more species from different areas, periods and anatomical parts. Secondly, comprehensive near infrared reflectance spectroscopy data base of grass products quality index needs to be improved to realize on-line quality and process control in grassproducts industry, which can guarantee the quality of the grass product. Thirdly, the near infrared reflectance spectroscopy quality index model of energy plant need to be built which can not only contribute to breed screening, but also improve the development of biomass industry. Besides, modeling approaches are required to be explored and perfected any further. Finally, the authors need to try our best to boost the advancement in the determination method of lignin, cellulose and hemi-cellulose by near infrared reflectance spectroscopy from the laboratory to the practical applications. Along with the method of determining the lignin, cellulose and hemi-cellulose by near infrared spectroscopy being unceasingly perfected and matured, this technique will actively have a positive effect on the development of papermaking, forage grass and energy grass industry. PMID:24611371

  11. Cryogenic temperatures as a path toward high-Q terahertz metamaterials Ranjan Singh,1,2

    E-print Network

    Oklahoma State University

    Cryogenic temperatures as a path toward high-Q terahertz metamaterials Ranjan Singh,1,2 Zhen Tian,1 terahertz time-domain spectroscopy. The operation of metamaterials at cryogenic temperatures is anticipated we investigate the behavior of terahertz planar MM at cryogenic temperatures. It is shown that thin

  12. Terahertz magneto-spectroscopy of a point contact based on CdTe/CdMgTe quantum well

    NASA Astrophysics Data System (ADS)

    Grigelionis, Ignas; Bia?ek, Marcin; Grynberg, Marian; Czapkiewicz, Magdalena; Kolkovskiy, Valery; Wiater, Maciej; Wojciechowski, Tomasz; Wróbel, Jerzy; Wojtowicz, Tomasz; Diakonova, Nina; Knap, Wojciech; ?usakowski, Jerzy

    2015-01-01

    To understand a terahertz (THz) response of a point contact device, a number of samples based on CdTe/CdMgTe quantum wells grown by a molecular beam epitaxy were investigated at low temperatures and high magnetic fields. The experiments involved magneto-transport, photocurrent, and transmission measurements carried out with monochromatic THz sources or a Fourier spectrometer. Samples of different geometry with and without gate metallization were used. We observed excitations of a two-dimensional electron plasma in the form of optically induced Shubnikov-de Haas oscillations, cyclotron resonance transitions, and magneto-plasmon resonances. A polaron effect was observed at magnetic fields higher than 10 T. A point contact device processed with an electron beam lithography was investigated as a detector of THz radiation. It was shown that the main mechanism responsible for a THz performance of the point contact was excitation of magneto-plasmons with a wavevector defined by geometrical constrictions of the device mesa.

  13. Applications of Ultrafast Terahertz Pulses for Intra-ExcitonicSpectroscopy of Quasi-2D Electron-Hole Gases

    SciTech Connect

    Kaindl, Robert A.; Carnahan, Marc A.; Hagele, Daniel; Chemla, D.S.

    2006-09-02

    Excitons are of fundamental interest and of importance foropto-electronic applications of bulk and nano-structured semiconductors.This paper discusses the utilization of ultrafast terahertz (THz) pulsesfor the study of characteristic low-energy excitations of photoexcitedquasi 2D electron-hole (e-h) gases. Optical-pump THz-probe spectroscopyat 250-kHz repetition rate is employed to detect characteristic THzsignatures of excitons and unbound e-h pairs in GaAs quantum wells.Exciton and free-carrier densities are extracted from the data using atwo-component model. We report the detailed THz response and pairdensities for different photoexcitation energies resonant to heavy-holeexcitons, light-hole excitons, or the continuum of unbound pairs. Suchexperiments can provide quantitative insights into wavelength, time, andtemperature dependence of the low-energy response and composition ofoptically excited e-h gases in low-dimensionalsemiconductors.

  14. Time-Domain Terahertz Spectroscopy (0.3 - 7.5 THz) of Molecular Ices of Simple Alcohols

    NASA Astrophysics Data System (ADS)

    McGuire, Brett A.; Ioppolo, Sergio; Allodi, Marco A.; de Vries, Xander; Finneran, Ian; Carroll, Brandon; Blake, Geoffrey

    2014-06-01

    We have recently constructed a time-domain TeraHertz (THz) spectrometer for the study of molecular ices in the far-infrared. Here, we present the results of a study of amorphous and crystalline ices of simple alcohols from methanol (CH_3OH) through butanol (CH_3(CH_2)_3OH) in the region of 0.3 - 7.5 THz. We examine the effects of the length and degree of branching of the carbon chain on the observed spectra arising from the bulk, large-amplitude motions which are prominent in this spectral region. We also discuss these results in an astrochemical context: the application of these spectra to astronomical observations of interstellar ices with Herschel PACS/SPIRE and SOFIA.

  15. Conducting dielectric polymer properties at Terahertz wavelength

    Microsoft Academic Search

    E. Nguema; J. D. Delagnes; A. Elfatimy; P Mounaix

    The dielectric function of polyaniline (Pani) doped by couple drug\\/solvent sulphonic camphoracid\\/dichloroacetic CSA\\/DCAA is studied in the terahertz range. Numerous films of this polymer with different doping level are measured by Terahertz Time-Domain Spectroscopy (THz-TDS). The Fourier transmission spectrum, the permittivity and conductivity are then precisely obtained between 0.1 and 4 THz. The behavior of the dielectric function does not

  16. IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, VOL. 4, NO. 2, MARCH/APRIL 1998 353 Optical Pump-Terahertz Probe Spectroscopy

    E-print Network

    Scherer, Norbert F.

    -terahertz probe data on h111i GaAs samples are presented, demonstrating the applicability of this spectrometer. This spectrometer routinely produces and detects terahertz pulses that exhibit signal-to-noise ratios (SNR's) greater than 6000 in the time domain and a spectral noise floor of magnitude 2.7 2 1004 . Hence

  17. Active terahertz metamaterials

    SciTech Connect

    Chen, Hou-tong [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory; Taylor, Antoinette J [Los Alamos National Laboratory

    2009-01-01

    In this paper we present an overview of research in our group in terahertz (THz) metamaterials and their applications. We have developed a series of planar metamaterials operating at THz frequencies, all of which exhibit a strong resonant response. By incorporating natural materials, e.g. semiconductors, as the substrates or as critical regions of metamaterial elements, we are able to effectively control the metamaterial resonance by the application of external stimuli, e.g., photoexcitation and electrical bias. Such actively controllable metamaterials provide novel functionalities for solid-state device applications with unprecedented performance, such as THz spectroscopy, imaging, and many others.

  18. Diagnostics of pigmented skin tumors based on laser-induced autofluorescence and diffuse reflectance spectroscopy

    SciTech Connect

    Borisova, E; Avramov, L [Institute of Electronics, Bulgarian Academy of Sciences, Sofia (Bulgaria); Troyanova, P [National Oncological Diagnostic Center, Sofia (Bulgaria); Pavlova, P [Technical University Sofia, branch Plovdiv (Bulgaria)

    2008-06-30

    Results of investigation of cutaneous benign and malignant pigmented lesions by laser-induced autofluorescence spectroscopy (LIAFS) and diffuse reflectance spectroscopy (DRS) are presented. The autofluorescence of human skin was excited by a 337-nm nitrogen laser. A broadband halogen lamp (400-900 nm) was used for diffuse reflectance measurements. A microspectrometer detected in vivo the fluorescence and reflectance signals from human skin. The main spectral features of benign (dermal nevi, compound nevi, dysplastic nevi) and malignant (melanoma) lesions are discussed. The combined usage of the fluorescence and reflectance spectral methods to determine the type of the lesion, which increases the total diagnostic accuracy, is compared with the usage of LIAFS or DRS only. We also applied colorimetric transformation of the reflectance spectra detected and received additional evaluation criteria for determination of type of the lesion under study. Spectra from healthy skin areas near the lesion were detected and changes between healthy and lesion skin spectra were revealed. The influence of the main skin pigments on the detected spectra is discussed and evaluation of possibilities for differentiation between malignant and benign lesions is performed based on their spectral properties. This research shows that the non-invasive and high-sensitive in vivo detection by means of appropriate light sources and detectors should be possible, related to the real-time determination of existing pathological conditions. (special issue devoted to application of laser technologies in biophotonics and biomedical studies)

  19. Reflectance-difference spectroscopy of mixed arsenic-rich phases of gallium arsenide ,,001... M. J. Begarney,1

    E-print Network

    Li, Lian

    Reflectance-difference spectroscopy of mixed arsenic-rich phases of gallium arsenide ,,001... M. J the reflectance difference spectra and the atomic structure of arsenic-rich recon- structions of GaAs 001 has been 4). In the reflectance difference spectra, negative peaks at 2.25 and 2.8 eV correlate with the c(4

  20. Reflection electron energy loss spectroscopy during initial stages of Ge growth on Si by molecular beam epitaxy

    E-print Network

    Atwater, Harry

    Reflection electron energy loss spectroscopy during initial stages of Ge growth on Si by molecular for publication 23 October 1990) Using a conventional reflection high-energy electron diffraction gun together intensities from Si L2 s and Ge L2,3 core losses with reflection electron diffraction data in order to analyze

  1. Reflection zone plates for 2D focusing and spectroscopy of hard X-rays

    NASA Astrophysics Data System (ADS)

    Löchel, H.; Brzhezinskaya, M.; Firsov, A.; Rehanek, J.; Erko, A.

    2013-03-01

    We propose the use of reflection zone plates (RZP) for two main applications: focusing and spectroscopy. A RZP combines three optical properties - reflection, imaging and dispersion - in one optical element. Having been successfully implemented into an X-ray fs-beamline at BESSY II, RZPs could be an important device in upcoming new high brilliance X-ray sources such as Free Electron Lasers (FEL). The reduction of the number of optical elements in a beamline would allow the highest possible transmission and satisfy the purpose of conserving the unique properties of FELs such as their high coherence.

  2. Development of techniques for advanced optical contamination measurement with internal reflection spectroscopy, phase 1, volume 1

    NASA Technical Reports Server (NTRS)

    Hayes, J. D.

    1972-01-01

    The feasibility of monitoring volatile contaminants in a large space simulation chamber using techniques of internal reflection spectroscopy was demonstrated analytically and experimentally. The infrared spectral region was selected as the operational spectral range in order to provide unique identification of the contaminants along with sufficient sensitivity to detect trace contaminant concentrations. It was determined theoretically that a monolayer of the contaminants could be detected and identified using optimized experimental procedures. This ability was verified experimentally. Procedures were developed to correct the attenuated total reflectance spectra for thick sample distortion. However, by using two different element designs the need for such correction can be avoided.

  3. Monitoring of (reactive) ion etching (RIE) with reflectance anisotropy spectroscopy (RAS) equipment

    NASA Astrophysics Data System (ADS)

    Barzen, Lars; Richter, Johannes; Fouckhardt, Henning; Wahl, Michael; Kopnarski, Michael

    2015-02-01

    Experimental results on the application of reflectance anisotropy spectroscopy (RAS) to the monitoring of (reactive) ion etching of monocrystalline semiconductor samples are described. To show the potential of this technique RAS signals collected during etching of GaAs/AlxGa1-xAs multilayer samples are compared to RAS data obtained before during molecular-beam epitaxial (MBE) growth of these very samples. A change of the RIE-RAS spectrum can be attributed to a change of material composition. And the current etch depth can be monitored with an accuracy at least down to several tens of nanometers - f. e. by recording the average reflected intensity.

  4. Combined use of hyperspectral VNIR reflectance spectroscopy and kriging to predict soil variables spatially

    Microsoft Academic Search

    A. Volkan Bilgili; Fevzi Akbas; Harold M. van Es

    2011-01-01

    Hyperspectral visible near infrared reflectance spectroscopy (VNIRRS) and geostatistical methods are considered for precision\\u000a soil mapping. This study evaluated whether VNIR or geostatistics, or their combined use, could provide efficient approaches\\u000a for assessing the soil spatially and associated reductions in sample size using soil samples from a 32 ha area (800 × 400 m)\\u000a in northern Turkey. Soil variables considered were CaCO3, organic matter,

  5. Fecal near-infrared reflectance spectroscopy calibrations for predicting diet quality and intake of donkeys

    E-print Network

    Kidane, Negusse Fessehaye

    2006-08-16

    .), Alemaya University of Agriculture, Ethiopia; M.Sc., University of Aberdeen, Scotland Chair of Advisory Committee: Dr. Jerry W. Stuth The objective of these studies was to develop near-infrared reflectance spectroscopy calibration equations from...-Jones 1994) of which more than 10% are donkeys. Over 95% of the donkeys are found in developing countries (Pritchard et al. 2005) and East Africa region (Eritrea, Ethiopia, Kenya, Tanzania and Uganda) alone accounts for more than 5.6 million donkeys...

  6. Potential of near-infrared reflectance spectroscopy and chemometrics to predict soil organic carbon fractions

    Microsoft Academic Search

    D. Cozzolino; A. Morón

    2006-01-01

    The potential of near-infrared reflectance spectroscopy (NIRS) to predict soil organic C in different particle-size fractions was evaluated. Soil samples (n=180) from various crop rotations in Uruguay were analysed by standard chemical and NIRS methods. Partial least squares (PLS) regression with cross validation was used to develop calibrations between reference data and NIRS spectra (n=87) and validated using an independent

  7. Prediction of indigestible cell wall fraction of grass silage by near infrared reflectance spectroscopy

    Microsoft Academic Search

    J. Nousiainen; S. Ahvenjärvi; M. Rinne; M. Hellämäki; P. Huhtanen

    2004-01-01

    Samples of grass silages harvested at different maturities of primary growth (n=27) and regrowth (n=25) of timothy-meadow fescue swards, and samples from commercial dairy farms (n=42) were used to explore the potential of near infrared reflectance spectroscopy (NIRS) in predicting indigestible neutral detergent fibre (INDF) and digestible neutral detergent fibre (DNDF) content. The silages were analysed for cell wall (neutral

  8. Feasibility of estimating peanut essential minerals by near infrared reflectance spectroscopy

    Microsoft Academic Search

    Kim-Yen Phan-Thien; Mirta Golic; Graeme C. Wright; N. Alice Lee

    2011-01-01

    The use of near infrared reflectance spectroscopy (NIRS) to evaluate the nutritional quality of peanut kernels has potential\\u000a applications in plant breeding as a rapid, non-destructive tool for seed\\/plant selection, and in quality control. We investigated\\u000a the feasibility of applying NIRS to the estimation of essential mineral composition in peanut kernels using two sample sets:\\u000a A, comprising 56 diverse genotypes

  9. The potential of diffuse reflectance spectroscopy for the determination of carbon inventories in soils

    Microsoft Academic Search

    J. Reeves; G. McCarty; T. Mimmo

    2002-01-01

    Investigations have shown that near- and mid-infrared reflectance spectroscopy can accurately determine organic-C in soil. Efforts have also demonstrated that both can differentiate between organic and inorganic-C in soils, but the mid-infrared produces more accurate calibrations. Nevertheless, the greatest benefit would come with in situ determinations where factors such as particle size, sample heterogeneity and moisture can be important. While

  10. Atmospheric absorption of terahertz radiation and water vapor continuum effects

    E-print Network

    Massachusetts at Lowell, University of

    Atmospheric absorption of terahertz radiation and water vapor continuum effects David M. Slocum a vapor Absorption Continuum Terahertz Spectroscopy a b s t r a c t The water vapor continuum absorption. The absorption coefficient as a function of frequency was determined and compared with theoretical predictions

  11. Titanium-silicon oxide film structures for polarization-modulated infrared reflection absorption spectroscopy

    PubMed Central

    Dunlop, Iain E.; Zorn, Stefan; Richter, Gunther; Srot, Vesna; Kelsch, Marion; van Aken, Peter A.; Skoda, Maximilian; Gerlach, Alexander; Spatz, Joachim P.; Schreiber, Frank

    2010-01-01

    We present a titanium-silicon oxide film structure that permits polarization modulated infrared reflection absorption spectroscopy on silicon oxide surfaces. The structure consists of a ~6 nm sputtered silicon oxide film on a ~200 nm sputtered titanium film. Characterization using conventional and scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy and X-ray reflectometry is presented. We demonstrate the use of this structure to investigate a selectively protein-resistant self-assembled monolayer (SAM) consisting of silane-anchored, biotin-terminated poly(ethylene glycol) (PEG). PEG-associated IR bands were observed. Measurements of protein-characteristic band intensities showed that this SAM adsorbed streptavidin whereas it repelled bovine serum albumin, as had been expected from its structure. PMID:20418963

  12. Prediction of erodibility in Oxisols using iron oxides, soil color and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Arantes Camargo, Livia; Marques, José, Jr.

    2015-04-01

    The prediction of erodibility using indirect methods such as diffuse reflectance spectroscopy could facilitate the characterization of the spatial variability in large areas and optimize implementation of conservation practices. The aim of this study was to evaluate the prediction of interrill erodibility (Ki) and rill erodibility (Kr) by means of iron oxides content and soil color using multiple linear regression and diffuse reflectance spectroscopy (DRS) using regression analysis by least squares partial (PLSR). The soils were collected from three geomorphic surfaces and analyzed for chemical, physical and mineralogical properties, plus scanned in the spectral range from the visible and infrared. Maps of spatial distribution of Ki and Kr were built with the values calculated by the calibrated models that obtained the best accuracy using geostatistics. Interrill-rill erodibility presented negative correlation with iron extracted by dithionite-citrate-bicarbonate, hematite, and chroma, confirming the influence of iron oxides in soil structural stability. Hematite and hue were the attributes that most contributed in calibration models by multiple linear regression for the prediction of Ki (R2 = 0.55) and Kr (R2 = 0.53). The diffuse reflectance spectroscopy via PLSR allowed to predict Interrill-rill erodibility with high accuracy (R2adj = 0.76, 0.81 respectively and RPD> 2.0) in the range of the visible spectrum (380-800 nm) and the characterization of the spatial variability of these attributes by geostatistics.

  13. Quantitative reflectance spectroscopy of buddingtonite from the Cuprite mining district, Nevada

    SciTech Connect

    Felzer, B.; Hauff, P.; Goetz, A.F.H. [Univ. of Colorado, Boulder, CO (United States)] [Univ. of Colorado, Boulder, CO (United States)

    1994-02-01

    Buddingtonite, an ammonium-bearing feldspar diagnostic of volcanic-hosted alteration, can be identified and, in some cases, quantitatively measured using short-wave infrared (SWIR) reflectance spectroscopy. In this study over 200 samples from Cuprite, Nevada, were evaluated by X ray diffraction, chemical analysis, scanning electron microscopy, and SWIR reflectance spectroscopy with the objective of developing a quantitative remote-sensing technique for rapid determination of the amount of ammonium or buddingtonite present, and its distribution across the site. Based upon the Hapke theory of radiative transfer from particulate surfaces, spectra from quantitative, physical mixtures were compared with computed mixture spectra. We hypothesized that the concentration of ammonium in each sample is related to the size and shape of the ammonium absorption bands and tested this hypothesis for samples of relatively pure buddingtonite. We found that the band depth of the 2.12-micron NH4 feature is linearly related to the NH4 concentration for the Cuprite buddingtonite, and that the relationship is approximately exponential for a larger range of NH4 concentrations. Associated minerals such as smectite and jarosite suppress the depth of the 2.12-micron NH4 absorption band. Quantitative reflectance spectroscopy is possible when the effects of these associated minerals are also considered.

  14. Ultra-broadband terahertz time-domain ellipsometric spectroscopy utilizing GaP and GaSe emitters and an epitaxial layer transferred photoconductive detector

    NASA Astrophysics Data System (ADS)

    Yamashita, Masatsugu; Takahashi, Hideki; Ouchi, Toshihiko; Otani, Chiko

    2014-02-01

    We present a reflection-type ultra-broadband terahertz (THz) time-domain spectroscopic ellipsometry system covering the frequency range of 0.5-30 THz. GaP (110) and z-cut GaSe crystals are used as emitters to generate the THz and mid-infrared pulses, respectively, and a photoconductive antenna switch using a low-temperature grown GaAs epitaxial layer transferred on Si substrate was used as a detector. By changing the emitter between the GaP and GaSe crystals, the measurable frequency range can be easily switched from the 0.5-7.8 THz range to the 7.8-30 THz range without additional optical alignment. We demonstrated the measurement of the dielectric function in a p-type InAs wafer and the optical conductivity of an indium tin oxide (ITO) thin film. The obtained carrier density and the mobility of the ITO thin film show good agreement with that obtained by the Hall measurement.

  15. Terahertz spectroscopic investigation of four kinds of vitamins

    NASA Astrophysics Data System (ADS)

    Zhao, Guozhong; Yu, Bin; Zhang, Cunlin

    2009-11-01

    The terahertz spectra of four kinds of vitamins are presented. The refractive index and absorption spectra of these vitamins are obtained by the terahertz time-domain spectroscopy. The full-geometry optimizations and frequency calculations using the density functional theory are applied to obtain the structure and vibration frequencies of these vitamin molecules. The calculated vibration frequencies are compared with the experimental data. The results show that there are terahertz fingerprint absorptions for all of four kinds of vitamins. The terahertz absorbance spectra of vitamins result from not only the intramolecular vibration modes, but also the intermolecular interaction or phonon modes.

  16. Terahertz Spectroscopy of Linear Triatomic CCC: High Precision Laboratory Measurement and Analysis of the Ro-Vibrational Bending Transitions

    NASA Astrophysics Data System (ADS)

    Gendriesch, Ralf; Pehl, Kai; Giesen, Thomas; Winnewisser, Gisbert; Lewen I., Frank

    2003-03-01

    We report concise measurements of the bending vibration transition (0,11,0) ? (0,00,0) near 63.416529(40) cm-1 of the carbon cluster CCC in the electronic ground state (X1?+g ). The ?2 vibration- rotation spectrum consists of P-, Q-, and R-branch transitions. A total of ten ro-vibrational transitions have been measured with the Cologne Sideband Spectrometer for Terahertz Applications, COSSTA. It is essentially a Backward Wave Oscillator (BWO) based, and frequency stabilized sideband spectrometer. The essential feature of COSSTA is the absolute frequency accuracy of the measurements. Absolute frequency calibration is better than 5 kHz at 2 THz, i. e. COSSTA reaches microwave accuracy. The band centre frequency was determined to be 1.901181506(162) THz: The derived molecular parameters are: (0,00,0) : B = 12908.242(142) MHz; D = 44.30(40) kHz; H = 4.068(184) Hz; (0,11,0) : B = 13262.946(109) MHz; D = 70.33(39) kHz; H = 7.71(38).

  17. Terahertz spectroscopy and solid-state density functional theory calculation of anthracene: Effect of dispersion force on the vibrational modes

    SciTech Connect

    Zhang, Feng; Tominaga, Keisuke, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-0013 (Japan)] [Molecular Photoscience Research Center, Kobe University, Nada, Kobe 657-0013 (Japan); Hayashi, Michitoshi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp; Wang, Houng-Wei [Center for Condensed Matter Sciences, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China)] [Center for Condensed Matter Sciences, National Taiwan University, 1 Roosevelt Rd., Sec. 4, Taipei 10617, Taiwan (China); Kambara, Ohki; Sasaki, Tetsuo [Research Institute of Electronics, Shizuoka University, 3-5-1 Jyohoku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan)] [Research Institute of Electronics, Shizuoka University, 3-5-1 Jyohoku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Nishizawa, Jun-ichi, E-mail: atmyh@ntu.edu.tw, E-mail: tominaga@kobe-u.ca.jp, E-mail: junichi.nishizawa@hanken.jp [Jun-ichi Nishizawa Memorial Research Center, Tohoku University, 519-1176 Aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)] [Jun-ichi Nishizawa Memorial Research Center, Tohoku University, 519-1176 Aoba, Aramaki, Aoba-ku, Sendai 980-0845 (Japan)

    2014-05-07

    The phonon modes of molecular crystals in the terahertz frequency region often feature delicately coupled inter- and intra-molecular vibrations. Recent advances in density functional theory such as DFT-D{sup *} have enabled accurate frequency calculation. However, the nature of normal modes has not been quantitatively discussed against experimental criteria such as isotope shift (IS) and correlation field splitting (CFS). Here, we report an analytical mode-decoupling method that allows for the decomposition of a normal mode of interest into intermolecular translation, libration, and intramolecular vibrational motions. We show an application of this method using the crystalline anthracene system as an example. The relationship between the experimentally obtained IS and the IS obtained by PBE-D{sup *} simulation indicates that two distinctive regions exist. Region I is associated with a pure intermolecular translation, whereas region II features coupled intramolecular vibrations that are further coupled by a weak intermolecular translation. We find that the PBE-D{sup *} data show excellent agreement with the experimental data in terms of IS and CFS in region II; however, PBE-D{sup *} produces significant deviations in IS in region I where strong coupling between inter- and intra-molecular vibrations contributes to normal modes. The result of this analysis is expected to facilitate future improvement of DFT-D{sup *}.

