WorldWideScience

Sample records for absorption line spectroscopy

  1. Interferometric measurement of lines shift in flames in connection with interpretation of lined absorption method in atomic absorption spectroscopy

    This paper is concerned with interferometric measuring of the line shift in flames in the view of interpretation of absorption lines in the atomic absorption spectroscopy. The newly measured line shifts were compared to the known data on Lorentz broadening of the same lines obtained by methods free of the systematic errors. The resonant lines of the alkaline earth elements (Sr, Ca, Ba) were investigated. To reduce self-absorption in the flame the solutions with minimum concentrations of the elements were used. The computation scheme includes the spectrometer apparatus width and line broadening due to the self-absorption. Formulae are given for computing the values studied. Good agreement was observed between the computed and experimental results. Error analysis was performed. It was concluded that any line shifts in the hydrocarbons were correctly taken into an account in the absolute computations of absorption

  2. High Dispersion Absorption-line Spectroscopy of AE Aqr

    Echevarria, J; Costero, R; Zharikov, S; Michel, R

    2008-01-01

    High-dispersion time-resolved spectroscopy of the unique magnetic cataclysmic variable AE Aqr is presented. A radial velocity analysis of the absorption lines yields K_2 = 168.7+/- 1 km/s. Substantial deviations of the radial velocity curve from a sinusoid are interpreted in terms of intensity variations over the secondary star's surface. A complex rotational velocity curve as a function of orbital phase is detected which has a modulation frequency of twice the orbital frequency, leading to an estimate of the binary inclination angle that is close to 70^o. The minimum and maximum rotational velocities are used to indirectly derive a mass ratio of q= 0.6 and a radial velocity semi-amplitude of the white dwarf of K_1 = 101+/-3 km/s. We present an atmospheric temperature indicator, based on the absorption line ratio of Fe I and Cr I lines, whose variation indicates that the secondary star varies from K0 to K4 as a function of orbital phase. The ephemeris of the system has been revised, using more than one thousa...

  3. Study of cancer cell lines with Fourier transform infrared (FTIR)/vibrational absorption (VA) spectroscopy

    Uceda Otero, E. P.; Eliel, G. S. N.; Fonseca, E. J. S.;

    2013-01-01

    In this work we have used Fourier transform infrared (FTIR) / vibrational absorption (VA) spectroscopy to study two cancer cell lines: the Henrietta Lacks (HeLa) human cervix carcinoma and 5637 human bladder carcinoma cell lines. Our goal is to experimentally investigate biochemical changes and d...

  4. Zeeman atomic absorption spectroscopy

    A new method of background correction in atomic absorption spectroscopy has recently been introduced, based on the Zeeman splitting of spectral lines in a magnetic field. A theoretical analysis of the background correction capability observed in such instruments is presented. A Zeeman atomic absorption spectrometer utilizing a 50 Hz sine wave modulated magnetic field is described. (Auth.)

  5. Constraining Variable High Velocity Winds from Broad Absorption Line Quasars with Multi-Epoch Spectroscopy

    Haggard, Daryl; Green, Paul J; Aldcroft, Tom; Anderson, Scott F

    2012-01-01

    Broad absorption line (BAL) quasars probe the high velocity gas ejected by luminous accreting black holes. BAL variability timescales place constraints on the size, location, and dynamics of the emitting and absorbing gas near the supermassive black hole. We present multi-epoch spectroscopy of seventeen BAL QSOs from the Sloan Digital Sky Survey (SDSS) using the Fred Lawrence Whipple Observatory's 1.5m telescope's FAST Spectrograph. These objects were identified as BALs in SDSS, observed with Chandra, and then monitored with FAST at observed-frame cadences of 1, 3, 9, 27, and 81 days, as well as 1 and 2 years. We also monitor a set of non-BAL quasars with matched redshift and luminosity as controls. We identify significant variability in the BALs, particularly at the 1 and 2 year cadences, and use its magnitude and frequency to constrain the outflows impacting the broad absorption line region.

  6. CRIRES spectroscopy and empirical line-by-line identification of FeH molecular absorption in an M dwarf

    Wende, S.; Reiners, A.; Seifahrt, A.; Bernath, P. F.

    2010-11-01

    Molecular FeH provides a large number of sharp and isolated absorption lines that can be used to measure radial velocity, rotation, or magnetic field strength with high accuracy. Our aim is to provide an FeH atlas for M-type stars in the spectral region from 986 nm to 1077 nm (Wing-Ford band). To identify these lines in CRIRES spectra of the magnetically inactive, slowly rotating, M5.5 dwarf GJ1002, we calculated model spectra for the selected spectral region with theoretical FeH line data. In general this line list agrees with the observed data, but several individual lines differ significantly in position or in line strength. After identification of as many as possible FeH lines, we corrected the line data for position and line strength to provide an accurate atlas of FeH absorption lines for use in high precision spectroscopy of low mass stars. For all lines, we used a Voigt function to obtain their positions and equivalent widths. Identification with theoretical lines was done by hand. For confirmation of the identified lines, we used statistical methods, cross-correlation techniques, and line intensities. Eventually, we were able to identify FeH lines from the (0,0), (1,0), (1,1), (2,1), (2,2), (3,2), and (4,3) vibrational bands in the observed spectra and correct the positions of the lines if necessary. The deviations between theoretical and observed positions follow a normal distribution approximately around zero. In order to empirically correct the line strength, we determined Teff, instrumental broadening (rotational broadening) and a van der Waals enhancement factor for the FeH lines in GJ1002. We also give the scaling factors for the Einstein A values to correct the line strengths. With the identified lines, we derived rotational temperatures from the line intensities for GJ1002. We conclude that FeH lines can be used for a wide variety of applications in astrophysics. With the identified lines it will be possible for example to characterize magnetically

  7. Line-Parameter Measurements and Stringent Tests of Line-Shape Models Based on Cavity-Enhanced Absorption Spectroscopy

    Bielska, Katarzyna; Fleisher, Adam J.; Hodges, Joseph T.; Lin, Hong; Long, David A.; Reed, Zachary D.; Sironneau, Vincent; Truong, Gar-Wing; Wójtewicz, Szymon

    2014-06-01

    Laser methods that are based on cavity-enhanced absorption spectroscopy (CEAS) are well-suited for measuring molecular line parameters under conditions of low optical density, and as such they are complementary to broadband Fourier-transform spectroscopy (FTS) techniques. Attributes of CEAS include relatively low detection limits, accurate and precise detuning axes and high fidelity measurements of line shape. In many cases these performance criteria are superior to those obtained using direct laser absorption spectroscopy and FTS-based systems. In this presentation we will survey several examples of frequency-stabilized cavity ring-down spectroscopy (FS-CRDS)1 measurements obtained with laser spectrometers developed at the National Institute of Standards and Technology (NIST) in Gaithersburg Maryland. These experiments, which are motivated by atmospheric monitoring and remote-sensing applications that require high-precision and accuracy, involve nearinfrared transitions of carbon dioxide, water, oxygen and methane. We discuss spectra with signal-to-noise ratios exceeding 106, frequency axes with absolute uncertainties in the 10 kHz to 100 kHz range and linked to a Cs clock, line parameters with relative uncertainties at the 0.2 % level and isotopic ratios measured with a precision of 0.03 %. We also present FS-CRDS measurements of CO2 line intensities which are measured at atmospheric concentration levels and linked to gravimetric standards for CO2 in air, and we quantify pressure-dependent deviations between various theoretical line profiles and measured line shapes. Finally we also present recent efforts to increase data throughput and spectral coverage in CEAS experiments. We describe three new high-bandwidth CEAS techniques including frequency-agile, rapid scanning spectroscopy (FARS)2, which enables continuous-wave measurements of cavity mode linewidth and acquisition of ringdown decays with no dead time during laser frequency tuning, heterodyne

  8. Fabry-Perot Absorption Line Spectroscopy of the Galactic Bar. I. Kinematics

    Rangwala, Naseem; Stanek, K Z

    2008-01-01

    We use Fabry-Perot absorption line imaging spectroscopy to measure radial velocities using the Ca II 8542 line in 3360 stars towards three lines of sight in the Milky Way's bar: Baade's Window and offset position at (l,b) ~ (+-5.0, -3.5). This sample includes 2488 bar red clump giants, 339 bar M/K-giants, and 318 disk main sequence stars. We measure the first four moments of the stellar velocity distribution of the red clump giants, and find it to be symmetric and flat-topped. We also measure the line-of-sight average velocity and dispersion of the red clump giants as a function of distance in the bar. We detect stellar streams at the near and far side of the bar with velocity difference > 30 km/s at l = +-5, but we do not detect two separate streams in Baade's Window. Our M-giants kinematics agree well with previous studies, but have dispersions systematically lower than those of the red clump giants by ~ 10 km/s. For the disk main sequence stars we measure a velocity dispersion of ~ 45 km/s for all three li...

  9. High-resolution absorption spectroscopy of the OH 2Pi 3/2 ground state line

    Wiesemeyer, Helmut; Heyminck, Stefan; Karl, Jacobs; Menten, Karl; Neufeld, David; Requena-Torres, Miguel Angel; Stutzki, Jürgen; 10.1051/0004-6361/201218915

    2012-01-01

    The chemical composition of the interstellar medium is determined by gas phase chemistry, assisted by grain surface reactions, and by shock chemistry. The aim of this study is to measure the abundance of the hydroxyl radical (OH) in diffuse spiral arm clouds as a contribution to our understanding of the underlying network of chemical reactions. Owing to their high critical density, the ground states of light hydrides provide a tool to directly estimate column densities by means of absorption spectroscopy against bright background sources. We observed onboard the SOFIA observatory the 2Pi3/2, J = 5/2 3/2 2.5 THz line of ground-state OH in the diffuse clouds of the Carina-Sagittarius spiral arm. OH column densities in the spiral arm clouds along the sightlines to W49N, W51 and G34.26+0.15 were found to be of the order of 10^14 cm^-2, which corresponds to a fractional abundance of 10^-7 to 10^-8, which is comparable to that of H_2O. The absorption spectra of both species have similar velocity components, and the...

  10. Subaru high resolution spectroscopy of complex metal absorption lines of QSO HS1603+3820

    Misawa, T; Takada-Hidai, M; Wang, Y; Kashikawa, N; Iye, M; Tanaka, I; Misawa, Toru; Yamada, Toru; Takada-Hidai, Masahide; Wang, Yiping; Kashikawa, Nobunari; Iye, Masanori; Tanaka, Ichi

    2002-01-01

    We present a high resolution spectrum of the quasar, HS1603+3820 (z_em=2.542), observed with the High Dispersion Spectrograph (HDS) on Subaru Telescope. This quasar, first discovered in the Hamburg/CfA Quasar Survey, has 11 C IV lines at 1.96 2.29 and resolves some of them into multiple narrow components with b 65 km/s). We use three properties of C IV lines, specifically, time variability, covering factor, and absorption line profile, to classify them into quasar intrinsic absorption lines (QIALs) and spatially intervening absorption lines (SIALs). The C IV lines at 2.42 < z_abs < 2.45 are classified as QIALs in spite of their large velocity shifts from the quasar. Perhaps they are produced by gas clouds ejected from the quasar with the velocity of v_ej = 8000 km/s -- 10000 km/s. On the other hand, three C IV lines at 2.48 < z_abs < 2.55 are classified as SIALs, which suggests there exist intervening absorbers near the quasar. We, however, cannot rule out QIALs for the two lines at z_abs ~ 2.54...

  11. Reconstruction of combustion temperature and gas concentration distributions using line-of-sight tunable diode laser absorption spectroscopy

    Zhang, Zhirong; Sun, Pengshuai; Pang, Tao; Xia, Hua; Cui, Xiaojuan; Li, Zhe; Han, Luo; Wu, Bian; Wang, Yu; Sigrist, Markus W.; Dong, Fengzhong

    2016-07-01

    Spatial temperature and gas concentration distributions are crucial for combustion studies to characterize the combustion position and to evaluate the combustion regime and the released heat quantity. Optical computer tomography (CT) enables the reconstruction of temperature and gas concentration fields in a flame on the basis of line-of-sight tunable diode laser absorption spectroscopy (LOS-TDLAS). A pair of H2O absorption lines at wavelengths 1395.51 and 1395.69 nm is selected. Temperature and H2O concentration distributions for a flat flame furnace are calculated by superimposing two absorption peaks with a discrete algebraic iterative algorithm and a mathematical fitting algorithm. By comparison, direct absorption spectroscopy measurements agree well with the thermocouple measurements and yield a good correlation. The CT reconstruction data of different air-to-fuel ratio combustion conditions (incomplete combustion and full combustion) and three different types of burners (one, two, and three flat flame furnaces) demonstrate that TDLAS has the potential of short response time and enables real-time temperature and gas concentration distribution measurements for combustion diagnosis.

  12. THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES FROM ABSORPTION LINE SPECTROSCOPY. II. RESULTS

    The spectral absorption lines in early-type galaxies contain a wealth of information regarding the detailed abundance pattern, star formation history, and stellar initial mass function (IMF) of the underlying stellar population. Using our new population synthesis model that accounts for the effect of variable abundance ratios of 11 elements, we analyze very high quality absorption line spectra of 38 early-type galaxies and the nuclear bulge of M31. These data extend to 1 μm and they therefore include the IMF-sensitive spectral features Na I, Ca II, and FeH at 0.82 μm, 0.86 μm, and 0.99 μm, respectively. The models fit the data well, with typical rms residuals ∼stars, are derived for individual galaxies. We find that the IMF becomes increasingly bottom-heavy with increasing velocity dispersion and [Mg/Fe]. At the lowest dispersions and [Mg/Fe] values the derived IMF is consistent with the Milky Way (MW) IMF, while at the highest dispersions and [Mg/Fe] values the derived IMF contains more low-mass stars (is more bottom-heavy) than even a Salpeter IMF. Our best-fit (M/L)stars values do not exceed dynamically based M/L values. We also apply our models to stacked spectra of four metal-rich globular clusters in M31 and find an (M/L)stars that implies fewer low-mass stars than a MW IMF, again agreeing with dynamical constraints. We discuss other possible explanations for the observed trends and conclude that variation in the IMF is the simplest and most plausible.

  13. Digital signal processor-based high-precision on-line Voigt lineshape fitting for direct absorption spectroscopy

    Xu, Lijun; Liu, Chang; Zheng, Deyan; Cao, Zhang; Cai, Weiwei

    2014-12-01

    To realize on-line high-accuracy measurement in direct absorption spectroscopy (DAS), a system-on-chip, high-precision digital signal processor-based on-line Voigt lineshape fitting implementation is introduced in this paper. Given that the Voigt lineshape is determined by the Gauss full width at half maximum (FWHM) and Lorentz FWHM, a look-up table, which covers a range of combinations of both, is first built to achieve rapid and accurate calculation of Voigt lineshape. With the look-up table and raw absorbance data in hand, Gauss-Newton nonlinear fitting module is implemented to obtain the parameters including both the Gauss and Lorentz FWHMs, which can be used to calculate the integrated absorbance. To realize the proposed method in hardware, a digital signal processor (DSP) is adopted to fit the Voigt lineshape in a real-time DAS measurement system. In experiment, temperature and H2O concentration of a flat flame are recovered from the transitions of 7444.36 cm-1 and 7185.6 cm-1 by the DSP-based on-line Voigt lineshape fitting and on-line integral of the raw absorbance, respectively. The results show that the proposed method can not only fit the Voigt lineshape on-line but also improve the measurement accuracy compared with those obtained from the direct integral of the raw absorbance.

  14. Measurement of water vapor line strengths in the 1.4-2.7 μm range by tunable diode laser absorption spectroscopy

    Pogány, Andrea; Klein, Alexander; Ebert, Volker

    2015-11-01

    Line strengths of nine water vapor absorption lines in the wavelength range between 1.37 and 2.71 μm with line strengths of 10-23-10-20 cm/molecule have been measured using direct tunable diode laser absorption spectroscopy (dTDLAS). Four different light sources were used: three distributed feedback (DFB) diode lasers with wavelengths of 1.37 μm, 2.55 μm and 2.71 μm for measuring one application-specifically selected absorption line with each laser, and a vertical-cavity surface-emitting laser (VCSEL) radiating around 1.39 μm for the measurement of six further absorption lines. Despite the different light sources and line strengths, a uniform measurement and data evaluation method was developed and applied to all lines, and the experimental set-up was kept as similar as possible. This allows a thorough and uniform uncertainty analysis and evaluation of the contributions of the individual experimental parameters to the uncertainty of the derived line strengths. A comprehensive and transparent uncertainty analysis is given for the measurements. Uncertainties of our measured line strengths are in the 1.1-2.5% range (k=2, 95% confidence level). Our measured line strength values agree well with line strengths in the HITRAN 2012 database and other literature sources, we realized lower uncertainties up to a factor of 5-10.

  15. High-resolution spectroscopy of V854 Cen in decline - absorption and emission lines of C2 molecules

    Kameswara Rao, N.; Lambert, David L.

    2000-04-01

    High-resolution optical spectra of the R Coronae Borealis (RCB) star V854 Centauri in the early stages of a decline show, in addition to the features reported for other RCBs in decline, narrow absorption lines from the C2 Phillips system. The low rotational temperature, Trot=1150K, of the C2 ground electronic state suggests the cold gas is associated with the developing shroud of carbon dust. These absorption lines were not seen at a fainter magnitude on the rise from minimum light, nor at maximum light. This is the first detection of cold gas around an RCB star.

  16. Laser-based absorption spectroscopy as a technique for rapid in-line analysis of respired gas concentrations of O2 and CO2

    Cummings, Beth; Hamilton, Michelle L.; Ciaffoni, Luca; Pragnell, Timothy R.; Peverall, Rob; Ritchie, Grant A. D.; Hancock, Gus; Robbins, Peter A.

    2011-01-01

    The use of sidestream analyzers for respired gas analysis is almost universal. However, they are not ideal for measurements of respiratory gas exchange because the analyses are both temporally dissociated from measurements of respiratory flow and also not generally conducted under the same physical conditions. This study explores the possibility of constructing an all optical, fast response, in-line breath analyzer for oxygen and carbon dioxide. Using direct absorption spectroscopy with a dio...

  17. X-ray Absorption Spectroscopy

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  18. Infrared heterodyne spectroscopy of astronomical and laboratory sources at 8.5 micron. [absorption line profiles of nitrogen oxide and black body emission from Moon and Mars

    Mumma, M.; Kostiuk, T.; Cohen, S.; Buhl, D.; Vonthuna, P. C.

    1974-01-01

    The first infrared heterodyne spectrometer using tuneable semiconductor (PbSe) diode lasers has been constructed and was used near 8.5 micron to measure absorption line profiles of N2O in the laboratory and black body emission from the Moon and from Mars. Spectral information was recorded over a 200 MHz bandwidth using an 8-channel filter bank. The resolution was 25 MHz and the minimum detectable (black body) power was 1 x 10 to the minus 16th power watts for 8 minutes of integration. The results demonstrate the usefulness of heterodyne spectroscopy for the study of remote and local sources in the infrared.

  19. Absorption Line Spectroscopy of Gravitationally-Lensed Galaxies: Further Evidence for an Increased Escape Fraction of Ionizing Photons at High Redshift

    Leethochawalit, Nicha; Ellis, Richard S; Stark, Daniel P; Zitrin, Adi

    2016-01-01

    The fraction of ionizing photons that escape from high redshift star forming galaxies remains a key obstacle in evaluating whether galaxies were the primary agents of cosmic reionization. In our earlier work, we proposed using the covering fraction of low ionization gas, measured via deep absorption line spectroscopy, as a proxy. We present a significant update using this method, sampling seven gravitationally-lensed sources in the redshift range 4absorption lines, we quantify possible biases and uncertainties. Collectively we find the average escape fraction could be reduced to no less than 11%, excluding the effect of spatial variations. For one of our lense...

  20. QSO Absorption Lines from QSOs

    Bowen, D V; Ménard, B; Chelouche, D; Inada, N; Oguri, M; Richards, G T; Strauss, M A; Vanden Berk, Daniel E; York, D G; Bowen, David V.; Hennawi, Joseph F.; Menard, Brice; Chelouche, Doron; Inada, Naohisa; Oguri, Masamune; Richards, Gordon T.; Strauss, Michael A.; Berk, Daniel E. Vanden; York, Donald G.

    2006-01-01

    We present the results of a search for metal absorption lines in the spectra of background QSOs whose sightlines pass close to foreground QSOs. We detect MgII(2796,2803) absorption in Sloan Digital Sky Survey (SDSS) spectra of four z>1.5 QSOs whose lines of sight pass within 26-98 kpc of lower redshift (z~0.5-1.5) QSOs. The 100% [4/4 pairs] detection of MgII in the background QSOs is clearly at odds with the incidence of associated (z_abs ~ z_em) systems -- absorbers which exist towards only a few percent of QSOs. Although the quality of our foreground QSO spectra is not as high as the SDSS data, absorption seen towards one of the background QSOs clearly does not show up at the same strength in the spectrum of the corresponding foreground QSO. This implies that the absorbing gas is distributed inhomogeneously around the QSO, presumably as a direct consequence of the anisotropic emission from the central AGN. We discuss possible origins for the MgII lines, including: absorption by gas from the foreground QSO h...

  1. Graphene intracavity spaser absorption spectroscopy

    Lozovik, Yu. E.; Nechepurenko, I. A.; Dorofeenko, A. V.

    2016-09-01

    We propose an intracavity plasmon absorption spectroscopy method based on graphene active plasmonics. It is shown that the plasmonic cavity contribution to the sensitivity is proportional to the quality factor Q of the graphene plasmonic cavity and reaches two orders of magnitude. The addition of gain medium into the cavity increases the sensitivity of method. Maximum sensitivity is reached in the vicinity of the plasmon generation threshold. The gain contribution to the sensitivity is proportional to Q1/2. The giant amplification of sensitivity in the graphene plasmon generator is associated with a huge path length, limited only by the decoherence processes. An analytical estimation of the sensitivity to loss caused by analyzed particles (molecules, nanoparticles, etc.) normalized by the single pass plasmon scheme is derived. Usage of graphene nanoflakes as plasmonic cavity allows a high spatial resolution to be reached, in addition to high sensitivity.

  2. Upper Limits on the 21 cm Power Spectrum at z = 5.9 from Quasar Absorption Line Spectroscopy

    Pober, Jonathan C; Mesinger, Andrei

    2016-01-01

    We present upper limits on the 21 cm power spectrum at $z = 5.9$ calculated from the model-independent limit on the neutral fraction of the intergalactic medium of $x_{\\rm H{\\small I }} < 0.06 + 0.05\\ (1\\sigma)$ derived from dark pixel statistics of quasar absorption spectra. Using 21CMMC, a Markov chain Monte Carlo Epoch of Reionization analysis code, we explore the probability distribution of 21 cm power spectra consistent with this constraint on the neutral fraction. We present 99 per cent confidence upper limits of $\\Delta^2(k) < 10$ to $20\\ {\\rm mK}^2$ over a range of $k$ from 0.5 to $2.0\\ h{\\rm Mpc}^{-1}$, with the exact limit dependent on the sampled $k$ mode. This limit can be used as a null test for 21 cm experiments: a detection of power at $z=5.9$ in excess of this value is highly suggestive of residual foreground contamination or other systematic errors affecting the analysis.

  3. Self-consistent absorption corrections for low-energy X-ray lines in energy-dispersive X-ray spectroscopy

    Quantification of energy-dispersive X-ray spectra in transmission electron microscopy is often unreliable for X-ray lines of low energy, as they are subject to strong absorption and fluorescence corrections which will depend critically on both the sample thickness and the detector properties (take-off angle, detector material and type, thickness and cleanliness of any detector window). By using the method to vary the take-off angle between repeated measurements in energy-dispersive X-ray spectroscopy from the same region, an attempt has been made to study our ability to determine the depth of a buried epitaxial thin layer within a plan-view sample and to correctly assess the composition of specimens containing lighter elements. By using several different Monte Carlo simulation programs, the attenuation of the X-rays along their path towards the detector can be calculated and the predicted results can be compared to experimental measurements. Comparison of two different programs to experimental results has been made, for an InAs quantum well buried beneath a GaAs cap layer and a NiO thin film specimen.

  4. Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy: Annual progress report

    Although only in operation since May, 1985, the X-11 participation research team (PRT) at the NSLS has already demonstrated that it is one of the leading centers of x-ray absorption spectroscopy (XAS). During this time, results have been obtained and programs initiated in a number of areas, for example: interfaces, including deposited metal-metal and metal-semiconductor systems, multilayers and ion implanted layers; electrochemical systems, including Pt electrode fuel cells, Ni oxide battery electrodes, conducting polymers, passivation and corrosion; catalysts, including highly-dispersed supported metal catalysts and zeolite systems; quasi-crystals, heavy fermion systems, uranium and neptunium compounds, rare gas clusters, disordered metals and semiconductors, ferroelectric transition; and, biological systems and related models, including synthetic porphyrins and a number of metalloproteins. In concert with these scientific results have been a number of developments involving the technique itself. These include implementation of unique optical systems on both the A and B lines for optical performance over their designed energy ranges, advances in experimental capability, particular in glancing angle studies, optimization of ion chambers for surface studies, the improvement of electron yield detectors, and improved software for data acquisition and analysis. This report emphasizes some of the research highlights and significant developments of our PRT which occurred during the past year. A detailed bibliography of papers and talks resulting from work done at our beamline and the progress reports for our PRT which were in the 1985 NSLS Annual Report are appended

  5. Tunable diode laser absorption spectroscopy-based tomography system for on-line monitoring of two-dimensional distributions of temperature and H2O mole fraction

    To monitor two-dimensional (2D) distributions of temperature and H2O mole fraction, an on-line tomography system based on tunable diode laser absorption spectroscopy (TDLAS) was developed. To the best of the authors’ knowledge, this is the first report on a multi-view TDLAS-based system for simultaneous tomographic visualization of temperature and H2O mole fraction in real time. The system consists of two distributed feedback (DFB) laser diodes, a tomographic sensor, electronic circuits, and a computer. The central frequencies of the two DFB laser diodes are at 7444.36 cm−1 (1343.3 nm) and 7185.6 cm−1 (1391.67 nm), respectively. The tomographic sensor is used to generate fan-beam illumination from five views and to produce 60 ray measurements. The electronic circuits not only provide stable temperature and precise current controlling signals for the laser diodes but also can accurately sample the transmitted laser intensities and extract integrated absorbances in real time. Finally, the integrated absorbances are transferred to the computer, in which the 2D distributions of temperature and H2O mole fraction are reconstructed by using a modified Landweber algorithm. In the experiments, the TDLAS-based tomography system was validated by using asymmetric premixed flames with fixed and time-varying equivalent ratios, respectively. The results demonstrate that the system is able to reconstruct the profiles of the 2D distributions of temperature and H2O mole fraction of the flame and effectively capture the dynamics of the combustion process, which exhibits good potential for flame monitoring and on-line combustion diagnosis

  6. Tunable diode laser absorption spectroscopy-based tomography system for on-line monitoring of two-dimensional distributions of temperature and H2O mole fraction

    Xu, Lijun; Liu, Chang; Jing, Wenyang; Cao, Zhang; Xue, Xin; Lin, Yuzhen

    2016-01-01

    To monitor two-dimensional (2D) distributions of temperature and H2O mole fraction, an on-line tomography system based on tunable diode laser absorption spectroscopy (TDLAS) was developed. To the best of the authors' knowledge, this is the first report on a multi-view TDLAS-based system for simultaneous tomographic visualization of temperature and H2O mole fraction in real time. The system consists of two distributed feedback (DFB) laser diodes, a tomographic sensor, electronic circuits, and a computer. The central frequencies of the two DFB laser diodes are at 7444.36 cm-1 (1343.3 nm) and 7185.6 cm-1 (1391.67 nm), respectively. The tomographic sensor is used to generate fan-beam illumination from five views and to produce 60 ray measurements. The electronic circuits not only provide stable temperature and precise current controlling signals for the laser diodes but also can accurately sample the transmitted laser intensities and extract integrated absorbances in real time. Finally, the integrated absorbances are transferred to the computer, in which the 2D distributions of temperature and H2O mole fraction are reconstructed by using a modified Landweber algorithm. In the experiments, the TDLAS-based tomography system was validated by using asymmetric premixed flames with fixed and time-varying equivalent ratios, respectively. The results demonstrate that the system is able to reconstruct the profiles of the 2D distributions of temperature and H2O mole fraction of the flame and effectively capture the dynamics of the combustion process, which exhibits good potential for flame monitoring and on-line combustion diagnosis.

  7. UV/VUV high sensitivity absorption spectroscopy

    High sensitivity absorption spectroscopy is a powerful diagnostic technique for reactive glow discharges plasmas. Absolute column densities of many chemical radicals have been measured in both deposition and etching plasmas. Modern photodiode or charge-coupled device (CCD) detector arrays vastly increase the sensitivity of traditional absorption experiments enabling one to observe fractional absorptions of ultraviolet (UV) and vacuum ultraviolet (VUV) radiation less than 0.0001. Stable arc lamps provide a continuum source in some experiments, but experiments at very high spectral resolution or at VUV wavelengths require the greater spectral radiance of synchrotron radiation. High sensitivity absorption spectroscopy has been applied to intense glow discharges used for lighting, for diamond film deposition, and for both depositing and etching Si films. Absorption spectroscopy provides absolute column densities, is useful for transitions that do not fluoresce, and approaches the sensitivity of laser-induced fluorescence (LIF) in glow discharges under some conditions

  8. Dust Sensitivity of Absorption-Line Indices

    MacArthur, L A

    2004-01-01

    We investigate the effects of dust extinction on integrated absorption-line indices that are widely used to derive constraints on the ages and metallicities of composite stellar systems. Typically, absorption-line studies have been performed on globular clusters or elliptical galaxies, which are mostly dust-free systems. However, many recent studies of integrated stellar populations have focused on spiral galaxies which may contain significant amounts of dust. It is almost universally assumed that the effects of dust extinction on absorption-line measurements are entirely negligible given the narrow baseline of the spectral features, but no rigorous study has yet been performed to verify this conjecture. In this analysis, we explore the sensitivity of the standard set of Lick absorption-line indices, the higher-order Balmer line indices, the 4000 A break, the near-IR calcium triplet indices, and the Rose indices to dust absorption according to population synthesis models that incorporate a multi-component mod...

  9. Isotope analysis by infrared laser absorption spectroscopy

    The feasibility of IR laser spectroscopy as a technique for the measurement of small abundances of stable and radioactive isotopes has been examined. Theoretical considerations and first experimental results with two laser systems are presented: 1) Coincidences between emission lines of a CO2-laser and absorption lines of 13C-subsituted ethylene can be used to determine the 13C-concentration of C2H4. 2) A tunable PbS-diode laser emitting in the 4.3 μm-spectral region of the rotation-vibration bands of CO2 can be used to determine abundances of 12C, 13C, 16O, 17O and 18O in small samples of CO2. With optimized performance, sensitivities up to 10-9-10-10 seem possible, and for higher abundances an accuracy of 10-3. This should allow geophysical isotope studies to be performed and it is hoped that the technique will eventually be applicable to measuring the activity of long-lived radioisotopes. (orig.)

  10. Communication: XUV transient absorption spectroscopy of iodomethane and iodobenzene photodissociation

    Drescher, L.; Galbraith, M. C. E.; Reitsma, G.; Dura, J.; Zhavoronkov, N.; Patchkovskii, S.; Vrakking, M. J. J.; Mikosch, J.

    2016-07-01

    Time-resolved extreme ultraviolet (XUV) transient absorption spectroscopy of iodomethane and iodobenzene photodissociation at the iodine pre-N4,5 edge is presented, using femtosecond UV pump pulses and XUV probe pulses from high harmonic generation. For both molecules the molecular core-to-valence absorption lines fade immediately, within the pump-probe time-resolution. Absorption lines converging to the atomic iodine product emerge promptly in CH3I but are time-delayed in C6H5I. We attribute this delay to the initial π → σ* excitation in iodobenzene, which is distant from the iodine reporter atom. We measure a continuous shift in energy of the emerging atomic absorption lines in CH3I, attributed to relaxation of the excited valence shell. An independent particle model is used to rationalize the observed experimental findings.

  11. CO2 Spectroscopy Evaluation Using Atmospheric Solar Absorption Spectra

    Sen, Bhaswar; Brown, Linda R.; Miller, Charles E.; Toon, Geoffrey C.; Toth, Robert A.; Washenfelder, Rebecca A.; Wennberg, Paul O

    2006-01-01

    We evaluated the improvements in successive versions (1996 - 2004) of HITRAN (1) and other molecular line parameter data set (2) to correctly simulate infrared (IR) and near-infrared (NIR) CO 2 transmittance spectra. Understanding the global sources and sinks of CO 2 requires highly accurate measurements (ó 0.3%) and makes extreme de- mands on the spectroscopy. We evaluated the line parameter data sets by fitting solar absorption spectra measured by the JPL MkIV FTIR spectrometer (3) and the ...

  12. Further advancement of differential optical absorption spectroscopy: theory of orthogonal optical absorption spectroscopy.

    Liudchik, Alexander M

    2014-08-10

    A modified version of the differential optical absorption spectroscopy (DOAS) method is presented. The technique is called orthogonal optical absorption spectroscopy (OOAS). A widespread variant of DOAS with smoothing of the registered spectrum and absorption cross sections being made employing a polynomial regression is a particular case of OOAS. The concept of OOAS provides a variety of new possibilities for constructing computational schemes and analyzing the influence of different error sources on calculated concentrations. PMID:25320931

  13. Infrared laser spectroscopy using a long pathlength absorption cell

    The authors developed two very long pathlength absorption cells to be used in conjunction with diode lasers. They were designed to operate at controlled temperatures with the optical pathlength variable up to approx. 1,5 Km. Not only very low sample pressures are used for studies with such cells but also the spectroscopic sensitivity is enhanced over conventional methods by a factor of 103 to 104. In this paper they present some analytical aspects of the diode laser spectroscopy using the long pathlength absorption cells in the areas of absorption line widths, pressure broadening coefficients, isotope composition measurements and trace impurity analysis

  14. Molecular absorption in transition region spectral lines

    Schmit, Donald; Ayres, Thomas; Peter, Hardi; Curdt, Werner; Jaeggli, Sarah

    2014-01-01

    Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra. Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence. Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary . The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales...

  15. The low-ion QSO absorption-line systems

    Various techniques are used to investigate the class of QSO absorption-line systems that exhibit low-ion absorption lines. Four separate investigations are conducted as follows: Spectroscopy of 32 QSOs at red wavelengths is presented and used to investigate intermediate-redshift MgII absorption. A total of 22 Mg II doublets are detected, from which properties of the Mg II absorbers are derived. Marginal evidence for intrinsic evolution of the number density of the Mg II absorbers with redshift is found. The data are combined with previous observations of C IV and C II seen in the same QSOs at blue wavelengths, and the properties of Mg II- and C IV-selected systems are compared. A sample is constructed of 129 QSOs for which are available published data suitable for detecting absorption-line systems that are optically thick to Lyman continuum radiation. A total of 53 such Lyman-limit systems are found, from which properties of the Lyman-limit systems are derived. It is found that the rate of incidence of the systems does not strongly evolved with redshift. This result is contrasted with the evolution found previously for systems selected on the basis of Mg II absorption. Spectroscopy at red wavelengths of eight QSOs with known damped Lyα absorption systems is presented. Spectroscopic and spectrophotometric observations aimed at detecting molecular hydrogen and dust in the z = 2.796 damped Lyα absorber toward Q1337 + 113 are presented

  16. The low-ion QSO absorption-line systems

    Lanzetta, K.M.

    1988-01-01

    Various techniques are used to investigate the class of QSO absorption-line systems that exhibit low-ion absorption lines. Four separate investigations are conducted as follows: Spectroscopy of 32 QSOs at red wavelengths is presented and used to investigate intermediate-redshift MgII absorption. A total of 22 Mg II doublets are detected, from which properties of the Mg II absorbers are derived. Marginal evidence for intrinsic evolution of the number density of the Mg II absorbers with redshift is found. The data are combined with previous observations of C IV and C II seen in the same QSOs at blue wavelengths, and the properties of Mg II- and C IV-selected systems are compared. A sample is constructed of 129 QSOs for which are available published data suitable for detecting absorption-line systems that are optically thick to Lyman continuum radiation. A total of 53 such Lyman-limit systems are found, from which properties of the Lyman-limit systems are derived. It is found that the rate of incidence of the systems does not strongly evolved with redshift. This result is contrasted with the evolution found previously for systems selected on the basis of Mg II absorption. Spectroscopy at red wavelengths of eight QSOs with known damped Ly{alpha} absorption systems is presented. Spectroscopic and spectrophotometric observations aimed at detecting molecular hydrogen and dust in the z = 2.796 damped Ly{alpha} absorber toward Q1337 + 113 are presented.

  17. Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy

    At the time of the submission of the original proposal more than 7 years ago, the X-11 PRT had set as a goal to develop one of the leading and most comprehensive x-ray absorption beam lines in the world. By any measure we have been successful. As is well documented in previous annual progress report and in the NSLS annual reports, our PRT has been extremely productive in a wide range of topics in materials science, solid state physics, chemistry and biology. Well over 100 papers have been published acknowledging the support of this contract and this continues at a rate of about 30 papers per year and about 20 invited presentations per year. Significant in this report are major studies in high Tc compounds, advances in interface studies, new results in premelting phenomena, several pioneering studies in application of XAS to electrochemistry and significant progress in our understanding of the structure of amorphous chalcogenide systems and their photostructural changes

  18. Theory of attosecond absorption spectroscopy in krypton

    Baggesen, Jan Conrad; Lindroth, Eva; Madsen, Lars Bojer

    2012-01-01

    A theory for time-domain attosecond pump–attosecond probe photoabsorption spectroscopy is formulated and related to the atomic response. The theory is illustrated through a study of attosecond absorption spectroscopy in krypton. The atomic parameters entering the formulation such as energies and...... Auger widths, as well as wave functions and dipole coupling matrix elements, are determined by accurate many-body structure calculations. We create a hole in a valence shell by an attosecond pump, couple an inner-shell electron to the hole by an attosecond probe, and then monitor the formation of the...

  19. Line Narrowing Parameter Measurement by Modulation Spectroscopy

    Dharamsi, Amin N.

    1998-01-01

    Accurate Characterization of Oxygen A-Band Line Parameters by Wavelength Modulation Spectroscopy with tunable diode lasers is an ongoing research at Old Dominion University, under sponsorship from NASA Langley research Center. The work proposed here will be undertaken under the guidance of Dr. William Chu and Dr. Lamont Poole of the Aerosol Research Branch at NASA Langley-Research Center in Hampton, Virginia. The research was started about two years ago and utilizes wavelength modulation absorption spectroscopy with higher harmonic detection, a technique that we developed at Old Dominion University, to obtain the absorption line characteristics of the Oxygen A-band rovibronic lines. Accurate characterization of this absorption band is needed for processing of data that will be obtained in experiments such as the NASA Stratospheric Aerosol and Gas Experiment III (SAGE III) as part of the US Mission to Planet Earth. The research work for Summer Fellowship undertook a measurement of the Dicke line-narrowing parameters of the Oxygen A-Band lines by using wavelength modulation spectroscopy. Our previous theoretical results had indicated that such a measurement could be done sensitively and in a convenient fashion by using this type of spectroscopy. In particular, theoretical results had indicated that the signal magnitude would depend on pressure in a manner that was very sensitive to the narrowing parameter. One of the major tasks undertaken during the summer of 1998 was to establish experimentally that these theoretical predictions were correct. This was done successfully and the results of the work are being prepared for publication. Experimental Results were obtained in which the magnitude of the signal was measured as a function of pressure, for various harmonic detection orders (N = 1, 2, 3, 4, 5). A comparison with theoretical results was made, and it was shown that the agreement between theory and experiment was very good. More importantly, however, it was shown

  20. Absorption spectroscopy with quantum cascade lasers

    Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.

    2001-01-01

    Novel pulsed and cw quantum cascade distributed feedback (QC-DFB) lasers operating near lambda=8 micrometers were used for detection and quantification of trace gases in ambient air by means of sensitive absorption spectroscopy. N2O, 12CH4, 13CH4, and different isotopic species of H2O were detected. Also, a highly selective detection of ethanol vapor in air with a sensitivity of 125 parts per billion by volume (ppb) was demonstrated.

  1. Narrow UV Absorption Line Outflows from Quasars

    Hamann, Fred; Hidalgo, Paola Rodriguez; Capellupo, Daniel

    2012-01-01

    Narrow absorption line (NAL) outflows are an important yet poorly understood part of the quasar outflow phenomenon. We discuss one particular NAL outflow that has high speeds, time variability, and moderate ionizations like typical BAL flows, at an estimated location just ~5 pc from the quasar. It also has a total column density and line widths (internal velocity dispersions) ~100 times smaller than BALs, with no substantial X-ray absorption. We argue that radiative shielding (in the form of an X-ray/warm absorber) is not critical for the outflow acceleration and that the moderate ionizations occur in dense substructures that have an overall small volume filling factor in the flow. We also present new estimates of the overall incidence of quasar outflow lines; e.g., ~43% of bright quasars have a C IV NAL outflow while ~68% have a C IV outflow line of any variety (NAL, BAL, or mini-BAL).

  2. Absorption effects in diffusing wave spectroscopy.

    Sarmiento-Gomez, Erick; Morales-Cruzado, Beatriz; Castillo, Rolando

    2014-07-20

    The effect of absorption in diffusing wave spectroscopy (DWS) was studied using an absorption-dependent diffusive equation for describing the light propagation within a turbid liquid where dielectric microspheres have been embedded. Here, we propose an expression for the time-averaged light intensity autocorrelation function that correctly describes the time fluctuations for the scattered light, in the regime where the diffusion approximation accurately describes the light propagation. This correction was suspected previously, but it was not formally derived from a light diffusive equation. As in the case of no absorption, we obtained that time fluctuations of the scattered light can be related to the mean square displacement of the embedded particles. However, if a correction for absorption is not taken into account, the colloidal dynamics can be misinterpreted. Experimental results show that this new formulation correctly describes the time fluctuations of scattered light. This new procedure extends the applicability of DWS, and it opens the possibility of doing microrheology with this optical method in systems where absorption cannot be avoided. PMID:25090203

  3. Gas in scattering media absorption spectroscopy - GASMAS

    Svanberg, Sune

    2008-09-01

    An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen. Also other dynamic processes such as drying of materials can be studied. The techniques have also been extended to remote-sensing applications (LIDAR-GASMAS).

  4. New on-line method for water isotope analysis of fluid inclusions in speleothems using laser absorption spectroscopy: Application to stalagmites from Borneo and Switzerland

    Affolter, Stéphane; Fleitmann, Dominik; Nele Meckler, Anna; Leuenberger, Markus

    2014-05-01

    Speleothems are recognised as key continental archives for paleoclimate reconstructions. They contain fluid inclusions representing past drip water trapped in the calcite structure. Speleothem can be precisely dated and therefore the oxygen (δ18O) and hydrogen (δD) isotopes of fluid inclusions constitute powerful proxies for paleotemperature or to investigate changes in the moisture source over several interglacial-glacial cycles. To liberate fluid inclusion water and to analyse its isotopic composition, a new online extraction method developed at Bern is used. The principle can be summarised as follows: Prior to crushing, the sample is placed into a copper tube, fixed to the line previously heated to 140° C and flushed with a nitrogen and standard water mixture. Thereafter, the speleothem sample is crushed using a simple hydraulic crushing device and the released water from fluid inclusions is transferred by the nitrogen-standard water mixture flow to a Picarro L1102-i isotopic liquid water and water vapor analyser. The measuring principle is based on wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) technology that allows us to simultaneously monitor hydrogen and oxygen isotopes. Reproducibility of standard water measurements is typically better than 1.5 o for δD and 0.4 o for δ18O. With this method, we successfully analysed δD and δ18O isotopic composition of a stalagmite from Northern Borneo (tropical West Pacific) covering almost two glacial-interglacial cycles from MIS 12 to early MIS 9 (460-330 ka) as well as recent samples from Switzerland and Borneo. These results are used in combination with calcite δ18O to reconstruct paleotemperature. Currently, we are measuring a stalagmite from Milandre cave (Jura, Switzerland) covering the Bølling-Allerød, Younger Dryas cold phase and the Holocene.

  5. Cavity-Enhanced Ultrafast Transient Absorption Spectroscopy

    Reber, Melanie A R; Allison, Thomas K

    2015-01-01

    We present a new technique using a frequency comb laser and optical cavities for performing ultrafast transient absorption spectroscopy with improved sensitivity. Resonantly enhancing the probe pulses, we demonstrate a sensitivity of $\\Delta$OD $ = 1 \\times 10^{-9}/\\sqrt{\\mbox{Hz}}$ for averaging times as long as 30 s per delay point ($\\Delta$OD$_{min} = 2 \\times 10^{-10}$). Resonantly enhancing the pump pulses allows us to produce a high excitation fraction at high repetition-rate, so that signals can be recorded from samples with optical densities as low as OD $\\approx 10^{-8}$, or column densities $< 10^{10}$ molecules/cm$^2$. This high sensitivity enables new directions for ultrafast spectroscopy.

  6. Diagnostic potential of cosmic-neutrino absorption spectroscopy

    Annihilation of extremely energetic cosmic neutrinos on the relic-neutrino background can give rise to absorption lines at energies corresponding to formation of the electroweak gauge boson Z0. The positions of the absorption dips are set by the masses of the relic neutrinos. Suitably intense sources of extremely energetic (1021-1025-eV) cosmic neutrinos might therefore enable the determination of the absolute neutrino masses and the flavor composition of the mass eigenstates. Several factors--other than neutrino mass and composition--distort the absorption lines, however. We analyze the influence of the time evolution of the relic-neutrino density and the consequences of neutrino decay. We consider the sensitivity of the line shape to the age and character of extremely energetic neutrino sources, and to the thermal history of the Universe, reflected in the expansion rate. We take into account Fermi motion arising from the thermal distribution of the relic-neutrino gas. We also note the implications of Dirac vs. Majorana relics, and briefly consider unconventional neutrino histories. We ask what kinds of external information would enhance the potential of cosmic-neutrino absorption spectroscopy, and estimate the sensitivity required to make the technique a reality

  7. Non-Voigt Lyalpha Absorption Line Profiles.

    Outram; Carswell; Theuns

    2000-02-01

    Recent numerical simulations have lead to a paradigm shift in our understanding of the intergalactic medium and the loss of a physical justification for Voigt profile fitting of the Lyalpha forest. Many individual lines seen in simulated spectra have significant departures from the Voigt profile, yet could be well fitted by a blend of two or more such lines. We discuss the expected effect on the line profiles due to ongoing gravitational structure formation and Hubble expansion. We develop a method to detect departures from Voigt profiles of the absorption lines in a statistical way and apply this method to simulated Lyalpha forest spectra, confirming that the profiles seen do statistically differ from Voigt profiles. PMID:10622758

  8. Absorption-line measurements of AGN outflows

    Fields, Dale L.