  18. Characterization of material degradation in ceramic matrix composites using infrared reflectance spectroscopy

    SciTech Connect

    Cooney, Adam T.; Flattum-Riemers, Richard Y. [Air Force Research Laboratory, Materials and Manufacturing Directorate, NonDestructive Evaluation Branch, Wright-Patterson AFB, OH (United States); Scott, Benjamin J. [Universal Technology Corporation, Dayton, OH (United States)

    2011-06-23

    Ceramic matrix composite materials for thermal protection systems are required to maintain operational performance in extreme thermal and mechanical environments. In-service inspection of materials capable of assessing the degree and extent of damage and degradation will be required to ensure the safety and readiness of future air vehicles. Infrared reflectance spectroscopy is an established material characterization technique capable of extracting information regarding the chemical composition of substances. The viability of this technique as a potentially powerful nondestructive evaluation method capable of monitoring degradation in thermal protection system materials subjected to extreme mechanical and thermal environments is analyzed. Several oxide-based and non-oxide-based ceramic matrix composite materials were stressed to failure in a high temperature environment and subsequently measured using infrared reflectance spectroscopy. Spectral signatures at locations along the length of the samples were compared resulting in distinct and monotonic reflectance peak changes while approaching the fracture point. The chemical significance of the observed signatures and the feasibility of infrared reflectance nondestructive evaluation techniques are discussed.

  19. Measurement of low loss and mirrors' reflectivity using cavity ring down spectroscopy with high accuracy

    NASA Astrophysics Data System (ADS)

    Yang, Dexing; Jiang, Yajun; Zhao, Jianlin; Di, Nan

    2006-02-01

    Differential laser gyro is an ideal equipment to solve the "lock-in" behavior. The ring cavity must be low loss and the reflectivity of mirrors in gyro must be more than 99.99%. But the insertion of a piece of quartz glass and a Faraday cell in the cavity will broaden the "lock-in" area due to additional loss, so it is very important to measure ultra-high reflectivity of mirrors and the loss of transparent glass plate used in gyro. 632.8nm He-Ne laser is the most suitable light to travel around the ring cavity in gyro, so the traditional cavity ring down spectroscopy (CRDS) must be improved by using continuous-wave (CW) He-Ne laser instead of pulsed one. The results show that the single-pass loss through the glass plate can be kept below 3.0×10 -11cm -1. Using combination of linear and folded cavity ring down spectroscopy, the loss such as absorption of gas in the cavity are counteracted due to the equalized length of cavity, so the reflectivity of the mirrors is measured with high accuracy. The ring down time of the cavity with and without a sample is obtained respectively, and then the total loss of the measured sample is calculated. The results show that the improved CRDS is suitable for accurately measuring low loss of medium and reflectivity of mirrors.

  20. Determination of Cellulose Fiber Structure Using IR Reflectance Spectroscopy of Paper

    NASA Astrophysics Data System (ADS)

    Derkacheva, O. Yu.

    2015-01-01

    A rapid and non-destructive method for analyzing the structure of cellulose fibers using IR reflectance spectroscopy from a paper surface was developed and verified for correctness. IR absorption and reflectance spectra of standard paper samples of known composition (sheets made of four fibers of different origin without additives and with additives of kaolin and chalk) were analyzed. Good correlations between these two spectral methods were found for the studied samples. Calibration curves were useful for assessing the structure of cellulose samples from XVIth century historical paper. Data on the degree of cellulose ordering that were obtained from the paper reflectance spectra indicated that the studied sheets consisted mainly of flax fibers with added cotton. This agreed fully with the historical fact that the studied samples were rag papers.

  1. Particular features of the application of IR reflection spectroscopy methods in studies in archeology and paleontology

    NASA Astrophysics Data System (ADS)

    Zolotarev, V. M.; Khlopachev, G. A.

    2013-06-01

    We have considered an optical model of a porous rough surface with optical properties of objects (bone, flint) that are typical of archeology and paleontology. We have formulated an approach that makes it possible to perform mathematical processing of the IR reflection spectra of objects of this kind using standard algorithms and determine criteria that ensure obtaining reliable information on objects with a rough surface in the course of interpretation of frequencies in their IR reflection spectra. The potential of the approach has been demonstrated using as an example an investigation by the IR Fourier-transform reflection spectroscopy of mineralization processes of mammoth tusks from two paleolithic sites (14000 and 16000 BCE) located by the town of Yudinovo, Bryansk oblast, Russia.

  2. Terahertz and far-infrared synchrotron spectroscopy and global modeling of methyl mercaptan, CH3(32)SH.

    PubMed

    Xu, Li-Hong; Lees, R M; Crabbe, G T; Myshrall, J A; Müller, H S P; Endres, C P; Baum, O; Lewen, F; Schlemmer, S; Menten, K M; Billinghurst, B E

    2012-09-14

    In this work, terahertz and Fourier transform far-infrared (FTFIR) synchrotron spectra of methyl mercaptan, CH(3)SH, have been investigated in order to provide new laboratory information for enhanced observations of this species in interstellar molecular clouds and star-forming regions. Like its methanol cousin, methyl mercaptan has particularly rich spectra associated with its large-amplitude internal rotation that extend throughout the THz and FIR regions. We have recorded new spectra for CH(3)SH from 1.1-1.5 and 1.790-1.808 THz at the University of Cologne as well as high-resolution FTFIR synchrotron spectra from 50-550 cm(-1) at 0.001 cm(-1) resolution on the far-IR beam-line at the Canadian Light Source. Assignments are reported for rotational quantum numbers up to J ? 40 and K ? 15, and torsional states up to v(t) = 2 for the THz measurements and v(t) = 3 for the FTFIR observations. The THz and FTFIR measurements together with literature results have been combined in a global analysis of a dataset comprising a total of 1725 microwave and THz frequencies together with ~18000 FTFIR transitions, ranging up to v(t) = 2 and J(max) = 30 for MW?THz and 40 for FTFIR. The global fit employs 78 torsion-rotation parameters and has achieved a weighted standard deviation of ~1.1. A prediction list (v(t) ? 2, J ? 45 and K ? 20) has been generated from the model giving essentially complete coverage of observable CH(3)(32)SH transitions within the bandwidths of major new astronomical facilities such as HIFI (Heterodyne Instrument for the Far Infrared) on the Herschel Space Observatory, ALMA (Atacama Large Millimeter Array), SOFIA (Stratospheric Observatory For Infrared Astronomy) and APEX (Atacama Pathfinder Experiment) to close to spectroscopic accuracy. PMID:22979865

  3. Polarization Modulation Infrared Reflection Absorption Spectroscopy at Elevated Pressures: CO Adsorption on Pd(111) at Atmospheric Pressures

    E-print Network

    Goodman, Wayne

    Adsorption on Pd(111) at Atmospheric Pressures Emrah Ozensoy, Douglas C. Meier, and D. Wayne Goodman systems at or near the pressures of technical catalysts, that is, ambient (atmospheric) pressures. PMPolarization Modulation Infrared Reflection Absorption Spectroscopy at Elevated Pressures: CO

  4. Terahertz analysis of an East Asian historical mural painting

    NASA Astrophysics Data System (ADS)

    Fukunaga, K.; Hosako, I.; Kohdzuma, Y.; Koezuka, T.; Kim, M.-J.; Ikari, T.; Du, X.

    2010-05-01

    Terahertz (THz) spectroscopy and THz and imaging techniques are expected to have great potential for the non-invasive analysis of artworks. We have applied THz imaging to analyse the historic mural painting of a Lamaism temple by using a transportable time-domain THz imaging system; such an attempt is the first in the world. The reflection image revealed that there are two orange colours in the painting, although they appear the same to the naked eye. THz imaging can also estimate the depth of cracks. The colours were examined by X-ray fluorescence and Raman spectroscopy, and the results were found to be in good agreement. This work proved that THz imaging can contribute to the non-invasive analysis of cultural heritage.

  5. Single nanowire photoconductive terahertz detectors.

    PubMed

    Peng, Kun; Parkinson, Patrick; Fu, Lan; Gao, Qiang; Jiang, Nian; Guo, Ya-Nan; Wang, Fan; Joyce, Hannah J; Boland, Jessica L; Tan, Hark Hoe; Jagadish, Chennupati; Johnston, Michael B

    2015-01-14

    Spectroscopy and imaging in the terahertz (THz) region of the electromagnetic spectrum has proven to provide important insights in fields as diverse as chemical analysis, materials characterization, security screening, and nondestructive testing. However, compact optoelectronics suited to the most powerful terahertz technique, time-domain spectroscopy, are lacking. Here, we implement single GaAs nanowires as microscopic coherent THz sensors and for the first time incorporated them into the pulsed time-domain technique. We also demonstrate the functionality of the single nanowire THz detector as a spectrometer by using it to measure the transmission spectrum of a 290 GHz low pass filter. Thus, nanowires are shown to be well suited for THz device applications and hold particular promise as near-field THz sensors. PMID:25490548

  6. Dual-band bandpass terahertz wave filter based on microstrip resonant structure

    NASA Astrophysics Data System (ADS)

    Liu, Yu-hang; Li, Jiu-sheng

    2012-03-01

    The terahertz (THz) band, which refers to the spectral region between 0.1 and 10THz, covers the fingerprints of many chemical and biological materials. Within the past few years, there are increasing demands for experiments in terahertz frequencies, in different areas such as biotechnology, nanotechnology, space science, security, chemical and biological sensing, terahertz wave communications, and medical diagnostics. For potential applications, the functional devices, such as beam polarizers, switchs and filters, are crucial components for a terahertz system. Terahertz wave filter based on two kinds of microstrip resonant structures, has been characterized by terahertz time-domain spectroscopy in the region from 0.1 to 3THz. The experimental results for the frequency dependence of the transmittance of the terahertz wave filter show that the terahertz wave transmittance peak is of 79.5% at 0.5THz and 82.5% at 0.81THz.

  7. Dual-band bandpass terahertz wave filter based on microstrip resonant structure

    NASA Astrophysics Data System (ADS)

    Liu, Yu-hang; Li, Jiu-sheng

    2011-11-01

    The terahertz (THz) band, which refers to the spectral region between 0.1 and 10THz, covers the fingerprints of many chemical and biological materials. Within the past few years, there are increasing demands for experiments in terahertz frequencies, in different areas such as biotechnology, nanotechnology, space science, security, chemical and biological sensing, terahertz wave communications, and medical diagnostics. For potential applications, the functional devices, such as beam polarizers, switchs and filters, are crucial components for a terahertz system. Terahertz wave filter based on two kinds of microstrip resonant structures, has been characterized by terahertz time-domain spectroscopy in the region from 0.1 to 3THz. The experimental results for the frequency dependence of the transmittance of the terahertz wave filter show that the terahertz wave transmittance peak is of 79.5% at 0.5THz and 82.5% at 0.81THz.

  8. Method for rapid multidiameter single-fiber reflectance and fluorescence spectroscopy through a fiber bundle.

    PubMed

    Hoy, Christopher L; Gamm, Ute A; Sterenborg, Henricus J C M; Robinson, Dominic J; Amelink, Arjen

    2013-10-01

    We have recently demonstrated a means for quantifying the absorption and scattering properties of biological tissue through multidiameter single-fiber reflectance (MDSFR) spectroscopy. These measurements can be used to correct single-fiber fluorescence (SFF) spectra for the influence of optical properties, enabling quantification of intrinsic fluorescence. In our previous work, we have used a series of pinholes to show that selective illumination and light collection using a coherent fiber bundle can simulate a single solid-core optical fiber with variable diameter for the purposes of MDSFR spectroscopy. Here, we describe the construction and validation of a clinical MDSFR/SFF spectroscopy system that avoids the limitations encountered with pinholes and free-space optics. During one measurement, the new system acquires reflectance spectra at the effective diameters of 200, 600, and 1000 ?m, and a fluorescence spectrum at an effective diameter of 1000 ?m. From these spectra, we measure the absolute absorption coefficient, ?(a), reduced scattering coefficient, ?'(s'), phase function parameter, ?, and intrinsic fluorescence, Q?(a,x)(f), across the measured spectrum. We validate the system using Intralipid- and polystyrene sphere-based scattering phantoms, with and without the addition of the absorber Evans Blue. Finally, we demonstrate the combined MDSFR/SFF of phantoms with varying concentrations of Intralipid and fluorescein, wherein the scattering properties are measured by MDSFR and used to correct the SFF spectrum for accurate quantification of Q?(a,x)(f). PMID:24126725

  9. Broadband reflectance spectroscopy for establishing a quantitative metric of vascular leak using the Miles assay

    NASA Astrophysics Data System (ADS)

    McMurdy, John; Reichner, Jonathan; Mathews, Zara; Markey, Mary; Intwala, Sunny; Crawford, Gregory

    2009-09-01

    Monitoring the physiological effects of biological mediators on vascular permeability is important for identifying potential targets for antivascular leak therapy. This therapy is relevant to treatments for pulmonary edema and other disorders. Current methods of quantifying vascular leak are in vitro and do not allow repeated measurement of the same animal. Using an in vivo diffuse reflectance optical method allows pharmacokinetic analysis of candidate antileak molecules. Here, vascular leak is assessed in mice and rats by using the Miles assay and introducing irritation both topically using mustard oil and intradermally using vascular endothelial growth factor (VEGF). The severity of the leak is assessed using broadband diffuse reflectance spectroscopy with a fiber reflectance probe. Postprocessing techniques are applied to extract an artificial quantitative metric of leak from reflectance spectra at vascular leak sites on the skin of the animal. This leak metric is calculated with respect to elapsed time from irritation in both mustard oil and VEGF treatments on mice and VEGF treatments on rats, showing a repeatable increase in leak metric with leak severity. Furthermore, effects of pressure on the leak metric are observed to have minimal effect on the reflectance spectra, while spatial positioning showed spatially nonuniform leak sites.

  10. Remote identification of the invasive tunicate Didemnum vexillum using reflectance spectroscopy.

    PubMed

    Leeuw, Thomas; Newburg, Seth O; Boss, Emmanuel S; Slade, Wayne H; Soroka, Michael G; Pederson, Judith; Chryssostomidis, Chryssostomos; Hover, Franz S

    2013-03-10

    Benthic coverage of the invasive tunicate Didemnum vexillum on Georges Bank is largely unknown. Monitoring of D. vexillum coverage is vital to understanding the impact this invasive species will have on the productive fishing grounds of Georges Bank. Here we investigate using reflectance spectroscopy as a method for remote identification of D. vexillum. Using two different systems, a NightSea Dive-Spec and a combination of LED light sources with a hyperspectral radiometer, we collected in-situ measurements of reflectance from D. vexillum colonies. In comparison to reflectance spectra of other common benthic substrates, D. vexillum appears to have a unique spectral signature between 500 and 600 nm. Measuring the slope of the spectrum between these wavelengths appears to be the most robust method for spectral identification. Using derivative analysis or principal component analysis, the reflectance spectra of D. vexillum can be identified among numerous other spectra of common benthic substrates. An optical system consisting of a radiometer, light source, and camera was deployed on a remotely operated vehicle to test the feasibility of using reflectance to assess D. vexillum coverage. Preliminary results, analyzed here, prove the method to be successful for the areas we surveyed and open the way for its use on large-scale surveys. PMID:23478782

  11. Working Process Development For Weathering Degree Mapping Of Stone Monument Using Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hyun, C.; Park, H.

    2008-12-01

    Most stone monuments have been weathered on the field with exposure of rain and wind during hundreds or thousands years. Reflectance spectroscopy can be applied to assess weathering degree of those stone monuments composed of granite which is the most general material of stone monument in Korea. Weathering degree was analyzed by using reflected and transmitted electromagnetic energy based on the theory of reflectance spectroscopy on the surface of rock to identify rock forming minerals using their diagnostic spectral absorption features. This method could be used as an improved nondestructive assessment method compared with conventional subjective and qualitative assessment methods. We tested feasibility of this technique for actual granite stone monuments. Granite is generally composed of quartz, feldspars and micas. Feldspars are changed to clay minerals such as kaolinite and illite after weathering process. Biotite of mica produce iron oxides which induce color changes on surface of rocks. The experiments were conducted using field spectrometer FieldSpec®3 of ASD Inc. and the range of measurement was form 350µm to 2500µm wavelength. Spectral reflectance of weathering products at each measuring point was processed by removing delineated convex hull from raw reflectance curves to exclude background effects and to extract quantitative absorption depths which indicate relative distribution degree of weathering products. We produced deterioration map on the surface of the monument by interpolating absorption depth values of each point with consideration of spatial distribution of measurements. For facilitation of practical uses a chain of working process of this method was designed using whole experimental processes.

  12. In vivo characterization of myocardial infarction using fluorescence and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Ti, Yalin; Chen, Poching; Lin, Wei-Chiang

    2010-05-01

    We explore the feasibility of using combined fluorescence and diffuse reflectance spectroscopy to characterize a myocardial infarct at different developing stages. An animal study is conducted using rats with surgically induced myocaridal infarction (MI). In vivo fluorescence spectra at 337-nm excitation and diffuse reflectance between 400 and 900 nm are measured from the heart. Spectral acquisition is performed: 1. for normal heart tissue; 2. for the area immediately surrounding the infarct; and 3. for the infarcted tissue itself, one, two, three, and four weeks into MI development. Histological and statistical analyses are used to identify unique pathohistological features and spectral alterations associated with the investigated regions. The main alterations (p<0.05) in diffuse reflectance spectra are identified primarily between 450 and 600 nm. The dominant fluorescence alterations are increases in peak fluorescence intensity at 400 and 460 nm. The extent of these spectral alterations is related to the duration of the infarction. The findings of this study support the concept that optical spectroscopy could be useful as a tool to noninvasively determine the in vivo pathophysiological features of a myocardial infarct and its surrounding tissue, thereby providing real-time feedback to surgeons during various surgical interventions for MI.

  13. High-Throughput Near-Infrared Reflectance Spectroscopy for Predicting Quantitative and Qualitative Composition Phenotypes of Individual Maize Kernels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near-infrared reflectance (NIR) spectroscopy can be used for fast and reliable prediction of organic compounds in complex biological samples. We used a recently developed NIR spectroscopy instrument to predict starch, protein, oil, and weight of individual maize (Zea mays) seeds. The starch, prote...

  14. Terahertz and Far-Infrared Spectroscopy of High-J Transitions of the Ground and v_2 = 1 States of NH_3

    NASA Astrophysics Data System (ADS)

    Pirali, O.; Martin, M.-A.; Vervloet, M.; Balcon, D.; Yu, S.; Pearson, J.; Drouin, B.; Endres, C. P.; Shiraishi, T.; Kobayashi, K.; Matsushima, F.

    2010-06-01

    Since its first detection in 1968, ammonia was discovered as a major constituent of several planetary atmospheres. More recently, ammonia has been suggested in the atmosphere of cool brown Dwarf and is expected to be present in quantity in the atmospheres of many newly discovered exoplanets and brown dwarf stars where temperatures are in the order of 1000 K For such temperatures, spectroscopic knowledge of ammonia's IR spectrum needs to be improved both in term of line positions and intensities. Even for the two lowest vibrational levels (ground state and v_2 = 1) its large amplitude inversion motion complicates the spectral modelling and the experimental dataset have been (up to now) limited to low quantum numbers (J of about 20). We associated experimental results obtained from far infrared techniques and terahertz spectroscopy to obtain accurate energies for highly excited J levels (as high as J=35) in the ground state and v_2 = 1. This work significantly increases the experimental dataset available to support astronomical observations; we will present the techniques developed in this work as well as the spectral analysis and fit of the new dataset. P. Delorme, X. Delfosse, L. Albert, et al., Astronomy and Astrophysics, 482, 961 (2008) M.J. Burgdorf, G.S. Orton, T. Encrenaz, G.R. Davis, S.D. Sidher, E. Lellouch, B.M. Swinyard, Planetary and Space Science, 52, 379 (2004). O. Pirali and M. Vervloet, Chemical Physics Letters, 423, 376--381 (2006) F. Matsushima, H. Odashima, D. Wang, S. Tsunekawa, and K. Takagi, Jpn. J. Appl. Phys. 33, 315 (1994) B.J. Drouin, F.W. Maiwald, and J.C. Pearson, Rev. Sci. Instrum., 76, 093113 (2005)

  15. Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

    SciTech Connect

    Lastras-Martínez, A., E-mail: alm@cactus.iico.uaslp.mx, E-mail: alastras@gmail.com; Ortega-Gallegos, J.; Guevara-Macías, L. E.; Nuñez-Olvera, O.; Balderas-Navarro, R. E.; Lastras-Martínez, L. F. [Instituto de Investigación en Comunicación Optica, Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, San Luis Potosí, SLP 78000 (Mexico); Lastras-Montaño, L. A. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Lastras-Montaño, M. A. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California 93106 (United States)

    2014-03-01

    We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

  16. Terahertz spectroscopic investigations of leather in terahertz wave range

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2011-11-01

    Pulsed THz time-domain spectroscopy is a coherent technique, in which both the amplitude and the phase of a THz pulse are measured. Recently, material characterization using THz spectroscopy has been applied to biochemicals, pharmaceuticals, polymers and semiconductors and has given us important information. Moreover, THz imaging has progressed and is expected to be applicable for the identification of narcotics and explosives. The most important and characteristic point of THz spectroscopy is said to be its ability to observe intermolecular vibrations in contrast to infrared spectroscopy (IR), which observes intramolecular vibrations. Coherent detection enables direct calculations of both the imaginary and the real parts of the refractive index without using the Kramers-Kronig relations. Terahertz wave spectroscopy has been used to study the properties and absorption spectra characteristic of materials. In this paper, the spectral characteristics of cow skin, pig skin sheep skin, horse skin and deer skin have been measured with terahertz time-domain spectroscopy in the range of 0.1~2.0THz. The results show that THz-TDS technology provides an important tool for quality analysis and detection of leathers.

  17. Terahertz spectroscopic investigations of leather in terahertz wave range

    NASA Astrophysics Data System (ADS)

    Song, Mei-jing; Li, Jiu-sheng

    2012-03-01

    Pulsed THz time-domain spectroscopy is a coherent technique, in which both the amplitude and the phase of a THz pulse are measured. Recently, material characterization using THz spectroscopy has been applied to biochemicals, pharmaceuticals, polymers and semiconductors and has given us important information. Moreover, THz imaging has progressed and is expected to be applicable for the identification of narcotics and explosives. The most important and characteristic point of THz spectroscopy is said to be its ability to observe intermolecular vibrations in contrast to infrared spectroscopy (IR), which observes intramolecular vibrations. Coherent detection enables direct calculations of both the imaginary and the real parts of the refractive index without using the Kramers-Kronig relations. Terahertz wave spectroscopy has been used to study the properties and absorption spectra characteristic of materials. In this paper, the spectral characteristics of cow skin, pig skin sheep skin, horse skin and deer skin have been measured with terahertz time-domain spectroscopy in the range of 0.1~2.0THz. The results show that THz-TDS technology provides an important tool for quality analysis and detection of leathers.

  18. Hygrothermal degradation of 3-glycidoxypropyltrimethoxysilane films studied by neutron and X-ray reflectivity and attenuated total reflection infrared spectroscopy.