    Investigations into the elemental abundances in two nearby active galaxies, the narrow-line Seyfert 1 Markarian 1044 and the Seyfert 1 Markarian 279, are reported. Spectra from three space-based observatories HST, FUSE, and CHANDRA, are used to measure absorption lines in material outflowing from the nucleus. I make multi-wavelength comparisons to better convert the ionic column densities into elemental column densities which can then be used to determine abundances (metallicities). Narrow-line Seyfert 1 galaxies are known to have extreme values of a number of properties compared to active galactic nuclei (AGNs) as a class. In particular, emission-line studies have suggested that NLS1s are unusually metal-rich compared to broad-line AGNs of comparable luminosity. To test these suggestions I perform absorption-line studies on the NLS1 Markarian 1044, a nearby and bright AGN. I use lines of H I, C IV, N V, and O VI to properly make the photoionization correction through the software Cloudy and determine abundances of Carbon, Nitrogen and Oxygen. I find two results. The first is that Markarian 1044 has a bulk metallicity greater than five times solar. The second is that the N/C ratio in Markarian 1044 is consistent with a solar mixture. This is in direct contradiction of extrapolations from local H II regions which state N/ C should scale with bulk metallicity. This implies a different enrichment history in Markarian 1044 than in the Galactic disk. I also report discovery of three new low-redshift Lya forest lines with log N HI >= 12:77 in the spectrum of Markarian 1044. This number is consistent with the 2.6 expected Lya forest lines in the path length to Markarian 1044. I also investigate the CHANDRA X-ray spectrum of Markarian 279, a broad-line Seyfert 1. I use a new code, PHASE, to self-consistently model the entire absorption spectrum simultaneously. Using solely the X-ray spectrum I am able to determine the physical parameters of this absorber to a degree only

  9. Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy: Annual progress report

    The research programs reported span virtually the entire range of condensed matter studies involving the fields of solid state physics, chemistry, electrochemistry, materials science and biochemistry. Results are discussed for various groups. Topics reported include work on amorphous chalcogenide semiconductors, particularly photostructural changes, kinetics of structural changes and rapid quenching, bond strengths, force constants and phonons. Also reported are temperature dependent EXAFS studies of bonding in high temperature alloys, amorphous systems, disordered alloys and studies of resolve electronic structure, EXAFS and XANES studies of permanent magnet systems based on Nd2Fe14B, glancing angle EXAFS study of Nb/Al and Nb/Si interfacial systems, x-ray absorption of krypton-implanted solids and high dose implants into silicon, and x-ray absorption and EXAFS studies of superconducting oxide compounds of Cu and related magnetic systems. Work is also reported on XAFS measurements on the icosahedral phase

  10. Diagnostic potential of cosmic-neutrino absorption spectroscopy

    Barenboim, Gabriela; /Valencia U.; Mena Requejo, Olga; Quigg, Chris; /Fermilab

    2004-12-01

    Annihilation of extremely energetic cosmic neutrinos on the relic-neutrino background can give rise to absorption lines at energies corresponding to formation of the electroweak gauge boson Z{sup 0}. The positions of the absorption dips are set by the masses of the relic neutrinos. Suitably intense sources of extremely energetic (10{sup 21} - 10{sup 25}-eV) cosmic neutrinos might therefore enable the determination of the absolute neutrino masses and the flavor composition of the mass eigenstates. Several factors--other than neutrino mass and composition--distort the absorption lines, however. We analyze the influence of the time-evolution of the relic-neutrino density and the consequences of neutrino decay. We consider the sensitivity of the lineshape to the age and character of extremely energetic neutrino sources, and to the thermal history of the Universe, reflected in the expansion rate. We take into account Fermi motion arising from the thermal distribution of the relic-neutrino gas. We also note the implications of Dirac vs. Majorana relics, and briefly consider unconventional neutrino histories. We ask what kinds of external information would enhance the potential of cosmic-neutrino absorption spectroscopy, and estimate the sensitivity required to make the technique a reality.

  11. X-ray absorption spectroscopy of semiconductors

    Ridgway, Mark

    2015-01-01

    X-ray Absorption Spectroscopy (XAS) is a powerful technique with which to probe the properties of matter, equally applicable to the solid, liquid and gas phases. Semiconductors are arguably our most technologically-relevant group of materials given they form the basis of the electronic and photonic devices that now so widely permeate almost every aspect of our society. The most effective utilisation of these materials today and tomorrow necessitates a detailed knowledge of their structural and vibrational properties. Through a series of comprehensive reviews, this book demonstrates the versatility of XAS for semiconductor materials analysis and presents important research activities in this ever growing field. A short introduction of the technique, aimed primarily at XAS newcomers, is followed by twenty independent chapters dedicated to distinct groups of materials. Topics span dopants in crystalline semiconductors and disorder in amorphous semiconductors to alloys and nanometric material as well as in-sit...

  12. Shape effects along the Z=82 line: study of the $\\beta$- decay of $^{188,190,192}$Pb using total absorption spectroscopy

    Caballero ontanaya, L; Garcia borge, M J; Malbrunot, S

    2002-01-01

    This proposal is aimed at the study of the $\\beta$- decay of the neutron-deficient $^{188,190,192}$Pb nuclei. The main motivation of the proposed experiment is to determine the Gamow-Teller strength distribution in the daughter nuclei using the Total Absorption Spectrometer "Lucrecia". Recent theoretical results show that from this measurement the shapes of the ground states of the decaying Pb nuclei can be inferred. This study offers an independent way to study the phenomenon of shape co-existence in a region of particular interest.

  13. Pathlength Determination for Gas in Scattering Media Absorption Spectroscopy

    Liang Mei

    2014-02-01

    Full Text Available Gas in scattering media absorption spectroscopy (GASMAS has been extensively studied and applied during recent years in, e.g., food packaging, human sinus monitoring, gas diffusion studies, and pharmaceutical tablet characterization. The focus has been on the evaluation of the gas absorption pathlength in porous media, which a priori is unknown due to heavy light scattering. In this paper, three different approaches are summarized. One possibility is to simultaneously monitor another gas with known concentration (e.g., water vapor, the pathlength of which can then be obtained and used for the target gas (e.g., oxygen to retrieve its concentration. The second approach is to measure the mean optical pathlength or physical pathlength with other methods, including time-of-flight spectroscopy, frequency-modulated light scattering interferometry and the frequency domain photon migration method. By utilizing these methods, an average concentration can be obtained and the porosities of the material are studied. The last method retrieves the gas concentration without knowing its pathlength by analyzing the gas absorption line shape, which depends upon the concentration of buffer gases due to intermolecular collisions. The pathlength enhancement effect due to multiple scattering enables also the use of porous media as multipass gas cells for trace gas monitoring. All these efforts open up a multitude of different applications for the GASMAS technique.

  14. Trace gas absorption spectroscopy using laser difference-frequency spectrometer for environmental application

    Chen, W.; Cazier, F.; Boucher, D.; Tittel, F. K.; Davies, P. B.

    2001-01-01

    A widely tunable infrared spectrometer based on difference frequency generation (DFG) has been developed for organic trace gas detection by laser absorption spectroscopy. On-line measurements of concentration of various hydrocarbons, such as acetylene, benzene, and ethylene, were investigated using high-resolution DFG trace gas spectroscopy for highly sensitive detection.

  15. Absorption spectroscopy of laser excited europium vapour

    Absorption spectra of europium vapour irradiated by intense, monochromatic resonance radiation at the wavelengths of the three principal resonance lines, 4f76s2, 8S(J=7/2)→4f76s6p, y 8P(J=5/2, 7/2 and 9/2) at 466.2, 462.7 and 459.4 nm respectively, have been photographed at high resolution. Pulsed resonance radiation was obtained from a tunable, narrow-band dye laser pumped by a nitrogen laser: a broad-band dye laser pumped by the same nitrogen laser provided background radiation. Our spectra covered the ranges 380-400 nm, and 410-450 nm, each one showing transitions from a single resonance level to upper levels in the region of either the 4f76s, 7S or the 4f76s, 9S ionization limit of EuII. In the shorter wavelength range the spectra consisted of weak autoionized series converging towards the 7S limit. In the longer wavelength range the three spectra were surprisingly dissimilar. The majority of the upper levels could be arranged into five highly-perturbed series, one corresponding to each of the J values 3/2, 5/2, 7/2, 9/2 and 11/2. These series arose from excitation of the 6p electron to high lying d-orbitals. The absorption transitions to the series members are only prominent in regions where the series are strongly perturbed, indicating that most of the line strength is derived from the perturbing levels. Possible origins for the perturbing levels are discussed. Little evidence was found for a series arising from excitation of the 6p electron to high lying s-orbitals. (author)

  16. Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy. Progress report

    This has been an exciting year for our PRT, highlighted by the running of the NSLS x-ray ring in an operational mode beginning in May of this year. Our line X-11A was the first to obtain an experimental spectrum and the first to publish a paper with results from the x-ray ring. These early successes have allowed us to run in an operational mode during the entire time that the x-raying ring itself has been operational. In addition to a number of exciting initial scientific results described, the initial results, particularly in the four crystal mode, have verified our original optical design and demonstrated an improved resolution using the four crystals. This will have a significant impact on near edge (XANES) studies

  17. [The Research for Trace Ammonia Escape Monitoring System Based on Tunable Diode Laser Absorption Spectroscopy].

    Zhang, Li-fang; Wang, Fei; Yu, Li-bin; Yan, Jian-hua; Cen, Ke-fa

    2015-06-01

    In order to on-line measure the trace ammonia slip of the commercial power plant in the future, this research seeks to measure the trace ammonia by using tunable diode laser absorption spectroscopy under ambient temperature and pressure, and at different temperatures, and the measuring temperature is about 650 K in the power plant. In recent years lasers have become commercially available in the near-infrared where the transitions are much stronger, and ammonia's spectroscopy is pretty complicated and the overlapping lines are difficult to resolve. A group of ammonia transitions near 4 433.5 cm(-1) in the v2 +v3 combination band have been thoroughly selected for detecting lower concentration by analyzing its absorption characteristic and considering other absorption interference in combustion gases where H2O and CO2 mole fraction are very large. To illustrate the potential for NH3 concentration measurements, predictions for NH3, H2O and CO2 are simultaneously simulated, NH3 absorption lines near 4 433.5 cm(-1) wavelength meet weaker H2O absorption than the commercial NH3 lines, and there is almost no CO2 absorption, all the parameters are based on the HITRAN database, and an improved detection limit was obtained for interference-free NH3 monitoring, this 2.25 μm band has line strengths several times larger than absorption lines in the 1.53 μm band which was often used by NH3 sensors for emission monitoring and analyzing. The measurement system was developed with a new Herriott cell and a heated gas cell realizing fast absorption measurements of high resolution, and combined with direct absorption and wavelenguh modulation based on tunable diode laser absorption spectroscopy at different temperatures. The lorentzian line shape is dominant at ambient temperature and pressure, and the estimated detectivity is approximately 0.225 x 10(-6) (SNR = 1) for the directed absorption spectroscopy, assuming a noise-equivalent absorbance of 1 x 10(-4). The heated cell

  18. Absorption Line Profile Recovery Based on TDLS and MEMS Micro-Mirror for Photoacoustic Gas Sensing

    LI Li; Norhana Arsad; George Stewart; Graham Thursby; Deepak Uttamchandani; Brian Culshaw; WANG Yi-ding

    2011-01-01

    A novel and efficient absorption line recovery technique is presented. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used to generate laser intensity modulation through the mirror reflection. Tunable diode laser spectroscopy (TDLS) and photoacoustic spectroscopy (PAS) are used to recover the target absorption line profile which is compared with the theoretical Voigt profile. The target gas is 0.01% acetylene (C2 H2 ) in a nitrogen host gas. The laser diode wavelength is swept across the P17 absorption line of acetylene at 1 535.4 nm by a current ramp, and an erbium-doped fibre amplifier (EDFA) is used to enhance the optical intensity and increase the signal-to-noise ratio (SNR). A SNR of about 35 is obtained with 100 mW laser power from the EDFA Good agreement is achieved between the experimental results and the theoretical simulation for the P17 absorption line profile.

  19. Tunable diode laser absorption spectroscopy-based tomography system for on-line monitoring of two-dimensional distributions of temperature and H{sub 2}O mole fraction

    Xu, Lijun, E-mail: lijunxu@buaa.edu.cn; Liu, Chang; Jing, Wenyang; Cao, Zhang [School of Instrument Science and Opto-Electronic Engineering, Beihang University, Beijing 100191 (China); Ministry of Education’s Key Laboratory of Precision Opto-Mechatronics Technology, Beijing 100191 (China); Xue, Xin; Lin, Yuzhen [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China)

    2016-01-15

    To monitor two-dimensional (2D) distributions of temperature and H{sub 2}O mole fraction, an on-line tomography system based on tunable diode laser absorption spectroscopy (TDLAS) was developed. To the best of the authors’ knowledge, this is the first report on a multi-view TDLAS-based system for simultaneous tomographic visualization of temperature and H{sub 2}O mole fraction in real time. The system consists of two distributed feedback (DFB) laser diodes, a tomographic sensor, electronic circuits, and a computer. The central frequencies of the two DFB laser diodes are at 7444.36 cm{sup −1} (1343.3 nm) and 7185.6 cm{sup −1} (1391.67 nm), respectively. The tomographic sensor is used to generate fan-beam illumination from five views and to produce 60 ray measurements. The electronic circuits not only provide stable temperature and precise current controlling signals for the laser diodes but also can accurately sample the transmitted laser intensities and extract integrated absorbances in real time. Finally, the integrated absorbances are transferred to the computer, in which the 2D distributions of temperature and H{sub 2}O mole fraction are reconstructed by using a modified Landweber algorithm. In the experiments, the TDLAS-based tomography system was validated by using asymmetric premixed flames with fixed and time-varying equivalent ratios, respectively. The results demonstrate that the system is able to reconstruct the profiles of the 2D distributions of temperature and H{sub 2}O mole fraction of the flame and effectively capture the dynamics of the combustion process, which exhibits good potential for flame monitoring and on-line combustion diagnosis.

  20. Ultrafast X-ray absorption spectroscopy of laser-excited materials

    Advanced Light Source (ALS) Beamline 6.0 is designed for x-ray absorption spectroscopy with femtosecond x-ray pulse generated by bunch 'slicing' technique. Soft and hard x-ray branch lines will cover a wide photon energy range from 120 eV to 10 KeV. A soft x-ray spectrograph will collect absorption spectra dispersively. The application of laminar gratings to dispersive x-ray absorption spectroscopy in the photon energy range 2-8 KeV has been investigated. (author)

  1. Ultranarrow absorptive spectral line induced by microwave field

    Hu Zheng-Feng; Ma Yi-Sheng; Deng Jian-Liao; He Hui-Juan; Wang Yu-Zhu

    2009-01-01

    This paper investigates the absorptive spectral lines of four-level atomic system driven by a coupling, probe and microwave fields. Due to the perturbation of the microwave field, the original electromagnetically induced transparency is changed to electromagnetically induced absorption and the absorptive spectral line can be very narrow. This ultranarrow spectral line has potential applications to the microwave atomic frequency standard and the measurement of very weak magnetic field.

  2. (EXAFS) X-ray absorption spectroscopy

    The technique EXAFS (Extended X-Ray Absorption Fine Structure) is presented and its applications using the synchrotron radiation as an incidente beam in Science of Materials and Biophysics are shown. (L.C.)

  3. Absorption and fluorescence spectroscopy on a smartphone

    Hossain, Md. Arafat; Canning, John; Cook, Kevin; Ast, Sandra; Rutledge, Peter J.; Jamalipour, Abbas

    2015-07-01

    A self-powered smartphone-based field-portable "dual" spectrometer has been developed for both absorption and fluorescence measurements. The smartphone's existing flash LED has sufficient optical irradiance to undertake absorption measurements within a 3D-printed case containing a low cost nano-imprinted polymer diffraction grating. A UV (λex ~ 370 nm) and VIS (λex ~ 450 nm) LED are wired into the circuit of the flash LED to provide an excitation source for fluorescence measurements. Using a customized app on the smartphone, measurements of absorption and fluorescence spectra are demonstrated using pH-sensitive and Zn2+-responsive probes. Detection over a 300 nm span with 0.42 nm/pixel spectral resolution is demonstrated. Despite the low cost and small size of the portable spectrometer, the results compare well with bench top instruments.

  4. Photonic sensing of the atmosphere by absorption spectroscopy

    Chemically reactive atmospheric species play a crucial role in tropospheric processes which affect regional air quality and global climate change. Contrary to long-lived species such as greenhouse gases, interference-free accurate and precise concentration assessments of strongly reactive short-lived species represent a real challenge. In this paper, we report on the recent progress in spectroscopic instrumental developments for monitoring of OH, NO3, HONO and NO2 by using modern photonic sources (Quantum Cascade Laser, distributed feedback diode laser, light emitting diode) in conjunction with high-sensitivity spectroscopic measurement techniques such as multi-pass cell based long optical path length absorption spectroscopy, wavelength-modulation enhanced off-axis integrated cavity output spectroscopy, Faraday rotation spectroscopy, incoherent broadband cavity enhanced absorption spectroscopy. The main techniques available for routine atmospheric measurements of OH, NO3 and HONO are overviewed, in comparison with the emerging modern photonic spectroscopy techniques.

  5. Photothermal Absorption Spectroscopy of Individual Semiconductor Nanocrystals

    Berciaud, Stéphane; Cognet, Laurent; Lounis, Brahim

    2007-01-01

    Photothermal heterodyne detection is used to record the first room-temperature absorption spectra of single CdSe/ZnS semiconductor nanocrystals. These spectra are recorded in the high cw excitation regime, and the observed bands are assigned to transitions involving biexciton and trion states. Comparison with the single nanocrystals photoluminescence spectra leads to the measurement of spectral Stokes shifts free from ensemble averaging.

  6. [Study of retrieving formaldehyde with differential optical absorption spectroscopy].

    Li, Yu-Jin; Xie, Pin-Hua; Qin, Min; Qu, Xiao-Ying; Hu, Lin

    2009-01-01

    The present paper introduces the method of retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS). The authors measured ambient HCHO in Beijing region with the help of differential optical absorption spectroscopy instrument made by ourself, and discussed numerous factors in retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS), especially, the choice of HCHO wave band, how to avoid absorption of ambient SO2, NO2 and O3, and the influence of the Xenon lamp spectrum structure on the absorption of ambient HCHO. The authors achieved the HCHO concentration by simultaneously retrieving the concentrations of HCHO, SO2, NO2 and O3 with non-linear least square fitting method, avoiding the effect of choosing narrow wave of HCHO and the residual of SO2, NO2, O3 and the Xenon lamp spectrum structure in retrieving process to attain the concentration of HCHO, Finally the authors analyzed the origin of error in retrieving the concentration of HCHO with differential optical absorption spectroscopy (DOAS), and the total error is within 13.7% in this method. PMID:19385238

  7. Kinematic Interpretation of the Centaurus A Absorption-Line System

    Eckart, A.; Wild, W.; Ageorges, N.

    1999-01-01

    The location of the gas responsible for the absorption-line system toward the nucleus of Centaurus A is a puzzle. It is generally accepted that the line features close to the systemic velocity originate in the disk. The redshifted line features in particular, however, are usually thought to be due t

  8. Atomic absorption spectroscopy with high temperature flames.

    Willis, J B

    1968-07-01

    An account is given of the history of the development of high temperature flames for the atomic absorption measurement of metals forming refractory oxides. The principles governing the design of premix burners for such flames, and the relative merits of different types of nebulizer burner systems are described. After a brief account of the structure and emission characteristics of the premixed oxygen-acetylene and nitrous oxide-acetylene flames, the scope and limitations of the latter flame in chemical analysis are discussed. PMID:20068790

  9. Differential optical absorption spectroscopy principles and applications

    Platt, Ulrich; Imboden, Dieter

    2008-01-01

    Measurement techniques form the basis of our knowledge about atmospheric composition and chemistry. Presently, important questions of atmospheric chemistry center on urban pollution, free-radical chemistry, degradation of greenhouse gases and the budgets of tropospheric and stratospheric ozone. Among the many different optical spectroscopic methods that are in use, DOAS has emerged as a universal technique to measure the concentrations of atmospheric trace gases by making use of the characteristic absorption features of gas molecules along a path of known length in the open atmosphere. This bo

  10. [The Diagnostics of Detonation Flow External Field Based on Multispectral Absorption Spectroscopy Technology].

    Lü, Xiao-jing; Li, Ning; Weng, Chun-sheng

    2016-03-01

    Compared with traditional sampling-based sensing method, absorption spectroscopy technology is well suitable for detonation flow diagnostics, since it can provide with us fast response, nonintrusive, sensitive solution for situ measurements of multiple flow-field parameters. The temperature and concentration test results are the average values along the laser path with traditional absorption spectroscopy technology, while the boundary of detonation flow external field is unknown and it changes all the time during the detonation engine works, traditional absorption spectroscopy technology is no longer suitable for detonation diagnostics. The trend of line strength with temperature varies with different absorption lines. By increasing the number of absorption lines in the test path, more information of the non-uniform flow field can be obtained. In this paper, based on multispectral absorption technology, the reconstructed model of detonation flow external field distribution was established according to the simulation results of space-time conservation element and solution element method, and a diagnostic method of detonation flow external field was given. The model deviation and calculation error of the least squares method adopted were studied by simulation, and the maximum concentration and temperature calculation error was 20.1% and 3.2%, respectively. Four absorption lines of H2O were chosen and detonation flow was scanned at the same time. The detonation external flow testing system was set up for the valveless gas-liquid continuous pulse detonation engine with the diameter of 80 mm. Through scanning H2O absorption lines with a high frequency of 10 kHz, the on-line detection of detonation external flow was realized by direct absorption method combined with time-division multiplexing technology, and the reconstruction of dynamic temperature distribution was realized as well for the first time, both verifying the feasibility of the test method. The test results

  11. Optical technique for broadband microwave absorption spectroscopy in aqueous media

    Precise measurements of microwave absorption over a large range of frequencies in aqueous media are difficult to obtain and can result in conflicting results as a consequences of small differences in instrumentation. Traditional methods of microwave spectroscopy that make use of time-domain spectrometers or network analyzer systems provide only indirect measurement of the microwave absorption coefficient because they measure the real and imaginary parts of the dielectric constant, ε' and ε'', separately. The absorption coefficient must then be calculated from ε' and ε'' taking into account the geometry (e.g., of the waveguide and mode) among other factors. It has been shown that direct measurement of the microwave absorption coefficient α is possible using phase fluctuation optical heterodyne spectroscopy. Taking advantage of this hybrid optical-microwave technique the authors report on a broadband spectrometer with demonstrated accurate operation from 3 to 20 GHz

  12. Discovery of Extremely Broad Balmer Absorption Lines in SDSS J152350.42+391405.2

    Zhang, Shaohua; Shi, Xiheng; Shu, Xinwen; Liu, Wenjuan; Ji, Tuo; Jiang, Peng; Sun, Luming; Zhou, Junyan; Pan, Xiang

    2015-01-01

    We present the discovery of Balmer line absorption from H$\\alpha$ to H$\\gamma$ in an iron low-ionization broad absorption line (FeLoBAL) quasar SDSS J152350.42+391405.2 (hereafter J1523), by the quasi-simultaneous optical and near-infrared spectroscopy. The Balmer line absorption is at $z_{absor}$ = 0.6039 +/-0.0021 and blueshifted by v=10,353 km/s with respect to the Balmer emission lines. All Balmer BALs have uniform absorption profile with the widths of $\\Delta$ v ~12,000 km/s. We also found the absorption trough in He 1* $\\lambda$10830 with the same velocity and width in the H-band TripleSpec spectrum of J1523. This object is only the tenth active galactic nucleus known to exhibit non-stellar Balmer absorption, and also the case with the highest velocity and broadest Balmer absorption lines which have ever been found. A CLOUDY analysis shows that the absorbers require an gas density of $log_{10} n_ e (cm^{-3})=9$ and an ionization parameter of $log_{10} U=-1.0$. They locate at a distance of ~0.2 pc from t...