    SciTech Connect

    Tallant, David Robert; Garcia, Manuel Joseph; Majewski, Jaroslaw (Los Alamos National Lab, Los Alamos, NM); Kent, Michael Stuart; Yim, Hyun

    2005-05-01

    Thin films of organosilanes have great technological importance in the areas of adhesion promotion, durability, and corrosion resistance. However, it is well-known that water can degrade organosilane films, particularly at elevated temperatures. In this work, X-ray and neutron reflectivity (XR and NR) were combined with attenuated total reflection infrared (ATR-IR) spectroscopy to study the chemical and structural changes within thin films of (3-glycidoxypropyl)trimethoxysilane (GPS) after exposure for various periods of time to air saturated with either D{sub 2}O or H{sub 2}O at 80 C. For NR and XR, ultrathin ({approx}100 {angstrom}) films were prepared by spin-coating. Both D{sub 2}O and H{sub 2}O provide neutron scattering contrast with GPS. Variations in the neutron scattering length density (SLD) profiles (a function of mass density and atomic composition) with conditioning time were measured after drying the samples out and also swelled with H{sub 2}O or D{sub 2}O vapor at room temperature. For samples that were dried out prior to measurement, little or no change was observed for H{sub 2}O conditioning up to 3.5 days, but large changes were observed after 30 days of conditioning. The range of conditioning time for this structural change was narrowed to between 4 and 10 days with XR. The SLD profiles indicated that the top portion of the GPS film was transformed into a thick low-density layer after conditioning, but the bottom portion showed little structural change. A previous NR study of as-prepared GPS films involving swelling with deuterated nitrobenzene showed that the central portion of the film has much lower cross-link density than the region nearest the substrate. The present data show that the central portion also swells to a much greater extent with water and hydrolyzes more rapidly. The chemical degradation mechanism was identified by IR as hydrolysis of siloxane bonds. For ATR-IR, GPS films were prepared by dip-coating, which resulted in a greater and more variable thickness than for the spin-coated samples. The IR spectra revealed an increase in vicinal silanol generation over the first 3 days of conditioning followed by geminal silanol generation. Thus, the structural change detected by NR and XR roughly coincided with the onset of geminal silanol generation. Finally, little change in the reflectivity data was observed for films conditioned with D{sub 2}O at 80 C for 1 month. This indicates that hydrolysis of Si-O-Si is much slower with D{sub 2}O than with H{sub 2}O.

  19. Negative Probability Sampling in Study of Reflection Surface Electron Spectroscopy Spectrum

    E-print Network

    Da, Bo; Ding, ZheJun

    2015-01-01

    We propose a sampling method to include the negative contribution to probability density distribution in a sampling procedure. This sampling method is a universal solution for all negative probability problem and shows extraordinarily power in negative cross section problem. A Monte Carlo simulation including negative cross section contribution is developed and successfully preformed to simulate reflection electron energy loss spectroscopy (REELS) spectra for Ag and Au as examples. Excellent agreement is found between simulated spectra and experimental measurements. Notably improved fits to experimental REELS spectra in low energy loss range illustrate the method's strength as well as the necessity of negative cross section contribution.

  20. Prediction of leaf chemistry by the use of visible and near infrared reflectance spectroscopy

    NASA Technical Reports Server (NTRS)

    Card, Don H.; Peterson, David L.; Matson, Pamela A.; Aber, John D.

    1988-01-01

    The chemical content of dry, ground leaf material sampled from deciduous and conifer tree species from sites in Alaska, Wisconsin, and California was estimated using visible and shortwave IR spectroscopy. Seven chemical components - sugar, starch, protein, cellulose, total chlorophyll, lignin, and total nitrogen - were analyzed by wet chemical methods and their concentrations regressed against log 1/rho and first and second differences of log 1/rho (where rho is measured reflectance) at wavelengths selected by stepwise regression. Predictions of chemical concentrations based on cross validation suggest that this technique may be useful for extracting vegetation canopy biochemical information by remote sensing.

  1. Attenuated total reflectance spectroscopy of simultaneous processes: Corrosion inhibition of cuprous oxide by benzotriazole

    NASA Astrophysics Data System (ADS)

    Bratescu, Maria Antoaneta; Allred, Daniel B.; Saito, Nagahiro; Sarikaya, Mehmet; Takai, Osamu

    2008-03-01

    Attenuated total reflectance (ATR) spectroscopy was used to perform in situ studies of the corrosion inhibition of cuprous oxide (Cu 2O) by benzotriazole (BTA) in aqueous solution at concentrations from 1 to 20 ?M. Because two separate processes occur simultaneously, that of Cu 2O corrosion and corrosion inhibition by BTA adsorption, the spectral information was subjected to deconvolution by a conjugate gradient minimization algorithm. Under these conditions, a solution phase concentration of 7-10 ?M BTA nearly completely inhibited the corrosion of Cu 2O in deionized water. Using a Langmuir adsorption model, this represented only 25% of the maximally covered surface area.

  2. Micromachined silicon attenuated total reflectance infrared spectroscopy: an emerging detection method in micro/nanofluidics.

    PubMed

    Karabudak, Engin

    2014-02-01

    Microfluidics is an emerging field with various applications. In situ analysis of liquids inside microfluidic channels is an important research subject for any of these applications. On the other hand, attenuated total reflectance infrared spectroscopy (ATR-IR) is a strong surface detection method. Recently, there have been various attempts to use ATR-IR for detection of liquids inside microfluidic channels. Micromachined silicon ATR-IR (?Si-ATR-IR) is an emerging analytical tool for micro/nanofluidics. This paper reviews ?Si-ATR-IR micro/nanofluidics detection devices and discusses the application fields, capabilities, advantages, and disadvantages of the method. PMID:24151006

  3. Remote diffuse reflectance spectroscopy sensor for tissue engineering monitoring based on blind signal separation

    PubMed Central

    Martín-Mateos, Pedro; Crespo-Garcia, Sergio; Ruiz-Llata, Marta; Lopez-Fernandez, José Ramón; Jorcano, José Luis; Del Rio, Marcela; Larcher, Fernando; Acedo, Pablo

    2014-01-01

    In this study the first results on evaluation and assessment of grafted bioengineered skin substitutes using an optical Diffuse Reflectance Spectroscopy (DRS) system with a remote optical probe are shown. The proposed system is able to detect early vascularization of skin substitutes expressing the Vascular Endothelial Growth Factor (VEGF) protein compared to normal grafts, even though devitalized skin is used to protect the grafts. Given the particularities of the biological problem, data analysis is performed using two Blind Signal Separation (BSS) methods: Principal Component Analysis (PCA) and Independent Component Analysis (ICA). These preliminary results are the first step towards point-of-care diagnostics for skin implants early assessment. PMID:25401034

  4. Diffuse reflectance spectroscopy with a self-calibrating fiber optic probe

    PubMed Central

    Yu, Bing; Fu, Henry; Bydlon, Torre; Bender, Janelle E.; Ramanujam, Nirmala

    2009-01-01

    Calibration of the diffuse reflectance spectrum for instrument response and time-dependent fluctuation as well as interdevice variations is complicated, time consuming, and potentially inaccurate. We describe a novel fiber optic probe with a real-time self-calibration capability that can be used for tissue optical spectroscopy. The probe was tested in a number of liquid phantoms over a relevant range of tissue optical properties. Absorption and scattering coefficients are extracted with an average absolute error and standard deviation of 6.9% ± 7.2% and 3.5% ± 1.5%, respectively. PMID:18709086

  5. Classification of the waxy condition of durum wheat by near infrared reflectance spectroscopy using wavelets and a genetic algorithm

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Near infrared (NIR) reflectance spectroscopy has been applied to the problem of differentiating four genotypes of durum wheat: ‘waxy’, wx-A1 null, wx-B1 null and wild type. The test data consisted of 95 NIR reflectance spectra of wheat samples obtained from a USDA-ARS wheat breeding program. A two...

  6. Mössbauer spectroscopy, magnetic characteristics, and reflection loss analysis of nickel-strontium substituted cobalt ferrite nanoparticles

    SciTech Connect

    Ghasemi, Ali, E-mail: ali13912001@yahoo.com [Materials Engineering Department, Malek Ashtar University of Technology, Shahin Shahr (Iran, Islamic Republic of); Paesano, Andrea; Cerqueira Machado, Carla Fabiana [Departamento de Física, Centro de Ciências Exatas, Universidade Estadual de Maringá, Maringá (Brazil); Shirsath, Sagar E. [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad (India); Spin Device Technology Center, Faculty of Engineering, Shinshu University, Nagano (Japan); Liu, Xiaoxi; Morisako, Akimitsu [Spin Device Technology Center, Faculty of Engineering, Shinshu University, Nagano (Japan)

    2014-05-07

    In current research work, Co{sub 1-x}Ni{sub x/2}Sr{sub x/2}Fe{sub 2}O{sub 4} (x?=?0–1 in a step of 0.2) ferrite nanoparticles were synthesized by a sol-gel method. According to the evolution in the subspectral areas obtained from Mössbauer spectroscopy, it was found that the relaxing iron belongs mostly to the site B, since the Mössbauer fraction of site A does not vary appreciably. With an increase in Ni-Sr substitution contents in cobalt ferrite, the coercivity and saturation of magnetization decrease. Variation of reflection loss versus frequency in microwave X-band demonstrates that the reflection peak shifts to lower frequency by adding substituted cations and the synthesized nanoparticles can be considered for application in electromagnetic wave absorber technology.

  7. Mössbauer spectroscopy, magnetic characteristics, and reflection loss analysis of nickel-strontium substituted cobalt ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Ghasemi, Ali; Paesano, Andrea; Cerqueira Machado, Carla Fabiana; Shirsath, Sagar E.; Liu, Xiaoxi; Morisako, Akimitsu

    2014-05-01

    In current research work, Co1-xNix/2Srx/2Fe2O4 (x = 0-1 in a step of 0.2) ferrite nanoparticles were synthesized by a sol-gel method. According to the evolution in the subspectral areas obtained from Mössbauer spectroscopy, it was found that the relaxing iron belongs mostly to the site B, since the Mössbauer fraction of site A does not vary appreciably. With an increase in Ni-Sr substitution contents in cobalt ferrite, the coercivity and saturation of magnetization decrease. Variation of reflection loss versus frequency in microwave X-band demonstrates that the reflection peak shifts to lower frequency by adding substituted cations and the synthesized nanoparticles can be considered for application in electromagnetic wave absorber technology.

  8. [Detection of erucic acid and glucosinolate in intact rapeseed by near-infrared diffuse reflectance spectroscopy].

    PubMed

    Riu, Yu-kui; Huang, Kun-lun; Wang, Wei-min; Guo, Jing; Jin, Yin-hua; Luo, Yun-bo

    2006-12-01

    With the rapid development of transgenic food, more and more transgenic food has been pouring into the market, raising great concern about transgenic food' s edible safety. To analyze the content of erucic acid and glucosinolate in transgenic rapeseed and its parents, all the seeds were scanned intact by continuous wave of near infrared diffuse reflectance spectrometry ranging from 12 000 to 4 000 cm(-1) with a resolution of 4 cm(-1) and 64 times of scanning. Bruker OPUS software package was applied for quantification, while the results were compared with the standard methods. The results showed that the method of NIRS was very precise, which proved that infrared diffuse reflectance spectroscopy can be applied to detect the toxins in transgenic food. On the other hand, the results also showed that the content of erucic acid in transgenic rapeseeds is 0. 5-1. 0 times PMID:17361706

  9. Spectral interference of terahertz pulses from two laser filaments in air

    NASA Astrophysics Data System (ADS)

    Chen, Yanping; Zhang, Zhelin; Zhang, Zhen; Yuan, Xiaohui; Liu, Feng; Chen, Min; Xu, Jianqiu; Yu, Jin; Sheng, Zhengming; Zhang, Jie

    2015-06-01

    Spectral interference is experimentally demonstrated by two terahertz pulses emitting from filaments induced by two successive femtosecond laser pulses in air. Here, a leading pulse is set to be weaker than a trailing pulse and their temporal separation is larger than the pulse duration of the terahertz pulses. When the leading pulse is stronger than the trailing pulse, the frequency modulation within the whole terahertz envelope is greatly deteriorated due to nonlinear effects applying on the trailing pulse through the plasmas generated by the leading pulses. Such unique terahertz spectrum may find applications in terahertz spectroscopy.

  10. Modeling changes in the hemoglobin concentration of skin with total diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Glennie, Diana L.; Hayward, Joseph E.; Farrell, Thomas J.

    2015-03-01

    The ability to monitor changes in the concentration of hemoglobin in the blood of the skin in real time is a key component to personalized patient care. Since hemoglobin has a unique absorption spectrum in the visible light range, diffuse reflectance spectroscopy is the most common approach. Although the collection of the diffuse reflectance spectrum with an integrating sphere (IS) has several calibration challenges, this collection method is sufficiently user-friendly that it may be worth overcoming the initial difficulty. Once the spectrum is obtained, it is commonly interpreted with a log-inverse-reflectance (LIR) or "absorbance" analysis that can only accurately monitor changes in the hemoglobin concentration when there are no changes to the nonhemoglobin chromophore concentrations which is not always the case. We address the difficulties associated with collection of the diffuse reflectance spectrum with an IS and propose a model capable of retrieving relative changes in hemoglobin concentration from the visible light spectrum. The model is capable of accounting for concentration changes in the nonhemoglobin chromophores and is first characterized with theoretical spectra and liquid phantoms. The model is then used in comparison with a common LIR analysis on temporal measurements from blanched and reddened human skin.

  11. Identification of mineral composition and weathering product of tuff using reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Hyun, C.; Park, H.

    2009-12-01

    Tuff is intricately composed of various types of rock blocks and ash matrixes during volcanic formation processes. Qualitative identification and quantitative assessment of mineral composition of tuff usually have been done using manual inspection with naked-eyes and various chemical analyses. Those conventional methods are destructive to objects, time consuming and sometimes carry out biased results from subjective decision making. To overcome limits from conventional methods, assessment technique using reflectance spectroscopy was applied to tuff specimens. Reflectance spectroscopy measures electromagnetic reflectance on rock surface and can extract diagnostic absorption features originated from chemical composition and crystal structure of constituents in the reflectance curve so mineral species can be discriminated qualitatively. The intrinsic absorption feature from particular mineral can be converted to absorption depth representing relative coverage of the mineral in the measurement area by removing delineated convex hull from raw reflectance curve. The spectral measurements were performed with field spectrometer FieldSpec®3 of ASD Inc. and the wavelength range of measurement was form 350nm to 2500nm. Three types of tuff blocks, ash tuff, green lapilli tuff and red lapilli tuff, were sampled from Hwasun County in Korea and the types of tuffs. The differences between green tuff and red tuff are from the color of their matrixes. Ash tuff consists of feldspars and quartz and small amount of chalcedony, calcite, dolomite, epidote and basalt fragments. Green lapilli tuff consists of feldspar, quartz and muscovite and small amount of calcite, chalcedony, sericite, chlorite, quartzite and basalt fragments. Red lapilli tuff consists of feldspar, quartz and muscovite and small amount of calcite, chalcedony, limonite, zircon, chlorite, quartzite and basalt fragments. The tuff rocks were coarsely crushed and blocks and matrixes were separated to measure standard spectral reflectance of each constituent. Unmixing of mineral composition and their weathering products of blocks and matrixes in tuff were conducted and the ratio of mineral composition was calculated for each specimen. This study was supported by National Research Institute of Cultural Heritage (project title: Development on Evaluation Technology for Weathering Degree of Stone Cultural Properties, project no.: 09B011Y-00150-2009).

  12. Terahertz Kerr effect

    E-print Network

    Hoffmann, Matthias C.

    We have observed optical birefringence in liquids induced by single-cycle terahertz pulses with field strengths exceeding 100 kV/cm. The induced change in polarization is proportional to the square of the terahertz electric ...

  13. Time-resolved reflectance spectroscopy for nondestructive assessment of fruit and vegetable quality

    NASA Astrophysics Data System (ADS)

    Torricelli, Alessandro; Spinelli, Lorenzo; Vanoli, Maristella; Rizzolo, Anna; Eccher Zerbini, Paola

    2007-09-01

    In the majority of food and feed, due to the microscopic spatial changes in the refractive index, visible (VIS) and near infrared (NIR) light undergoes multiple scattering events and the overall light distribution is determined more by scattering rather than absorption. Conventional steady state VIS/NIR reflectance spectroscopy can provide information on light attenuation, which depends both on light absorption and light scattering, but cannot discriminate these two effects. On the contrary, time-resolved reflectance spectroscopy (TRS) provides a complete optical characterisation of diffusive media in terms of their absorption coefficient and reduced scattering coefficient. From the assessment of the absorption and reduced scattering coefficients, information can then be derived on the composition and internal structure of the medium. Main advantages of the technique are the absolute non-invasiveness, the potentiality for non-contact measurements, and the capacity to probe internal properties with no influence from the skin. In this work we review the physical and technical issues related to the use of TRS for nondestructive quality assessment of fruit and vegetable. A laboratory system for broadband TRS, based on tunable mode-locked lasers and fast microchannel plate photomultiplier, and a portable setup for TRS measurements, based on pulsed diode lasers and compact metal-channel photomultiplier, will be described. Results on broadband optical characterisation of fruits and applications of TRS to the detection of internal defects in pears and to maturity assessment in nectarines will be presented.

  14. [Quantitative measurement of induced skin reddening using optical reflection spectroscopy--methodology and clinical application].

    PubMed

    Smesny, S; Riemann, S; Riehemann, S; Bellemann, M E; Sauer, H

    2001-10-01

    Optical reflection spectroscopy is a simple and quick method for the quantification of colour intensity, and is thus suitable for the determination of changes in skin reddening (erythema) due to local vasodilatation. To quantify the time course of this erythema, the oxyhaemoglobin absorption double peak with maxima at 542 and 577 nm is an appropriate parameter. A compact handheld optical spectrometer makes the technique applicable to clinical use, an example being the niacin patch test described herein. This noninvasive test provides information about the cell membrane metabolism via the skin flush induced by niacin (vitamin B3) and mediated by prostaglandin. The aim of this study was to adapt optical reflection spectroscopy to the requirements of the clinical niacin patch test. To that end, we investigated 60 healthy volunteers. Analysis of the spectroscopic data with regard to physiological covariables of niacin sensitivity revealed faster and more intense erythema in females--a gender effect that to our knowledge has not previously been reported. In the light of these results, the findings of other researchers based on semi-quantitative test methods should be reassessed, with consideration given to the gender effect. PMID:11721583

  15. Reflections

    NSDL National Science Digital Library

    Carlyn Little

    1997-01-01

    In this quick activity, Dracula has a hole in his house and learners help solve the problem by using a mirror and protractor to reflect incoming light out of his house. This activity introduces learners to vocabulary associated with light and optics including reflected ray, angle of incident, and angle of reflection. This Dracula-themed activity also works well during Halloween.

  16. Femtosecond demodulation in low-temperature-grown gallium arsenide: A high-spectral-purity submillimeter and terahertz source for spectroscopy

    NASA Astrophysics Data System (ADS)

    Demers, Joseph Raymond

    The development of a submm source capable of producing high spectral purity THz radiation for high resolution Doppler limited spectroscopy is technologically difficult. However, the potential usefulness of such a source for spectroscopy has driven our development of a technique whereby pulses from an 800 MHz, 200 femtosecond mode-locked Ti:sapphire laser are demodulated with a Low Temperature Grown GaAs Photo-Conductive Switch (LTG GaAs PCS) and the resulting submm radiation used for molecular spectroscopy. Current technology incorporates a sputtered gold antenna on the surface of the LTG GaAs substrate and the pulse train from the mode-locked laser is focused onto the 5 ?m gap at the center of the biased antenna structure. The antenna radiates all the spectral components produced by the demodulation process into free space. A single component from this ``comb'' of frequencies may then be employed for molecular spectroscopy. Scanning through the molecular transition is achieved by changing the length of the laser cavity, and, therefore, the spacing of the spectral components. The spectral purity of the source is dependent upon fluctuations in the timing of the optical pulses. In this thesis, the noise on passively mode-locked Ti:sapphire lasers is developed completely from the frequency domain using simple Frequency Modulation (FM) theory. It will be shown that the primary source of ``noise'' on these systems is a result of AM noise on the Argon Ion pump laser. It will also be shown that the inclusion of low frequency amplitude fluctuations and white noise from the Argon Ion pump laser as sources of FM results in power spectrum ``skirts'' which match those commonly found on higher order spectral components. While understanding the spectral purity and laser characteristics is a major portion of this research, the primary goal of this thesis work was to produce a spectrometer capable of measuring molecular rotational transitions at frequencies above 1 THz. Towards this goal, initial studies involving rotational transitions in the molecules carbonyl sulfide and carbon monoxide were used to characterize and calibrate the system at frequencies around 1 THz. Novel studies of hydrogen peroxide at frequencies around 1.3 THz were also successfully performed.

  17. The Use of UV-Visible Reflectance Spectroscopy as an Objective Tool to Evaluate Pearl Quality

    PubMed Central

    Agatonovic-Kustrin, Snezana; Morton, David W.

    2012-01-01

    Assessing the quality of pearls involves the use of various tools and methods, which are mainly visual and often quite subjective. Pearls are normally classified by origin and are then graded by luster, nacre thickness, surface quality, size, color and shape. The aim of this study was to investigate the capacity of Artificial Neural Networks (ANNs) to classify and estimate the quality of 27 different pearls from their UV-Visible spectra. Due to the opaque nature of pearls, spectroscopy measurements were performed using the Diffuse Reflectance UV-Visible spectroscopy technique. The spectra were acquired at two different locations on each pearl sample in order to assess surface homogeneity. The spectral data (inputs) were smoothed to reduce the noise, fed into ANNs and correlated to the pearl’s quality/grading criteria (outputs). The developed ANNs were successful in predicting pearl type, mollusk growing species, possible luster and color enhancing, donor condition/type, recipient/host color, donor color, pearl luster, pearl color, origin. The results of this study shows that the developed UV-Vis spectroscopy-ANN method could be used as a more objective method of assessing pearl quality (grading) and may become a valuable tool for the pearl grading industry. PMID:22851919

  18. High pressure sample cell for total internal reflection fluorescence spectroscopy at pressures up to 2500 bar

    NASA Astrophysics Data System (ADS)

    Koo, Juny; Czeslik, Claus

    2012-08-01

    Total internal reflection fluorescence (TIRF) spectroscopy is a surface sensitive technique that is widely used to characterize the structure and dynamics of molecules at planar liquid-solid interfaces. In particular, biomolecular systems, such as protein adsorbates and lipid membranes can easily be studied by TIRF spectroscopy. Applying pressure to molecular systems offers access to all kinds of volume changes occurring during assembly of molecules, phase transitions, and chemical reactions. So far, most of these volume changes have been characterized in bulk solution, only. Here, we describe the design and performance of a high pressure sample cell that allows for TIRF spectroscopy under high pressures up to 2500 bar (2.5 × 108 Pa), in order to expand the understanding of volume effects from the bulk phase to liquid-solid interfaces. The new sample cell is based on a cylindrical body made of Nimonic 90 alloy and incorporates a pressure transmitting sample cuvette. This cuvette is composed of a fused silica prism and a flexible rubber gasket. It contains the sample solution and ensures a complete separation of the sample from the liquid pressure medium. The sample solution is in contact with the inner wall of the prism forming the interface under study, where fluorescent molecules are immobilized. In this way, the new high pressure TIRF sample cell is very useful for studying any biomolecular layer that can be deposited at a planar water-silica interface. As examples, high pressure TIRF data of adsorbed lysozyme and two phospholipid membranes are presented.

  19. Evaluation of vitamin C content in kiwifruit by diffuse reflectance FT-NIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Fu, Xiaping; Ying, Yibin; Lu, Huishan; Yu, Haiyan; Liu, Yande

    2005-11-01

    Vitamin C is considered an important nutrition component of fruits, especially of kiwifruit. Traditional destructive method for vitamin C measurement is very complex and fussy. Near Infrared (NIR)spectroscopy is a promising technique for nondestructive measurement of fruit internal qualities, such as soluble solid content (SSC), valid acidity (VA). The objective of this research was to study the potential of NIR diffuse reflectance spectroscopy as a way for nondestructive measurement of vitamin C content in "Qinmei" kiwifruit. NIR spectral data were collected in the spectral range of 800-2500 nm with different combinations of resolution (4 cm-1, 16 cm-1 and 32 cm-1) and scan number (32, 64 and 128). Statistical models were developed using partial least square (PLS) method. The combination with resolution of 4 cm-1 and scan number of 64 gave the best result when all samples were used in calibration sample set. Then two spectral pretreatments multiplicative signal correction (MSC) and standard normal variate (SNV), and three kinds of mathematical treatment of original spectra, first derivative spectra and second derivative spectra were discussed. The PLS model of second derivative spectra using SNV pretreatment turned out better prediction results: correlation coefficient (r) of 0. 93, root mean square error of calibration (RMSEC) of 9.24 mg/100g and root mean square error of prediction (RMSEP) of 10.3 mg/100g. The results of this study showed that NIR diffuse reflectance spectroscopy could be used for kiwifruit vitamin C prediction. The higher the resolution, the better the results, but longer time will be taken, which may not be suitable for on-line use. Therefore, further research still needs to be done.

  20. Flexible waveguide enabled single-channel terahertz endoscopic system

    NASA Astrophysics Data System (ADS)

    Doradla, Pallavi; Alavi, Karim; Joseph, Cecil S.; Giles, Robert H.

    2015-03-01

    Colorectal cancer is the third most commonly diagnosed cancer in the world. The current standard of care for colorectal cancer is the conventional colonoscopy, which relies exclusively on the Physician's experience. Continuous wave terahertz (THz) imaging has the potential to offer a safe, noninvasive medical imaging modality for detecting cancers. The current study demonstrates the design and development of a prototype terahertz endoscopic system based on flexible metal-coated terahertz waveguides. A CO2 pumped Far-Infrared molecular gas laser operating at 584 GHz frequency was used for illuminating the tissue, while the reflected signals were detected using liquid Helium cooled silicon bolometer. The continuous-wave terahertz imaging system utilizes a single waveguide channel to transmit the radiation and collect the back reflected intrinsic terahertz signal from the sample and is capable of operation in both transmission and reflection modalities. The two dimensional reflectance images obtained using a prototype terahertz endoscopic system showed intrinsic contrast between cancerous and normal regions of the colorectal tissue, thereby demonstrating the potential impact of terahertz imaging for in vivo cancer detection.

  1. Quantitative estimation of concentrations of dissolved rare earth elements using reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Dai, Jingjing; Wang, Denghong; Wang, Runsheng; Chen, Zhenghui

    2013-01-01

    Characteristic spectral parameters such as the wavelength and depth of absorption bands are widely used to quantitatively estimate the composition of samples from hyperspectral reflectance data in soil science, mineralogy as well as vegetation study. However, little research has been conducted on the spectral characteristic of rare earth elements (REE) and their relationship with chemical composition of aqueous solutions. Reflectance spectra of ore leachate solutions and contaminated stream water from a few REE mines in the Jiangxi Province, China, are studied for the first time in this work. The results demonstrate that the six diagnostic absorption features of the rare earths are recognized in visible and near-infrared wavelengths at 574, 790, 736, 520, 861, and 443 nm. The intensity of each of these six absorption bands is linearly correlated with the abundance of total REE, with the r2 value >0.95 and the detection limit at ?75,000 ?g/L. It is suggested that reflectance spectroscopy provides an ideal routine analytical tool for characterizing leachate samples. The outcome of this study also has implications for monitoring the environmental effect of REE mining, in particular in stream water systems by hyperspectral remote sensing.

  2. Technique for examining biological materials using diffuse reflectance spectroscopy and the kubelka-munk function

    DOEpatents

    Alfano, Robert R.; Yang, Yuanlong

    2003-09-02

    Method and apparatus for examining biological materials using diffuse reflectance spectroscopy and the Kubelka-Munk function. In one aspect, the method is used to determine whether a tissue sample is cancerous or not and comprises the steps of (a) measuring the diffuse reflectance from the tissue sample at a first wavelength and at a second wavelength, wherein the first wavelength is a wavelength selected from the group consisting of 255-265 nm and wherein the second wavelength is a wavelength selected from the group consisting of 275-285 nm; (b) using the Kubelka-Munk function to transform the diffuse reflectance measurement obtained at the first and second wavelengths; and (c) comparing a ratio or a difference of the transformed Kubelka-Munk measurements at the first and second wavelengths to appropriate standards determine whether or not the tissue sample is cancerous. One can use the spectral profile of KMF between 250 nm to 300 nm to determine whether or not the tissue sample is cancerous or precancerous. According to the value at the first and second wavelengths determine whether or not the malignant tissue is invasive or mixed invasive and in situ or carcinoma in situ.

  3. Monitoring the in-situ oxide growth on uranium by ultraviolet-visible reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Schweke, Danielle; Maimon, Chen; Chernia, Zelig; Livneh, Tsachi

    2012-11-01

    We demonstrate the in-situ monitoring of oxide growth on U-0.1 wt. % Cr by means of UV-visible reflectance spectroscopy in the thickness range of ˜20-150 nm. Two different approaches are presented: In the "modeling approach," we employ a model for a metallic substrate covered by a dielectric layer, while taking into account the buildup of oxygen gradient and surface roughness. Then, we fit the simulated spectra to the experimental one. In the "extrema analysis," we derive an approximated analytical expression, which relates the oxide thickness to the position of the extrema in the reflectance spectra based on the condition for optical interference of the reflected light. Good agreement is found between the values extracted by the two procedures. Activation energy of ˜21 kcal/mole was obtained by monitoring the oxide growth in the temperature range of 22-90 °C. The upper bound for the thickness determination is argued to be mostly dictated by cracking and detachment processes in the formed oxide.

  4. Development of transient attenuated total reflectance spectroscopy and investigation of photoinduced kinetics in thin films

    NASA Astrophysics Data System (ADS)

    Simon, Anne M.

    The efficiency of photoconversion systems such as organic photovoltaic cells and photocatalytic water-splitting cells is largely governed by the interfacial charge transfer processes. Understanding the structure-function relationship, specifically at the molecular thin film/transparent conducting oxide interface will allow for engineering these interfaces to promote charge transfer and reduce the rate of charge recombination. Important factors that are hypothesized to influence charge transfer are morphology, chemical characteristics, electronic properties and molecular orientation. As molecules are bound to a transparent conducting oxide or incorporated into a thin film, the local solid-state molecular environment greatly influences the excited state properties of the molecule. Pathways for quenching, radiative and nonradiative decay drastically limit the excited state lifetimes. In order to investigate the photoinduced kinetics of thin films and at interfaces a instrument was developed coupling transient absorbance spectroscopy to attenuated total reflectance spectroscopy. The photoinduced kinetics of a thin film of bacteriorhodopsin was used to evaluate the instrument performance, and it was determined that 1% of a close-packed monolayer could be detected with this geometry. The properties of a molecular thin film/transparent conducting oxide were investigated by tethering zinc porphyrin to ITO. The electrochemical properties were influenced by the functional group of the binding moiety. To improve our understanding of how the solid state molecular environment affects excited states lifetimes, zinc porphyrins were incorporated into mono- and multilayer thin films and measured with transient ATR spectroscopy. Finally, multilayer films related to photocatalytic water-splitting were investigated with the incorporation of inorganic nanosheets. The nanosheets helped to create a stratified assembly for multilayer films, spatially segregating electron donor (palladium porphyrin) and electron acceptor (poly(viologen)) molecules. The role of the nanosheets in the electron transfer between the donor and acceptor was studied by monitoring the triplet state lifetimes of a palladium porphyrin with transient ATR spectroscopy.

  5. Mineralogical and spectroscopic investigation of enstatite chondrites by X-ray diffraction and infrared reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Izawa, M. R.; King, P. L.; Flemming, R. L.; Peterson, R. C.; McCausland, P. J.

    2009-05-01

    Reflectance spectroscopy of well-characterized meteorites provides an important means of linking meteorites to potential parent objects; an important objective in meteoritics research. There is a lack of such sample- correlated spectroscopic and mineralogical data sets in the literature to date. In an effort to improve this situation, the bulk mineralogy and infrared reflectance spectra of 13 enstatite chondrite meteorite finds, spanning the full range of textural alteration grades in both EL and EH classes have been investigated, including eleven recovered from the Antarctic and one from Northwest Africa. Rietveld refinement of high- resolution powder X-ray diffraction (XRD) data was used to identify the major mineral phases and quantify their modal abundances. The mineralogy and modes agree well with those of well-documented enstatite chondrites. Terrestrial weathering products such as Fe-oxyhydroxides, gypsum, and carbonates also occur in most of the meteorites from Antarctica. The mineral abundances determined via Rietveld refinement have been used to calculate model grain densities for each meteorite (i.e. density of the solid phases). Bulk magnetic susceptibility measurements combined with modal mineralogy reveal that as terrestrial weathering increases, both grain density and bulk susceptibility decrease. Sample-correlated thermal infrared (400-4500 cm-1, 2-25 ?m) biconical (Diffuse) Reflectance Infrared Fourier Transform Spectroscopy data were collected for each meteorite to facilitate comparison with remote sensing data. The meteorite spectra are dominated by features corresponding to enstatite. Terrestrial weathering manifests itself as a broad, asymmetric H2O band centered near ~3400 cm-1, analogous to the "3 ?m water of hydration feature" recognized in asteroid spectra, particularly from the enigmatic W-type asteroids. Additional sharp features superimposed on this band, as well as the sharpness of an asymmetric feature related to bound molecular water at ~1625 cm-1 correlate with the degree of weathering of the meteorites. These reflectance IR data provide an analog for remotely-sensed IR spectra from water-bearing asteroid regoliths and point to the need for instruments with much higher spectral resolution to identify structurally- bound water in asteroid regolith.

  6. Andreev Reflection Spectroscopy of Nb-doped Bi2Se3 Topological Insulator

    NASA Astrophysics Data System (ADS)

    Kurter, C.; Finck, A. D. K.; Qiu, Y.; Huemiller, E.; Weis, A.; Atkinson, J.; Medvedeva, J.; Hor, Y. S.; van Harlingen, D. J.

    2015-03-01

    Doped topological insulators are speculated to realize p-wave superconductivity with unusual low energy quasiparticles, such as surface Andreev bound states. We present point contact spectroscopy of thin exfoliated flakes of Nb-doped Bi2Se3 where superconductivity persists up to ~ 1 K, compared to 3.2 K in bulk crystals. The critical magnetic field is strongly anisotropic, consistent with quasi-2D behavior. Andreev reflection measurements of devices with low resistance contacts result in prominent BTK-like behavior with an enhanced conductance plateau at low bias. For high resistance contacts, we observe a split zero bias conductance anomaly and additional features at the superconducting gap. Our results suggest that this material is a promising platform for studying topological superconductivity. We acknowledge support from Microsoft Project Q.

  7. Layer-dependent optical conductivity in atomic thin WS? by reflection contrast spectroscopy.

    PubMed

    Nayak, Pramoda K; Yeh, Chao-Hui; Chen, Yu-Chen; Chiu, Po-Wen

    2014-09-24

    Optical conductivity, which originates from the interband transition due to electron-phonon interaction, is one of the powerful tools used for studying the electronic states in layered transition metal dichalcogenides (TMDCs). Here, we report for the first time the optical conductivity of WS2, one of the emerging classes of TMDCs, prepared directly on SiO2/Si substrate using reflection contrast spectroscopy. The measured optical conductivity at direct excitonic transition point K of the Brillouin zone for monolayer WS2 shows a value of 0.37 e(2)/?? in the visible range of the energy spectrum. Our results reveal that the optical conductivity of WS2 layers is frequency-dependent and show additional features in the conductivity spectra for bilayer to bulk counterparts, signifying a transition from direct band gap to indirect band gap with the evolution of layer numbers as predicted by our calculations. PMID:25153193

  8. [Applications of near infrared reflectance spectroscopy technique (NIRS) to soil attributes research].

    PubMed

    Liu, Yan-De; Xiong, Song-Sheng; Liu, De-Li

    2014-10-01

    Soil is a much complicated substance, because animals, plants and microbes live together, organic and inorganic exist together. So soil contains a large amount of information. The traditional method in laboratory is a time-consuming effort. But the technology of near infrared reflectance spectroscopy (NIRS) has been widely used in many areas, owing to its rapidness, high efficiency, no pollution and low cost, NIRS has become the most important method to detect the composition of soil. This paper mainly introduce some traditional methods in laboratory, the basic processes of soil detection by NIRS, some algorithms for data preprocessing and modeling. Besides, the present paper illustrates the latest research progress and the development of portable near infrared instruments of the soil. According to this paper, the authors also hope to promote the application conditions of NIRS in the grassland ecology research in China, and accelerate the modernization of research measures in this area. PMID:25739200

  9. Strategies for Detecting Organic Liquids on Soils Using Mid-Infrared Reflection Spectroscopy

    SciTech Connect

    Gallagher, Neal B.; Gassman, Paul L.; Blake, Thomas A.

    2008-08-01

    Stand-off monitoring for chemical spills can provide timely information for clean-up efforts and mid-infrared reflection-absorption spectroscopy is one approach being investigated. Anomaly and target detection strategies were examined for detection of four different low-volatility organic liquids on two different soil types. Several preprocessing and signal weighting strategies were studied. Anomaly detection for C?H bands was very good using second derivative preprocessing and provided similar performance to target detection approaches such as generalized least squares (GLS) and partial least squares (PLS) with detections at soil loads of approximately 0.6 to 1.5 mg/cm2. Good performance was also found for detection of P=O, O–H and C=O bands but the optimal strategy varied. The simplicity and generality of anomaly detection is attractive, however target detection provides more capability for classification.

  10. Femtosecond high-resolution hard X-ray spectroscopy using reflection zone plates.

    PubMed

    Löchel, Heike; Braig, Christoph; Brzhezinskaya, Maria; Siewert, Frank; Baumgärtel, Peter; Firsov, Alexander; Erko, Alexei

    2015-04-01

    An off-axis total external reflection zone plate is applied to wavelength-dispersive X-ray spectrometry in the range from 7.8 keV to 9.0 keV. The resolving power E/?E of up to 1.1 × 102, demonstrated in a synchrotron proof-of-concept experiment, competes well with existing energy-dispersive instruments in this spectral range. In conjunction with the detection efficiency of (2.2 ± 0.6)%, providing a fairly constant count rate across the 1.2 keV band, the temporal pulse elongation to no more than 1.5 × 10-15 s opens the door to wide-range, ultra-fast hard X-ray spectroscopy at free-electron lasers (FELs). PMID:25968716

  11. Determination of in vivo skin moisture level by near-infrared reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Saknite, Inga; Spigulis, Janis

    2015-03-01

    Near-infrared spectroscopy has a potential for noninvasive determination of skin moisture level due to high water absorption. In this study, diffuse reflectance spectra of in vivo skin were acquired in the spectral range of 900 nm to 1700 nm by using near-infrared spectrometer, optical fiber and halogen bulb light source. Absorption changes after applying skin moisturizers were analyzed over time at different body sites. Results show difference in absorption when comparing dry and normal skin. Comparison of absorption changes over time after applying moisturizer at different body sites is analyzed and discussed. Some patterns of how skin reacts to different skin moisturizers are shown, although no clear pattern can be seen due to signal noise.

  12. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy of a single endothelial cell.

    PubMed

    Wrobel, Tomasz P; Marzec, Katarzyna M; Majzner, Katarzyna; Kochan, Kamila; Bartus, Magdalena; Chlopicki, Stefan; Baranska, Malgorzata

    2012-09-21

    Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) with the use of a slide-on germanium accessory followed by chemometric analysis allowed for providing meaningful information about the biochemical composition of a single endothelial cell. In this work, the methodology of the ATR-FTIR measurements of dried cells and dried cells immersed in water solution is presented. The contact of the cell and Ge crystal was set up manually and monitored through the integration of the amide I band. Additionally, the cell imaging in transreflection mode was tested, but the spectral differences between sub-cellular structures were not prominent in the registered spectra. It has been shown that the ATR-FTIR method gives better results due to the increased spatial resolution and S/R ratio as well as small contribution of the optical artifacts. PMID:22854681

  13. The role of total-reflection X-ray fluorescence in atomic spectroscopy

    NASA Astrophysics Data System (ADS)

    Tölg, G.; Klockenkämper, R.

    1993-02-01

    Total-reflection X-ray fluorescence (TXRF) is a universal and economic method for the simultaneous determination of elements with atomic numbers > 11 down to the lower pg-level. It is a microanalytical tool for the analysis of small sample amounts placed on flat carriers and for contaminations on flat sample surfaces. Analyses of stratified near-surface layers are made possible by varying the incident angle of the primary beam in the region of total-reflection. This non-destructive method is especially suitable for thin layers of a few nanometres, deposited on wafer material although not usable as a microprobe method with a high lateral resolution. Furthermore, depth profiles of biological samples can be recorded by means of microtome sectioning of only a few micrometres, as, for example in the gradient analysis of human organs. In addition to micro- and surface-layer analysis, TXRF is effectively applied to element trace analysis. Homogeneous solutions, for example aqueous solutions, high-purity adds or body fluids, are pipetted onto carriers and, after evaporation, the dry residues are analysed directly down to the pg/ml region. Particularly advantageous is the absence of matrix effects, so that an easy calibration can be carried out by adding a single internal standard element. A digestion or separation step preceding the actual determination becomes necessary if a more complex matrix is to be analysed or especially low detection limits have to be reached. A critical evaluation of the recent developments in atomic spectroscopy places TXRF in a leading position. Its outstanding features compete with those of e.g. electrothermal atomic absorption spectrometry (ETAAS), microwave induced plasma optical emission spectroscopy (MIP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) in the field of micro- and trace analysis and with Rutherford backscattering (RBS) and secondary ion mass spectrometry (SIMS) in the surface-layer analysis.

  14. Diffuse Reflectance Spectroscopy as a Qualitative Indicator of Paleopigment Concentrations in Lake Sediment

    NASA Astrophysics Data System (ADS)

    Robinson, K. D.; Ortiz, J. D.; Rosenmeier, M. F.; Augustinus, P. C.

    2008-12-01

    In natural waters, the presence of chlorophyll a (Chl a) and its isomer and degradation products (commonly referred to as CDP) results in a ubiquitous absorption feature in the visible-near infrared red portion of the electromagnetic spectrum (660-720 nm). Recent studies have identified this feature in lacustrine sedimentary profiles and have correlated its relative magnitude to analytically-derived CDP and Chl a concentrations using visible-near infrared diffuse reflectance spectroscopy (VNIRS). Here, we utilize VNIRS to determine sedimentary CDP and Chl a concentrations in lakes from the Baroon Taiga Mountains of northern Mongolia and the North Island of New Zealand. This study further tests the potential of VNIRS as a rapid, inexpensive, and non-destructive method of qualitative sedimentary paleopigment concentration analysis and as a possible proxy for lake productivity reconstructions. Direct regression of VNIRS-derived data with CDP + Chl a concentration values determined by high potential liquid chromatography and spectrophotometry in sediment cores from lakes Sanjin Nuur and Ganbold Nuur, northern Mongolia, provide high and significant coefficients of correlation (r2 > 0.8, p < 0.0001). Specific factors resulting from principle component analysis of the spectral data provide less significant but similarly acceptable correlation to CDP + Chl a values (r2 > 0.3, p < 0.01). Application of the VNIRS method to multiple sediment profiles replicates previously determined biogenic silica and organic matter-inferred paleoproductivity records from several regional lake systems. Visible-near infrared reflectance spectroscopy of sediments from a lake of dissimilar geographic, ecological, and physical characteristics (Lake Pupuke, New Zealand) provides an additional test of the method's validity. The resultant Lake Pupuke VNIRS-inferred CDP and Chl a profile is compared to associated organic matter concentration and C/N ratio records to initially assess its value as a paleoproductivity indicator.

  15. Attenuated total reflectance Fourier-transform infrared spectroscopy of carboxylic acids adsorbed onto mineral surfaces

    NASA Astrophysics Data System (ADS)

    Kubicki, J. D.; Schroeter, L. M.; Itoh, M. J.; Nguyen, B. N.; Apitz, S. E.

    1999-09-01

    A suite of naturally-occurring carboxylic acids (acetic, oxalic, citric, benzoic, salicylic and phthalic) and their corresponding sodium salts were adsorbed onto a set of common mineral substrates (quartz, albite, illite, kaolinite and montmorillonite) in batch slurry experiments. Solution pH's of approximately 3 and 6 were used to examine the effects of pH on sorption mechanisms. Attenuated total reflectance Fourier-transform infrared (ATR FTIR) spectroscopy was employed to obtain vibrational frequencies of the organic ligands on the mineral surfaces and in solution. UV/visible spectroscopy on supernatant solutions was also employed to confirm that adsorption from solution had taken place for benzoic, salicylic and phthalic acids. Molecular orbital calculations were used to model possible surface complexes and interpret the experimental spectra. In general, the tectosilicates, quartz and albite feldspar, did not chemisorb (i.e., strong, inner-sphere adsorption) the carboxylate anions in sufficient amounts to produce infrared spectra of the organics after rinsing in distilled water. The clays (illite, kaolinite and montmorillonite) each exhibited similar ATR FTIR spectra. However, the illite sample used in this study reacted to form strong surface and aqueous complexes with salicylic acid before being treated to remove free Fe-hydroxides. Chemisorption of carboxylic acids onto clays is shown to be limited without the presence of Fe-hydroxides within the clay matrix.

  16. Tracing the acetalization of cyclohexanone in CO2-expanded alcohols by attenuated total reflection infrared spectroscopy.

    PubMed

    Seki, Tsunetake; Andanson, Jean-Michel; Jutz, Fabian; Baiker, Alfons

    2009-09-01

    The CO(2)-catalyzed acetalization is regarded as a promising alternative to the conventional acid-catalyzed method from a viewpoint of green chemistry (C. A. Eckert et al., Ind. Eng. Chem. Res. 43, 2605 (2004)). We have applied in situ attenuated total reflection infrared (ATR-IR) spectroscopy for elucidating and monitoring the acetalization of cyclohexanone in CO(2)-expanded ethylene glycol and methanol at 50 degrees C and 3 MPa. The ATR-IR spectra of the reaction mixtures periodically recorded with a ZnSe crystal demonstrate that ATR-IR spectroscopy is a practical tool for tracing the kinetics of acetalizations in situ. In addition, the rate of CO(2) dissolution as well as CO(2) solubility into the cyclohexanone-alcohol mixtures could be evaluated from the CO(2)-nu(3)-antisymmetric stretching band. The ZnSe ATR crystal, however, was corroded during longer use under the acidic conditions realized by the dissolution of CO(2) in the alcohols. In contrast, the corrosion did not occur when a Ge crystal was used instead of a ZnSe crystal, and therefore the application of a Ge ATR crystal is recommended for continuous long-term experiments with these media. PMID:19796482

  17. Near-infrared reflectance spectroscopy is a rapid, cost-effective predictor of seagrass nutrients.

    PubMed

    Lawler, Ivan R; Aragones, Lemnuel; Berding, Nils; Marsh, Helene; Foley, William

    2006-06-01

    Near-infrared reflectance spectroscopy was used to analyze nutrient composition of tropical and subtropical seagrasses in Queensland, Australia, as part of a broader study of impacts of grazing by dugongs on seagrass. Seagrass samples of 10 species were collected, transported to the laboratory, and separated into leaf and root/rhizome fractions. They were dried, ground, and near-infrared spectra (400-2500 nm) were collected. We used partial least-squares regression to develop calibration equations relating spectral data to standard compositional analyses performed in the laboratory. These compositional analyses focused on attributes believed to be important determinants of nutritional quality of marine vertebrate herbivores (nitrogen, organic matter, neutral detergent fiber, acid detergent fiber, lignin, neutral starch, water-soluble carbohydrates, and in vitro dry matter digestibility). Calibration equations for each attribute were developed separately for (1) roots/rhizomes and (2) leaves, irrespective of plant species. An equation that combined both plant parts was equally robust. These studies demonstrated the utility of near-infrared spectroscopy in providing rapid and cost-effective analysis of marine plants, which, in turn, permits a rigorous statistical approach to be applied to studies of foraging by marine herbivores. PMID:16770723

  18. Growth monitoring by reflectance anisotropy spectroscopy in MOVPE reactors for device fabrication

    NASA Astrophysics Data System (ADS)

    Kurpas, P.; Rumberg, A.; Weyers, M.; Knorr, K.; Bergunde, T.; Sato, M.; Richter, W.