  13. Speciesion arsenic and selenium using hydride method atomic absorption spectroscopy

    Hydrides production - atomic absorption spectroscopy system was studied. Hydrides production tool and gas-liquid separator were tested and successfully used in this work. Hydride was produced through natrium borohydride reaction with sample solution. Emitted gas was separated by gas-liquid separator before it is carried by nitrogen gas through T tube which is put in atomic absorption flame spectrophotometer. Efficiency of the system was tested through standard reference sample and seawater / sediment samples which is collected from Negeri Johor water bays

  14. Determination of trace amounts of scandium by atomic absorption spectroscopy.

    Chau, Y K

    1968-05-01

    Optimum instrumental conditions were investigated for the determination of trace quantities of scandium by atomic-absorption spectroscopy. Enhancement effects by organic solvents and by complex extractions were also studied. (46)Sc was used to establish the optimum extraction conditions. A sensitivity of 0.06 ppm of Sc was observed when using extraction into oxine-butanol and atomic absorption was measured with an acetylene-nitrous oxide flame. PMID:18960315

  15. Absorption lines and the radio structure of quasars

    High angular resolution radio observations at lambda6cm of 20 quasars are presented, all but two of which have been selected from a sample used by previous authors for a survey of absorption lines. The additional two, 1246-057 and 1333 + 286, are quasars with broad absorption lines and appear to be radio quiet. The radio structures for the entire sample of 66 sources of the previous authors are summarized and an investigation is made of whether the radio structure might provide clues on understanding the origin of the absorption lines in the range Zsub(em)-Zsub(ab) approx. 3000-18000 kms-1. The frequency of occurrence of absorption lines appears to be similar for both radio and optically selected quasars. (author)

  16. Developing a Transdisciplinary Teaching Implement for Atomic Absorption Spectroscopy

    Drew, John

    2008-01-01

    In this article I explain why I wrote the set of teaching notes on Atomic Absorption Spectroscopy (AAS) and why they look the way they do. The notes were intended as a student reference to question, highlight and write over as much as they wish during an initial practical demonstration of the threshold concept being introduced, in this case…

  17. Laser photothermal spectroscopy of light-induced absorption

    Skvortsov, L A [Institute of Cryptography, Communications and Informatics, Moscow (Russian Federation)

    2013-01-31

    Basic methods of laser photothermal spectroscopy, which are used to study photoinduced absorption in various media, are briefly considered. Comparative analysis of these methods is performed and the latest results obtained in this field are discussed. Different schemes and examples of their practical implementation are considered. (review)

  18. Absorption and Emission Spectroscopy of a Lasing Material: Ruby

    Esposti, C. Degli; Bizzocchi, L.

    2007-01-01

    Ruby is a crystalline material, which comes very expensive and is of great significance, as it helped in the creation of first laser. An experiment to determine the absorption and emission spectroscopy, in addition to the determination of the room-temperature lifetime of the substance is being described.

  19. Calculations of line absorption for the Voigt profile

    Kato, I.; Iwasaki, A.; Adachi, A.; Shimizu, T.

    1978-07-01

    Line-absorption calculations of the 388.9 nm triplet and the 501.6 nm singlet lines of helium have been performed for the Voigt profile. These results can be used to measure the absolute concentration of He 2s /sup 3/S and 2s /sup 1/S metastable atoms for the various discharge conditions by the reabosorption method.

  20. High sensitivity ultra-broad-band absorption spectroscopy of inductively coupled chlorine plasma

    Marinov, Daniil; Foucher, Mickaël; Campbell, Ewen; Brouard, Mark; Chabert, Pascal; Booth, Jean-Paul

    2016-06-01

    We propose a method to measure the densities of vibrationally excited Cl2(v) molecules in levels up to v  =  3 in pure chlorine inductively coupled plasmas (ICPs). The absorption continuum of Cl2 in the 250–450 nm spectral range is deconvoluted into the individual components originating from the different vibrational levels of the ground state, using a set of ab initio absorption cross sections. It is shown that gas heating at constant pressure is the major depletion mechanism of the Cl2 feedstock in the plasma. In these line-integrated absorption measurements, the absorption by the hot (and therefore rarefied) Cl2 gas in the reactor centre is masked by the cooler (and therefore denser) Cl2 near the walls. These radial gradients in temperature and density make it difficult to assess the degree of vibrational excitation in the centre of the reactor. The observed line-averaged vibrational distributions, when analyzed taking into account the radial temperature gradient, suggest that vibrational and translational degrees of freedom in the plasma are close to local equilibrium. This can be explained by efficient vibrational-translational (VT) relaxation between Cl2 and Cl atoms. Besides the Cl2(v) absorption band, a weak continuum absorption is observed at shorter wavelengths, and is attributed to photodetachment of Cl‑ negative ions. Thus, line-integrated densities of negative ions in chlorine plasmas can be directly measured using broad-band absorption spectroscopy.

  1. Estimation of molar absorptivities and pigment sizes for eumelanin and pheomelanin using femtosecond transient absorption spectroscopy

    Piletic, Ivan R.; Matthews, Thomas E.; Warren, Warren S.

    2009-11-01

    Fundamental optical and structural properties of melanins are not well understood due to their poor solubility characteristics and the chemical disorder present during biomolecular synthesis. We apply nonlinear transient absorption spectroscopy to quantify molar absorptivities for eumelanin and pheomelanin and thereby get an estimate for their average pigment sizes. We determine that pheomelanin exhibits a larger molar absorptivity at near IR wavelengths (750nm), which may be extended to shorter wavelengths. Using the molar absorptivities, we estimate that melanin pigments contain ˜46 and 28 monomer units for eumelanin and pheomelanin, respectively. This is considerably larger than the oligomeric species that have been recently proposed to account for the absorption spectrum of eumelanin and illustrates that larger pigments comprise a significant fraction of the pigment distribution.

  2. Light-induced changes in subband absorption in a-Si:H using photoluminescence absorption spectroscopy

    Gu, S. Q.; Taylor, P. C.; Nitta, S.

    1991-08-01

    We have used the photoluminescence (PL) generated in a thin-film sample of a-Si:H to probe low absorption levels by measuring the absorption of the PL as it travels down the length of the film in a waveguide mode. This technique, which we have called PL absorption spectroscopy of PLAS, allows the measurement of values of the absorption coefficient α down to about 0.1 cm-1. Because this technique probes the top and bottom surfaces of the a-Si:H sample, it is important to separate surface from bulk absorption mechanisms. An improved sample geometry has been employed to facilitate this separation. One sample consisted of an a-Si1-xNix:H/a-Si:H/ a-Si1-xNx:H/NiCr layered structure where the silicon nitride layers served as the cladding layers for the waveguide. In a second sample the a-Si:H layer was interrupted near the middle for two separate, thin (100 Å) layers of a-Si1-xNx:H in order to check for the importance of the absorption at the silicon/silicon nitride interfaces in these PLAS measurements. Changes in the below-gap absorption on light soaking were examined using irradiation from an Ar+ laser (5145 Å, ˜200 mW/cm2 for 5.5 hours at 300 K). The silicon/silicon nitride interface is responsible for an absorption which has a shoulder near 1.2 eV while the bulk a-Si:H absorption exhibits no such shoulder. The metastable, optically-induced increase in the below gap absorption appears to come entirely from the bulk of the a-Si:H. These low temperature PLAS measurements are compared with those obtained at 300 K by photothermal deflection spectroscopy.

  3. Transient x-ray absorption spectroscopy of hydrated halogen atom

    Elles, Christopher G; Crowell, Robert A; Arms, Dohn A; Landahl, Eric C

    2007-01-01

    Time-resolved x-ray absorption spectroscopy monitors the transient species generated by one-photon detachment of an electron from aqueous bromide. Hydrated bromine atoms with a lifetime of ca. 17 ns were observed, nearly half of which react with excess Br- to form Br2-. The K-edge spectra of the Br atom and Br2- anion exhibit distinctive resonant transitions that are absent for the Br- precursor. The absorption spectra indicate that the solvent shell around a Br0 atom is defined primarily by hydrophobic interactions, in agreement with a Monte Carlo simulation of the solvent structure.

  4. Broad Absorption Line Quasar catalogues with Supervised Neural Networks

    We have applied a Learning Vector Quantization (LVQ) algorithm to SDSS DR5 quasar spectra in order to create a large catalogue of broad absorption line quasars (BALQSOs). We first discuss the problems with BALQSO catalogues constructed using the conventional balnicity and/or absorption indices (BI and AI), and then describe the supervised LVQ network we have trained to recognise BALQSOs. The resulting BALQSO catalogue should be substantially more robust and complete than BI-or AI-based ones.

  5. Self-absorption influence on the optical spectroscopy of zinc oxide laser produced plasma

    De Posada, E; Arronte, M A; Ponce, L; Rodriguez, E; Flores, T [Centro de Investigacion en Ciencia Aplicada y TecnologIa Avanzada-Unidad Altamira, Tamaulipas (Mexico); Lunney, J G, E-mail: edeposada@ipn.mx [School of Physics, Trinity College Dublin (Ireland)

    2011-01-01

    Optical spectroscopy is used to study the laser ablation process of ZnO targets. It is demonstrated that even if Partial Local Thermal Equilibrium is present, self absorption process leads to a decrease of recorded lines emission intensities and have to be taken into account to obtain correct values of such parameters. It is presented a method that combines results of both Langmuir probe technique and Anisimov model to obtain correct values of plasma parameters.

  6. Self-absorption influence on the optical spectroscopy of zinc oxide laser produced plasma

    Optical spectroscopy is used to study the laser ablation process of ZnO targets. It is demonstrated that even if Partial Local Thermal Equilibrium is present, self absorption process leads to a decrease of recorded lines emission intensities and have to be taken into account to obtain correct values of such parameters. It is presented a method that combines results of both Langmuir probe technique and Anisimov model to obtain correct values of plasma parameters.

  7. Infrared absorption spectroscopy and chemical kinetics of free radicals

    Curl, R.F.; Glass, G.P. [Rice Univ., Houston, TX (United States)

    1993-12-01

    This research is directed at the detection, monitoring, and study of chemical kinetic behavior by infrared absorption spectroscopy of small free radical species thought to be important intermediates in combustion. During the last year, infrared kinetic spectroscopy using excimer laser flash photolysis and color-center laser probing has been employed to study the high resolution spectrum of HCCN, the rate constant of the reaction between ethynyl (C{sub 2}H) radical and H{sub 2} in the temperature region between 295 and 875 K, and the recombination rate of propargyl (CH{sub 2}CCH) at room temperature.

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

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

    2016-06-13

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

  9. Infrared-laser spectroscopy using a long-pathlength absorption cell

    The absorption measurements in an ordinary cell may require typically a few torr pressure of sample gas. At these pressures the absorption lines are usually pressure-broadened and, therefore, closely spaced transitions are poorly resolved even at diode-laser resolution. This situation is greatly improved in Doppler-limited spectroscopy at extremely low sample pressures. Two very long-pathlength absorption cells were developed to be used in conjunction with diode lasers. They were designed to operate at controlled temperatures with the optical pathlength variable up to approx. 1.5 km. Not only very low sample pressures are used for studies with such cells but also the spectroscopic sensitivity is enhanced over conventional methods by a factor of 103 to 104, improving the analytical capability of measuring particle densities to the order of 1 x 10'' molecules/cm3. This paper presents some analytical aspects of the diode laser spectroscopy using the long-pathlength absorption cells in the areas of absorption line widths, pressure broadening coefficients, isotope composition measurements and trace impurity analysis

  10. Multi axis differential optical absorption spectroscopy (MAX-DOAS)

    Hönninger, G.; Von Friedeburg, C.; U. Platt

    2004-01-01

    Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) in the atmosphere is a novel measurement technique that represents a significant advance on the well-established zenith scattered sunlight DOAS instruments which are mainly sensitive to stratospheric absorbers. MAX-DOAS utilizes scattered sunlight received from multiple viewing directions. The spatial distribution of various trace gases close to the instrument can be derived by combining several viewing directions. Ground...

  11. Multi axis differential optical absorption spectroscopy (MAX-DOAS)

    Hönninger, G.; Friedeburg, C.; U. Platt

    2004-01-01

    Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) in the atmosphere is a novel measurement technique that represents a significant advance on the well-established zenith scattered sunlight DOAS instruments which are mainly sensitive to stratospheric absorbers. MAX-DOAS utilizes scattered sunlight received from multiple viewing directions. The spatial distribution of various trace gases close to the instrument can be derived by combining sev...

  12. Constraining FeLoBAL outflows from absorption line variability

    McGraw, S M; Hamann, F W; Capellupo, D M; Gallagher, S C; Brandt, W N

    2015-01-01

    FeLoBALs are a rare class of quasar outflows with low-ionization broad absorption lines (BALs), large column densities, and potentially large kinetic energies that might be important for `feedback' to galaxy evolution. In order to probe the physical properties of these outflows, we conducted a multiple-epoch, absorption line variability study of 12 FeLoBAL quasars spanning a redshift range between 0.7 and 1.9 over rest frame time-scales of approximately 10 d to 7.6 yr. We detect absorption line variability with greater than 8 sigma confidence in 3 out of the 12 sources in our sample over time-scales of 0.6 to 7.6 yr. Variable wavelength intervals are associated with ground and excited state Fe II multiplets, the Mg II 2796, 2803 doublet, Mg I 2852, and excited state Ni II multiplets. The observed variability along with evidence of saturation in the absorption lines favors transverse motions of gas across the line of sight (LOS) as the preferred scenario, and allows us to constrain the outflow distance from th...

  13. Discovery of Broad Soft X-ray Absorption Lines from the Quasar Wind in PDS 456

    Reeves, James; Nardini, Emanuele; Behar, Ehud; O'Brien, Paul; Tombesi, Francesco; Turner, Tracey Jane; Costa, Michele

    2016-01-01

    High resolution soft X-ray spectroscopy of the prototype accretion disk wind quasar, PDS 456, is presented. Here, the XMM-Newton RGS spectra are analyzed from the large 2013-2014 XMM-Newton campaign, consisting of 5 observations of approximately 100 ks in length. During the last observation (hereafter OBS. E), the quasar is at a minimum flux level and broad absorption line profiles are revealed in the soft X-ray band, with typical velocity widths of $\\sigma_{\\rm v}\\sim 10,000$ km s$^{-1}$. During a period of higher flux in the 3rd and 4th observations (OBS. C and D, respectively), a very broad absorption trough is also present above 1 keV. From fitting the absorption lines with models of photoionized absorption spectra, the inferred outflow velocities lie in the range $\\sim 0.1-0.2c$. The absorption lines likely originate from He and H-like neon and L-shell iron at these energies. Comparison with earlier archival data of PDS 456 also reveals similar absorption structure near 1 keV in a 40 ks observation in 20...

  14. Incoherent broadband cavity enhanced absorption spectroscopy using supercontinuum and superluminescent diode sources.

    Aalto, Antti; Genty, Goëry; Laurila, Toni; Toivonen, Juha

    2015-09-21

    We investigate incoherent broadband cavity enhanced absorption spectroscopy using a tailored supercontinuum source. By tailoring the supercontinuum spectrum to match the high reflectivity bandwidth of the mirrors, we achieve an unprecedented spectral brightness of more than 7 dBm/nm at wavelengths where the effective absorption path length in the cavity exceeds 40 km. We demonstrate the potential of the source in spectrally broadband measurement of weak overtone transitions of carbon dioxide and methane in the near-infrared 1590 nm - 1700 nm range and evaluate its performance against that of a typical superluminescent diode source. Minimum detectable absorption coefficients (3σ) of 2.2 × 10(-9) cm(-1) and 6.2 × 10(-9) cm(-1) are obtained with the supercontinuum and the superluminescent diode sources, respectively. We further develop a spectral fitting method based on differential optical absorption spectroscopy to fully and properly account for the combined effect of absorption line saturation and limited spectral resolution of the detection. The method allows to cope with high dynamic range of absorption features typical of real-world multi-component measurements. PMID:26406720

  15. The earliest galaxies seen in 21 cm line absorption

    Xu, Yidong; Chen, Xuelei

    2010-01-01

    We investigate the 21 cm absorption lines produced by non-linear structures during the early stage of reionization, i.e. the starless minihalos and the dwarf galaxies. After a detailed modelling of their properties, with particular attention to the coupling physics, we determine their 21 cm absorption line profiles. The infalling gas velocity around minihalos/dwarf galaxies strongly affects the line shape, and with the low spin temperatures outside the virial radii of the systems, gives rise to horn-like line profiles. The optical depth of a dwarf galaxy is reduced for lines of sight penetrating through its HII region, and especially, a large HII region created by a dwarf galaxy with higher stellar mass and/or a top-heavy initial mass function results in an optical depth trough rather than an absorption line. We compute synthetic spectra of 21 cm forest for both high redshift quasars and radio afterglows of gamma ray bursts (GRBs). Even with the planned SKA, radio afterglows of most if not all GRBs would stil...

  16. Intermediate-redshift galaxy halos - Results from QSO absorption lines

    For a sample of Mg II-selected QSO absorption-line systems for which the absorbing galaxies have been successfully identified, the rest-frame equivalent widths of the Mg II 2796-A absorption lines are examined as a function of the known impact parameters between the background QSOs and the absorbing galaxies. There appears to exist a relationship between the equivalent widths and the impact parameters, in the sense that larger equivalent widths occur at smaller impact parameters. No trend of the doublet ratio is found with impact parameter, and neither the equivalent widths nor the doublet ratios are correlated with the absolute luminosities or redshifts of the absorbing galaxies. These results apparently indicate that the main factor that determines the equivalent width of a particular absorption system is the impact parameter between the background QSO and the absorbing galaxy. 32 refs

  17. Intermediate-redshift galaxy halos - Results from QSO absorption lines

    Lanzetta, K.M.; Bowen, D. (Cambridge Univ. (England) Royal Greenwich Observatory, Cambridge (England))

    1990-07-01

    For a sample of Mg II-selected QSO absorption-line systems for which the absorbing galaxies have been successfully identified, the rest-frame equivalent widths of the Mg II 2796-A absorption lines are examined as a function of the known impact parameters between the background QSOs and the absorbing galaxies. There appears to exist a relationship between the equivalent widths and the impact parameters, in the sense that larger equivalent widths occur at smaller impact parameters. No trend of the doublet ratio is found with impact parameter, and neither the equivalent widths nor the doublet ratios are correlated with the absolute luminosities or redshifts of the absorbing galaxies. These results apparently indicate that the main factor that determines the equivalent width of a particular absorption system is the impact parameter between the background QSO and the absorbing galaxy. 32 refs.

  18. Hydrogen absorption line profiles of ionizing star clusters

    Angeles I. Díaz

    1988-01-01

    This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Díaz, A.I. Hydrogen absorption line profiles of ionizing star clusters. Monthly Notices of the Royal Astronomical Society 231 (1988): 57-67 and Microfiche MN 231/1

  19. APPLICATION OF ABSORPTION SPECTROSCOPY TO ACTINIDE PROCESS ANALYSIS AND MONITORING

    Lascola, R.; Sharma, V.

    2010-06-03

    The characteristic strong colors of aqueous actinide solutions form the basis of analytical techniques for actinides based on absorption spectroscopy. Colorimetric measurements of samples from processing activities have been used for at least half a century. This seemingly mature technology has been recently revitalized by developments in chemometric data analysis. Where reliable measurements could formerly only be obtained under well-defined conditions, modern methods are robust with respect to variations in acidity, concentration of complexants and spectral interferents, and temperature. This paper describes two examples of the use of process absorption spectroscopy for Pu analysis at the Savannah River Site, in Aiken, SC. In one example, custom optical filters allow accurate colorimetric measurements of Pu in a stream with rapid nitric acid variation. The second example demonstrates simultaneous measurement of Pu and U by chemometric treatment of absorption spectra. The paper concludes with a description of the use of these analyzers to supplement existing technologies in nuclear materials monitoring in processing, reprocessing, and storage facilities.

  20. Study on the elemental mercury absorption cross section based on differential optical absorption spectroscopy

    Zheng, Haiming; Yao, Penghui

    2015-08-01

    With the method of ultraviolet absorption spectrum, the exact absorption cross-section with the light source of the low-pressure mercury lamp was determined, during which the optimum wavelength for mercury concentrations inversion was 253.69 nm, the highest detection limit was 0.177 μg/cm3, and the lowest detection limit was 0.034 μg/cm3. Furthermore, based on the differential optical absorption spectroscopy(DOAS), the relationship between the integral parameters (IP) and the concentration as well as the signal-noise ration (SNR) under the conditions of gas flow was determined and the lowest detection limit was figured out to be 0.03524 μg/cm3, providing a method of DOAS to de-noise through the comparison between the mercury concentration values produced by DOAS and that produced by the wavelet de-noising method (db5). It turned out that the differential optical absorption spectroscopy had a strong anti-interference ability, while the wavelet de-noising method was not suitable for measuring the trace concentration change.

  1. The sub-millimeter properties of broad absorption line quasars

    Willott, Chris J.; Rawlings, Steve; Grimes, Jennifer A.

    2003-01-01

    We have carried out the first systematic survey of the sub-millimeter properties of broad absorption line (BAL) quasars. 30 BAL quasars drawn from a homogeneously selected sample from the Sloan Digital Sky Survey at redshifts 2 3 sigma significance. The far-infrared luminosities of these quasars are > 10^{13} L_solar. There is no correlation of sub-millimeter flux with either the strength of the broad absorption feature or with absolute magnitude in our sample. We compare the sub-millimeter f...

  2. The Connection Between Galaxies and Intergalactic Absorption Lines at Redshift 2

    Adelberger, K L; Steidel, C C; Pettini, M; Erb, D K; Reddy, N A

    2005-01-01

    Absorption-line spectroscopy of 23 background QSOs and numerous background galaxies has let us measure the spatial distribution of metals and neutral hydrogen around 1044 UV-selected galaxies at redshifts 1.8260 km/s) and produces very strong absorption lines (N_CIV >> 10^14 cm^-2) in the spectra of background objects. Absorption with an average column density of N_CIV ~ 10^14 cm^-2 extends to 80 kpc, a radius large enough to imply that most strong intergalactic CIV absorption is associated with star-forming galaxies like those in our sample. We find that the galaxy-CIV cross-correlation length increases with CIV column density and is similar to the galaxy-galaxy length (r_0 ~ 4 h^-1 Mpc) for N_CIV > 10^12.5 cm^-2. Distortions in the redshift-space galaxy-CIV correlation function on small scales may imply that some of the CIV systems have large peculiar velocities. Four of the five detected OVI absorption systems in our sample lie within 400 proper kpc of a known galaxy. Strong Lyman-a absorption is produced ...

  3. Operando X-ray absorption and infrared fuel cell spectroscopy

    Lewis, Emily A.; Kendrick, Ian; Jia, Qingying; Grice, Corey; Segre, Carlo U.; Smotkin, Eugene S. (NuVant); (IIT); (NEU)

    2011-11-17

    A polymer electrolyte fuel cell enables operando X-ray absorption and infrared spectroscopy of the membrane electrode assembly catalytic layer with flowing fuel and air streams at controlled temperature. Time-dependent X-ray absorption near edge structure spectra of the Pt and Ni edge of Pt based catalysts of an air-breathing cathode show that catalyst restructuring, after a potential step, has time constants from minutes to hours. The infrared Stark tuning plots of CO adsorbed on Pt at 100, 200, 300 and 400 mV vs. hydrogen reference electrode were obtained. The Stark tuning plots of CO adsorbed at 400 mV exhibit a precipitous drop in frequency coincident with the adsorption potential. The turn-down potential decreases relative to the adsorption potential and is approximately constant after 300 mV. These Stark tuning characteristics are attributed to potential dependent adsorption site selection by CO and competitive adsorption processes.

  4. Study on Differential Optical Absorption Spectroscopy : Technique and its Applications

    Liu, Jianguo

    2002-01-01

    ln the first part of speech, with a description of the principle of DOAS (Differential Optical Absorption Spectroscopy), the design and realization of two different kinds of DOAS systems are nresented. 0ne is using a slotted disc raoid scanning device with a photomultiplier, which is suitable for ambient air quality measurement. It can measure total 16 kinds of pollutants such as SO_2, NO, N02, NH_3, O_3, C_6H_6, C_7H_8 and CH_2O etc., with detection limits of 1-2ppb. The other is using a UV ...