    1997-01-01

    Reflectance anisotropy spectroscopy (RAS) has proved its capability to study surface processes during metalorganic vapour phase epitaxy (MOVPE) growth of a variety of III-V compounds. However, these investigations up to now have been mostly restricted to specialized research reactors. Therefore, we studied the feasibility of in-situ monitoring by RAS during growth on two production-type MOVPE reactors: horizontal 2 inch single wafer reactor AIX 200 and Planetary Reactor™ AIX 2000 for 5 × 3 inch. The slight modifications of the reactors necessary to gain normal incidence optical access to the sample do not alter the properties of the grown materials. While in the horizontal reactor the strain-free optical window allows one to obtain well-resolved RAS spectra the signals in the multiwafer reactor are affected by the anisotropy of the ceiling plate. Even in this case RAS spectra can be extracted. First measurements on rotating samples in the horizontal reactor demonstrate the possibility to obtain RAS spectra by multitransient spectroscopy. As an application monitoring of the growth of p-type layers for the base of {GaInP}/{GaAs} hetero-bipolar-transistors (HBTs) is discussed. The linear electro-optic effect (LEO) gives information on doping type and doping level. Time-resolved transients at specific energies are used to study the impact of different switching schemes on the properties of the base-emitter interface.

  19. High pressure sample cell for total internal reflection fluorescence spectroscopy at pressures up to 2500 bar.

    PubMed

    Koo, Juny; Czeslik, Claus

    2012-08-01

    Total internal reflection fluorescence (TIRF) spectroscopy is a surface sensitive technique that is widely used to characterize the structure and dynamics of molecules at planar liquid-solid interfaces. In particular, biomolecular systems, such as protein adsorbates and lipid membranes can easily be studied by TIRF spectroscopy. Applying pressure to molecular systems offers access to all kinds of volume changes occurring during assembly of molecules, phase transitions, and chemical reactions. So far, most of these volume changes have been characterized in bulk solution, only. Here, we describe the design and performance of a high pressure sample cell that allows for TIRF spectroscopy under high pressures up to 2500 bar (2.5 × 10(8) Pa), in order to expand the understanding of volume effects from the bulk phase to liquid-solid interfaces. The new sample cell is based on a cylindrical body made of Nimonic 90 alloy and incorporates a pressure transmitting sample cuvette. This cuvette is composed of a fused silica prism and a flexible rubber gasket. It contains the sample solution and ensures a complete separation of the sample from the liquid pressure medium. The sample solution is in contact with the inner wall of the prism forming the interface under study, where fluorescent molecules are immobilized. In this way, the new high pressure TIRF sample cell is very useful for studying any biomolecular layer that can be deposited at a planar water-silica interface. As examples, high pressure TIRF data of adsorbed lysozyme and two phospholipid membranes are presented. PMID:22938334

  20. Near IR Scanning Angle Total Internal Reflection Raman Spectroscopy at Smooth Gold Films

    SciTech Connect

    McKee, Kristopher; Meyer, Matthew; Smith, Emily

    2012-04-13

    Total internal reflection (TIR) Raman and reflectivity spectra were collected for nonresonant analytes as a function of incident angle at sapphire or sapphire/smooth 50 nm gold interfaces using 785 nm excitation. For both interfaces, the Raman signal as a function of incident angle is well-modeled by the calculated interfacial mean square electric field (MSEF) relative to the incident field times the thickness of the layer being probed in the Raman measurement (D{sub RS}). The Raman scatter was reproducibly enhanced at the interface containing a gold film relative to the sapphire interface by a factor of 4.3–4.6 for aqueous pyridine or 2.2–3.7 for neat nitrobenzene, depending on the analyzed vibrational mode. The mechanism for the increased Raman signal is the enhanced MSEF at incident angles where propagating surface plasmons are excited in the metal film. The background from the TIR prism was reduced by 89–95% with the addition of the gold film, and the percent relative uncertainty in peak area was reduced from 15 to 1.7% for the 1347 cm–1 mode of nitrobenzene. Single monolayers of benzenethiol (S/N = 6.8) and 4-mercaptopyridine (S/N = 16.5) on gold films were measured by TIR Raman spectroscopy with 785 nm excitation (210 mW) without resonant enhancement in 1 min.

  1. [Rapid quantitative analysis of hydrocarbon composition of furfural extract oils using attenuated total reflection infrared spectroscopy].

    PubMed

    Li, Na; Yuan, Hong-Fu; Hu, Ai-Qin; Liu, Wei; Song, Chun-Feng; Li, Xiao-Yu; Song, Yi-Chang; He, Qi-Jun; Liu, Sha; Xu, Xiao-Xuan

    2014-07-01

    A set of rapid analysis system for hydrocarbon composition of heavy oils was designed using attenuated total reflection FTIR spectrometer and chemometrics to determine the hydrocarbon composition of furfural extract oils. Sixty two extract oil samples were collected and their saturates and aromatics content data were determined according to the standard NB/SH/T0509-2010, then the total contents of resins plus asphaltenes were calculated by the subtraction method in the percentage of weight. Based on the partial least squares (PLS), calibration models for saturates, aromatics, and resin+asphaltene contents were established using attenuated total reflection FTIR spectroscopy, with their SEC, 1.43%, 0.91% and 1.61%, SEP, 1.56%, 1.24% and 1.81%, respectively, meeting the accuracy and repeatability required for the standard. Compared to the present standard method, the efficiency of hydrocarbon composition analysis for furfural extract oils is significantly improved by the new method which is rapid and simple. The system could also be used for other heavy oil analysis, with excellent extension and application foreground. PMID:25269288

  2. Impact of one-layer assumption on diffuse reflectance spectroscopy of skin

    NASA Astrophysics Data System (ADS)

    Hennessy, Ricky; Markey, Mia K.; Tunnell, James W.

    2015-02-01

    Diffuse reflectance spectroscopy (DRS) can be used to noninvasively measure skin properties. To extract skin properties from DRS spectra, you need a model that relates the reflectance to the tissue properties. Most models are based on the assumption that skin is homogenous. In reality, skin is composed of multiple layers, and the homogeneity assumption can lead to errors. In this study, we analyze the errors caused by the homogeneity assumption. This is accomplished by creating realistic skin spectra using a computational model, then extracting properties from those spectra using a one-layer model. The extracted parameters are then compared to the parameters used to create the modeled spectra. We used a wavelength range of 400 to 750 nm and a source detector separation of 250 ?m. Our results show that use of a one-layer skin model causes underestimation of hemoglobin concentration [Hb] and melanin concentration [mel]. Additionally, the magnitude of the error is dependent on epidermal thickness. The one-layer assumption also causes [Hb] and [mel] to be correlated. Oxygen saturation is overestimated when it is below 50% and underestimated when it is above 50%. We also found that the vessel radius factor used to account for pigment packaging is correlated with epidermal thickness.

  3. Improved depth resolution in near-infrared diffuse reflectance spectroscopy using obliquely oriented fibers

    NASA Astrophysics Data System (ADS)

    Thilwind, Rachel Estelle; 't Hooft, Gert; Uzunbajakava, Natallia E.

    2009-03-01

    We demonstrate a significant improvement of depth selectivity when using obliquely oriented fibers for near-infrared (NIR) diffuse reflectance spectroscopy. This is confirmed by diffuse reflectance measurements of a two-layer tissue-mimicking phantom across the spectral range from 1000 to 1940 nm. The experimental proof is supported by Monte Carlo simulations. The results reveal up to fourfold reduction in the mean optical penetration depth, twofold reduction in its variation, and a decrease in the number of scattering events when a single fiber is oriented at an angle of 60 deg. The effect of reducing the mean optical penetration depth is enhanced by orienting both fibers inwardly. Using outwardly oriented fibers enables more selective probing of deeper layers, while reducing the contribution from surface layers. We further demonstrate that the effect of an inward oblique arrangement can be approximated to a decrease in fiber-to-fiber separation in the case of a perpendicular fiber arrangement. This approximation is valid in the weak- or absorption-free regime. Our results assert the advantages of using obliquely oriented fibers when attempting to specifically address superficial tissue layers, for example, for skin cancer detection, or in noninvasive glucose monitoring. Such flexibility could be further advantageous in a range of minimally invasive applications, including catheter-based interventions.

  4. Nondestructive inspection of organic films on sandblasted metals using diffuse reflectance infrared spectroscopy

    SciTech Connect

    Powell, G.L. [Oak Ridge Y-12 Plant, TN (United States); Cox, R.L. [Oak Ridge National Lab., TN (United States); Barber, T.E. [Sam Houston State Univ., Huntsville, TX (United States); Neu, J.T. [Surface Optics Corp., San Diego, CA (United States)

    1996-07-08

    Diffuse reflectance infrared spectroscopy is a very useful tool for the determination of surface contamination and characterization of films in manufacturing applications. Spectral data from the surfaces of a host of practical materials may be obtained with sufficient insensitivity to characterize relatively thick films, such as paint, and the potential exists to detect very thin films, such as trace oil contamination on metals. The SOC 400 Surface Inspection Machine/InfraRed (SIMIR) has been developed as a nondestructive inspection tool to exploit this potential in practical situations. This SIMIR is a complete and ruggidized Fourier transform infrared spectrometer with a very efficient and robust barrel ellipse diffuse reflectance optical collection system and operating software system. The SIMIR weighs less than 8 Kg, occupies less than 14 L volume, and may be manipulated into any orientation during operation. The surface to be inspected is placed at the focal point of the SIMIR by manipulating the SIMIR or the surface. The SIMIR may or may not contact the surface being inspected. For flat or convex items, there are no size limits to items being inspected. For concave surfaces, the SIMIR geometry limits the surface to those having a radius of curvature greater than 0.2 m. For highly reflective metal surfaces, the SIMIR has a noise level approaching 1 {times} 10{sup {minus}4} absorbance units, which is sufficient for detecting nanometer thick organic film residues on metals. The use of this nondestructive inspection tool is demonstrated by the spatial mapping of organic stains on sand blasted metals in which organic stains such as silicone oils, mineral oils, and triglycerides are identified both qualitatively and quantitatively over the surface of the metal specimen.

  5. Reflections.

    PubMed

    Mauksch, Larry B; Fogarty, Colleen T

    2015-03-01

    Times that prompt reflection include anniversaries, deaths, and birthday celebrations. September 2014, Donald A. Bloch, MD died. He started this Journal (formerly Family Systems Medicine) and the Collaborative Family Health Care Association (formerly Coalition). Don’s death occurred just one month before CFHA celebrated its 20th year. In this issue and our June issue, Families, Systems and Health devotes space for reflection. We begin with a remembrance of Don, written by his friend, mentee, and colleague, David Seaburn, PhD, LMFT. We also reflect on the 20th annual CFHA meeting, where we could see Don’s vision at work in the plenaries. In our June issue we will publish a second article written by CJ Peek, PhD, about Don’s vision of the field, the organization (CFHA), and this Journal. The article will ask readers to reflect. PMID:25751178

  6. Grafstrom et al. Vol. 13, No. 1/January 1996/J. Opt. Soc. Am. B 3 Reflection spectroscopy of spin-polarized

    E-print Network

    Suter, Dieter

    that are either bare or silicone coated. For this purpose, we reflect a laser beam that is resonant with the Na evidence that wall relaxation can be observed by reflection spectroscopy. © 1996 Optical Society of America These techniques use the resonant modification of the reflectivity by atomic transitions. The selective-reflection

  7. Design and measurement of all-rod terahertz photonic crystal fiber with air-core

    NASA Astrophysics Data System (ADS)

    Zhang, Le; Li, Jiu-sheng

    2015-06-01

    An all-rod terahertz wave air-core photonic crystal fiber is designed and fabricated. Transmission spectra through the sample are measured by using terahertz time-domain spectroscopy system. Periodic transmission band and low loss of the fiber are experimentally proved. Measurement results show that the power loss of the present terahertz wave photonic crystal fiber is less than 1.9 dB/cm in transmission bands. The wave confinement ability of the fiber is also demonstrated.

  8. An electrochemical enrichment procedure for the determination of heavy metals by total-reflection X-ray fluorescence spectroscopy

    Microsoft Academic Search

    A. Ritschel; P Wobrauschek; E Chinea; F Grass; Ch Fabjan

    1999-01-01

    An electrolytic separation and enrichment technique was developed for the determination of trace elements by total-reflection X-ray fluorescence spectroscopy (TXRF). The elements of interest are electrodeposited out of the sample solution onto a solid, polished disc of pure niobium which is used as sample carrier for the TXRF measurement. The electrochemical deposition leads to a high enrichment of the analytes

  9. Test of validity of the V -type approach for electron trajectories in reflection electron energy loss spectroscopy

    Microsoft Academic Search

    F. Yubero; N. Pauly; A. Dubus; S. Tougaard

    2008-01-01

    An electron reaching the detector after being backscattered from a solid surface in a reflection electron energy loss spectroscopy (REELS) experiment follows a so-called V -type trajectory if it is reasonable to consider that it has only one large elastic scattering event along its total path length traveled inside the solid. V -type trajectories are explicitly assumed in the dielectric

  10. Book Review published by Analysis, 1997: Reflection Electron Microscopy and Spectroscopy for Surface Analysis, By Zhong Lin Wang

    E-print Network

    Wang, Zhong L.

    Book Review published by Analysis, 1997: Reflection Electron Microscopy and Spectroscopy for Surface Analysis, By Zhong Lin Wang Professor John F. Watts University of Surrey The book describes, but the author is considerate enough to define them all in the early pages of his book. The dust-cover notes

  11. Determination of In-shell Peanuts Moisture, Oil and Fatty Acids Composition Using Near Infrared Reflectance Spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Oil and moisture content of peanuts are important factors in peanut grading. A method that could rapidly and nondestructively measure these parameters for in-shell peanuts would be extremely useful. NIR reflectance spectroscopy was used to analyze the moisture, total oil and fatty acid content of V...

  12. Diffuse-reflectance fourier-transform mid-infrared spectroscopy as a method of characterizing changes in soil organic matter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Diffuse-Reflectance Fourier-Transform Mid-Infrared Spectroscopy (MidIR) can identify the presence of important organic functional groups in soil organic matter (SOM). Soils contain myriad organic and inorganic components that absorb in the MidIR so spectral interpretation needs to be validated in or...

  13. Application of micro-attenuated total reflectance FTIR spectroscopy in the forensic study of questioned documents involving red seal inks

    Microsoft Academic Search

    Warnadi Dirwono; Jin Sook Park; M. R. Agustin-Camacho; Jiyeon Kim; Hyun-Mee Park; Yeonhee Lee; Kang-Bong Lee

    2010-01-01

    Red seal inks from Korea (6), Japan (1) and China (6) were studied to investigate the feasibility of micro-attenuated total reflectance (ATR) FTIR spectroscopy as a tool in the forensic study of questioned documents involving seal inks. The technique was able to differentiate red seal inks of similar colors and different manufacturers. Blind testing has shown that micro-ATR FTIR can

  14. Heat Induced Damage Detection by Terahertz (THz) Radiation

    Microsoft Academic Search

    Ehsan Kabiri Rahani; Tribikram Kundu; Ziran Wu; Hao Xin

    2011-01-01

    Terahertz (THz) and sub-terahertz imaging and spectroscopy are becoming increasingly popular nondestructive evaluation techniques\\u000a for damage detection and characterization of materials. THz radiation is being used for inspecting ceramic foam tiles used\\u000a in TPS (Thermal Protection System), thick polymer composites and polymer tiles that are not good conductors of ultrasonic\\u000a waves. Capability of THz electromagnetic waves in detecting heat induced

  15. Terahertz spectroscopic imaging and properties of gastrointestinal tract in a rat model

    PubMed Central

    Ji, Young Bin; Kim, Sang-Hoon; Jeong, Kiyoung; Choi, Yuna; Son, Joo-Hiuk; Park, Dong Woo; Noh, Sam Kyu; Jeon, Tae-In; Huh, Yong-Min; Haam, Seungjoo; Lee, Sang Kil; Oh, Seung Jae; Suh, Jin-Suck

    2014-01-01

    We have investigated basic properties of normal gastrointestinal (GI) tract tissues, including glandular stomach (GS), fore stomach (FS), large intestine (LI), small intestine (SI), and esophagus (ESO), from a rat model using terahertz (THz) reflection imaging and spectroscopy. The THz images collected from stratified squamous epithelia (SSE) of FS and ESO show a lower peak-to-peak value compared to those from columnar epithelia (CE) of GS, LI, or SI because the SSE contains less water than CE. The refractive index and absorption coefficient of FS were less than those of GS or LI, both having values similar to those of water. Additionally, we report internal reflection THz signals from ESO, although we were unable to determine the exact interface for this internal reflection. PMID:25574429

  16. Terahertz spectroscopic imaging and properties of gastrointestinal tract in a rat model.

    PubMed

    Ji, Young Bin; Kim, Sang-Hoon; Jeong, Kiyoung; Choi, Yuna; Son, Joo-Hiuk; Park, Dong Woo; Noh, Sam Kyu; Jeon, Tae-In; Huh, Yong-Min; Haam, Seungjoo; Lee, Sang Kil; Oh, Seung Jae; Suh, Jin-Suck

    2014-12-01

    We have investigated basic properties of normal gastrointestinal (GI) tract tissues, including glandular stomach (GS), fore stomach (FS), large intestine (LI), small intestine (SI), and esophagus (ESO), from a rat model using terahertz (THz) reflection imaging and spectroscopy. The THz images collected from stratified squamous epithelia (SSE) of FS and ESO show a lower peak-to-peak value compared to those from columnar epithelia (CE) of GS, LI, or SI because the SSE contains less water than CE. The refractive index and absorption coefficient of FS were less than those of GS or LI, both having values similar to those of water. Additionally, we report internal reflection THz signals from ESO, although we were unable to determine the exact interface for this internal reflection. PMID:25574429

  17. [Testing of germination rate of hybrid rice seeds based on near-infrared reflectance spectroscopy].

    PubMed

    Li, Yi-nian; Jiang, Dan; Liu, Ying-ying; Ding, Wei-min; Ding, Qi-shuo; Zha, Liang-yu

    2014-06-01

    Germination rate of rice seeds was measured according to technical stipulation of germination testing for agricultural crop seeds at present. There existed many faults for this technical stipulation such as long experimental period, more costing and higher professional requirement. A rapid and non-invasive method was put forward to measure the germination rate of hybrid rice seeds based on near-infrared reflectance spectroscopy. Two varieties of hybrid rice seeds were aged artificially at temperature 45 degrees C and humidity 100% condition for 0, 24, 48, 72, 96, 120 and 144 h. Spectral data of 280 samples for 2 varieties of hybrid rice seeds with different aging time were acquired individually by near-infrared spectra analyzer. Spectral data of 280 samples for 2 varieties of hybrid rice seeds were randomly divided into calibration set (168 samples) and prediction set (112 samples). Gormination rate of rice seed with different aging time was tested. Regression model was established by using partial least squares (PLS). The effect of the different spectral bands on the accuracy of models was analyzed and the effect of the different spectral preprocessing methods on the accuracy of models was also compared. Optimal model was achieved under the whole bands and by using standardization and orthogonal signal correction (OSC) preprocessing algorithms with CM2000 software for spectral data of 2 varieties of hybrid rice seeds, the coefficient of determination of the calibration set (Rc) and that of the prediction set (Rp) were 0.965 and 0.931 individually, standard error of calibration set (SEC) and that of prediction set (SEP) were 1.929 and 2.899 respectively. Relative error between tested value and predicted value for prediction set of rice seeds is below 4.2%. The experimental results show that it is feasible that rice germination rate is detected rapidly and nondestructively by using the near-infrared spectroscopy analysis technology. PMID:25358159

  18. The clinical effectiveness of reflectance optical spectroscopy for the in vivo diagnosis of oral lesions

    PubMed Central

    Messadi, Diana V; Younai, Fariba S; Liu, Hong-Hu; Guo, Gao; Wang, Cun-Yu

    2014-01-01

    Optical spectroscopy devices are being developed and tested for the screening and diagnosis of oral precancer and cancer lesions. This study reports a device that uses white light for detection of suspicious lesions and green–amber light at 545?nm that detect tissue vascularity on patients with several suspicious oral lesions. The clinical grading of vascularity was compared to the histological grading of the biopsied lesions using specific biomarkers. Such a device, in the hands of dentists and other health professionals, could greatly increase the number of oral cancerous lesions detected in early phase. The purpose of this study is to correlate the clinical grading of tissue vascularity in several oral suspicious lesions using the Identafi® system with the histological grading of the biopsied lesions using specific vascular markers. Twenty-one patients with various oral lesions were enrolled in the study. The lesions were visualized using Identafi® device with white light illumination, followed by visualization of tissue autofluorescence and tissue reflectance. Tissue biopsied was obtained from the all lesions and both histopathological and immunohistochemical studies using a vascular endothelial biomarker (CD34) were performed on these tissue samples. The clinical vascular grading using the green–amber light at 545?nm and the expression pattern and intensity of staining for CD34 in the different biopsies varied depending on lesions, grading ranged from 1 to 3. The increase in vascularity was observed in abnormal tissues when compared to normal mucosa, but this increase was not limited to carcinoma only as hyperkeratosis and other oral diseases, such as lichen planus, also showed increase in vascularity. Optical spectroscopy is a promising technology for the detection of oral mucosal abnormalities; however, further investigations with a larger population group is required to evaluate the usefulness of these devices in differentiating benign lesions from potentially malignant lesions. PMID:25059250

  19. Terahertz Physics

    NASA Astrophysics Data System (ADS)

    Lewis, R. A.

    2013-01-01

    1. Introduction; Part I. Basics: 2. Oscillations; 3. Combining oscillations; 4. Light; 5. Matter; 6. Interaction of light and matter; Part II. Components: 7. Sources; 8. Optics; 9. Detectors; Part III. Applications: 10. Spectroscopy; 11. Imaging; Glossary; Appendices; Index.

  20. Making use of x-ray optical effects in photoelectron-, Auger electron-, and x-ray emission spectroscopies: Total reflection, standing-wave excitation,

    E-print Network

    Fadley, Charles

    spectroscopies: Total reflection, standing-wave excitation, and resonant effects S.-H. Yang, A. X. Gray, A. M spectroscopies: Total reflection, standing-wave excitation, and resonant effects S.-H. Yang,1 A. X. Gray,2,3,4 AMaking use of x-ray optical effects in photoelectron-, Auger electron-, and x-ray emission

  1. Perfect terahertz absorber using fishnet based metafilm

    SciTech Connect

    Azad, Abul Kalam [Los Alamos National Laboratory; Shchegolkov, Dmitry Yu [Los Alamos National Laboratory; Chen, Houtong [Los Alamos National Laboratory; Taylor, Antoinette [Los Alamos National Laboratory; Smirnova, E I [Los Alamos National Laboratory; O' Hara, John F [Los Alamos National Laboratory

    2009-01-01

    We present a perfect terahertz (THz) absorber working for a broad-angle of incidence. The two fold symmetry of rectangular fishnet structure allows either complete absorption or mirror like reflection depending on the polarization of incident the THz beam. Metamaterials enable the ability to control the electromagnetic wave in a unique fashion by designing the permittivity or permeability of composite materials with desired values. Although the initial idea of metamaterials was to obtain a negative index medium, however, the evolution of metamaterials (MMs) offers a variety of practically applicable devices for controlling electromagnetic wave such as tunable filters, modulators, phase shifters, compact antenna, absorbers, etc. Terahertz regime, a crucial domain of the electromagnetic wave, is suffering from the scarcity of the efficient devices and might take the advantage of metamaterials. Here, we demonstrate design, fabrication, and characterization of a terahertz absorber based on a simple fishnet metallic film separated from a ground mirror plane by a dielectric spacer. Such absorbers are in particular important for bolometric terahertz detectors, high sensitivity imaging, and terahertz anechoic chambers. Recently, split-ring-resonators (SRR) have been employed for metamaterial-based absorbers at microwave and THz frequencies. The experimental demonstration reveals that such absorbers have absorptivity close to unity at resonance frequencies. However, the downside of these designs is that they all employ resonators of rather complicated shape with many fine parts and so they are not easy to fabricate and are sensitive to distortions.

  2. Field spectroscopy sampling strategies for improved measurement of Earth surface reflectance

    NASA Astrophysics Data System (ADS)

    Mac Arthur, A.; Alonso, L.; Malthus, T. J.; Moreno, J. F.

    2013-12-01

    Over the last two decades extensive networks of research sites have been established to measure the flux of carbon compounds and water vapour between the Earth's surface and the atmosphere using eddy covariance (EC) techniques. However, contributing Earth surface components cannot be determined and (as the ';footprints' are spatially constrained) these measurements cannot be extrapolated to regional cover using this technique. At many of these EC sites researchers have been integrating spectral measurements with EC and ancillary data to better understand light use efficiency and carbon dioxide flux. These spectroscopic measurements could also be used to assess contributing components and provide support for imaging spectroscopy, from airborne or satellite platforms, which can provide unconstrained spatial cover. Furthermore, there is an increasing interest in ';smart' database and information retrieval systems such as that proposed by EcoSIS and OPTIMISE to store, analyse, QA and merge spectral and biophysical measurements and provide information to end users. However, as Earth surfaces are spectrally heterogeneous and imaging and field spectrometers sample different spatial extents appropriate field sampling strategies require to be adopted. To sample Earth surfaces spectroscopists adopt either single; random; regular grid; transect; or 'swiping' point sampling strategies, although little comparative work has been carried out to determine the most appropriate approach; the work by Goetz (2012) is a limited exception. Mac Arthur et al (2012) demonstrated that, for two full wavelength (400 nm to 2,500 nm) field spectroradiometers, the measurement area sampled is defined by each spectroradiometer/fore optic system's directional response function (DRF) rather than the field-of-view (FOV) specified by instrument manufacturers. Mac Arthur et al (2012) also demonstrated that each reflecting element within the sampled area was not weighted equally in the integrated measurement recorded. There were non-uniformities of spectral response with the spectral ';weighting' per wavelength interval being positionally dependent and unique to each spectroradiometer/fore optic system investigated. However, Mac Arthur et al (2012) did not provide any advice on how to compensate for these systematic errors or advise on appropriate sampling strategies. The work reported here will provide the first systematic study of the effect of field spectroscopy sampling strategies for a range of different Earth surface types. Synthetic Earth surface hyperspectral data cubes for each surface type were generated and convolved with a range of the spectrometer/fore optic system directional response functions generated by Mac Arthur et al 2013, to simulate spectroscopic measurements of Earth surfaces. This has enabled different field sampling strategies to be directly compared and their suitability for each measurement purpose and surface type to be assessed and robust field spectroscopy sampling strategy recommendations to be made. This will be particularly of interest to the carbon and water vapour flux communities and assist the development of sampling strategies for field spectroscopy from rotary-wing Unmanned Aerial Vehicles, which will aid acquiring measurements in the spatial domain, and generally further the use of field spectroscopy for quantitative Earth observation.

  3. Integrated heterodyne terahertz transceiver

    DOEpatents

    Lee, Mark (Albuquerque, NM); Wanke, Michael C. (Albuquerque, NM)

    2009-06-23

    A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. An antenna connected to the Schottky diode receives a terahertz signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

  4. Integrated heterodyne terahertz transceiver

    DOEpatents

    Wanke, Michael C. (Albuquerque, NM); Lee, Mark (Albuquerque, NM); Nordquist, Christopher D. (Albuquerque, NM); Cich, Michael J. (Albuquerque, NM)

    2012-09-25

    A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. A terahertz signal can be received by an antenna connected to the mixer, an end facet or sidewall of the laser, or through a separate active section that can amplify the incident signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

  5. Diffuse near-infrared reflectance spectroscopy during heatstroke in a mouse model: pilot study.

    PubMed

    Abookasis, David; Zafrir, Elad; Nesher, Elimelech; Pinhasov, Albert; Sternklar, Shmuel; Mathews, Marlon S

    2012-10-01

    Heatstroke, a form of hyperthermia, is a life-threatening condition characterized by an elevated core body temperature that rises above 40°C (104°F) and central nervous system dysfunction that results in delirium, convulsions, or coma. Without emergency treatment, the victim lapses into a coma and death soon follows. The study presented was conducted with a diffuse reflectance spectroscopy (DRS) setup to assess the effects of brain dysfunction that occurred during heatstroke in mice model (n=6). It was hypothesized that DRS can be utilized in small animal studies to monitor change in internal brain tissue temperature during heatstroke injury since it induces a sequence of pathologic changes that change the tissue composition and structure. Heatstroke was induced by exposure of the mice body under general anesthesia, to a high ambient temperature. A type of DRS in which the brain tissue was illuminated through the intact scalp with a broadband light source and diffuse reflected spectra was employed, taking in the spectral region between 650 and 1000 nm and acquired at an angle of 90 deg at a position on the scalp ?12??mm from the illumination site. The temperature at the onset of the experiment was ?34°C (rectal temperature) with increasing intervals of 1°C until mouse death. The increase in temperature caused optical scattering signal changes consistent with a structural alteration of brain tissue, ultimately resulting in death. We have found that the peak absorbance intensity and its second derivative at specific wavelengths correlate well with temperature with an exponential dependence. Based on these findings, in order to estimate the influence of temperature on the internal brain tissue a reflectance-temperature index was established and was seen to correlate as well with measured temperature. Overall, results indicate variations in neural tissue properties during heatstroke and the feasibility to monitor and assess internal temperature variations using DRS. Although several approaches have described the rise in temperature and its impact on tissue, to the best of our knowledge no information is available describing the ability to monitor temperature during heatstroke with DRS. The motivation of this study was to successfully describe this ability. PMID:23085983

  6. Reflection

    NSDL National Science Digital Library

    In this activity, students learn that infrared light is reflected in the same manner as visible light. Students align a series of mirrors so that they can turn on a TV with a remote control when the remote is not in a direct line with the TV. As a result of their experiment with reflection, students deduce that infrared light is another form of light and is a part of the electromagnetic spectrum. Section 1 of the activity guide includes teacher notes, information on materials and preparation, student misconceptions and a student pre-test. Each activity section also includes teacher notes, student activity sheets, and answer keys. This activity requires a TV and remote control. It is the third of four activities in Active Astronomy, which are designed to complement instruction on the electromagnetic spectrum, focusing on infrared light.

  7. Characterization of early stage cartilage degradation using diffuse reflectance near infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Brown, C. P.; Jayadev, C.; Glyn-Jones, S.; Carr, A. J.; Murray, D. W.; Price, A. J.; Gill, H. S.

    2011-04-01

    Interest in localized and early stage treatment technologies for joint conditions such as osteoarthritis is growing rapidly. It has therefore become important to develop objective measures capable of characterizing the earliest (non-visible) changes associated with degeneration to aid treatment procedures. In addition to assessing tissue before treatment, it is further important to develop an effective, non-destructive means of monitoring post-treatment tissue healing, and of providing the high-quality data needed for trials of developing treatment methods. To investigate its ability to detect the early stages of degeneration in cartilage-on-bone, diffuse reflectance near infrared spectroscopy was applied to normal and osteoarthritic joints. A discriminating function was developed to relate absorbance peaks of interest and track degradation around focal osteoarthritic defects. The function could distinguish between normal and degraded tissue (100% separation of normal tissue from that within 25 mm of a defect) and between different stages of osteoarthritic progression (p < 0.05). This technique allows simple, practical and non-destructive assessment of component-level properties over the full depth of the tissue. It has the potential to increase our understanding of the underlying etiologic and pathogenic processes in early stage degeneration, to assist classification and the development of new treatment methods.

  8. White-light time-resolved reflectance spectroscopy for monitoring constituents concentrations in layered diffusive media

    NASA Astrophysics Data System (ADS)

    Giusto, A.; D'Andrea, C.; Spinelli, L.; Contini, D.; Torricelli, A.; Martelli, F.; Zaccanti, G.; Cubeddu, R.

    2007-07-01

    We performed reflectance measurements with a time-resolved white-light spectroscopy system to monitor concentrations changes in a two-layer liquid phantom with optical properties similar to human tissues. By varying the concentrations of three inks with different spectral features, we changed the absorption coefficient of the upper and lower layer to simulate either haemodynamics changes in the muscle covered by adipose layer, or functional brain activation with systemic response in the scalp. Data were analyzed by a time-resolved spectrally constrained fitting method based on a homogeneous model of photon diffusion. Although this approach is based on a homogeneous model and employs a single 2cm source-detector distance, the technique is able to monitor changes in the lower layer, while it is scarcely affected by variation in the upper layer. Preliminary in vivo measurements have been performed on one healthy volunteer to monitor oxy- and deoxy-haemoglobin changes in the muscle during arterial occlusion and in the brain during a motor task. Even if the overall sensitivity of the technique is reduced, in vivo results are in general agreement with the findings of dedicated system for tissue oximetry.

  9. Recent progress in noninvasive diabetes screening by diffuse reflectance near-infrared skin spectroscopy

    NASA Astrophysics Data System (ADS)

    Heise, H. M.; Haiber, S.; Licht, M.; Ihrig, D. F.; Moll, C.; Stuecker, M.

    2006-02-01

    Near infrared spectroscopy exhibits a tremendous potential for clinical chemistry and tissue pathology. Owing to its penetration depth into human skin, near infrared radiation can probe chemical and structural information non-invasively. Metabolic diseases such as diabetes mellitus increase nonenzymatic glycation with the effect of glucose molecules bonding chemically to proteins. In addition, glycation accumulates on tissue proteins with the clearest evidence found in extracellular skin collagen, affecting also covalent crosslinking between adjacent protein strands, which reduces their flexibility, elasticity, and functionality. Non-enzymatically glycated proteins in human skin and following chemical and structural skin changes were our spectroscopic target. We carried out measurements on 109 subjects using two different NIR-spectrometers equipped with diffuse reflection accessories. Spectra of different skin regions (finger and hand/forearm skin) were recorded for comparison with clinical blood analysis data and further patient information allowing classification into diabetics and non-diabetics. Multivariate analysis techniques for supervised classification such as linear discriminant analysis (LDA) were applied using broad spectral interval data or a number of optimally selected wavelengths. Based on fingertip skin spectra recorded by fiber-optics, it was possible to classify diabetics and non-diabetics with a maximum accuracy of 87.8 % using leave-5-out cross-validation (sensitivity of 87.5. %, specificity of 88.2 %). With the results of this study, it can be concluded that ageing and glycation at elevated levels cannot always be separated from each other.

  10. Crop/weed discrimination using near-infrared reflectance spectroscopy (NIRS)

    NASA Astrophysics Data System (ADS)

    Zhang, Yun; He, Yong

    2006-09-01

    The traditional uniform herbicide application often results in an over chemical residues on soil, crop plants and agriculture produce, which have imperiled the environment and food security. Near-infrared reflectance spectroscopy (NIRS) offers a promising means for weed detection and site-specific herbicide application. In laboratory, a total of 90 samples (30 for each species) of the detached leaves of two weeds, i.e., threeseeded mercury (Acalypha australis L.) and fourleafed duckweed (Marsilea quadrfolia L.), and one crop soybean (Glycine max) was investigated for NIRS on 325- 1075 nm using a field spectroradiometer. 20 absorbance samples of each species after pretreatment were exported and the lacked Y variables were assigned independent values for partial least squares (PLS) analysis. During the combined principle component analysis (PCA) on 400-1000 nm, the PC1 and PC2 could together explain over 91% of the total variance and detect the three plant species with 98.3% accuracy. The full-cross validation results of PLS, i.e., standard error of prediction (SEP) 0.247, correlation coefficient (r) 0.954 and root mean square error of prediction (RMSEP) 0.245, indicated an optimum model for weed identification. By predicting the remaining 10 samples of each species in the PLS model, the results with deviation presented a 100% crop/weed detection rate. Thus, it could be concluded that PLS was an available alternative of for qualitative weed discrimination on NTRS.

  11. [Experimental study of the red-bed pigment with diffuse reflectance spectroscopy].

    PubMed

    Jiang, Lian-Ting; Chen, Guo-Neng; Peng, Zhuo-Lun

    2013-10-01

    Red pigment of continental red-bed is known originating from the fine-particle hematite in the rocks. Advance of researches on the origin of continental red-bed demonstrates that the red pigment of red-bed originated from its diagenetic but not depositional process. The high diagenetic temperature causes the dehydration of iron hydrate to form hematite, generating the red pigment. For examining the above hypothesis, the authors of this paper designed an experiment to approach the reddening process, i.e. formation of the red pigment of continental red-bed. Black ooze sampled from the Holocene sediments of the Pearl River Delta was heated in different ways. The diffuse reflectance spectroscopy (DRS) of those heated ooze samples were detected with Perkin-Elmer Lamdba 950 ultraviolet/visible/near-infrared spectrophotometer, and moreover, red-values of the samples were calculated for determining their coloring levels. Iron in black ooze sediment is predominantly in the form of goethite. Experimental results verified that initial dehydration-temperature of goethite is about 150 degrees C, either enhancing temperature or prolonging heating time is accompanied with decreasing goethite and increasing hematite, and a positive relationship exists between red-value of samples and peak-height of hematite. The experimental results strongly support the idea of thermal origin of continental red-bed. PMID:24409725

  12. Electronic and optical properties of Fe, Pd, and Ti studied by reflection electron energy loss spectroscopy

    SciTech Connect

    Tahir, Dahlang [Department of Physics, Hasanuddin University, Makassar 90245 (Indonesia); Kraaer, Jens; Tougaard, Sven [Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, DK-5230 Odense M (Denmark)

    2014-06-28

    We have studied the electronic and optical properties of Fe, Pd, and Ti by reflection electron energy-loss spectroscopy (REELS). REELS spectra recorded for primary energies in the range from 300?eV to 10?keV were corrected for multiple inelastically scattered electrons to determine the effective inelastic-scattering cross section. The dielectric functions and optical properties were determined by comparing the experimental inelastic-electron scattering cross section with a simulated cross section calculated within the semi-classical dielectric response model in which the only input is Im(?1/?) by using the QUEELS-?(k,?)-REELS software package. The complex dielectric functions ?(k,?), in the 0–100?eV energy range, for Fe, Pd, and Ti were determined from the derived Im(?1/?) by Kramers-Kronig transformation and then the refractive index n and extinction coefficient k. The validity of the applied model was previously tested and found to give consistent results when applied to REELS spectra at energies between 300 and 1000?eV taken at widely different experimental geometries. In the present paper, we provide, for the first time, a further test on its validity and find that the model also gives consistent results when applied to REELS spectra in the full range of primary electron energies from 300?eV to 10000?eV. This gives confidence in the validity of the applied method.

  13. Spectral characteristics of chlorites and Mg-serpentines using high- resolution reflectance spectroscopy

    USGS Publications Warehouse

    King, T.V.V.; Clark, R.N.

    1989-01-01

    The present laboratory study using high-resolution reflectance spectroscopy (0.25-2.7 ??m) focuses on two primary phyllosilicate groups, serpentines and chlorites. The results show that it is possible to spectrally distinguish between isochemical end-members of the Mg-rich serpentine group (chrysotile, antigorite, and lizardite) and to recognize spectral variations in chlorites as a function of Fe/Mg ratio (~8-38 wt% Fe). The position and relative strength of the 1.4-??m absorption feature in the trioctahedral chlorites appear to be correlated to the total iron content and/or the Mg/Si ratio and the loss on ignition values of the sample. Spectral differences in the 2.3-??m wavelength region can be attributed to differences in lattice environments and are characteristic for specific trioctahedral chlorites. The 1.4-??m feature in the isochemical Mg-rich serpentines (total iron content ~1.5-7.0 wt%) show marked spectral differences, apparently due to structural differences. -Authors

  14. Optical characterization of thin nickel films on polymer substrates using reflectance difference spectroscopy

    SciTech Connect

    Rinnerbauer, V. [Institut fuer Experimentalphysik, Johannes Kepler Universitaet Linz, Altenbergerstr. 69, A-4040 Linz (Austria); Hueck Folien GmbH, Gewerbepark 30, A-4342 Baumgartenberg (Austria); Schmidegg, K. [Hueck Folien GmbH, Gewerbepark 30, A-4342 Baumgartenberg (Austria); Hohage, M.; Sun, L. D.; Flores-Camacho, J. M.; Zeppenfeld, P. [Institut fuer Experimentalphysik, Johannes Kepler Universitaet Linz, Altenbergerstr. 69, A-4040 Linz (Austria)

    2009-06-15

    We have used reflectance difference spectroscopy (RDS) and its extension, azimuth-dependent RDS (ADRDS), to study the properties of sputtered and evaporated nickel films on biaxially oriented poly(ethylene terephtalate) (PET) films in a roll to roll web-coating process. From the full set of ADRDS spectra we extract and analyze both the intrinsic RDS spectra and the azimuthal orientation of the effective optical anisotropy of the samples. From the latter, contributions to the RDS spectra arising from the nickel layer and the PET substrate with different orientations of the optical eigenaxes can be inferred. We find an attenuation of the characteristic RDS signal of the PET substrate with increasing nickel film thickness which is in good agreement with the theoretical prediction. For film thicknesses above 20 nm another contribution to the RDS signal attributed to the optical anisotropy of the deposited nickel layers can be observed. Its strength depends on the deposition method, and is considerably larger for evaporated films than for sputtered ones. With increasing nickel film thickness, the azimuthal orientation of the sample anisotropy changes from the initial value of the PET substrate by about 20 deg.toward the machine direction of the foil. We demonstrate that RDS is also a valuable tool for inline monitoring in the roll to roll process, as the attenuation of the RDS signal, under proper consideration of the orientation of the effective anisotropy, is a function of the film thickness and characteristic for the deposited material.

  15. Monitoring the sorption of propanoic acid by montmorillonite using Diffuse Reflectance Fourier Transform Infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Parker, R. W.; Frost, R. L.

    1998-06-01

    This paper describes how Diffuse Reflectance Fourier Transform Infrared (DRIFT) spectroscopy was used to monitor the sorption behavior of a short chain fatty acid, propanoic acid, on the clay mineral, montmorillonite. Organic acids bind to montmorillonite in two ways, either by dipole interaction with the oxygens in the interlayer space, or by bonding of the carboxylate anions to exposed aluminum ions. The DRIFT spectra of propanoic acid-montmorillonite complexes have bands at 1728 and 1554 cm-1, which are attributed to the symmetric, and antisymmetric stretching vibrations, respectively, of the C=O, ?(C=O)s, and O-C-O, ?(O-C-O)a, bonds of the carboxylic acid group. Each band represents one of the two different binding modes. These bands can be used to monitor the physical and chemical adsorption of the acid by the montmorillonite. When the peak area of each vibration is plotted against increasing acid concentration, both increase to a maximum. However the peak area for the ?(O-C-O)a vibration reaches a maximum at a much lower acid concentration than the ?(O=O)s vibration. The former maximum corresponds to saturation of the available binding sites on the edge surface aluminum ions. This concentration can be used to calculate the number of binding sites on the clay crystal. Where propanoic acid is allowed to diffuse from the clay, the bound fraction remains on the montmorillonite reducing the available acid that can be desorbed or leached from the clay.

  16. Estimation of heavy metal concentrations in reclaimed mining soils using reflectance spectroscopy.

    PubMed

    Tan, Kun; Ye, Yuan-yuan; Du, Pei-jun; Zhang, Qian-qian

    2014-12-01

    A selection of soil samples from reclaimed mining areas were prepared to establish the quantitative inversion models of the soil heavy metal (As, Zn, Cu, Cr, and Pb) concentrations. The concentrations of the soil heavy metals and the visible and near-infrared spectra of the soil samples were obtained in a darkroom. Firstly, smoothing processing was used to smooth the noise in the original spectra, and the spectral transformation techniques of first derivative (FD), continuum removal (CR), and standard normal variate (SNV) were used to promote the model stability and the accuracy of the prediction. Through correlation analysis, the feature bands of the different transformed spectra were extracted. Finally, three different inversion models were adopted and compared, i. e., traditional multiple linear regression (MLR), partial least squares regression (PLSR), and least squares support vector machines (LS-SVM) modeling. The results indicated that: (1) the stability and accuracy of the inversion models established by the different transformed spectra was high, in which LS-SVM was better than PLSR, and PLSR was better than MLR (except for a few cases); and (2) the spectral features extracted from the different transformed spectra had a certain influence on the inversion model, in which the results based on CR transformation and SNV transformation were better than the FD transformation. Therefore, the quantitative estimation of heavy metal concentrations by the use of reflectance spectroscopy is feasible, and the pre-processing is essential to improve the accuracy of the model. PMID:25881431

  17. 3D Effect in Determination of Spin Polarization using Andreev Reflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gifford, Jessica; Snider, Charles; Martinez, Jonny; Chen, Tingyong

    2013-03-01

    Andreev Reflection Spectroscopy (ARS) has been utilized to measure spin polarization of magnetic materials, as well as the superconducting gap of superconductors. These values are extracted by a modified Blonder-Tinkham-Klapwijk (BTK) model or the more recent Chen-Tesanovic-Chien (CTC) model. Both consider the F/S interface as one dimensional (1D). However, a tip may have a point angle with three dimensional (3D) effects. We present both theoretical and experimental studies of the 3D effects in the determination of spin polarization. We have found that for an ideal interface without interfacial scattering (Z), the 3D ARS spectra are the same as 1D spectra. But for non-ideal interfaces the 3D effect can drastically change the conductance spectra depending on the point angle of the tip. The 3D spectra can be well described by the 1D model with a different interfacial scattering factor and a slightly different inelastic scattering factor. The spin polarization and superconducting gap is the same as the1D model, demonstrating that 1D ARS model can be utilized to determine spin polarization as long as Z is not of any concern. Finally, we apply the both the 1D and the 3D models to a set of ARS data and show that the extracted spin polarization value is the same for both models.

  18. Ultrahigh resolution total organic carbon analysis using Fourier Transform Near Infrarred Reflectance Spectroscopy (FT-NIRS)

    NASA Astrophysics Data System (ADS)

    Pearson, Emma J.; Juggins, Steve; Tyler, Jonathan

    2014-01-01

    Fourier transform near infrared reflectance spectroscopy (FT-NIRS) is a cheap, rapid, and nondestructive method for analyzing organic sediment components. Here, we examine the robustness of a within lake FT-NIRS calibration using a data set of almost 400 core samples from Lake Suigetsu, Japan, as a means to rapidly reconstruct % total organic carbon (TOC). We evaluate the best spectra pretreatment, examine different statistical approaches, and provide recommendations for the optimum number of calibration samples required for accurate predictions. Results show that the most robust method is based on first-order derivatives of all spectra modeled with partial least squares regression. We construct a TOC model training set using 247 samples and a validation test set using 135 samples (for test set R2 = 0.951, RMSE = 0.280) to determine TOC and illustrate the use of the model in an ultrahigh resolution (e.g., 1 mm/annual) study of a long sediment core from a climatically sensitive archive.

  19. Non-invasive detection of periodontal disease using diffuse reflectance spectroscopy: a clinical study

    NASA Astrophysics Data System (ADS)

    Prasanth, Chandra Sekhar; Betsy, Joseph; Subhash, Narayanan; Jayanthi, Jayaraj L.; Prasanthila, Janam

    2012-03-01

    In clinical diagnostic procedures, gingival inflammation is considered as the initial stage of periodontal breakdown. This is often detected clinically by bleeding on probing as it is an objective measure of inflammation. Since conventional diagnostic procedures have several inherent drawbacks, development of novel non-invasive diagnostic techniques assumes significance. This clinical study was carried out in 15 healthy volunteers and 25 patients to demonstrate the applicability of diffuse reflectance (DR) spectroscopy for quantification and discrimination of various stages of inflammatory conditions in periodontal disease. The DR spectra of diseased lesions recorded using a point monitoring system consisting of a tungsten halogen lamp and a fiber-optic spectrometer showed oxygenated hemoglobin absorption dips at 545 and 575 nm. Mean DR spectra on normalization shows marked differences between healthy and different stages of gingival inflammation. Among the various DR intensity ratios investigated, involving oxy Hb absorption peaks, the R620/R575 ratio was found to be a good parameter of gingival inflammation. In order to screen the entire diseased area and its surroundings instantaneously, DR images were recorded with an EMCCD camera at 620 and 575 nm. We have observed that using the DR image intensity ratio R620/R575 mild inflammatory tissues could be discriminated from healthy with a sensitivity of 92% and specificity of 93%, and from moderate with a sensitivity of 83% and specificity of 96%. The sensitivity and specificity obtained between moderate and severe inflammation are 82% and 76% respectively.

  20. Diffuse reflectance spectroscopy and optical polarization imaging of in-vivo biological tissue

    NASA Astrophysics Data System (ADS)

    Mora-Núñez, A.; Castillejos, Y.; García-Torales, G.; Martínez-Ponce, G.