  5. Fingerprints of polycyclic aromatic hydrocarbons (PAHs) in infrared absorption spectroscopy

    Tommasini, Matteo; Lucotti, Andrea; Alfè, Michela; Ciajolo, Anna; Zerbi, Giuseppe

    2016-01-01

    We have analyzed a set of 51 PAHs whose structures have been hypothesized from mass spectrometry data collected on samples extracted from carbon particles of combustion origin. We have obtained relationships between infrared absorption signals in the fingerprint region (mid-IR) and the chemical structures of PAHs, thus proving the potential of IR spectroscopy for the characterization of the molecular structure of aromatic combustion products. The results obtained here for the spectroscopic characterization of PAHs can be also of interest in Materials Science and Astrophysics.

  6. High Resolution Spectroscopy on an X-ray Absorption Beamline

    Hazemann, Jean-Louis; Proux, Olivier; Nassif, Vivian; Palancher, Hervé; Lahera, Eric; Da Silva, Cécile; Braillard, Aurélien; Testemale, Denis; Diot, Marie-Ange; Alliot, Isabelle; Delnet, William; Manceau, A.; Gélébart, Frédéric; Morand, Marc; Dermigny, Quentin

    2008-01-01

    Abstract A bent crystal spectrometer based on the Rowland circle geometry has been tested on the BM30b/FAME beamline at the European Synchrotron Radiation Facility. The energy resolution of the spectrometer (1.3eV at the Cu K1 energy, i.e. 8047.78eV) allows to perform different kinds of measurements, including X-ray Absorption Spectroscopy, Resonant Inelastic X-ray Scattering and X-ray Raman Scattering experiments. The simplicity of the experimental device makes it easily implemented on a cl...

  7. Calculations of line absorption for the Voigt profile and some specific lines of helium

    Kato, I.; Yonehara, A.

    1980-07-01

    Calculations of the line absorption for the 396.5- , 361.4- , 318.7- , 492.2- , 587.6- , and 447.1-nm lines of helium have been performed for the Voigt profile. These results can be used to measure the absolute concentration of helium metastable atoms and several other excited atoms by the reabsorption method.

  8. Space Launch System Base Heating Test: Tunable Diode Laser Absorption Spectroscopy

    Parker, Ron; Carr, Zak; MacLean, Matthew; Dufrene, Aaron; Mehta, Manish

    2016-01-01

    This paper describes the Tunable Diode Laser Absorption Spectroscopy (TDLAS) measurement of several water transitions that were interrogated during a hot-fire testing of the Space Launch Systems (SLS) sub-scale vehicle installed in LENS II. The temperature of the recirculating gas flow over the base plate was found to increase with altitude and is consistent with CFD results. It was also observed that the gas above the base plate has significant velocity along the optical path of the sensor at the higher altitudes. The line-by-line analysis of the H2O absorption features must include the effects of the Doppler shift phenomena particularly at high altitude. The TDLAS experimental measurements and the analysis procedure which incorporates the velocity dependent flow will be described.

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

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

    1972-01-01

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

  10. Non-Voigt Lyman-$\\alpha$ absorption line profiles

    Outram, P J; Theuns, T

    1999-01-01

    Recent numerical simulations have lead to a paradigm shift in our understanding of the intergalactic medium, and the loss of a physical justification for Voigt profile fitting of the Lyman-alpha forest. Many individual lines seen in simulated spectra have significant departures from the Voigt profile, yet could be well fitted by a blend of two or more such lines. We discuss the expected effect on the line profiles due to ongoing gravitational structure formation and Hubble expansion. We develop a method to detect departures from Voigt profiles of the absorption lines in a statistical way and apply this method to simulated Lyman-alpha forest spectra, confirming that the profiles seen do statistically differ from Voigt profiles.

  11. Model galactic coronae: Ionization structure and absorption-line spectra

    We describe a general model for a gaseous galactic corona, and demonstrate that it is in harmony with a variety of observational and theoretical constraints. We then compute the ionization equilibria of H, He, C, N, O, Si, and S atoms in the corona and determine the strengths of resonance absorption lines arising therein. To this end, we obtain approximate cross sections for ionization of the heavy-element ions by photons of energy E/sub γ/< or =100 eV.We use our results first to discuss the expected absorption spectrum of our Galaxy's corona. Subsequently, we discuss in detail the relevance of our computed equilibria to the suggestion that galactic coronae produce some redshift systems in quasar absorption spectra. Because our model coronae are not isothermal, the ionization structure existing along various lines of sight through them is not in accord with the concept of ''reasonable ionization equilibrium'': a concept assumed to be valid in most analyses of quasar spectra. However, our calculations indicate that typically one well-established redshift system in each quasar absorption spectrum could arise in the corona of an intervening galaxy. This is the number expected from statistical arguments if quasar redshifts are fully cosmological in origin

  12. Radiation pressure confinement - IV. Application to broad absorption line outflows

    Baskin, Alexei; Stern, Jonathan

    2014-01-01

    A fraction of quasars present broad absorption lines, produced by outflowing gas with typical velocities of 3000 - 10,000 km/s. If the outflowing gas fills a significant fraction of the volume where it resides, then it will be highly ionized by the quasar due to its low density, and will not produce the observed UV absorption. The suggestion that the outflow is shielded from the ionizing radiation was excluded by recent observations. The remaining solution is a dense outflow with a filling factor $f<10^{-3}$. What produces such a small $f$? Here we point out that radiation pressure confinement (RPC) inevitably leads to gas compression and the formation of dense thin gas sheets/filaments, with a large gradient in density and ionization along the line of sight. The total column of ionized dustless gas is a few times $10^{22}$ cm$^{-2}$, consistent with the observed X-ray absorption and detectable P V absorption. The predicted maximal columns of various ions show a small dependence on the system parameters, a...

  13. Tunable Diode Laser Atomic Absorption Spectroscopy for Detection of Potassium under Optically Thick Conditions.

    Qu, Zhechao; Steinvall, Erik; Ghorbani, Ramin; Schmidt, Florian M

    2016-04-01

    Potassium (K) is an important element related to ash and fine-particle formation in biomass combustion processes. In situ measurements of gaseous atomic potassium, K(g), using robust optical absorption techniques can provide valuable insight into the K chemistry. However, for typical parts per billion K(g) concentrations in biomass flames and reactor gases, the product of atomic line strength and absorption path length can give rise to such high absorbance that the sample becomes opaque around the transition line center. We present a tunable diode laser atomic absorption spectroscopy (TDLAAS) methodology that enables accurate, calibration-free species quantification even under optically thick conditions, given that Beer-Lambert's law is valid. Analyte concentration and collisional line shape broadening are simultaneously determined by a least-squares fit of simulated to measured absorption profiles. Method validation measurements of K(g) concentrations in saturated potassium hydroxide vapor in the temperature range 950-1200 K showed excellent agreement with equilibrium calculations, and a dynamic range from 40 pptv cm to 40 ppmv cm. The applicability of the compact TDLAAS sensor is demonstrated by real-time detection of K(g) concentrations close to biomass pellets during atmospheric combustion in a laboratory reactor. PMID:26938713

  14. Spectropolarimetry of Radio-Selected Broad Absorption Line Quasars

    DiPompeo, M. A.; Brotherton, M. S.; Becker, R. H.; Tran, H. D.; Gregg, M. D.; White, R L; Laurent-Muehleisen, S. A.

    2010-01-01

    We report spectropolarimetry of 30 radio-selected broad absorption line (BAL) quasars with the Keck Observatory, 25 from the sample of Becker et al. (2000). Both high and low-ionization BAL quasars are represented, with redshifts ranging from 0.5 to 2.5. The spectropolarimetric properties of radio-selected BAL quasars are very similar to those of radio-quiet BAL quasars: a sizeable fraction (20%) show large continuum polarization (2-10%) usually rising toward short wavelengths, emission lines...

  15. Polarization properties of broad absorption line QSOs : new statistical clues

    H. Lamy; Hutsemekers, Damien

    2004-01-01

    We report the results of several statistical tests performed on a large sample of 139 broad absorption line (BAL) QSOs with good quality optical spectra and/or optical polarization data. Correlations between ten optical indices and the polarization degree p[SUB]0[/SUB] are systematically searched for. We find six significant non-trivial correlations. In order to identify the most important correlations, we perform a principal component analysis with a sample of 30 BAL QSOs and eight quantitie...

  16. The missing UV absorption lines of NGC 4151

    In this paper we discuss new, near-simultaneous high-dispersion long- and short-wavelength International Ultraviolet Explorer (IUE) observations of the Seyfert galaxy NGC 4151. Previous observations revealed a narrow absorption system in Mg II not present in Ly α or C IV. The new observations confirm the presence of this system in Mg II and its absence in the other lines. Possible reasons for this are discussed. (author)

  17. What sodium absorption lines tell us about type Ia supernovae

    Soker, Noam

    2014-01-01

    We propose that the sodium responsible for the variable Na I D absorption lines in some type Ia supernovae (SN Ia) originate from dust residing at ~1pc from the supernovae. In this Na-from-dust absorption (NaDA) model the process by which the SN Ia peak luminosity releases sodium from dust at ~1pc from the SN is similar to the processes by which solar radiation releases sodium from comet dust when comets approach a distance of ~1AU from the Sun. The dust grains are not sublimated but rather stay intact, and release sodium by photon-stimulated desorption (PSD; or photo-sputtering). We apply the NaDA model to SN 2006X and SN 2007le, and find it to comply better with the observed time variability of the Na I D absorption lines than the Na recombination model. The mass in the dusty shell of the NaDA model is much too high to be accounted for in the single-degenerate scenario for SN Ia. Therefore, the presence of variable Na I D lines in some SN Ia further weakens the already very problematic single-degenerate sce...

  18. Monitoring the Variability of Intrinsic Absorption Lines in Quasar Spectra

    Misawa, Toru; Eracleous, Michael

    2014-01-01

    We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 years (1-3.5 years in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems nor in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable broad absorption lines. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density $\\sim$ 10$^3$-10$^5$ cm$^{-3}$ and upper limits on the distance of the absorbers from the central engine of order a few kpc. Motivate...

  19. Transient C IV Broad Absorption Lines in radio detected QSOs

    Vivek, M; Gupta, N

    2015-01-01

    We study the transient (i.e. emerging or disappearing) C IV broad absorption line (BAL) components in 50 radio detected QSOs using multi-epoch spectra available in Sloan Digital Sky Survey DR10. We report the detectionof 6 BALQSOs having at least one distinct transient C IV absorption component. Based on the structure function analysis of optical light curves, we suggest that the transient absorption is unlikely to be triggered by continuum variations. Transient absorption components usually have low C IV equivalent widths ( 10000 \\kms) and typically occur over rest-frame timescales > 800 days. The detection rate of transient C IV absorption seen in our sample is higher than that reported in the literature. Using a control sample of QSOs, we show that this difference is most likely due to the longer monitoring time-scale of sources in our sample while the effect of small number statistics cannot be ignored. Thus, in order to establish the role played by radio jets in driving the BAL outflows, we need a larger...

  20. Mid-infrared absorption spectroscopy using quantum cascade lasers

    Haibach, Fred; Erlich, Adam; Deutsch, Erik

    2011-06-01

    Block Engineering has developed an absorption spectroscopy system based on widely tunable Quantum Cascade Lasers (QCL). The QCL spectrometer rapidly cycles through a user-selected range in the mid-infrared spectrum, between 6 to 12 μm (1667 to 833 cm-1), to detect and identify substances on surfaces based on their absorption characteristics from a standoff distance of up to 2 feet with an eye-safe laser. It can also analyze vapors and liquids in a single device. For military applications, the QCL spectrometer has demonstrated trace explosive, chemical warfare agent (CWA), and toxic industrial chemical (TIC) detection and analysis. The QCL's higher power density enables measurements from diffuse and highly absorbing materials and substrates. Other advantages over Fourier Transform Infrared (FTIR) spectroscopy include portability, ruggedness, rapid analysis, and the ability to function from a distance through free space or a fiber optic probe. This paper will discuss the basic technology behind the system and the empirical data on various safety and security applications.

  1. [Retrieval of monocyclic aromatic hydrocarbons with differential optical absorption spectroscopy].

    Xie, Pin-Hua; Fu, Qiang; Liu, Jian-Guo; Liu, Wen-Qing; Qin, Min; Li, Ang; Liu, Shi-Sheng; Wei, Qing-Nong

    2006-09-01

    Differential optical absorption spectroscopy (DOAS) technique has been used to measure trace gases in the atmosphere by their strongly structured absorption of radiation in the UV and visible spectral range, e. g. SO2, NO2, O3 etc. However, unlike the absorption spectra of SO2 and NO2, the analysis of aromatic compounds is difficult and strongly suffers from the cross interference of other absorbers (Herzberg bands of oxygen, ozone and sulfur dioxide), especially with relatively low concentrations of aromatic compounds in the atmosphere. In the present paper, the DOAS evaluation of aromatic compounds was performed by nonlinear least square fit with two interpolated oxygen optical density spectra at different path lengths and reference spectra of ozone at different temperature and SO2 cross section to correct the interference from absorbers of O2, O3 and SO2. The measurement of toluene, benzene, (m, p, o) xylene and phenol with a DOAS system showed that DOAS method is suitable for monocyclic aromatic compounds monitoring in the atmosphere. PMID:17112022

  2. Femtosecond transient absorption spectroscopy of silanized silicon quantum dots

    Kuntermann, Volker; Cimpean, Carla; Brehm, Georg; Sauer, Guido; Kryschi, Carola; Wiggers, Hartmut

    2008-03-01

    Excitonic properties of colloidal silicon quantum dots (Si qdots) with mean sizes of 4nm were examined using stationary and time-resolved optical spectroscopy. Chemically stable silicon oxide shells were prepared by controlled surface oxidation and silanization of HF-etched Si qdots. The ultrafast relaxation dynamics of photogenerated excitons in Si qdot colloids were studied on the picosecond time scale from 0.3psto2.3ns using femtosecond-resolved transient absorption spectroscopy. The time evolution of the transient absorption spectra of the Si qdots excited with a 150fs pump pulse at 390nm was observed to consist of decays of various absorption transitions of photoexcited electrons in the conduction band which overlap with both the photoluminescence and the photobleaching of the valence band population density. Gaussian deconvolution of the spectroscopic data allowed for disentangling various carrier relaxation processes involving electron-phonon and phonon-phonon scatterings or arising from surface-state trapping. The initial energy and momentum relaxation of hot carriers was observed to take place via scattering by optical phonons within 0.6ps . Exciton capturing by surface states forming shallow traps in the amorphous SiOx shell was found to occur with a time constant of 4ps , whereas deeper traps presumably localized in the Si-SiOx interface gave rise to exciton trapping processes with time constants of 110 and 180ps . Electron transfer from initially populated, higher-lying surface states to the conduction band of Si qdots (>2nm) was observed to take place within 400 or 700fs .

  3. Time-resolved detection of temperature, concentration, and pressure in a shock tube by intracavity absorption spectroscopy

    Fjodorow, Peter; Fikri, Mustapha; Schulz, Christof; Hellmig, Ortwin; Baev, Valery M.

    2016-06-01

    In this paper, we demonstrate the first application of intracavity absorption spectroscopy (ICAS) for monitoring species concentration, total pressure, and temperature in shock-tube experiments. ICAS with a broadband Er3+-doped fiber laser is applied to time-resolved measurements of absorption spectra of shock-heated C2H2. The measurements are performed in a spectral range between 6512 and 6542 cm-1, including many absorption lines of C2H2, with a time resolution of 100 µs and an effective absorption path length of 15 m. Up to 18-times increase of the total pressure and a temperature rise of up to 1200 K have been monitored. Due to the ability of simultaneously recording many absorption lines in a broad spectral range, the presented technique can also be applied to multi-component analysis of transient single-shot processes in reactive gas mixtures in shock tubes, pulse detonation engines, or explosions.

  4. Optical re-injection in cavity-enhanced absorption spectroscopy

    Leen, J. Brian, E-mail: b.leen@lgrinc.com; O’Keefe, Anthony [Los Gatos Research, 67 E. Evelyn Avenue, Suite 3, Mountain View, California 94041 (United States)

    2014-09-15

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10{sup −10} cm{sup −1}/√(Hz;) an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features.

  5. Optical re-injection in cavity-enhanced absorption spectroscopy

    Leen, J. Brian; O’Keefe, Anthony

    2014-01-01

    Non-mode-matched cavity-enhanced absorption spectrometry (e.g., cavity ringdown spectroscopy and integrated cavity output spectroscopy) is commonly used for the ultrasensitive detection of trace gases. These techniques are attractive for their simplicity and robustness, but their performance may be limited by the reflection of light from the front mirror and the resulting low optical transmission. Although this low transmitted power can sometimes be overcome with higher power lasers and lower noise detectors (e.g., in the near-infrared), many regimes exist where the available light intensity or photodetector sensitivity limits instrument performance (e.g., in the mid-infrared). In this article, we describe a method of repeatedly re-injecting light reflected off the front mirror of the optical cavity to boost the cavity's circulating power and deliver more light to the photodetector and thus increase the signal-to-noise ratio of the absorption measurement. We model and experimentally demonstrate the method's performance using off-axis cavity ringdown spectroscopy (OA-CRDS) with a broadly tunable external cavity quantum cascade laser. The power coupled through the cavity to the detector is increased by a factor of 22.5. The cavity loss is measured with a precision of 2 × 10−10 cm−1/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$\\sqrt {{\\rm Hz;}}$\\end{document} Hz ; an increase of 12 times over the standard off-axis configuration without reinjection and comparable to the best reported sensitivities in the mid-infrared. Finally, the re-injected CRDS system is used to measure the spectrum of several volatile organic compounds, demonstrating the improved ability to resolve weakly absorbing spectroscopic features. PMID:25273701

  6. UNSHIFTED METASTABLE He I* MINI-BROAD ABSORPTION LINE SYSTEM IN THE NARROW-LINE TYPE 1 QUASAR SDSS J080248.18+551328.9

    Ji, Tuo; Zhou, Hongyan; Jiang, Peng; Wang, Tinggui; Wang, Huiyuan; Liu, Wenjuan; Yang, Chenwei [Polar Research Institute of China, 451 Jinqiao Road, Pudong, Shanghai 200136 (China); Ge, Jian; Hamann, Fred [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Komossa, S.; Yuan, Weimin [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Beijing 100012 (China); Zuther, Jens [Physikalisches Institut, Universität zu Köln, Zülpicher Strasse 77, D-50937 Köln (Germany); Lu, Honglin [Key Laboratory for Research in Galaxies and Cosmology, The University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui, 230026 (China); Zuo, Wenwen, E-mail: jituo@pric.gov.cn [Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China)

    2015-02-10

    We report the identification of an unusual absorption-line system in the quasar SDSS J080248.18+551328.9 and present a detailed study of the system, incorporating follow-up optical and near-IR spectroscopy. A few tens of absorption lines are detected, including He I*, Fe II*, and Ni II*, which arise from metastable or excited levels, as well as resonant lines in Mg I, Mg II, Fe II, Mn II, and Ca II. All of the isolated absorption lines show the same profile of width Δv ∼ 1500 km s{sup –1} centered at a common redshift as that of the quasar emission lines, such as [O II], [S II], and hydrogen Paschen and Balmer series. With narrow Balmer lines, strong optical Fe II multiplets, and weak [O III] doublets, its emission-line spectrum is typical for that of a narrow-line Seyfert 1 galaxy (NLS1). We have derived reliable measurements of the gas-phase column densities of the absorbing ions/levels. Photoionization modeling indicates that the absorber has a density of n {sub H} ∼ (1.0-2.5) × 10{sup 5} cm{sup –3} and a column density of N {sub H} ∼ (1.0-3.2) × 10{sup 21} cm{sup –2} and is located at R ∼100-250 pc from the central supermassive black hole. The location of the absorber, the symmetric profile of the absorption lines, and the coincidence of the absorption- and emission-line centroid jointly suggest that the absorption gas originates from the host galaxy and is plausibly accelerated by stellar processes, such as stellar winds and/or supernova explosions. The implications for the detection of such a peculiar absorption-line system in an NLS1 are discussed in the context of coevolution between supermassive black hole growth and host galaxy buildup.

  7. An energy dispersive x-ray absorption spectroscopy beamline, X6A, at NSLS

    An energy dispersive x-ray absorption spectroscopy instrument has been built at the X6A beam port of the x-ray ring at the National Synchrotron Light Source (NSLS). This instrument allows the collection of extended x-ray-absorption fine structure and/or x-ray absorption near-edge structure spectra for many elements on the millisecond time scale. The beamline employs a four-point crystal bender and a rectangular Si 220 crystal to access incident energies between 6.5 and 21 keV. Because the polychromator focuses the synchrotron beam to a narrow 100-μm line, this experimental apparatus is ideal for x-ray absorption spectroscopy experiments in special environments such as at high pressures, for in situ experiments, and/or for very small samples. In this manuscript we will describe the instrument design and present data with which to evaluate the instrument. This beamline is available through the NSLS user proposal system

  8. Development of an x-ray beam line at the NSLS for studies in materials science using x-ray absorption spectroscopy. Progress report, February 1, 1985-January 31, 1986

    Research is reported for x-ray studies at NSLS. Energy-loss spectroscopy experiments (EXAFS) were performed on various materials including iron, silicon, gold, glass, niobium-aluminum alloys, and metglass

  9. Behaviors of harmonic signals in wavelength-modulated spectroscopy under high absorption strength

    Yuntao Wang; Haiwen Cai; Jianxin Geng; Zhengqing Pan; Dijun Chen; Zujie Fang

    2007-01-01

    @@ Behaviors of harmonic signals in wavelength modulation spectroscopy (WMS) for gas detection with Lorentzian line under high absorption strength are investigated. Approximate analytic expressions of the second, fourth, and sixth harmonics on the strength are presented in concise forms. Simulations show that the expressions are in agreement with the Fourier expansion by numerical integration. It is expected theoretically and experimentally in a WMS system for methane detection that there are not only a maximum, but also a null point in the harmonics versus strength relations, which should be of practical importance in methane sensing applications.

  10. Dual-laser absorption spectroscopy of C2H2 at 1.4 μ m

    Fasci, E.; Odintsova, T. A.; Castrillo, A.; De Vizia, M. D.; Merlone, A.; Bertiglia, F.; Moretti, L.; Gianfrani, L.

    2016-04-01

    Spectroscopic parameters (line intensity factor, pressure self-broadening, and shifting coefficients) of C2H2 at 1.4 μ m were accurately measured using a dual-laser approach, based upon the technique of optical phase locking. This generated an absolute frequency scale underneath the absorption spectra. A pair of extended-cavity diode lasers was used. One of them, the probe laser, is forced to maintain a precise frequency offset from a reference laser, which is an optical frequency standard based on noise-immune cavity-enhanced optical heterodyne molecular spectroscopy. Laser-gas interaction takes place inside an isothermal multipass cell that is stabilized at the temperature of the triple point of water. The fidelity in the observation of the shape associated to the Pe(14) line of the 2 ν3+ν5 band allowed us to measure the spectroscopic parameters, with a global uncertainty for the line strength of 0.22%.