    2013-11-01

    A number of optical techniques have been reported in the scientific literature as accomplishable methodologies to diagnose diseases in biological tissue, for instance, diffuse reflectance spectroscopy (DRS) and optical polarization imaging (OPI). The skin is the largest organ in the body and consists of three primary layers, namely, the epidermis (the outermost layer exposed to the world), the dermis, and the hypodermis. The epidermis changes from to site to site, mainly because of difference in hydration. A lower water content increase light scattering and reduce the penetration depth of radiation. In this work, two hairless mice have been selected to evaluate their skin features by using DRS and OPI. Four areas of the specimen body were chosen to realize the comparison: back, abdomen, tail, and head. From DRS, it was possible to distinguish the skin nature because of different blood irrigation at dermis. In the other hand, OPI shows pseudo-depolarizing regions in the measured Mueller images related to a spatially varying propagation of the scattered light. This provides information about the cell size in the irradiated skin.

  1. The underlying terahertz vibrational spectrum of explosives solids Joseph S. Melinger,1,a

    E-print Network

    Oklahoma State University

    spectroscopy is the detection and identifica- tion of explosive materials.1­3 Previous work has measuredThe underlying terahertz vibrational spectrum of explosives solids Joseph S. Melinger,1,a N. Laman of the underlying terahertz vibrational spectrum of the explosive solids hexahydro-1,3,5-trinitro-1,3,5- triazine

  2. Assessment of Various Organic Matter Properties by Infrared Reflectance Spectroscopy of Sediments and Filters

    NASA Astrophysics Data System (ADS)

    Alaoui, G.; Leger, M.; Gagne, J.; Tremblay, L.

    2009-05-01

    The goal of this work was to evaluate the capability of infrared reflectance spectroscopy for a fast quantification of the elemental and molecular compositions of sedimentary and particulate organic matter (OM). A partial least-squares (PLS) regression model was used for analysis and values were compared to those obtained by traditional methods (i.e., elemental, humic and HPLC analyses). PLS tools are readily accessible from software such as GRAMS (Thermo-Fisher) used in spectroscopy. This spectroscopic-chemometric approach has several advantages including its rapidity and use of whole unaltered samples. To predict properties, a set of infrared spectra from representative samples must first be fitted to form a PLS calibration model. In this study, a large set (180) of sediments and particles on GFF filters from the St. Lawrence estuarine system were used. These samples are very heterogenous (e.g., various tributaries, terrigenous vs. marine, events such as landslides and floods) and thus represent a challenging test for PLS prediction. For sediments, the infrared spectra were obtained with a diffuse reflectance, or DRIFT, accessory. Sedimentary carbon, nitrogen, humic substance contents as well as humic substance proportions in OM and N:C ratios were predicted by PLS. The relative root mean square error of prediction (%RMSEP) for these properties were between 5.7% (humin content) and 14.1% (total humic substance yield) using the cross-validation, or leave-one out, approach. The %RMSEP calculated by PLS for carbon content was lower with the PLS model (7.6%) than with an external calibration method (11.7%) (Tremblay and Gagné, 2002, Anal. Chem., 74, 2985). Moreover, the PLS approach does not require the extraction of POM needed in external calibration. Results highlighted the importance of using a PLS calibration set representative of the unknown samples (e.g., same area). For filtered particles, the infrared spectra were obtained using a novel approach based on attenuated total reflectance, or ATR, allowing the direct analysis of the filters. In addition to carbon and nitrogen contents, amino acid and muramic acid (a bacterial biomarker) yields were predicted using PLS. Calculated %RMSEP varied from 6.4% (total amino acid content) to 18.6% (muramic acid content) with cross-validation. PLS regression modeling does not require a priori knowledge of the spectral bands associated with the properties to be predicted. In turn, the spectral regions that give good PLS predictions provided valuable information on band assignment and geochemical processes. For instance, nitrogen and humin contents were greatly determined by an absorption band caused by aluminosilicate OH group. This supports the idea that OM-clay interactions, important in humin formation and OM preservation, are mediated by nitrogen-containing groups.

  3. Waveguide mode imaging and dispersion analysis with terahertz near-field microscopy

    NASA Astrophysics Data System (ADS)

    Mitrofanov, Oleg; Tan, Thomas; Mark, Paul R.; Bowden, Bradley; Harrington, James A.

    2009-04-01

    Propagation of terahertz waves in hollow metallic waveguides depends on the waveguide mode. Near-field scanning probe terahertz microscopy is applied to identify the mode structure and composition in dielectric-lined hollow metallic waveguides. Spatial profiles, relative amplitudes, and group velocities of three main waveguide modes are experimentally measured and matched to the HE11, HE12, and TE11 modes. The combination of near-field microscopy with terahertz time-resolved spectroscopy opens the possibility of waveguide mode characterization in the terahertz band.

  4. High Power Terahertz Conductive Antenna with Chaotic Electrodes

    NASA Astrophysics Data System (ADS)

    Kim, Christopher; Graber, Benjamin; Wu, Dong Ho

    2015-03-01

    Time domain terahertz spectroscopy (TDTS) is now widely adopted and being used for various purposes, including chemical and material analysis as well as detection of hazardous materials in the laboratories. While there are several different methods available to generate a wideband terahertz pulse for the TDTS, currently a terahertz photoconductive antenna may be the most popular one, as it can produce a wideband terahertz pulse very efficiently. However our experimental investigation indicates that the conventional photoconductive antenna with a pair of parallel electrodes can produce a terahertz pulse at most about 100 micro-Watts. When attempted to produce a higher power terahertz pulse the antenna may experience irrevocable failure. In order to overcome this problem we recently redesigned the photoconductive antenna and implemented electrodes that lead to a chaotic trajectories of charged particles. With the new electrodes we have demonstrated a high power (>2 mW) coherent terahertz beam, and we found that the lifetime of the antenna is also substantially longer than that of the conventional antenna. In this talk I will present our experimental results and disclose some of our new antenna designs. Supported by DTRA and Naval Research Laboratory.

  5. Exploiting Optical Contrasts for Cervical Precancer Diagnosis via Diffuse Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Chang, Vivide Tuan-Chyan

    Among women worldwide, cervical cancer is the third most common cancer with an incidence rate of 15.3 per 100,000 and a mortality rate of 7.8 per 100,000 women. This is largely attributed to the lack of infrastructure and resources in the developing countries to support the organized screening and diagnostic programs that are available to women in developed nations. Hence, there is a critical global need for a screening and diagnostic paradigm that is effective in low-resource settings. Various strategies are described to design an optical spectroscopic sensor capable of collecting reliable diffuse reflectance data to extract quantitative optical contrasts for cervical cancer screening and diagnosis. A scalable Monte Carlo based optical toolbox can be used to extract absorption and scattering contrasts from diffuse reflectance acquired in the cervix in vivo. [Total Hb] was shown to increase significantly in high-grade cervical intraepithelial neoplasia (CIN 2+), clinically the most important tissue grade to identify, compared to normal and low-grade intraepithelial neoplasia (CIN 1). Scattering was not significantly decreased in CIN 2+ versus normal and CIN 1, but was significantly decreased in CIN relative to normal cervical tissues. Immunohistochemistry via anti-CD34, which stains the endothelial cells that line blood vessels, was used to validate the observed absorption contrast. The concomitant increase in microvessel density and [total Hb] suggests that both are reactive to angiogenic forces from up-regulated expression of VEGF in CIN 2+. Masson's trichrome stain was used to assess collagen density changes associated with dysplastic transformation of the cervix, hypothesized as the dominant source of decreased scattering observed. Due to mismatch in optical and histological sampling, as well as the small sample size, collagen density and scattering did not change in a similar fashion with tissue grade. Dysplasia may also induce changes in cross-linking of collagen without altering the amount of collagen present. Further work would be required to elucidate the exact sources of scattering contrast observed. Common confounding variables that limit the accuracy and clinical acceptability of optical spectroscopic systems are calibration requirements and variable probe-tissue contact pressures. Our results suggest that using a real-time self-calibration channel, as opposed to conventional post-experiment diffuse reflectance standard calibration measurements, significantly improved data integrity for the extraction of scattering contrast. Extracted [total Hb] and scattering were also significantly associated with applied contact probe pressure in colposcopically normal sites. Hence, future contact probe spectroscopy or imaging systems should incorporate a self-calibration channel and ensure spectral acquisition at a consistent contact pressure to collect reliable data with enhanced absorption and scattering contrasts. Another method to enhance optical contrast is to selectively interrogate different depths in the dysplastic cervix. For instance, scattering has been shown to increase in the epithelium (increase in nuclear-to-cytoplasmic ratio) while decrease in the stroma (re-organization of the extra-cellular matrix and changes in of collagen fiber cross-links). A fiber-optic probe with 45° illumination and collection fibers with a separation distance of 330 ?m was designed and constructed to selectively interrogate the cervical epithelium. Mean extraction errors from liquid phantoms with optical properties mimicking the cervical epithelium for ?a and ?s' were 11.3 % and 12.7 %, respectively. Diffuse reflectance spectra from 9 sites in four loop electrosurgical excision procedure (LEEP) patients were analyzed. Preliminary data demonstrate the utility of the oblique fiber geometry in extracting scattering contrast in the cervical epithelium. Further work is needed to study the systematic error in optical property extraction and to incorporate simultaneous extraction of epithelial and stromal contrasts using both flat an

  6. Terahertz spectrum of gallic acid

    NASA Astrophysics Data System (ADS)

    Wu, Meng; Zhao, Guozhong; Wang, Haiyan; Liang, Chengshen

    2009-11-01

    Gallic acid is natural polyphenol compound found in many green plants. More and more experiments have demonstrated that the gallic acid has comprehensive applications. In the field of medicine, the gallic acid plays an important role in antianaphylaxis, antineoplastic, antimycotic, anti-inflammatory, antivirotic, antiasthmatic and inhibiting the degradation of insulin. It also has a lot of applications in chemical industry, food industry and light industry. So it is important to study the terahertz time-domain spectroscopy of gallic acid. Terahertz time-domain spectroscopy (THz-TDS) is a new coherent spectral technology based on the femtosecond laser. In this work, the spectral characteristics of gallic acid in the range of 0.4 THz to 2.6 THz have been measured by THz-TDS. We obtained its absorption and refraction spectra at room temperature. The vibration absorption spectrum of the single molecule between 0.4 THz and 2.6 THz is simulated based on the Density Functional Theory (DFT). It is found that the gallic acid has the spectral response to THz wave in this frequency range. The results show the abnormal dispersion at 1.51 THz and 2.05 THz. These results can be used in the qualitative analysis of gallic acid and the medicine and food inspection.

  7. Terahertz spectroscopy of dynamics of coupling between the coherent longitudinal optical phonon and plasmon in the surge current of instantaneously photogenerated carriers flowing through the i-GaAs layer of an i-GaAs/n-GaAs epitaxial structure

    NASA Astrophysics Data System (ADS)

    Takeuchi, Hideo; Tsuruta, Syuichi; Nakayama, Masaaki

    2011-07-01

    We demonstrate the dynamics of coupling between the coherent longitudinal optical (LO) phonon and plasmon of instantaneously photogenerated electrons in an undoped GaAs/n-type GaAs (i-GaAs/n-GaAs) epitaxial structure using time-domain terahertz spectroscopy. Initially, we experimentally and numerically clarify the presence of the built-in electric field in the i-GaAs layer of the i-GaAs/n-GaAs epitaxial layer. Next, we performed the terahertz-wave measurements of the i-GaAs/n-GaAs epitaxial structure at various excitation conditions from a low density excitation regime to a high excitation regime. The LO-phonon-plasmon coupled (LOPC) mode has been confirmed from the terahertz-wave measurement. It is found that the frequency of the LOPC mode is determined by the pump-beam power. This fact demonstrates that the LOPC mode is formed in the i-GaAs layer. In addition, we performed the time-partitioning Fourier transform in order to reveal the dynamical change in the LOPC mode as a function of time delay. Using this analysis, we have observed that the disappearance of the LOPC mode immediately occurs within the time delay of 0.6 ps. Following the disappearance of the LOPC mode, only the bare coherent GaAs LO phonon dominates the terahertz waves.

  8. Propagation through terahertz waveguides with photonic crystal boundaries

    NASA Astrophysics Data System (ADS)

    Bingham, Adam L.

    Scope and method of study. The research presented in this dissertation investigates the integration of photonic crystal lattices into parallel plate waveguides at terahertz frequencies. The experimental data was obtained by measuring the terahertz pulses through the photonic crystal waveguides in a standard terahertz time-domain spectroscopy system. The terahertz pulses were generated and detected via optoelectronic means utilizing lithographically fabricated transmitting and receiving antennas and a femtosecond laser. Findings and conclusions. The main findings of this research are that metallic photonic crystal waveguides are a potential two-dimensional interconnect, and photonic waveguides act as an excellent guided-wave filter. The photonic crystal waveguides demonstrate attenuation approximating that of a comparable metallic waveguide, and demonstrate the capability to integrate guided-wave components with a high level of performance. The photonic waveguides act as a powerful filter, and the mode-matching theory allows complete design control over the waveguides.

  9. Mapping of egg yolk and animal skin glue paint binders in Early Renaissance paintings using near infrared reflectance imaging spectroscopy.

    PubMed

    Dooley, Kathryn A; Lomax, Suzanne; Zeibel, Jason G; Miliani, Costanza; Ricciardi, Paola; Hoenigswald, Ann; Loew, Murray; Delaney, John K

    2013-09-01

    In situ chemical imaging techniques are being developed to provide information on the spatial distribution of artists' pigments used in polychrome works of art such as paintings. The new methods include reflectance imaging spectroscopy and X-ray fluorescence mapping. Results from these new methods have extended the knowledge obtained from site-specific chemical analyses widely in use. While these mapping methods have aided in determining the distribution of pigments, there is a growing interest to develop methods capable of identifying and mapping organic paint binders as well. Near infrared (NIR) reflectance spectroscopy has been extensively used in the remote sensing field as well as in the chemical industry to detect organic compounds. NIR spectroscopy provides a rapid method to assay organics by utilizing vibrational overtones and combination bands of fundamental absorptions that occur in the mid-IR. Here we explore the utility of NIR reflectance imaging spectroscopy to map organic binders in situ by examining a series of panel paintings known to have been painted using distemper (animal skin glue) and tempera (egg yolk) binders as determined by amino acid analysis of samples taken from multiple sites on the panels. In this report we demonstrate the success in identifying and mapping these binders by NIR reflectance imaging spectroscopy in situ. Three of the four panel paintings from Cosimo Tura's The Annunciation with Saint Francis and Saint Louis of Toulouse (ca. 1475) are imaged using a highly sensitive, line-scanning hyperspectral imaging camera. The results show an animal skin glue binder was used for the blue skies and blue robe of the Virgin Mary, and egg yolk tempera was used for the red robes and brown landscape. The mapping results show evidence for the use of both egg yolk and animal skin glue in the faces of the figures. The strongest absorption associated with lipidic egg yolk features visually correlates with areas that appear to have white highlights. The results are in agreement with prior site-specific amino acid analysis, underscoring the synergy of both methods. The work here demonstrates that NIR reflectance imaging spectroscopy is a useful technique that can identify and map paint binding media based on differences in chemical composition. PMID:23799233

  10. Detection of defect states in low-k dielectrics using reflection electron energy loss spectroscopy

    NASA Astrophysics Data System (ADS)

    King, S. W.; French, B.; Mays, E.

    2013-01-01

    Reflection electron energy loss spectroscopy (REELS) has been utilized to measure the band gap (Eg) and energy position of sub-gap defect states for both non-porous and porous low dielectric constant (low-k) materials. We find the surface band gap for non-porous k = 2.8-3.3 a-SiOC:H dielectrics to be ? 8.2 eV and consistent with that measured for a-SiO2 (Eg = 8.8 eV). Ar+ sputtering of the non-porous low-k materials was found to create sub-gap defect states at ? 5.0 and 7.2 eV within the band gap. Based on comparisons to observations of similar defect states in crystalline and amorphous SiO2, we attribute these sub-gap defect states to surface oxygen vacancy centers. REELS measurements on a porous low-k a-SiOC:H dielectric with k = 2.3 showed a slightly smaller band gap (Eg = 7.8 eV) and a broad distribution of defects states ranging from 2 to 6 eV. These defect states are attributed to a combination of both oxygen vacancy defects created by the UV curing process and carbon residues left in the film by incomplete removal of the sacrificial porogen. Plasma etching and ashing of the porous low-k dielectric were observed to remove the broad defect states attributed to carbon residues, but the oxygen vacancy defects remained.

  11. Infrared reflection absorption spectroscopy of amphipathic model peptides at the air/water interface.

    PubMed

    Kerth, Andreas; Erbe, Andreas; Dathe, Margitta; Blume, Alfred

    2004-06-01

    The linear sequence KLAL (KLALKLALKALKAALKLA-NH(2)) and its corresponding d,l-isomers k(9)a(10)-KLAL (KLALKLALkaLKAALKLA-NH(2)) and l(11)k(12)-KLAL (KLALKLALKAlkAALKLA-NH(2)) are model compounds for potentially amphipathic alpha-helical peptides which are able to bind to membranes and to increase the membrane permeability in a structure- and target-dependent manner (Dathe and Wieprecht, 1999) We first studied the secondary structure of KLAL and its analogs bound to the air/water using infrared reflection absorption spectroscopy. For the peptide films the shape and position of the amide I and amide II bands indicate that the KLAL adopts at large areas per molecule an alpha-helical secondary structure, whereas at higher surface pressures or smaller areas it converts into a beta-sheet structure. This transition could be observed in the compression isotherm as well as during the adsorption at the air/water interface from the subphase as a function of time. The secondary structures are essentially orientated parallel to the air/water interface. The analogs with d-amino acids in two different positions of the sequence, k(9)a(10)-KLAL and l(11)k(12)-KLAL, form only beta-sheet structures at all surface pressures. The observed results are interpreted using a comparison of hydrophobic moments calculated for alpha-helices and beta-sheets. The differences between the hydrophobic moments calculated using the consensus scale are not large. Using the optimal matching hydrophobicity scale or the whole-residue hydrophobicity scale the beta-sheet even has the larger hydrophobic moment. PMID:15189871

  12. The potential of near infrared reflectance spectroscopy (NIRS) for the estimation of agroindustrial compost quality.

    PubMed

    Galvez-Sola, L; Moral, R; Perez-Murcia, M D; Perez-Espinosa, A; Bustamante, M A; Martinez-Sabater, E; Paredes, C

    2010-02-15

    Composting is an environmentally friendly alternative for the recycling of organic wastes and its use is increasing in recent years. An exhaustive monitoring of the composting process and of the final compost characteristics is necessary to certify that the values of compost characteristics are within the limits established by the legislation in order to obtain a safe and marketable product. The analysis of these parameters on each composting batch in the commercial composting plant is time-consuming and expensive. So, their estimation in the composting facilities based on the use of near infrared reflectance spectroscopy (NIRS) could be an interesting approach in order to monitor compost quality. In this study, more than 300 samples from 20 different composting procedures were used to calibrate and validate the NIRS estimation of compost properties (pH, electrical conductivity (EC), total organic matter (TOM), total organic carbon (TOC), total nitrogen (TN) and C/N ratio, macronutrient contents (N, P, K) and potentially pollutant element concentrations (Fe, Cu, Mn and Zn)). The composts used were elaborated using different organic wastes from agroindustrial activities (GS: grape stalk; EGM: exhausted grape marc; GM: grape marc; V: vinasse; CJW: citrus juice waste; Alpeorujo: olive-oil waste; AS: almond skin; EP: exhausted peat; TSW: tomato soup waste; SMS: spent mushroom substrate) co-composted with manures (CM: cattle manure; PM: poultry manure) or urban wastes (SS: sewage sludge) The estimation results showed that the NIRS technique needs to be fitted to each element and property, using specific spectrum transformations, in order to achieve an acceptable accuracy in the prediction. However, excellent prediction results were obtained for TOM and TOC, successful calibrations for pH, EC, Fe and Mn, and moderately successful estimations for TN, C/N ratio, P, K, Cu and Zn. PMID:20061002

  13. Evaluation of various polyethylene as potential dosimeters by attenuated total reflectance-Fourier-transform infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Halperin, Fred; Collins, Greta; DiCicco, Michael; Logar, John

    2014-12-01

    Various types of polyethylene (PE) have been evaluated in the past for use as a potential dosimeter, chiefly via the formation of an unsaturated transvinylene (TV) double-bond resulting from exposure to ionizing radiation. The utilization of attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy in characterizing TV formation in irradiated PE for a potential dosimeter has yet to be fully developed. In this initial investigation, various PE films/sheets were exposed to ionizing radiation in a high-energy 5 megaelectron volt (MeV) electron beam accelerator in the 10-500 kilogray (kGy) dose range, followed by ATR-FTIR analysis of TV peak formation at the 965 cm-1 wavenumber. There was an upward trend in TV formation for low-density polyethylene (LDPE) films and high-density polyethylene (HDPE) sheets as a function of absorbed dose in the 10-50 kGy dose range, however, the TV response could not be equated to a specific absorbed dose. LDPE film displayed a downward trend from 50 kGy to 250 kGy and then scattering up to 500 kGy; HDPE sheets demonstrated an upward trend in TV formation up to 500 kGy. For ultra-high molecular weight polyethylene (UHMWPE) sheets irradiated up to 150 kGy, TV response was equivalent to non-irradiated UHMWPE, and a minimal upward trend was observed for 200 kGy to 500 kGy. The scatter of the data for the irradiated PE films/sheets is such that the TV response could not be equated to a specific absorbed dose. A better correlation of the post-irradiation TV response to absorbed dose may be attained through a better understanding of variables.

  14. 3D Effect in Determination of Spin Polarization using Andreev Reflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gifford, Jessica; Snider, Charles; Martinez, Jonny; Chen, Tingyong

    2012-10-01

    Andreev Reflection Spectroscopy (ARS) has been utilized to measure spin polarization of many magnetic materials including some half metals, as well as the superconducting gap of superconductors which include the recently discovered Fe superconductors and topological superconductors. The values of spin polarization and superconducting gap are extracted from the ARS data often by a modified Blonder-Tinkham-Klapwijk (BTK) model or the more recent Chen-Tesanovic-Chien (CTC) model. Both consider the ferromagnet/superconductor interface as one dimensional (1D). However, in reality, a tip may have a point angle with three dimensional (3D) effects. In this work, we present both theoretical and experimental studies of the 3D effects in the determination of spin polarization using ARS. We have found that for an ideal interface without interfacial scattering, the 3D ARS spectra are the same as 1D spectra. But for non-ideal interfaces the 3D effect can drastically change the conductance spectra depending on the point angle of the tip. Most importantly, the 3D spectra can be well described by the 1D model with a different interfacial scattering factor and a slightly different inelastic scattering factor. The spin polarization and superconducting gap extracted from the 3D ARS is the same as that extracted using the 1D model, demonstrating that 1D ARS model can be utilized to determine spin polarization as long as interfacial scattering is not of any concern. Finally, we apply the both the 1D and the 3D models to a set of ARS data and show that the extracted spin polarization value is the same for both models.

  15. Diffuse reflectance spectroscopy of epithelial tissue with a smart fiber-optic probe

    PubMed Central

    Yu, Bing; Shah, Amy; Nagarajan, Vivek K.; Ferris, Daron G.

    2014-01-01

    Diffuse reflectance spectroscopy (DRS) with a fiber-optic probe can noninvasively quantify the optical properties of epithelial tissues and has shown the potential as a cost-effective, fast and sensitive tool for diagnosis of early precancerous changes in the cervix and oral cavity. However, current DRS systems are susceptible to several sources of systematic and random errors, such as uncontrolled probe-to-tissue pressure and lack of a real-time calibration that can significantly impair the measurement accuracy, reliability and validity of this technology as well as its clinical utility. In addition, such systems use bulky, high power and expensive optical components which impede their widespread use in low- and middle-income countries (LMICs) where epithelial cancer related death is disproportionately high. In this paper we report a portable, easy-to-use and low cost, yet accurate and reliable DRS device that can aid in the screening and diagnosis of oral and cervical cancer. The device uses an innovative smart fiber-optic probe to eliminate operator bias, state-of-the-art photonics components to reduce size and power consumption, and automated software to reduce the need of operator training. The device showed a mean error of 1.4 ± 0.5% and 6.8 ± 1.7% for extraction of phantom absorption and reduced scattering coefficients, respectively. A clinical study on healthy volunteers indicated that a pressure below 1.0 psi is desired for oral mucosal tissues to minimize the probe effects on tissue physiology and morphology. PMID:24688805

  16. Generation of Terahertz Radiation by Interaction of Intense Femtosecond Laser Pulses with a Metal Surface

    NASA Astrophysics Data System (ADS)

    Akhmedzhanov, R. A.; Ilyakov, I. E.; Mironov, V. A.; Oladyshkin, I. V.; Suvorov, E. V.; Fadeev, D. A.; Shishkin, B. V.

    2015-04-01

    We present the results of experimental and theoretical studies of generation of terahertz radiation during reflection of a femtosecond-long laser pulse from a metal surface. It is shown that a greater part of the experimental results (narrow directivity of the terahertz waves and dependence of its energy on the polarization and incidence angle of the laser radiation) can be interpreted within the model of ?erenkov radiation. Some new features of generation of terahertz radiation are considered, which appear during an optical breakdown of the medium near the metal surface. Structural changes in the terahertz signal, which take place in the process of formation of the near-surface plasma, are studied.

  17. Assessment of Mass Flows and Fuel Quality During Mechanical Dehydration of Silages Using Near Infrared Reflectance Spectroscopy

    Microsoft Academic Search

    Daniela Perbandt; Jürgen Reulein; Felix Richter; Reinhold Stülpnagel; Michael Wachendorf

    2010-01-01

    This study was implemented to evaluate the potential of near-infrared reflectance spectroscopy (NIRS) technology to estimate\\u000a chemical composition of dried press cake samples characterised by a wide range of parent materials. A total of 210 samples,\\u000a derived from two studies on production of solid fuels from agricultural crops by application of the IFBB technology (Integrated\\u000a production of solid fuels and

  18. Results of an analytical study of spacecraft deposition contamination by internal reflection spectroscopy. [(haze on spacecraft windows from space debris)

    NASA Technical Reports Server (NTRS)

    Mookherji, T.

    1976-01-01

    Outgassing, deposition, and desorption kinetics of silicone compounds, are examined as examples of optical surface contaminants of spacecraft windows. Their behavior in a space environment after exposure to ultraviolet radiation is also examined. The use of internal reflection spectroscopy is shown to provide a viable means of real-time, in-situ identification of contaminants of orbiting spacecraft. The instrumental techniques are proposed as the basis of further investigations and the development of flight hardware.

  19. Feasibility of using near-infrared reflectance spectroscopy for the analysis of C, N, P, and diatoms in lake sediments

    Microsoft Academic Search

    D. F. Malley; H. Rönicke; D. L. Findlay; Forename Surname

    1999-01-01

    The present study explored whether rapid, non-destructive near-infrared reflectance spectroscopy (NIRS) could complement conventional paleolimnological and chemical analyses of sediment cores for greater efficiency and cost-effectiveness. The study used a 47-cm long freeze-core from the deepest point in Lake Arendsee, Mecklenburg Plain in northern Germany taken in 1993 to elucidate eutrophication history and to identify the pre-impact algal communities in

  20. Bell et al. Eros Low Phase Spectra 1 Near-IR Reflectance Spectroscopy of 433 Eros from the NIS Instrument

    E-print Network

    Bell III, James F.

    Bell et al. Eros Low Phase Spectra 1 1 Near-IR Reflectance Spectroscopy of 433 Eros from the NIS , B.E. Clark1 , C. Peterson1 , M.J. Gaffey4 , J. Joseph1 , B. Carcich1 , A. Harch1 , M.E. Bell1 , J8@cornell.edu #12;Bell et al. Eros Low Phase Spectra 2 2 Abstract From February 13 to May 13, 2000

  1. Comparison of Near-Infrared Reflectance Spectroscopy and Texture Analyzer for Measuring Wheat Bread Changes in Storage

    Microsoft Academic Search

    Feng Xie; Floyd E. Dowell; Xiuzhi S. Sun

    2003-01-01

    Cereal Chem. 80(1):25-29 Bread staling affects bread texture properties and is one of the most common problems in bread storage. Bread firmness, as measured in com- pression mode by a texture analyzer (TA) has been commonly used to measure bread staling. This study investigated the potential of visible and near-infrared reflectance spectroscopy (NIRS) to detect bread changes during storage by

  2. Determination of In-Shell Peanut Oil and Fatty Acid Composition Using Near-Infrared Reflectance Spectroscopy

    Microsoft Academic Search

    Jaya SundaramChari; Chari V. Kandala; Ronald A. Holser; Christopher L. Butts; William R. Windham

    2010-01-01

    NIR reflectance spectroscopy was used to analyze the total oil and fatty acid concentration of Virginia and Valencia types\\u000a of in-shell peanuts rapidly and nondestructively. NIR absorbance spectra were collected in the wavelength range from 400 to\\u000a 2,500 nm using a NIR instrument. Average total oil concentrations of all samples were determined by a standard Soxtec extraction\\u000a method. Fatty acids were

  3. An in-line diffuse reflection spectroscopy study of the oxidation of stainless steel under boiling water reactor conditions

    Microsoft Academic Search

    C. Degueldre; S. O'Prey; W. Francioni

    1996-01-01

    A novel cell unit was constructed to measure in-line the oxide layer build-up on a stainless steel sample by Diffuse Reflection Spectroscopy (DRS; ultraviolet, visible, near infrared) under boiling water reactor (BWR) conditions. The stainless steel samples, observed in the cell through a sapphire window, are contacted with oxidising hot water (300 °C, 9.0 MPa). Using a cold finger with

  4. Mesoscopic structuring and dynamics of alcohol/water solutions probed by terahertz time-domain spectroscopy and pulsed field gradient nuclear magnetic resonance.

    PubMed

    Li, Ruoyu; D'Agostino, Carmine; McGregor, James; Mantle, Michael D; Zeitler, J Axel; Gladden, Lynn F

    2014-08-28

    Terahertz and PFG-NMR techniques are used to explore transitions in the structuring of binary alcohol/water mixtures. Three critical alcohol mole fractions (x1, x2, x3) are identified: methanol (10, 30, 70 mol %), ethanol (7, 15, 60 mol %), 1-propanol (2, 10, 50 mol %), and 2-propanol (2, 10, 50 mol %). Above compositions of x1 no isolated alcohol molecules exist, and below x1 the formation of large hydration shells around the hydrophobic moieties of the alcohol is favored. The maximum number of water molecules, N0, in the hydration shell surrounding a single alcohol molecule increases with the length of the carbon chain of the alcohol. At x2 the greatest nonideality of the liquid structure exists with the formation of extended hydrogen bonded networks between alcohol and water molecules. The terahertz data show the maximum absorption relative to that predicted for an ideal mixture at that composition, while the PFG-NMR data exhibit a minimum in the alkyl chain self-diffusivity at x2, showing that the alcohol has reached a minimum in diffusion when this extended alcohol-water network has reached the highest degree of structuring. At x3 an equivalence of the alkyl and alcohol hydroxyl diffusion coefficients is determined by PFG-NMR, suggesting that the molecular mobility of the alcohol molecules becomes independent of that of the water molecules. PMID:25117060

  5. Single fiber reflectance spectroscopy on cervical premalignancies: the potential for reduction of the number of unnecessary biopsies

    NASA Astrophysics Data System (ADS)

    Hariri Tabrizi, Sanaz; Mahmoud Reza Aghamiri, S.; Farzaneh, Farah; Amelink, Arjen; Sterenborg, Henricus J. C. M.

    2013-01-01

    We have assessed the value of single fiber reflectance (SFR) spectroscopy in prediction of cervical squamous intraepithelial lesions (SIL). SFR was used to measure reflected light from 32 patients undergoing standard colposcopy. Seven parameters extracted from the spectra in addition to two biographic parameters were compared in biopsy-confirmed SIL versus nonSIL. The significant parameters in the model were determined using stepwise logistic regression. The classification performance was evaluated by a leave-one-out cross-validation method and reported by receiver operating characteristic (ROC) curves. Light absorption properties and biographic characteristics of the patient contributed significantly to the accuracy of the model. Combining important parameters, the best retrospective sensitivity, specificity and area under the ROC curve for SIL sites versus nonSIL were 89%, 80% and 0.89%, respectively. SFR spectroscopy shows promise as a noninvasive, real-time method to guide the clinician in reducing the number of unnecessary biopsies. Discrimination of SIL from other abnormalities compares favorably with that obtained by fluorescence alone and by fluorescence combined with reflectance spectroscopy while the simplicity and low cost of the presented system are dominant.

  6. A New Diffuse Reflecting Material with Applications Including Integrating Cavity Ring-Down Spectroscopy 

    E-print Network

    Cone, Michael Thomas

    2014-04-16

    We report the development of a new diffuse reflecting material with measured diffuse reflectivity values as high as 0.9992 at 532 nm, and 0.9969 at 266 nm. These values are, to the author’s best knowledge, the highest diffuse reflectivity values...

  7. Terahertz Imaging System for Medical Applications and Related High Efficiency Terahertz Devices

    NASA Astrophysics Data System (ADS)

    Ouchi, Toshihiko; Kajiki, Kousuke; Koizumi, Takayuki; Itsuji, Takeaki; Koyama, Yasushi; Sekiguchi, Ryota; Kubota, Oichi; Kawase, Kodo

    2013-07-01

    A terahertz (THz) imaging system and high efficient terahertz sources and detectors for medical applications were developed. A fiber laser based compact time domain terahertz tomography system was developed with a high depth resolution of less than 20 ?m. Three-dimensional images of porcine skin were obtained including some physical properties such as applied skin creams. The discrimination between healthy human tissue and tumor tissue has been achieved using reflection spectra. To improve the THz imaging system, a ridge waveguide LiNbO3 based nonlinear terahertz generator was studied to achieve high output power. A ridge waveguide with 5-7 ?m width was designed for high efficiency emission from the LiNbO3 crystal by the electro-optic Cherenkov effect. Terahertz electronic sources and detectors were also realized for future imaging systems. As electronic source devices, resonant tunneling diode (RTD) oscillators with a patch antenna were fabricated using an InGaAs/InAlAs/AlAs triple barrier structure. On the other side, Schottky barrier diode (SBD) detectors with a log-periodic antenna were fabricated by thin-film technology on a Si substrate. Both devices operate above 1 THz at room temperature. This electronic THz device set could provide a future high performance imaging system.

  8. Discrimination of herbal medicines according to geographical origin with near infrared reflectance spectroscopy and pattern recognition techniques.

    PubMed

    Woo, Y A; Kim, H J; Cho, J H; Chung, H

    1999-11-01

    Herbal medicines have an important role in clinical therapy in Asian countries such as Korea, Japan, and China. The objective of this study is to develop a nondestructive and accurate analytical method to discriminate herbal medicines according to geographical origin. Even though they are the same species, their qualities are different by growing conditions such as climate and soil. Near infrared (NIR) reflectance spectroscopy and a pattern recognition technique were applied for discrimination of herbal medicines according to geographical origin (Korea and China). Astragali Radix (AR), Ganoderma, and Smilacis Rhizoma (SR) were examined. It is shown that the representative NIR reflectance spectra in each group are different according to geographical origin after second derivatization to enhance spectral features. Also, the NIR reflectance spectra of Chinese and Korean samples were differentiated using principal component (PC) score plots. To establish the discrimination rule, Mahalanobis distance and discriminant analysis with PLS2 were utilized. PMID:10703997

  9. Tissue differentiation by diffuse reflectance spectroscopy for automated oral and maxillofacial laser surgery: ex vivo pilot study

    NASA Astrophysics Data System (ADS)

    Zam, Azhar; Stelzle, Florian; Tangermann-Gerk, Katja; Adler, Werner; Nkenke, Emeka; Schmidt, Michael; Douplik, Alexandre

    2010-02-01

    Remote laser surgery lacks of haptic feedback during the laser ablation of tissue. Hence, there is a risk of iatrogenic damage or destruction of anatomical structures like nerves or salivary glands. Diffuse reflectance spectroscopy provides a straightforward and simple approach for optical tissue differentiation. We measured diffuse reflectance from seven various tissue types ex vivo. We applied Linear Discriminant Analysis (LDA) to differentiate the seven tissue types and computed the area under the ROC curve (AUC). Special emphasis was taken on the identification of nerves and salivary glands as the most crucial tissue for maxillofacial surgery. The results show a promise for differentiating tissues as guidance for oral and maxillofacial laser surgery by means of diffuse reflectance.

  10. Terahertz metamaterials for sensing and detection

    NASA Astrophysics Data System (ADS)

    Wilbert, David Shawn

    The function of metamaterials targeted for operation at terahertz frequencies was investigated including split-ring resonators, perfect absorbers, and flexible absorbers. The devices were designed through simulation by finite element method commercial software and fabricated by photolithographic lift-off process using electron beam evaporation for the deposition of metal layers. The terahertz time domain spectroscopy measurement technique was used to characterize the devices in both transmission and reflection modes. Each device was composed of arrays of subwavelength resonant structures. The split-ring resonator study focused on the effects caused by the addition of a passivation layer, which served to effectively lower the resonant frequencies of the rings, as well as the addition of a second layer of rings that led to a broadening of the resonant response of the structures. The perfect absorber investigation was focused on the polarization insensitive nature of the frequency selective surface elements. A mechanism for this property was proposed along with an equivalent circuit model that can describe and predict the resonant behavior. The perfect absorber were based on a unit cell structure with four-fold symmetry that consisted of a metal ground, a polyimide dielectric spacer layer, and top frequency selective surface layer. The flexible absorber chapter reports the simulation and characterization of perfect absorber structures fabricated on a polyimide flexible substrate that consisted of a metal ground plane, a dielectric spacer, and a frequency selective surface composed of two layers of differently sized, nonconcentric, circular rings separated by another dielectric spacer layer. Specifically, the frequency selective surface was seen to exhibit a frequency response dependent upon the position of the individual resonant elements with respect to each other. The functionality of the flexible absorbers during deformation was also evaluated through the use of two custom designed vacuum holders. Characterization of the flexible absorbers before and after removal from the sacrificial substrate, as well as under both types of deformation, revealed that the structures had little change in functionality. The flexible absorbers were shown to be suitable for future incorporation in sensing applications and to have the potential to lead to future applications in cloaking.

  11. Imaging with terahertz radiation

    NASA Astrophysics Data System (ADS)

    Chan, Wai Lam; Deibel, Jason; Mittleman, Daniel M.

    2007-08-01

    Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies.

  12. A Mechanism Study of Reflectance Spectroscopy for Investigating Heavy Metals in Soils

    Microsoft Academic Search

    Yunzhao Wu; Jun Chen; Junfeng Ji; Peng Gong; Qilin Liao; Qingjiu Tian; Hongrui Ma

    2007-01-01

    Conventional methods for investigating heavy metal contamination in soil are time consuming and expensive. In this study, we (i) explored refl ectance spectroscopy as an alternative method for assessing heavy metals, and (ii) further explored the physicochemical mechanism that allows estima- tion of heavy metals with the refl ectance spectroscopy method. We fi rst investigated the spectral response of changing

  13. Attenuated total reflection infrared spectroscopy of white-rot decayed beech wood

    Microsoft Academic Search

    Behbood Mohebby

    2005-01-01

    Small blocks of beech wood were exposed to the white-rot fungus Trametes versicolor for a period of 84 days to investigate chemical alteration in decayed wood by infrared spectroscopy. Decayed samples were analyzed at 2 week intervals by using attenuated total teflection (ATR) infrared spectroscopy as a rapid method. Analyses showed that chemical alteration in wood began after the second

  14. Prediction of wheat chemical and physical characteristics and nutritive value by near-infrared reflectance spectroscopy.

    PubMed

    Owens, B; McCann, M E E; McCracken, K J; Park, R S

    2009-01-01

    1. The aims of this study were to investigate the potential of near infrared reflectance spectroscopy (NIRS) to predict the chemical and physical characteristics of wheat and also to predict the nutritive value of wheat for broiler chickens. 2. A total of 164 wheat samples, collected from a wide range of different sources (England, Northern Ireland and Canada), varieties and years, were used in this study. 3. Chemical and physical parameters measured included specific weight, thousand grain weight, in vitro viscosity, gross energy, nitrogen, neutral detergent fibre (NDF), starch, total and soluble non-starch polysaccharides (NSP), lysine, threonine, amylose, hardness, rate of starch digestion and protein profiles. 4. A total of 94 wheat samples were selected for inclusion in three bird trials and included at 650 g/kg in a typical UK starter/grower diet. Birds were housed in individual wire metabolism cages from 7 to 28 d and offered water and food ad libitum. Dry matter intake (DMI), live weight gain (LWG) and gain:feed ratio were measured weekly. A balance collection was carried out from d 14 to 21 for determination of apparent metabolisable energy (AME), ME:gain and dry matter retention. At 28 d the birds were humanely killed, the contents of the jejunum removed for determination of in vivo viscosity and the contents of the ileum removed for determination of ileal dry matter, starch and protein digestibility. 5. The wheat samples were scanned as whole and milled wheat, both dried and undried and NIRS calibrations, first excluding and then including the Canadian wheat samples, were developed. 6. NIRS calibrations for milled wheat samples may be useful for determining specific weight (R(cv)(2) = 0.75, for milled wheat dried), nitrogen (R(cv)(2) = 0.983 for milled and dried) and rate of starch digestion (R(cv)(2) = 0.791 for milled, dried and undried). 7. NIRS calibrations for whole wheat samples (undried) may be useful for determining wheat nutritive value, with good predictions for live weight gain (R(cv)(2) = 0.817) and feed conversion efficiency (R(cv)(2) = 0.825). 8. Inclusion of the Canadian wheat samples in the NIRS analysis provided additional robust calibrations for gross energy (R(cv)(2) = 0.86, dried and milled) and starch content (R(cv)(2) = 0.79, undried and milled). 9. This study shows that NIR is a useful tool in the accurate and rapid determination of wheat chemical parameters and nutritive value and could be extremely beneficial to both the poultry and wheat industry. 10. Further extension of the dataset would be recommended to further validate these findings. PMID:19234935

  15. Terahertz broadband spectroscopic investigations of amino acid

    NASA Astrophysics Data System (ADS)

    Zhu, De-chong; Zhang, Liang-liang; Zhong, Hua; Zhang, Cun-lin

    2011-08-01

    We present an experimental terahertz (THz) spectroscopic investigation of amino acid using an air-breakdown-coherent detection (ABCD) system. The strong and ultra-broadband (0.1 to 10THz) terahertz radiations generated by two-color laser induced air plasma and measured by coherent heterodyne detection. The broadband THz reflection spectra of L-Lysine (C6H14N2O2) and L-Arginine (C6H14N2O2) are obtained. To solve the phase-retrieval problem in RTDS, the absorption signatures of the materials are extracted directly from the first derivative of the relative reflectance with respect to frequency. The absorption features of the two amino acids are characterized in the 0.5~6 THz region. It is found that both the two amino acids have an absorption peak at 1.10 THz.

  16. Estimation of soil clay and organic matter using two quantitative methods (PLSR and MARS) based on reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Nawar, Said; Buddenbaum, Henning; Hill, Joachim

    2014-05-01

    A rapid and inexpensive soil analytical technique is needed for soil quality assessment and accurate mapping. This study investigated a method for improved estimation of soil clay (SC) and organic matter (OM) using reflectance spectroscopy. Seventy soil samples were collected from Sinai peninsula in Egypt to estimate the soil clay and organic matter relative to the soil spectra. Soil samples were scanned with an Analytical Spectral Devices (ASD) spectrometer (350-2500 nm). Three spectral formats were used in the calibration models derived from the spectra and the soil properties: (1) original reflectance spectra (OR), (2) first-derivative spectra smoothened using the Savitzky-Golay technique (FD-SG) and (3) continuum-removed reflectance (CR). Partial least-squares regression (PLSR) models using the CR of the 400-2500 nm spectral region resulted in R2 = 0.76 and 0.57, and RPD = 2.1 and 1.5 for estimating SC and OM, respectively, indicating better performance than that obtained using OR and SG. The multivariate adaptive regression splines (MARS) calibration model with the CR spectra resulted in an improved performance (R2 = 0.89 and 0.83, RPD = 3.1 and 2.4) for estimating SC and OM, respectively. The results show that the MARS models have a great potential for estimating SC and OM compared with PLSR models. The results obtained in this study have potential value in the field of soil spectroscopy because they can be applied directly to the mapping of soil properties using remote sensing imagery in arid environment conditions. Key Words: soil clay, organic matter, PLSR, MARS, reflectance spectroscopy.

  17. Gate-controlled nonlinear conductivity of Dirac fermion in graphene field-effect transistors measured by terahertz time-domain spectroscopy.

    PubMed

    Maeng, Inhee; Lim, Seongchu; Chae, Seung Jin; Lee, Young Hee; Choi, Hyunyong; Son, Joo-Hiuk

    2012-02-01

    We present terahertz spectroscopic measurements of Dirac fermion dynamics from a large-scale graphene that was grown by chemical vapor deposition and on which carrier density was modulated by electrostatic and chemical doping. The measured frequency-dependent optical sheet conductivity of graphene shows electron-density-dependence characteristics, which can be understood by a simple Drude model. In a low carrier density regime, the optical sheet conductivity of graphene is constant regardless of the applied gate voltage, but in a high carrier density regime, it has nonlinear behavior with respect to the applied gate voltage. Chemical doping using viologen was found to be efficient in controlling the equilibrium Fermi level without sacrificing the unique carrier dynamics of graphene. PMID:22214292

  18. Use of near infrared reflectance spectroscopy (NIRS) to investigate selection and nutrient utilization of bamboo and to monitor the physiological status of giant pandas (Ailuropoda melanoleuca) 

    E-print Network

    Wiedower, Erin Elizabeth

    2009-05-15

    The objective of this study was to develop near infrared reflectance spectroscopy (NIRS) calibration equations from bamboo and fecal samples to predict diet composition and the physiological status of giant pandas. Discrimination between branch...

  19. Systematic study of terahertz response of SrTiO3 based heterostructures: Influence of strain, temperature, and electric field

    NASA Astrophysics Data System (ADS)

    Skoromets, V.; Kadlec, C.; Drahokoupil, J.; Schubert, J.; Hlinka, J.; Kužel, P.

    2014-06-01

    Epitaxial heterostructures consisting of a variable number of SrTiO3/DyScO3 bilayers deposited on DyScO3 substrates were investigated using time-domain terahertz spectroscopy down to helium temperatures. Interdigitated electrodes deposited on top of the structures allowed probing of the terahertz response upon an applied electric field. The phase transition into a ferroelectric state is observed in SrTiO3 films in all samples close to room temperature (between 250 and 310 K) due to in-plane epitaxial strain induced by the substrate and intercalated layers of DyScO3. Evolution of the dielectric spectra with temperature and external electric field is described by a general model which involves a damped harmonic oscillator (soft mode) coupled to a Debye relaxation (central mode). Both modes are connected with the soft mode eigenvector, as recently shown by molecular dynamics simulations, and they reflect a strong anharmonicity of the soft-mode potential. At high temperatures the soft-mode frequency variation drives all the changes observed in the spectra with temperature and applied field. At low temperatures, deep in the ferroelectric phase, the soft mode significantly hardens and loses its importance for the terahertz dynamics; the central mode becomes stronger and it almost completely determines the shape of the measured spectra. The observed variation of phase transition temperature and of the dielectric response among the structures is ascribed to a partial epitaxial strain relaxation confirmed also by x-ray diffraction.

  20. Identification of Hydrated Sulfates Collected in the Northern Rio Tinto Valley by Reflectance and Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Chemtob, S. M.; Arvidson, R. E.; Fernandez-Remolar, D. C.; Amils, R.; Morris, R. V.; Ming, D. W.; Prieto-Ballesteros, O.; Mustard, J. F.; Hutchinson, L.; Stein, T. C.; Donovan, C. E.; Fairchild, G. M.; Friedlander, L. R.; Karas, N. M.; Klasen, N.; Mendenhall, M. P.; Robinson, E. M.; Steinhardt, S. E.; Weber, L. R.

    2006-01-01

    OMEGA recently identified spectral signatures of kieserite, gypsum, and other polyhydrated sulfates at multiple locations on the surface of Mars [1,2]. The presence of sulfates was confirmed through in situ spectroscopy by MER Opportunity [3]. An approach to validate these interpretations is to collect corresponding spectral data from sulfate-rich terrestrial analog sites. The northern Rio Tinto Valley near Nerva, Spain, is a good Martian analog locale because it features extensive seasonal sulfate mineralization driven by highly acidic waters [4]. We report on mineralogical compositions identified by field VNIR spectroscopy and laboratory Raman spectroscopy.