  11. Mercury pollution surveys in Riga by Zeeman atomic absorption spectroscopy

    Practical sessions of mercury pollution measurements in Riga (Latvia) have been performed in several districts using an RA-915+ Zeeman atomic absorption spectrometer coupled with a global positioning system (GPS). The measurements were taken from a driving car and in different days at one particular location (the Institute of Atomic Physics and Spectroscopy) for monitoring the changes in atmospheric mercury concentration. GPS was used to relate the measurement results to particular places, which made it possible to create a digitalized database of pollution for different geographic coordinates in different time spans. The measurements have shown that the background level of mercury concentration in Riga does not exceed 5 ng/m3, although there are several areas of elevated mercury pollution that need particular attention. (Authors)

  12. Simultaneous surface plasmon resonance and x-ray absorption spectroscopy

    Serrano, A. [Instituto de Ceramica y Vidrio (ICV-CSIC), Cantoblanco, 28049 Madrid (Spain); Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Rodriguez de la Fuente, O. [Departamento de Fisica de Materiales, Universidad Complutense de Madrid, 28040 Madrid (Spain); Collado, V.; Rubio-Zuazo, J.; Castro, G. R. [SpLine, Spanish CRG Beamline at the ESRF, F-38043 Grenoble, Cedex 09, France and Instituto de Ciencia de Materiales de Madrid, (ICMM-CSIC), Cantoblanco, 28049 Madrid (Spain); Monton, C. [Department of Physics and Center for Advanced Nanoscience, University of California San Diego, La Jolla, California 92093 (United States); Garcia, M. A. [Instituto de Ceramica y Vidrio (ICV-CSIC), Cantoblanco, 28049 Madrid (Spain); IMDEA Nanociencia, Cantoblanco, 28049 Madrid (Spain)

    2012-08-15

    We present an experimental setup for the simultaneous measurement of surface plasmon resonance (SPR) and x-ray absorption spectroscopy (XAS) on metallic thin films at a synchrotron beamline. The system allows measuring in situ and in real time the effect of x-ray irradiation on the SPR curves to explore the interaction of x-rays with matter. It is also possible to record XAS spectra while exciting SPR in order to study changes in the films induced by the excitation of surface plasmons. Combined experiments recording simultaneously SPR and XAS curves while scanning different parameters can be also carried out. The relative variations in the SPR and XAS spectra that can be detected with this setup range from 10{sup -3} to 10{sup -5}, depending on the particular experiment.

  13. Investigating Actinide Molecular Adducts From Absorption Edge Spectroscopy

    Den Auwer, C.; Conradson, S.D.; Guilbaud, P.; Moisy, P.; Mustre de Leon, J.; Simoni, E.; /SLAC, SSRL

    2006-10-27

    Although Absorption Edge Spectroscopy has been widely applied to the speciation of actinide elements, specifically at the L{sub III} edge, understanding and interpretation of actinide edge spectra are not complete. In that sense, semi-quantitative analysis is scarce. In this paper, different aspects of edge simulation are presented, including semi-quantitative approaches. Comparison is made between various actinyl (U, Np) aquo or hydroxy compounds. An excursion into transition metal osmium chemistry allows us to compare the structurally related osmyl and uranyl hydroxides. The edge shape and characteristic features are discussed within the multiple scattering picture and the role of the first coordination sphere as well as contributions from the water solvent are described.

  14. Arsenic speciation in solids using X-ray absorption spectroscopy

    Foster, Andrea L.; Kim, Chris S.

    2014-01-01

    Synchrotron-based X-ray absorption spectroscopy (XAS) is an in situ, minimally-destructive, element-specific, molecular-scale structural probe that has been employed to study the chemical forms (species) of arsenic (As) in solid and aqueous phases (including rocks, soils, sediment, synthetic compounds, and numerous types of biota including humans) for more than 20 years. Although several excellent reviews of As geochemistry and As speciation in the environment have been published previously (including recent contributions in this volume), the explosion of As-XAS studies over the past decade (especially studies employing microfocused X-ray beams) warrants this new review of the literature and of data analysis methods.

  15. On The Formation Of Multiple Absorption Troughs In Broad Absorption Line QSOs

    Pereyra, Nicolas A

    2013-01-01

    We present theoretical CIV 1548,1550 absorption line profiles for QSOs calculated assuming the accretion disk wind (ADW) scenario. The results suggest that the multiple absorption troughs seen in many QSOs may be due to the discontinuities in the ion balance of the wind (caused by X-rays), rather than discontinuities in the density/velocity structure. The profiles are calculated from a 2.5D time-dependent hydrodynamic simulation of a line-driven disk wind for a typical QSO black hole mass, a typical QSO luminosity, and for a standard Shakura-Sunyaev disk. We include the effects of ionizing X-rays originating from within the inner disk radius by assuming that the wind is shielded from the X-rays from a certain viewing angle up to 90o ("edge on"). In the shielded region we assume constant ionization equilibrium, and thus constant line-force parameters. In the non-shielded region we assume that both the line-force and the C+3 populations are nonexistent. The model, at viewing angles close to the angle that separ...

  16. Polar Outflows in Six Broad Absorption Line Quasars

    Zhou, Hongyan; Wang, Tinggui; Wang, Huiyuan; Wang, Junxian; Yuan, Weimin; Lu, Yu

    2005-01-01

    Using the radio observations by FIRST and NVSS, we build a sample of 151 radio variable quasars selected from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Six (probably another two) among them are classified as broad absorption line (BAL) quasars, with radio flux variations of a few 10 percent within 1.5-5 years. Such large amplitudes of the variations imply brightness temperatures much higher than the inverse Compton limits (10$^{12}$ K) in all the BAL quasars, suggesting the pres...

  17. Integrating cavity ring-down spectroscopy (ICRDS) and the direct measurement of absorption coefficients

    Fry, Edward S.; Mason, John D.

    2016-04-01

    Absorption of light at various wavelengths (i.e. absorption spectroscopy) is a powerful tool for identifying the presence of chemical compounds or specific substances in a sample. Cavity ring down spectroscopy (CRDS) is a well-known technique for very high sensitivity absorption spectroscopy. Another technique, integrating cavity spectroscopy has the additional unique feature of providing accurate absorption data even in the presence of severe scattering. This paper describes a combination of these two techniques that has led to an extremely powerful and useful new technology—integrating CRDS.

  18. Identification of Metal Absorption Lines on Quasar Spectra of SDSS DR9

    Cai-Juan Pan; Cheng-Yu Su; Mu-Sheng Li; Wei-Rong Huang

    2014-09-01

    Absorption lines are an important tool for probing the gas in the Universe. Our group aim to identify the metal absorption lines imprinted on the quasar spectra of the BOSS. In this work, we show the metal absorption lines identified in the spectrum of SDSS J160032.95+323638.7.

  19. Sulfur K-edge absorption spectroscopy on selected biological systems

    Sulfur is an essential element in organisms. In this thesis investigations of sulfur compounds in selected biological systems by XANES (X-ray Absorption Near Edge Structure) spectroscopy are reported. XANES spectroscopy at the sulfur K-edge provides an excellent tool to gain information about the local environments of sulfur atoms in intact biological samples - no extraction processes are required. Spatially resolved measurements using a Kirkpatrick-Baez mirror focusing system were carried out to investigate the infection of wheat leaves by rust fungi. The results give information about changes in the sulfur metabolism of the host induced by the parasite and about the extension of the infection into visibly uninfected plant tissue. Furthermore, XANES spectra of microbial mats from sulfidic caves were measured. These mats are dominated by microbial groups involved in cycling sulfur. Additionally, the influence of sulfate deprivation and H2S exposure on sulfur compounds in onion was investigated. To gain an insight into the thermal degradation of organic material the influence of roasting of sulfur compounds in coffee beans was studied. (orig.)

  20. Ultraviolet observations of interstellar absorption lines toward SN 1987A

    Savage, Blair D.; Jenkins, Edward B.; Joseph, Charles L.; De Boer, Klass S.

    1989-01-01

    High-dispersion IUE echelle spectra of SN 1987A were averaged in order to obtain UV absorption-line profiles of the highest possible quality in the direction of SN 1987A. The profiles for Si IV and C IV are quite similar and have much less structure than the Al III profile. On relating column densities, while the C IV and Si IV ratio is relatively constant over the 0-100 km/s velocity range, the C IV to Al III and Si IV to Al III ratios vary by nearly a factor of 10. This suggests that the C IV and Si IV along this sight line in the Galaxy and its halo may have a common origin which differs from that for Al III.

  1. Measurement of exhaled nitric oxide in beef cattle using tunable diode laser absorption spectroscopy

    Roller, C. B.; Holland, B. P.; McMillen, G.; Step, D. L.; Krehbiel, C. R.; Namjou, K.; McCann, P. J.

    2007-03-01

    Measurement of nitric oxide (NO) in the expired breath of crossbred calves received at a research facility was performed using tunable diode laser absorption spectroscopy. Exhaled NO (eNO) concentrations were measured using NO absorption lines at 1912.07 cm-1 and employing background subtraction. The lower detection limit and measurement precision were determined to be ˜330 parts in 1012 per unit volume. A custom breath collection system was designed to collect lower airway breath of spontaneously breathing calves while in a restraint chute. Breath was collected and analyzed from calves upon arrival and periodically during a 42 day receiving period. There was a statistically significant relationship between eNO, severity of bovine respiratory disease (BRD) in terms of number of times treated, and average daily weight gain over the first 15 days postarrival. In addition, breathing patterns and exhaled CO2 showed a statistically significant relationship with BRD morbidity.

  2. [Measurement of OH radicals in flame with high resolution differential optical absorption spectroscopy].

    Liu, Yu; Liu, Wen-Qing; Kan, Rui-Feng; Si, Fu-Qi; Xu, Zhen-Yu; Hu, Ren-Zhi; Xie, Pin-Hua

    2011-10-01

    The present paper describes a new developed high resolution differential optical absorption spectroscopy instrument used for the measurement of OH radicals in flame. The instrument consists of a Xenon lamp for light source; a double pass high resolution echelle spectrometer with a resolution of 3.3 pm; a multiple-reflection cell of 20 meter base length, in which the light reflects in the cell for 176 times, so the whole path length of light can achieve 3 520 meters. The OH radicals'6 absorption lines around 308 nm were simultaneously observed in the experiment. By using high resolution DOAS technology, the OH radicals in candles, kerosene lamp, and alcohol burner flames were monitored, and their concentrations were also inverted. PMID:22250529

  3. The Sloan Digital Sky Survey Reverberation Mapping Project: Rapid CIV Broad Absorption Line Variability

    Grier, C. J.; Hall, P. B.; Brandt, W. N.; Trump, J. R.; Shen, Yue; Vivek, M.; Filiz Ak, N.; Chen, Yuguang; Dawson, K. S.; Denney, K. D.; Green, Paul J.; Jiang, Linhua; Kochanek, C. S.; McGreer, Ian D.; Pâris, I.; Peterson, B. M.; Schneider, D. P.; Tao, Charling; Wood-Vasey, W. M.; Bizyaev, Dmitry; Ge, Jian; Kinemuchi, Karen; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey

    2015-06-01

    We report the discovery of rapid variations of a high-velocity C iv broad absorption line trough in the quasar SDSS J141007.74+541203.3. This object was intensively observed in 2014 as a part of the Sloan Digital Sky Survey Reverberation Mapping Project, during which 32 epochs of spectroscopy were obtained with the Baryon Oscillation Spectroscopic Survey spectrograph. We observe significant (>4σ) variability in the equivalent width (EW) of the broad (˜4000 km s-1 wide) C iv trough on rest-frame timescales as short as 1.20 days (˜29 hr), the shortest broad absorption line variability timescale yet reported. The EW varied by ˜10% on these short timescales, and by about a factor of two over the duration of the campaign. We evaluate several potential causes of the variability, concluding that the most likely cause is a rapid response to changes in the incident ionizing continuum. If the outflow is at a radius where the recombination rate is higher than the ionization rate, the timescale of variability places a lower limit on the density of the absorbing gas of ne ≳ 3.9 × 105 cm-3. The broad absorption line variability characteristics of this quasar are consistent with those observed in previous studies of quasars, indicating that such short-term variability may in fact be common and thus can be used to learn about outflow characteristics and contributions to quasar/host-galaxy feedback scenarios.

  4. A Variable PV Broad Absorption Line and Quasar Outflow Energetics

    Capellupo, Daniel M; Barlow, Tom A

    2014-01-01

    Broad absorption lines (BALs) in quasar spectra identify high velocity outflows that might exist in all quasars and could play a major role in feedback to galaxy evolution. The viability of BAL outflows as a feedback mechanism depends on their kinetic energies, as derived from the outflow velocities, column densities, and distances from the central quasar. We estimate these quantities for the quasar, Q1413+1143 (redshift $z_e = 2.56$), aided by the first detection of PV $\\lambda\\lambda$1118,1128 BAL variability in a quasar. In particular, PV absorption at velocities where the CIV trough does not reach zero intensity implies that the CIV BAL is saturated and the absorber only partially covers the background continuum source (with characteristic size 22.3 (cm^-2). Variability in the PV and saturated CIV BALs strongly disfavors changes in the ionization as the cause of the BAL variability, but supports models with high-column density BAL clouds moving across our lines of sight. The observed variability time of ...

  5. Monitoring the variability of intrinsic absorption lines in quasar spectra , ,

    We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 yr (1-3.5 yr in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems or in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable BALs. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density ∼103-105 cm–3 and upper limits on the distance of the absorbers from the central engine of the order of a few kiloparsecs. Motivated by the observed variability properties, we suggest that mini-BALs can vary because of fluctuations of the ionizing continuum or changes in partial coverage while NALs can vary primarily because of changes in partial coverage.

  6. Quantitative investigation of two metallohydrolases by X-ray absorption spectroscopy near-edge spectroscopy

    The last several years have witnessed a tremendous increase in biological applications using X-ray absorption spectroscopy (BioXAS), thanks to continuous advancements in synchrotron radiation (SR) sources and detector technology. However, XAS applications in many biological systems have been limited by the intrinsic limitations of the Extended X-ray Absorption Fine Structure (EXAFS) technique e.g., the lack of sensitivity to bond angles. As a consequence, the application of the X-ray absorption near-edge structure (XANES) spectroscopy changed this scenario that is now continuously changing with the introduction of the first quantitative XANES packages such as Minut XANES (MXAN). Here we present and discuss the XANES code MXAN, a novel XANES-fitting package that allows a quantitative analysis of experimental data applied to Zn K-edge spectra of two metalloproteins: Leptospira interrogans Peptide deformylase (LiPDF) and acutolysin-C, a representative of snake venom metalloproteinases (SVMPs) from Agkistrodon acutus venom. The analysis on these two metallohydrolases reveals that proteolytic activities are correlated to subtle conformation changes around the zinc ion. In particular, this quantitative study clarifies the occurrence of the LiPDF catalytic mechanism via a two-water-molecules model, whereas in the acutolysin-C we have observed a different proteolytic activity correlated to structural changes around the zinc ion induced by pH variations

  7. Quantitative investigation of two metallohydrolases by X-ray absorption spectroscopy near-edge spectroscopy

    Zhao, W. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Chu, W.S.; Yang, F.F.; Yu, M.J.; Chen, D.L.; Guo, X.Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhou, D.W.; Shi, N. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Marcelli, A. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy); Niu, L.W.; Teng, M.K. [Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027 (China); Gong, W.M. [Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101 (China); Benfatto, M. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy); Wu, Z.Y. [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati, P.O. Box 13, Frascati 00044 (Italy)], E-mail: wuzy@ihep.ac.cn

    2007-09-21

    The last several years have witnessed a tremendous increase in biological applications using X-ray absorption spectroscopy (BioXAS), thanks to continuous advancements in synchrotron radiation (SR) sources and detector technology. However, XAS applications in many biological systems have been limited by the intrinsic limitations of the Extended X-ray Absorption Fine Structure (EXAFS) technique e.g., the lack of sensitivity to bond angles. As a consequence, the application of the X-ray absorption near-edge structure (XANES) spectroscopy changed this scenario that is now continuously changing with the introduction of the first quantitative XANES packages such as Minut XANES (MXAN). Here we present and discuss the XANES code MXAN, a novel XANES-fitting package that allows a quantitative analysis of experimental data applied to Zn K-edge spectra of two metalloproteins: Leptospira interrogans Peptide deformylase (LiPDF) and acutolysin-C, a representative of snake venom metalloproteinases (SVMPs) from Agkistrodon acutus venom. The analysis on these two metallohydrolases reveals that proteolytic activities are correlated to subtle conformation changes around the zinc ion. In particular, this quantitative study clarifies the occurrence of the LiPDF catalytic mechanism via a two-water-molecules model, whereas in the acutolysin-C we have observed a different proteolytic activity correlated to structural changes around the zinc ion induced by pH variations.

  8. Gas in Scattering Media Absorption Spectroscopy -- Laser Spectroscopy in Unconventional Environments

    Svanberg, Sune

    2010-02-01

    An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. The GASMAS technique combines narrow-band diode-laser spectroscopy with optical propagation in diffuse media. Whereas solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures. These are typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. Molecular oxygen and water vapor have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied, demonstrating new possibilities for characterization and diagnostics. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen gas, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the human sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen, while breathing normally through the mouth. A clinical study comprising 40 patients has been concluded.

  9. Absorption spectroscopy of oxygen, carbon dioxide and water species for applications in combustion diagnostics

    Mei, Anhua

    Laser absorption spectroscopy has been a useful tool applied in combustion diagnostics because of its capability to measure the species' concentration, particularly to measure concentration, temperature, and pressure simultaneously. These measurements provide the necessary information for dynamic combustion control. Due to its advantages such as fast response, non-intrusive nature and applicability under harsh environment like high temperature and high pressure, absorption laser spectroscopy makes it possible to monitor combustion system on-line and in situ. Since its development for more than thirty years, laser spectroscopy has matured, and the novel and advanced laser sensors have pushed it to be applied fast. On the other hand, industry still needs cheaper and more operable spectroscopy, which becomes an important consideration in the development and application of modern laser spectroscopy. This study presents an instrumental structure including the algorithm of the spectrum computation and the hardware configuration. The algorithm applied the central maximum value of the spectrum to simplify the computation. The whole calculation was done extensively using Beer-Lambert theory and HITRAN database which makes it efficient and applicable. This research conducted the simulations of high temperature species, such as CO2, H2O to carry out the algorithm, which were compared with published data. Also, this research designed and performed the experiments of measuring oxygen and its mixture with Helium by using a 760 nm diode laser and a 655 nm Helium/Neon laser sensor with fixed wavelength structures. The results of this research also conclude the following: (1) extensive literature survey, field research and laboratory work; (2) studying the significant theories and experimental methods of the laser spectroscopy; (3) developing efficient and simplified algorithm for spectrum calculation; (4) simulating high temperature species H2O and CO2; (5) designing and building

  10. Cavity-Enhanced Absorption Spectroscopy and Photoacoustic Spectroscopy for Human Breath Analysis

    Wojtas, J.; Tittel, F. K.; Stacewicz, T.; Bielecki, Z.; Lewicki, R.; Mikolajczyk, J.; Nowakowski, M.; Szabra, D.; Stefanski, P.; Tarka, J.

    2014-12-01

    This paper describes two different optoelectronic detection techniques: cavity-enhanced absorption spectroscopy and photoacoustic spectroscopy. These techniques are designed to perform a sensitive analysis of trace gas species in exhaled human breath for medical applications. With such systems, the detection of pathogenic changes at the molecular level can be achieved. The presence of certain gases (biomarkers), at increased concentration levels, indicates numerous human diseases. Diagnosis of a disease in its early stage would significantly increase chances for effective therapy. Non-invasive, real-time measurements, and high sensitivity and selectivity, capable of minimum discomfort for patients, are the main advantages of human breath analysis. At present, monitoring of volatile biomarkers in breath is commonly useful for diagnostic screening, treatment for specific conditions, therapy monitoring, control of exogenous gases (such as bacterial and poisonous emissions), as well as for analysis of metabolic gases.

  11. Determining the Fraction of Intrinsic CIV Absorption in Quasi-Stellar Object Absorption Line Systems

    Richards, G T; Yanny, B; Kollgaard, R I; Laurent-Mühleisen, S A; Vanden Berk, Daniel E; Richards, Gordon T.; York, Donald G.; Yanny, Brian; Kollgaard, Ronald I.; Berk, Daniel E. Vanden

    1999-01-01

    We present the results of a study of QSO Absorption Line Systems (QSOALSs) with respect to intrinsic QSO properties using an updated catalog of data in the literature. We have searched the literature for 6 and 20 cm radio flux densities and have studied 20 cm maps from the FIRST VLA Survey in order to compare the absorption properties with radio luminosity, radio spectral index and radio morphology. This work focuses particularly on the nature of CIV QSOALSs and their distribution in velocity space in light of intrinsic QSO properties. We find that the distribution of narrow, CIV absorption systems with relative velocities exceeding 5000 km/s is dependent not only on the optical luminosity of the QSOs, but also on the radio luminosity, the radio spectral index and the radio morphology of the QSOs. These observations are apparently inconsistent with the hypothesis that these systems are entirely due to intervening galaxies and it would seem that the contamination of the intervening systems (from 5000 to 75000 ...

  12. On the Absorption of X-ray Bright Broad Absorption Line Quasars

    Giustini, Margherita; Vignali, Cristian

    2008-01-01

    Most X-ray studies of BALQSOs found significant (N_H~10^{22-24} cm^{-2}) intrinsic column densities of gas absorbing an underlying typical power-law continuum emission, in agreement with expectations from radiatively driven accretion disk wind models. However, direct spectral analysis was performed only on a limited number of bright sources. We investigate the X-ray emission of a large BALQSO sample at medium to high redshift (0.8 ~ 5 x 10^{22} cm^{-2}) even including the faintest sources analyzed through hardness ratio analysis. The mean photon index is Gamma~1.9, with no significant evolution with redshift. The alpha_ox are typical of radio-quiet broad line AGN, in contrast with the known (from previous X-ray studies) ``soft X-ray weakness'' of BALQSOs and in agreement with the lack of X-ray absorption. We found the low-Absorption Index (AI) subsample to host the lowest X-ray absorbing column densities of the entire sample. X-ray selected BALQSOs show lower X-ray absorption than purely optically selec ted o...

  13. Multi axis differential optical absorption spectroscopy (MAX-DOAS

    G. Hönninger

    2004-01-01

    Full Text Available Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS in the atmosphere is a novel measurement technique that represents a significant advance on the well-established zenith scattered sunlight DOAS instruments which are mainly sensitive to stratospheric absorbers. MAX-DOAS utilizes scattered sunlight received from multiple viewing directions. The spatial distribution of various trace gases close to the instrument can be derived by combining several viewing directions. Ground based MAX-DOAS is highly sensitive to absorbers in the lowest few kilometres of the atmosphere and vertical profile information can be retrieved by combining the measurements with Radiative Transfer Model (RTM calculations. The potential of the technique for a wide variety of studies of tropospheric trace species and its (few limitations are discussed. A Monte Carlo RTM is applied to calculate Airmass Factors (AMF for the various viewing geometries of MAX-DOAS. Airmass Factors can be used to quantify the light path length within the absorber layers. The airmass factor dependencies on the viewing direction and the influence of several parameters (trace gas profile, ground albedo, aerosol profile and type, solar zenith and azimuth angles are investigated. In addition we give a brief description of the instrumental MAX-DOAS systems realised and deployed so far. The results of the RTM studies are compared to several examples of recent MAX-DOAS field experiments and an outlook for future possible applications is given.

  14. Decay Heat Measurements Using Total Absorption Gamma-ray Spectroscopy

    Rice, S.; Valencia, E.; Algora, A.; Taín, J. L.; Regan, P. H.; Podolyák, Z.; Agramunt, J.; Gelletly, W.; Nichols, A. L.

    2012-09-01

    A knowledge of the decay heat emitted by thermal neutron-irradiated nuclear fuel is an important factor in ensuring safe reactor design and operation, spent fuel removal from the core, and subsequent storage prior to and after reprocessing, and waste disposal. Decay heat can be readily calculated from the nuclear decay properties of the fission products, actinides and their decay products as generated within the irradiated fuel. Much of the information comes from experiments performed with HPGe detectors, which often underestimate the beta feeding to states at high excitation energies. This inability to detect high-energy gamma emissions effectively results in the derivation of decay schemes that suffer from the pandemonium effect, although such a serious problem can be avoided through application of total absorption γ-ray spectroscopy (TAS). The beta decay of key radionuclei produced as a consequence of the neutron-induced fission of 235U and 239Pu are being re-assessed by means of this spectroscopic technique. A brief synopsis is given of the Valencia-Surrey (BaF2) TAS detector, and their method of operation, calibration and spectral analysis.

  15. Reconstructing the intergalactic UV background with QSO absorption lines

    Fechner, Cora

    2011-01-01

    We present a new approach to constrain the spectral energy distribution of the intergalactic UV background observationally by studying metal absorption systems. We study single-component metal line systems exhibiting various well-measured species. Among the observed transitions at least two ratios of ionization stages from the same element are required, e.g. CIII/CIV and SiIII/SiIV. For each system photoionization models are constructed varying the spectrum of the ionizing radiation. The spectral energy distribution can then be constrained by comparing the models with the observed column density ratios. Extensive tests with artificial absorbers show that the spectrum of the ionizing radiation cannot be reconstructed unambiguously, but it is possible to constrain the main characteristics of the spectrum. Furthermore, the resulting physical parameters of the absorber, such as ionization parameter, metallicity, and relative abundances, may depend strongly on the adopted ionizing spectrum. Even in case of well-fi...

  16. Radio Structures of Compact Quasars with Broad Absorption Lines

    Kunert-Bajraszewska, Magdalena; Gawroński, Marcin P.

    2010-05-01

    Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is due to a geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a catalog of BAL QSOs from SDSS/DR3, we have constructed a new sample of compact radio-loud BAL QSOs, which constitutes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis of the BAL QSOs radio morphology, orientation, and jet evolution using the European VLBI Network (EVN) at 1.6 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz.

  17. Broad Absorption Line Variability in Radio-Loud Quasars

    Welling, C A; Brandt, W N; Capellupo, D M; Gibson, R R

    2014-01-01

    We investigate C IV broad absorption line (BAL) variability within a sample of 46 radio-loud quasars (RLQs), selected from SDSS/FIRST data to include both core-dominated (39) and lobe-dominated (7) objects. The sample consists primarily of high-ionization BAL quasars, and a substantial fraction have large BAL velocities or equivalent widths; their radio luminosities and radio-loudness values span ~2.5 orders of magnitude. We have obtained 34 new Hobby-Eberly Telescope (HET) spectra of 28 BAL RLQs to compare to earlier SDSS data, and we also incorporate archival coverage (primarily dual-epoch SDSS) for a total set of 78 pairs of equivalent width measurements for 46 BAL RLQs, probing rest-frame timescales of ~80-6000 d (median 500 d). In general, only modest changes in the depths of segments of absorption troughs are observed, akin to those seen in prior studies of BAL RQQs. Also similar to previous findings for RQQs, the RLQs studied here are more likely to display BAL variability on longer rest-frame timescal...

  18. Quasar Outflow Constraints using Broad Absorption Line Variability Studies

    McGraw, Sean; Shields, Joseph C.; Hamann, Fred; Capellupo, Daniel M.; Gallagher, Sarah; Brandt, W. Niel; Herbst, Hanna

    2016-01-01

    Quasar outflows are plausible candidates for AGN feedback processes influencing the host galaxy and may explain the established correlations between the supermassive black hole (SMBH) and the surrounding bulge. In order to better understand feedback and the physical conditions of the outflowing gas, observational constraints on absorber kinematics and energetics are needed. We are utilizing multiple epoch, rest frame UV quasar spectra to establish limits on outflow locations and total column densities for the purpose of estimating wind kinetic energies and momenta. We are also investigating the variability patterns of broad absorption lines (BALs) and mini-BALs across a range of ionization states to probe underlying connections between the various classes of absorbers. This work employs observations from the Sloan Digital Sky Survey, Hobby Eberly Telescope, and MDM observatory. We detect BAL variability in 3 out of 12 FeLoBAL quasars over multiple year timescales and conclude that the variable absorbers lie within tens of parsecs of the SMBH based on interpretations of the Fe II and Mg II BALS. We also measure significant BAL changes across daily to yearly timescales in a sample of 71 quasars with plausible detections of the P V 1117,1128 BAL. Detecting phosphorus in absorption is notable because it traces high column density outflows and is therefore relevant for studying AGN feedback. Constraints on outflow energetics and other selected results will be presented.

  19. Peculiar Broad Absorption Line Quasars found in DPOSS

    Brunner, R J; Djorgovski, S G; Gal, R R; Mahabal, A A; Lopes, P A A; De Carvalho, R R; Odewahn, S C; Castro, S; Thompson, D; Chaffee, F; Darling, J; Desai, V; Brunner, Robert J.; Hall, Patrick B.

    2003-01-01

    With the recent release of large (i.e., > hundred million objects), well-calibrated photometric surveys, such as DPOSS, 2MASS, and SDSS, spectroscopic identification of important targets is no longer a simple issue. In order to enhance the returns from a spectroscopic survey, candidate sources are often preferentially selected to be of interest, such as brown dwarfs or high redshift quasars. This approach, while useful for targeted projects, risks missing new or unusual species. We have, as a result, taken the alternative path of spectroscopically identifying interesting sources with the sole criterion being that they are in low density areas of the g - r and r - i color-space defined by the DPOSS survey. In this paper, we present three peculiar broad absorption line quasars that were discovered during this spectroscopic survey, demonstrating the efficacy of this approach. PSS J0052+2405 is an Iron LoBAL quasar at a redshift z = 2.4512 with very broad absorption from many species. PSS J0141+3334 is a reddened...

  20. Outflow and hot dust emission in broad absorption line quasars

    We have investigated a sample of 2099 broad absorption line (BAL) quasars with z = 1.7-2.2 built from the Sloan Digital Sky Survey Data Release Seven and the Wide-field Infrared Survey. This sample is collected from two BAL quasar samples in the literature and is refined by our new algorithm. Correlations of outflow velocity and strength with a hot dust indicator (βNIR) and other quasar physical parameters—such as an Eddington ratio, luminosity, and a UV continuum slope—are explored in order to figure out which parameters drive outflows. Here βNIR is the near-infrared continuum slope, which is a good indicator of the amount of hot dust emission relative to the accretion disk emission. We confirm previous findings that outflow properties moderately or weakly depend on the Eddington ratio, UV slope, and luminosity. For the first time, we report moderate and significant correlations of outflow strength and velocity with βNIR in BAL quasars. It is consistent with the behavior of blueshifted broad emission lines in non-BAL quasars. The statistical analysis and composite spectra study both reveal that outflow strength and velocity are more strongly correlated with βNIR than the Eddington ratio, luminosity, and UV slope. In particular, the composites show that the entire C IV absorption profile shifts blueward and broadens as βNIR increases, while the Eddington ratio and UV slope only affect the high and low velocity part of outflows, respectively. We discuss several potential processes and suggest that the dusty outflow scenario, i.e., that dust is intrinsic to outflows and may contribute to the outflow acceleration, is most likely.

  1. The intensity calculation of the gas absorption line by multi-line Voigt fitting

    ZHOU Meng-ran; LI Zhen-bi; ZHONG Ming-yu; HE Gang

    2008-01-01

    Adopted the distribution feedback type (DFB) laser to measure the coal mine gas methane, according to the methane located 1.6 lain nearby 2v3 with a R9 direct ab-sorption spectrum, attraction wire intensity of each line was calculated through the multi-line Voigt fitting. The experimental result indicates that in the obtained four attraction recover of wire, the maximum deviation is 2.7%, and the minimum deviation is 0.02%, other results are all in experimental error scope. This research method may apply in the spectrum survey methane gas density, it has characteristics including high precision, strong selectivity, fast response and so on.

  2. Doppler-free spectroscopy on Cs D$_1$ line with a dual-frequency laser

    Hafiz, Moustafa Abdel; De Clercq, Emeric; Boudot, Rodolphe

    2016-01-01

    We report on Doppler-free laser spectroscopy in a Cs vapor cell using a dual-frequency laser system tuned on the Cs D$_1$ line. Using counter-propagating beams with crossed linear polarizations, an original sign-reversal of the usual saturated absorption dip and large increase in Doppler-free atomic absorption is observed. This phenomenon is explained by coherent population trapping (CPT) effects. The impact of laser intensity and light polarization on absorption profiles is reported in both single-frequency and dual-frequency regimes. In the latter, frequency stabilization of two diode lasers was performed, yielding a beat-note fractional frequency stability at the level of $3 \\times 10^{-12}$ at 1 s averaging time. These performances are about an order of magnitude better than those obtained using a conventional single-frequency saturated absorption scheme.

  3. Development of the CRIS (Collinear Resonant Ionisation Spectroscopy) beam line

    The CRIS (Collinear Resonant Ionisation Spectroscopy) beam line is a new experimental set up at the ISOLDE facility at CERN. CRIS is being constructed for high-resolution laser spectroscopy measurements on radioactive isotopes. These measurements can be used to extract nuclear properties of isotopes far from stability. The CRIS beam line has been under construction since 2009 and testing of its constituent parts have been performed using stable and radioactive ion beams, in preparation for its first on-line run. This paper will present the current status of the CRIS experiment and highlight results from the recent tests.

  4. Correction of the self-absorption for reversed spectral lines: application to two resonance lines of neutral aluminium

    A new method for the correction of reversed spectral lines, in consequence of self-absorption, is proposed in this article. This method was applied to two resonance lines of neutral aluminium (Al I) obtained by a laser pulse on an aluminium solid placed in air. Several spectra of these lines were corrected for various delays after the laser pulse. The evolution of several parameters of these lines was computed as a function of this delay after the correction of self-absorption

  5. Line absorption of He-like triplet lines by Li-like ions. Caveats of using line ratios of triplets for plasma diagnostics

    Mehdipour, M.; Kaastra, J. S.; Raassen, A. J. J.

    2015-01-01

    He-like ions produce distinctive series of triplet lines under various astrophysical conditions. However, this emission can be affected by line absorption from Li-like ions in the same medium. We investigate this absorption of He-like triplets and present the implications for diagnostics of plasmas in photoionisation equilibrium using the line ratios of the triplets. Our computations were carried out for the O VI and Fe XXIV absorption of the O VII and Fe XXV triplet emission lines, respectiv...

  6. A High Temperature Calcium Vapor Cell for Spectroscopy on the 4s^2 1S0 to 4s4p 3P1 Intercombination Line

    Erickson, Christopher J.; Neyenhuis, Brian; Durfee, Dallin S.

    2005-01-01

    We have demonstrated a high temperature vapor cell for absorption spectroscopy on the Ca intercombination line. The cell uses a dual chamber design to achieve the high temperatures necessary for an optically dense vapor while avoiding the necessity of high temperature vacuum valves and glass-to-metal seals. We have observed over 50 percent absorption in a single pass through the cell. Although pressure broadening in the cell prevented us from performing saturated-absorption spectroscopy, the ...

  7. Nonlinear femtosecond pump-probe spectroscopy using a power-encoded soliton delay line.

    Saint-Jalm, Sarah; Andresen, Esben Ravn; Bendahmane, Abdelkrim; Kudlinski, Alexandre; Rigneault, Hervé

    2016-01-01

    We show femtosecond time-resolved nonlinear pump-probe spectroscopy using a fiber soliton as the probe pulse. Furthermore, we exploit soliton dynamics to record an entire transient trace with a power-encoded delay sweep. The power-encoded delay line takes advantage of the dependency of the soliton trajectory in the (λ,z) space upon input power; the difference in accumulated group delay between trajectories converts a fast power sweep into a fast delay sweep. We demonstrate the concept by performing transient absorption spectroscopy in a test sample and validate it against a conventional pump-probe setup. PMID:26696172

  8. The Physical Nature of Polar Broad Absorption Line Quasars

    Ghost, Kajal; Punsly, Brian

    2007-01-01

    It has been shown based on radio variability arguments that some BALQSOs (broad absorption line quasars) are viewed along the polar axis (o rthogonal to accretion disk) in the recent article of Zhou et a. Thes e arguments are based on the brightness temperature, T(sub b) exceedi ng 10(exp 12) K which leads to the well-known inverse Compton catastr ophe unless the radio jet is relativistic and is viewed along its axi s. In this letter, we expand the Zhou et al sample of polar BALQSOs u sing their techniques applied to SDSS DR5. In the process, we clarify a mistake in their calculation of brightness temperature. The expanded sample of high T(sub b) BALQSOS, has an inordinately large fraction of LoBALQSOs (low ionization BALQSOs). We consider this an important clue to understanding the nature of the polar BALQSOs. This is expec ted in the polar BALQSO analytical/numerical models of Punsly that pr edicted that LoBALQSOs occur when the line of sight is very close to the polar axis, where the outflow density is the highest.

  9. Integrative fitting of absorption line profiles with high accuracy, robustness, and speed

    Skrotzki, Julian; Habig, Jan Christoph; Ebert, Volker

    2014-08-01

    The principle of the integrative evaluation of absorption line profiles relies on the numeric integration of absorption line signals to retrieve absorber concentrations, e.g., of trace gases. Thus, it is a fast and robust technique. However, previous implementations of the integrative evaluation principle showed shortcomings in terms of accuracy and the lack of a fit quality indicator. This has motivated the development of an advanced integrative (AI) fitting algorithm. The AI fitting algorithm retains the advantages of previous integrative implementations—robustness and speed—and is able to achieve high accuracy by introduction of a novel iterative fitting process. A comparison of the AI fitting algorithm with the widely used Levenberg-Marquardt (LM) fitting algorithm indicates that the AI algorithm has advantages in terms of robustness due to its independence from appropriately chosen start values for the initialization of the fitting process. In addition, the AI fitting algorithm shows speed advantages typically resulting in a factor of three to four shorter computational times on a standard personal computer. The LM algorithm on the other hand retains advantages in terms of a much higher flexibility, as the AI fitting algorithm is restricted to the evaluation of single absorption lines with precomputed line width. Comparing both fitting algorithms for the specific application of in situ laser hygrometry at 1,370 nm using direct tunable diode laser absorption spectroscopy (TDLAS) suggests that the accuracy of the AI algorithm is equivalent to that of the LM algorithm. For example, a signal-to-noise ratio of 80 and better typically yields a deviation of <1 % between both fitting algorithms. The properties of the AI fitting algorithm make it an interesting alternative if robustness and speed are crucial in an application and if the restriction to a single absorption line is possible. These conditions are fulfilled for the 1,370 nm TDLAS hygrometry at the

  10. Nocturnal Measurements of HONO by Differential Optical Absorption Spectroscopy

    Wojtal, P.; McLaren, R.

    2011-12-01

    Differential optical absorption spectroscopy (DOAS) was used to quantify the concentration of HONO, NO2 and SO2 in the nocturnal urban atmosphere at York University over a period of one year. These measurements form a comprehensive HONO data set, including a large range of temperatures, relative humidity, surface conditions (snow, water, dry, etc.) and NO2 concentrations. Laboratory studies and observations within the nocturnal boundary layer reported in the literature suggest heterogeneous conversion of NO2 on surface adsorbed water as the major nighttime source of HONO. HONO formation and photolysis is believed to represent a major source term in the hydroxyl radical budget in polluted continental regions. Currently, most air quality models tend to significantly underpredict HONO, caused by the lack of understanding of HONO formation processes and the parameters that affect its concentration. Recently, we reported nocturnal pseudo steady states (PSS) of HONO in an aqueous marine environment and a conceptual model for HONO formation on aqueous surfaces was proposed. The data set collected at York University is being analyzed with a view towards further understanding the nighttime HONO formation mechanism and testing several hypotheses: 1) A HONO PSS can exist during certain times at night in an urban area in which the HONO concentration is independent of NO2, given the surface contains sufficient water coverage and is saturated with nitrogen containing precursors; 2) The concentration of HONO is positively correlated with temperature during periods where a PSS exists; 3) Different conversion efficiencies of NO2 to HONO exist on dry, wet and snow surfaces; 4) HONO formation has a NO2 order dependence between 0 and 2nd order, dependant on NO2 concentration, relative humidity, etc. The data set will be presented along with statistical analysis that sheds new light on the source of HONO in urban areas at night.

  11. On time resolved gas temperature measurements in a pulsed dc plasma using quantum cascade laser absorption spectroscopy

    With a time resolution of 33 µs, the gas temperature in a pulsed dc air plasma admixed with 0.8% NO has been measured by quantum cascade laser absorption spectroscopy (QCLAS). For this purpose, the temperature dependent intensity ratios of two absorption structures of NO at 1900 cm−1 (5.26 µm) have been used. The QCLAS system worked in the Intra Pulse Mode with a pulse repetition frequency of 30 kHz leading to a spectrum recorded each 33 µs. In a low pressure discharge, the influence of nonlinear absorption phenomena causing strong distorted absorption structures of NO has been taken into account by a calibration routine based on tabulated line strengths. Different mean plasma currents have been applied to the discharge leading to gas temperature values ranging from about 300 K up to about 500 K. (paper)

  12. Broadband fitting approach for the application of supercontinuum broadband laser absorption spectroscopy to combustion environments

    Göran Blume, Niels; Ebert, Volker; Dreizler, Andreas; Wagner, Steven

    2016-01-01

    In this work, a novel broadband fitting approach for quantitative in-flame measurements using supercontinuum broadband laser absorption spectroscopy (SCLAS) is presented. The application and verification of this approach in an atmospheric, laminar, non-premixed CH4/air flame (Wolfhard-Parker burner, WHP) is discussed. The developed fitting scheme allows for an automatic recognition and fitting of a B-spline curve reference intensity for SCLAS broadband measurements while automatically removing the influence of absorption peaks. This approach improves the fitting residual locally (in between absorption lines) and globally by 23% and 13% respectively, while improving the in-flame SNR by a factor of 2. Additionally, the approach inherently improves the time-wavelength-correlation based on recorded in-flame measurements itself in combination with a theoretical spectrum of the analyte. These improvements have allowed for the recording of complete spatially resolved methane concentration profiles in the WHP burner. Comparison of the measured absolute mole fraction profile for methane with previously measured reference data shows excellent agreement in position, shape and absolute values. These improvements are a prerequisite for the application of SCLAS in high-pressure combustion systems.

  13. DISCOVERY OF THE TRANSITION OF A MINI-BROAD ABSORPTION LINE INTO A BROAD ABSORPTION LINE IN THE SDSS QUASAR J115122.14+020426.3

    Hidalgo, Paola Rodriguez; Eracleous, Michael; Charlton, Jane [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Hamann, Fred [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Murphy, Michael T. [Center for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, Victoria 3122 (Australia); Nestor, Daniel [Department of Physics and Astronomy, University of California, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095 (United States)

    2013-09-20

    We present the detection of a rare case of dramatic strengthening in the UV absorption profiles in the spectrum of the quasar J115122.14+020426.3 between observations {approx}2.86 yr apart in the quasar rest frame. A spectrum obtained in 2001 by the Sloan Digital Sky Survey shows a C IV ''mini-broad'' absorption line (FWHM = 1220 km s{sup -1}) with a maximum blueshift velocity of {approx}9520 km s{sup -1}, while a later spectrum from the Very Large Telescope shows a significantly broader and stronger absorption line, with a maximum blueshift velocity of {approx}12, 240 km s{sup -1} that qualifies as a broad absorption line. A similar variability pattern is observed in two additional systems at lower blueshifted velocities and in the Ly{alpha} and N V transitions as well. One of the absorption systems appears to be resolved and shows evidence for partial covering of the quasar continuum source (C{sub f} {approx} 0.65), indicating a transverse absorber size of, at least, {approx}6 Multiplication-Sign 10{sup 16} cm. In contrast, a cluster of narrower C IV lines appears to originate in gas that fully covers the continuum and broad emission line sources. There is no evidence for changes in the centroid velocity of the absorption troughs. This case suggests that at least some of the absorbers that produce ''mini-broad'' and broad absorption lines in quasar spectra do not belong to intrinsically separate classes. Here, the ''mini-broad'' absorption line is most likely interpreted as an intermediate phase before the appearance of a broad absorption line due to their similar velocities. While the current observations do not provide enough constraints to discern among the possible causes for this variability, future monitoring of multiple transitions at high resolution will help achieve this goal.

  14. UV-vis spectroscopy for on-line monitoring of Au nanoparticles size during growth

    Gold nanoparticles have been prepared by alcoholic reduction of Au(III) ions in presence of a polymeric stabilizer (poly(N-vinyl pyrrolidone), PVP). On-line UV-vis spectroscopic characterization and transmission electron microscopy (TEM) analysis are presented. Optical spectroscopy data show that the temporal evolution of absorption spectra and the absorbance peak properties are correlated to the off-line size measurements obtained at chemical reaction end by TEM micrographs. The Au cluster size behaves linearly with time above a threshold temperature (70 deg. C), according to a deposition-controlled growth mechanism

  15. Near infrared tunable diode laser absorption spectroscopy for ethylene concentration analysis

    Pan, W. D. D.; Dai, J. M. M.; Zhang, Y. F. F.; Zhang, L.

    2013-01-01

    The absorption spectra of ethylene (C2H4) located at v5+v9 band near 1626nm involve some strong peaks that are suitable for trace gas concentration detection. They are interference free from other abundant molecules that are normally present in the atmosphere. An ethylene analysis system has been developed based on the tunable diode laser absorption spectroscopy. The high resolution transmission of ethylene near 1626nm has been measured by this system under different concentration. The severe overlapping between neighboring spectral lines of ethylene is observed and they cannot be separated with each other easily under atmospheric pressure and room temperature, so a multi-peaks spectrum recognition method is proposed to separate the ethylene spectrum from other interference gas while the ethylene concentration is ultra low. A mixture of high concentration methane, low concentration ethylene with air is used to evaluate the recognition efficiency. The result shows that the ethylene line can be abstract from strong background interference using multi-peaks spectrum recognition method and the accuracy of concentration measurement can reach about 5% comparing with a mass flow meter.

  16. Damped Lyman-alpha absorption by disk galaxies with large redshifts. III. Intermediate-resolution spectroscopy

    New intermediate-resolution spectroscopy for six members of a sample of 68 moderate- to high-redshift QSOs is presented. Evidence is reported which indicates that seven strong absorption features in the QSO spectra are due to damped Ly-alpha absorption. A standard curve-of-growth analysis on five of the damped systems is performed, and relevant properties are tabulated and discussed. Six of the seven damped Ly-alpha systems have H I column densities of 2 x 10 to the 20th/sq cm or larger, while the remaining system has an H I column density of about 10 to the 20th/sq cm. It is suggested that damped Ly-alpha systems arise when a sight line intercepts a high-redshift protogalaxy disk containing a quiescent cloud component characterized by high column density and low effective velocity dispersion. At the same time, the sight line usually intercepts a broader turbulent component, which is identified as the halo, characterized by much lower column density and higher effective velocity dispersion. 42 refs

  17. Damped Lyman-alpha absorption by disk galaxies with large redshifts. III. Intermediate-resolution spectroscopy

    Turnshek, D.A.; Wolfe, A.M.; Lanzetta, K.M.; Briggs, F.H.; Cohen, R.D. (Space Telescope Science Institute, Baltimore, MD (USA); Multiple Mirror Telescope Observatory, Tucson, AZ (USA); Pittsburgh Univ., PA (USA); California Univ., La Jolla (USA))

    1989-09-01

    New intermediate-resolution spectroscopy for six members of a sample of 68 moderate- to high-redshift QSOs is presented. Evidence is reported which indicates that seven strong absorption features in the QSO spectra are due to damped Ly-alpha absorption. A standard curve-of-growth analysis on five of the damped systems is performed, and relevant properties are tabulated and discussed. Six of the seven damped Ly-alpha systems have H I column densities of 2 x 10 to the 20th/sq cm or larger, while the remaining system has an H I column density of about 10 to the 20th/sq cm. It is suggested that damped Ly-alpha systems arise when a sight line intercepts a high-redshift protogalaxy disk containing a quiescent cloud component characterized by high column density and low effective velocity dispersion. At the same time, the sight line usually intercepts a broader turbulent component, which is identified as the halo, characterized by much lower column density and higher effective velocity dispersion. 42 refs.

  18. First on-line results from the CRIS (Collinear Resonant Ionisation Spectroscopy) beam line at ISOLDE

    The CRIS (Collinear Resonant Ionisation Spectroscopy) experiment at the on-line isotope separator facility, ISOLDE, CERN, has been constructed for high-sensitivity laser spectroscopy measurements on radioactive isotopes. The technique determines the magnetic dipole and electric quadrupole moments, nuclear spin and changes in mean-square charge radii of exotic nuclei via measurement of their hyperfine structures and isotope shifts. In November 2011 the first on-line run was performed using the CRIS beam line, when the hyperfine structure of 207Fr was successfully measured. This paper will describe the technique and experimental setup of CRIS and present the results from the first on-line experiment.

  19. The impacts of temperature on the absorption spectral lines of carbon monoxide

    In order to study the change of temperature on the effects of carbon monoxide absorption spectral lines, first of all proceed from the principle of absorption spectra, using theoretical analysis method, and the transmission and absorption database of the high-resolution molecular educed the carbon monoxide absorption spectrum intensity of spectral lines, integrated widening line type function and absorption coefficient concerned with temperature, then we got the change curve between carbon monoxide absorption spectrum intensity of spectral lines, integrated widening line type function and absorption coefficient with temperature by the numerical simulation of MATLAB, and analyzed and discussed the relationship between the temperature and them. The results showed that the temperature on the effects of carbon monoxide absorption spectral lines, especially on an Integrated widening line type function is complex, and different laser frequencies will also affect the relationship of the line type function and the absorption coefficient change with temperature, which has important reference value for the absorption and measurement of carbon in practical application.

  20. XANES determination of chromium oxidation states in glasses: comparison with optical absorption spectroscopy

    Villain, Olivier; Calas, Georges; Galoisy, Laurence; Cormier, Laurent; Hazemann, Jean-Louis

    2007-01-01

    The oxidation state of chromium in glasses melted in an air atmosphere with and without refining agents was investigated by Cr K-edge X-ray Absorption Near-Edge Structure (XANES) and optical absorption spectroscopy. A good agreement in the relative proportion of Cr(III) and Cr(VI) is obtained between both methods. We show that the chemical dependence of the absorption coefficient of Cr(III) is less important in XANES than in optical absorption spectroscopy. The comparison of glasses melted un...

  1. Absolute absorption on the potassium D lines: theory and experiment

    Hanley, Ryan K.; Gregory, Philip D.; Hughes, Ifan G.; Cornish, Simon L.

    2015-10-01

    We present a detailed study of the absolute Doppler-broadened absorption of a probe beam scanned across the potassium D lines in a thermal vapour. Spectra using a weak probe were measured on the 4S \\to 4P transition and compared to the theoretical model of the electric susceptibility detailed by Zentile et al (2015 Comput. Phys. Commun. 189 162-74) in the code named ElecSus. Comparisons were also made on the 4S \\to 5P transition with an adapted version of ElecSus. This is the first experimental test of ElecSus on an atom with a ground state hyperfine splitting smaller than that of the Doppler width. An excellent agreement was found between ElecSus and experimental measurements at a variety of temperatures with rms errors ˜ {10}-3. We have also demonstrated the use of ElecSus as an atomic vapour thermometry tool, and present a possible new measurement technique of transition decay rates which we predict to have a precision of ˜3 {kHz}.

  2. Tracing Inflows and Outflows with Absorption Lines in Circumgalactic Gas

    Ford, Amanda Brady; Oppenheimer, Benjamin D; Katz, Neal; Kollmeier, Juna A; Thompson, Robert; Weinberg, David H

    2013-01-01

    We examine how HI and metal absorption lines within low-redshift galaxy halos trace the dynamical state of circumgalactic gas, using cosmological hydrodynamic simulations that include a well-vetted heuristic model for galactic outflows. We categorize inflowing, outflowing, and ambient gas based on its history and fate as tracked in our simulation. Following our earlier work showing that the ionisation level of absorbers was a primary factor in determining the physical conditions of absorbing gas, we show here that it is also a governing factor for its dynamical state. Low-ionisation metal absorbers (e.g. MgII) tend to arise in gas that will fall onto galaxies within several Gyr, while high-ionisation metal absorbers (e.g. OVI) generally trace material that was deposited by outflows many Gyr ago. Inflowing gas is dominated by enriched material that was previously ejected in an outflow, hence accretion at low redshifts is typically substantially enriched. Recycling wind material is preferentially found closer t...

  3. X-Ray Continua of Broad Absorption Line Quasars

    Mathur, S.

    1999-01-01

    The targets for this program, PG1416-129 and LBQS 2212-1759 were known to be Broad Absorption Line Quasars (BALQSOs). BALQSOs are highly absorbed in soft X-rays. Good high energy response of Rossi-XTE made them ideal targets for observation. We observed LBQS 2212-1759 with PCA. We have now analyzed the data and found that the source was not detected. Since our target was expected to be faint, reliable estimate of background was very important. With the release of new FTOOLS (version 4.1) we were able to do so. We also analyzed a well known bright object and verified our results with the published data. This gave us confidence in the non-detection of our target LBQS 2212-1759. We are currently investigating the implications of this non-detection. Due to some scheduling problems, our second target PG1416-129 was not observed in A01. It was observed on 06/26/98. This target was detected with RXTE. We are now working on the spectral analysis with XSPEC.

  4. Double resonant absorption measurement of acetylene symmetric vibrational states probed with cavity ring down spectroscopy

    Karhu, J; Vainio, M; Metsälä, M; Hoekstra, S; Halonen, L

    2016-01-01

    A novel mid-infrared/near-infrared double resonant absorption setup for studying infrared-inactive vibrational states is presented. A strong vibrational transition in the mid-infrared region is excited using an idler beam from a singly resonant continuous-wave optical parametric oscillator, to populate an intermediate vibrational state. High output power of the optical parametric oscillator and the strength of the mid-infrared transition result in efficient population transfer to the intermediate state, which allows measuring secondary transitions from this state with a high signal-to-noise ratio. A secondary, near-infrared transition from the intermediate state is probed using cavity ring down spectroscopy, which provides high sensitivity in this wavelength region. Due to the narrow linewidths of the excitation sources, the rovibrational lines of the secondary transition are measured with sub-Doppler resolution. The setup is used to access a previously unreported symmetric vibrational state of acetylene, $\

  5. Invisible Active Galactic Nuclei. II Radio Morphologies & Five New HI 21 cm Absorption Line Detections

    Yan, Ting; Darling, Jeremy; Momjian, Emmanuel; Sharma, Soniya; Kanekar, Nissim

    2015-01-01

    We have selected a sample of 80 candidates for obscured radio-loud active galactic nuclei and presented their basic optical/near-infrared (NIR) properties in Paper 1. In this paper, we present both high-resolution radio continuum images for all of these sources and HI 21cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz VLA continuum observations find that 52 sources are compact or have substantial compact components with size 0.1 Jy at 4.9 GHz. The most compact 36 sources were then observed with the VLBA at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, a detection rate of CSOs ~3 times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty seven sources were observed for HI 21cm absorption at their photometric or spectroscopic redshifts with only ...

  6. Doppler-free two-photon absorption spectroscopy of rovibronic transition of naphthalene calibrated with an optical frequency comb

    Nishiyama, A.; Nakashima, K.; Matsuba, A.; Misono, M.

    2015-12-01

    We performed Doppler-free two-photon absorption spectroscopy of naphthalene using an optical frequency comb as a frequency reference. Rotationally resolved rovibronic spectra were observed, and absolute frequencies of the rovibronic transitions were determined with an uncertainty of several tens of kHz. The resolution and precision of our system are finer than the natural width of naphthalene. We assigned 1466 lines of the Q (Ka) Q (J) transition and calculated molecular constants. We attribute systematic spectral line shifts to the Coriolis interaction, and discuss the origin of the spectral linewidths.

  7. Study of self-absorption in laser induced breakdown spectroscopy

    We present a simple analytical expression for self-absorption correction of a spectrum recorded in the image mode of a CCD camera. It is assumed that two spectra are available, F2 recorded with a back mirror and F1 recorded without. The corrected spectrum F0, free of self-absorption, is given by the following simple expression F0=(2F1)/(1+(F2−F1)/(GF1) ) . We discuss the influence of noise on subsequent inverse Abel transform. An example, illustrating proposed method for self-absorption correction and Abel inversion is given in details. - Highlights: • We present a simple expression for self-absorption correction in LIBS plasma. • Method needs two spectra recorded in the image mode of the CCD. • Abel transform is not necessary for self-absorption correction

  8. The Sloan Digital Sky Survey Reverberation Mapping Project: Rapid CIV Broad Absorption Line Variability

    Grier, C J; Brandt, W N; Trump, J R; Shen, Yue; Vivek, M; Ak, N Filiz; Chen, Yuguang; Dawson, K; Denney, K D; Jiang, Linhua; Kochanek, C S; McGreer, Ian D; Pâris, I; Peterson, B M; Schneider, D P; Tao, Charling; Wood-Vasey, W M; Bizyaev, Dmitry; Ge, Jian; Kinemuchi, Karen; Oravetz, Daniel; Pan, Kaike; Simmons, Audrey

    2015-01-01

    We report the discovery of rapid variations of a high-velocity CIV broad absorption line trough in the quasar SDSS J141007.74+541203.3. This object was intensively observed in 2014 as a part of the Sloan Digital Sky Survey Reverberation Mapping Project, during which 32 epochs of spectroscopy were obtained with the Baryon Oscillation Spectroscopic Survey spectrograph. We observe significant (>4sigma) variability in the equivalent width of the broad (~4000 km/s wide) CIV trough on rest-frame timescales as short as 1.20 days (~29 hours), the shortest broad absorption line variability timescale yet reported. The equivalent width varied by ~10% on these short timescales, and by about a factor of two over the duration of the campaign. We evaluate several potential causes of the variability, concluding that the most likely cause is a rapid response to changes in the incident ionizing continuum. If the outflow is at a radius where the recombination rate is higher than the ionization rate, the timescale of variability...

  9. The intensity calculation of the gas absorption line by multi-line Voigt fitting

    ZHOU Meng-ran; LI Zhen-bi; ZHONG Ming-yu; HE Gang

    2008-01-01

    Adopted the distribution feedback type (DFB) laser to measure the coal minegas methane,according to the methane located 1.6 pm nearby 2 v3 with a R9 direct ab-sorption spectrum,attraction wire intensity of each line was calculated through the multi-line Voigt fitting.The experimental result indicates that in the obtained four attraction recover of wire,the maximum deviation is 2.7%,and the minimum deviation is 0.02%,other results are all in experimental error scope.This research method may apply in the spectrum survey methane gas density,it has characteristics including high precision,strong selectivity,fast response and so on.

  10. Femtosecond time-resolved absorption spectroscopy of astaxantin in solution and in alpha-crustacyanin

    Ilagan, R.P.; Christensen, R.L.; Chapp, T.W.; Frank, H.A.; Polívka, Tomáš; Pascher, T.

    2005-01-01

    Roč. 109, č. 14 (2005), s. 3120-3127. ISSN 1089-5639 Institutional research plan: CEZ:AV0Z50510513 Keywords : absorption spectroscopy * astaxantin Subject RIV: BO - Biophysics Impact factor: 2.898, year: 2005

  11. Absorption spectroscopy characterization measurements of a laser-produced Na atomic beam

    Ching, C.H.; Bailey, J.E.; Lake, P.W.; Filuk, A.B.; Adams, R.G.; McKenney, J.

    1996-06-01

    This work describes a pulsed Na atomic beam source developed for spectroscopic diagnosis of a high-power ion diode on the Particle Beam Fusion Accelerator II. The goal is to produce a {approximately} 10{sup 12}-cm{sup {minus}3}-density Na atomic beam that can be injected into the diode acceleration gap to measure electric and magnetic fields from the Stark and Zeeman effects through laser-induced-fluorescence or absorption spectroscopy. A {approximately} 10 ns fwhm, 1.06 {micro}m, 0.6 J/cm{sup 2} laser incident through a glass slide heats a Na-bearing thin film, creating a plasma that generates a sodium vapor plume. A {approximately} 1 {micro}sec fwhm dye laser beam tuned to 5,890 {angstrom} is used for absorption measurement of the Na I resonant doublet by viewing parallel to the film surface. The dye laser light is coupled through a fiber to a spectrograph with a time-integrated CCD camera. A two-dimensional mapping of the Na vapor density is obtained through absorption measurements at different spatial locations. Time-of-flight and Doppler broadening of the absorption with {approximately} 0.1 {angstrom} spectral resolution indicate that the Na neutral vapor temperature is about 0.5 to 2 eV. Laser-induced-fluorescence from {approximately} 1 {times} 10{sup 12}-cm{sup {minus}3} Na I 3s-3p lines observed with a streaked spectrograph provides a signal level sufficient for {approximately} 0.06 {angstrom} wavelength shift measurements in a mock-up of an ion diode experiment.

  12. Utilization of synchrotron radiation in analytical chemistry. Soft X-ray emission and absorption spectroscopy

    Synchrotron soft X-ray spectroscopy includes three major types of spectroscopy such as X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES), and X-ray photoelectron spectroscopy (XPS). This paper takes up XAS and XES of soft X-rays, and briefly describes the principle. XAS is roughly classified into XANES (X-ray absorption near-edge structure) and EXAFS (extended X-ray absorption fine structure), and XANES is mainly used in the analysis based on XAS of soft X-rays. As the examples of the latest soft X-ray analyses, the following are introduced: (1) bandgap of boron implantation diamond and the local structure of boron, (2) catalytic sites in solid fuel cell carbon electrode, and (3) soft X-ray analysis under atmospheric pressure. (A.O.)

  13. Line-absorption of He-like triplet lines by Li-like ions: Caveats of using line ratios of triplets for plasma diagnostics

    Mehdipour, M; Raassen, A J J

    2015-01-01

    He-like ions produce distinctive series of triplet lines under various astrophysical conditions. However, this emission can be affected by line-absorption from Li-like ions in the same medium. We investigate this absorption of He-like triplets and present the implications for diagnostics of plasmas in photoionisation equilibrium using the line ratios of the triplets. Our computations are carried out for the O VI and Fe XXIV absorption of the O VII and Fe XXV triplet emission lines, respectively. The fluorescent emission by the Li-like ions and continuum absorption of the He-like ion triplet lines are also investigated. We determine the absorption of the triplet lines as a function of Li-like ion column density and velocity dispersion of the emitting/absorbing medium. We find O VI line-absorption can significantly alter the O VII triplet line ratios in optically-thin plasmas, by primarily absorbing the intercombination lines and to lesser extent the forbidden line. Due to intrinsic line-absorption by O VI insi...

  14. In situ gas temperature measurements by UV-absorption spectroscopy

    Fateev, Alexander; Clausen, Sønnik

    2009-01-01

    range from 23 degrees C to 1,500 degrees C. The gas temperature was evaluated (1) from the analysis of the structure of selected NO high-resolution gamma-absorption bands and (2) from the analysis of vibrational distribution in the NO gamma-absorption system in the (211-238) nm spectral range. The......The absorption spectrum of the NO A(2)Sigma(+) <- X(2)Pi gamma-system can be used for in situ evaluation of gas temperature. Experiments were performed with a newly developed atmospheric-pressure high-temperature flow gas cell at highly uniform and stable gas temperatures over a 0.533 m path in the...... accuracy of both methods is discussed. Validation of the classical Lambert-Beer law has been demonstrated at NO concentrations up to 500 ppm and gas temperatures up to 1,500 degrees C over an optical absorption path length of 0.533 m....

  15. Multiple scattering approach to X-ray absorption spectroscopy

    2003-01-01

    In this paper we present the state of the art of the theoretical background needed for analyzing X-ray absorption spectra in the whole energy range. The multiple-scattering (MS) theory is presented in detail with some applications on real systems. We also describe recent progress in performing geometrical fitting of the XANES (X-ray absorption near-edge structure) energy region and beyond using a full multiple-scattering approach.

  16. Quantum cascade laser absorption sensor for carbon monoxide in high-pressure gases using wavelength modulation spectroscopy.

    Spearrin, R M; Goldenstein, C S; Jeffries, J B; Hanson, R K

    2014-03-20

    A tunable quantum cascade laser sensor, based on wavelength modulation absorption spectroscopy near 4.8 μm, was developed to measure CO concentration in harsh, high-pressure combustion gases. The sensor employs a normalized second harmonic detection technique (WMS-2f/1f) at a modulation frequency of 50 kHz. Wavelength selection at 2059.91  cm⁻¹ targets the P(20) transition within the fundamental vibrational band of CO, chosen for absorption strength and relative isolation from infrared water and carbon dioxide absorption. The CO spectral model is defined by the Voigt line-shape function, and key line-strength and line-broadening spectroscopic parameters were taken from the literature or measured. Sensitivity analysis identified the CO-N₂ collisional broadening coefficient as most critical for uncertainty mitigation in hydrocarbon/air combustion exhaust measurements, and this parameter was experimentally derived over a range of combustion temperatures (1100-2600 K) produced in a shock tube. Accuracy of the wavelength-modulation-spectroscopy-based sensor, using the refined spectral model, was validated at pressures greater than 40 atm in nonreactive shock-heated gas mixtures. The laser was then free-space coupled to an indium-fluoride single-mode fiber for remote light delivery. The fiber-coupled sensor was demonstrated on an ethylene/air pulse detonation combustor, providing time-resolved (~20  kHz), in situ measurements of CO concentration in a harsh flow field. PMID:24663473

  17. Testing Disk-Wind Models with Quasar CIV 1549Å Associated Absorption Lines

    Vestergaard, Marianne

    2012-01-01

    Narrow associated C IV 1549Å absorption lines (NALs) with a rest equivalent width EW =3 Å detected in z ˜ 2 radio-loud and radio-quiet quasars, (a) exhibit evidence of an origin in radiatively accelerated gas, and (b) may be closely related to broad absorption line (BAL) outflows. These NALs and...

  18. Proposal of snapshot line-imaging Fourier spectroscopy for smartphone

    Kawashima, Natsumi; Sato, Shun; Ishida, Akane; Inohara, Daichi; Tanaka, Naotaka; Wada, Kenji; Nishiyama, Akira; Fujiwara, Masaru; Ishimaru, Ichiro

    2015-03-01

    We propose the extremely-compact-size line-imaging Fourier spectroscopy for smartphones. We realize the near common-path interferometer with strong robustness for mechanical vibrations by installing the transmission-type relative-inclined phase-shifter. The interferogram of an imaging line is formed as 2-dimensional fringe pattern on imaging sensor, such as CCD camera. In other words, the horizontal axis on an imaging sensor is assigned to phase-shift value. And the vertical axis is corresponds to image formation coordinate. Thus, by installing a relatively-inclined thin glass into imaging optics, such as smartphone, we will realize the line-imaging Fourier spectroscopy for healthcare sensor in daily-life environments.

  19. Two-wavelength absorption modulation spectroscopy of bandtail absorption in GaAs quantum wells

    We have discovered that below-band-gap photoexcitation produces large bleaching of the exciton absorption in GaAs quantum well heterostructures. We have used this effect to perform the first investigation of room-temperature bandtail absorption in these structures. We find that the below-band-gap absorption follows a spectral Urbach's rule. In addition, proton-bombarded samples show an Urbach energy correlated with bombardment-induced defects. This sensitive technique has enabled us to study samples as thin as 1 μm at energies where the absorption coefficient is approx.10 cm-1

  20. Ultrafast terahertz conductivity and transient optical absorption spectroscopy of silicon nanocrystal thin films

    Titova, Lyubov V.; Harthy, Rahma Al; Cooke, David;

    We use time-resolved THz spectroscopy and transient optical absorption spectroscopy as two complementary techniques to study ultrafast carrier dynamics in silicon nanocrystal thin films. We find that the photoconductive dynamics in these materials is dominated by interface trapping, and we observe...

  1. Application of quantum cascade laser absorption spectroscopy to studies of fluorocarbon molecules

    Welzel, S; Roepcke, J [Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Str. 2, D-17489 Greifswald (Germany); Stepanov, S; Meichsner, J, E-mail: welzel@inp-greifswald.d [Institute of Physics, Ernst-Moritz-Arndt University, Felix-Hausdorff-Str. 6, D-17489 Greifswald (Germany)

    2009-03-01

    The recent advent of quantum cascade lasers (QCLs) enables room-temperature mid-infrared spectrometer operation which is particularly favourable for industrial process monitoring and control, i.e. the detection of transient and stable molecular species. Conversely, fluorocarbon containing radio-frequency discharges are of special interest for plasma etching and deposition as well as for fundamental studies on gas phase and plasma surface reactions. The application of QCL absorption spectroscopy to such low pressure plasmas is typically hampered by non-linear effects connected with the pulsed mode of the lasers. Nevertheless, adequate calibration can eliminate such effects, especially in the case of complex spectra where single line parameters are not available. In order to facilitate measurements in fluorocarbon plasmas, studies on complex spectra of CF{sub 4} and C{sub 3}F{sub 8} at 7.86{mu}m (1269 - 1275 cm{sup -1}) under low pressure conditions have been performed. The intra-pulse mode, i.e. pulses of up to 300 ns, was applied yielding highly resolved spectral scans of {approx}1 cm{sup -1} coverage. Effective absorption cross sections were determined and their temperature dependence was studied in the relevant range up to 400 K and found to be non-negligible.

  2. Theoretical experimental study of the factors that govern the molybdenum absorption signal by means of electro thermic atomic absorption spectroscopy

    The formation of molybdenum carbides in the atomizer, used in the electro thermic atomic absorption spectroscopy, is responsible for incomplete analyte removal in its analysis. This generates the apparition of the memory effect and little precision in the results. In this work, different variables that could affect the molybdenum absorption sign were investigated, as well as the influence of hydrochloric acid on the memory effect, by means of studies in the different stages: drying, calcination and atomization, and the samples deposition order in molybdenum solutions, either acidified or not acidified

  3. High-Resolution X-ray Emission and X-ray Absorption Spectroscopy

    de Groot, F. M. F.

    2001-01-01

    In this review, high-resolution X-ray emission and X-ray absorption spectroscopy will be discussed. The focus is on the 3d transition-metal systems. To understand high-resolution X-ray emission and reso-nant X-ray emission, it is first necessary to spend some time discussing the X-ray absorption process. Section II discusses 1s X-ray absorption, i.e., the K edges, and section III deals with 2p X-ray absorption, the L edges. X-ray emission is discussed in, respectively, the L edges. X-ray emis...

  4. Optimization of polarization spectroscopy for rubidium D lines

    Sun Jian-Fang; Yin Shi-Qi; Xu Zhen; Hong Tao; Wang Yu-Zhu

    2013-01-01

    Polarization spectroscopy of the D lines of rubidium atoms is investigated experimentally,especially with different pump powers and cell temperatures.We find that there are four candidate transitions suitable for frequency stabilization,and optimal pump powers and cell temperatures are also presented to obtain a perfect signal with maximal amplitude and slope.The optimal signal is insensitive to the fluctuations of laser power and the temperature,which can enhance the performance of frequency locking.

  5. Beam line design for synchrotron spectroscopy in the VUV

    The character of the radiation source provided by an electron storage ring is briefly reviewed from the point of view of utilization for VUV spectroscopy. The design of beam line components is then considered with special reference to the problems of contamination of optical surfaces and vacuum protection. The issues involved in designing mirrors for use with storage rings are considered with emphasis on the questions of power dissipation, image quality and materials selection

  6. Absorption spectroscopy of electronic states near Fermi level

    This paper reports that the temperature behavior of the absorption spectra of superconducting YBa2-Cu3-O7-δ textured films is measured in a 1.5 + 3.0 eV energy region with varying temperatures from 25 to 300 K. The spectra are found to be sensitive to a superconducting transition: the temperature-dependent behavior of absorption at T > Tc undergoes critical changes under the superconducting transition and for T c the spectrum ceases to depend on temperature. The spectra display an exciton maximum in the optical gap Eg = 1.95 eV. The spectrum freezing at Tc can be explained assuming that the Fermi level is in temperature resonance with a narrow local level which is responsible for a delta-like singularity in the density of states

  7. Is there a connection between Broad Absorption Line Quasars and Narrow Line Seyfert 1 galaxies?

    Grupe, Dirk

    2014-01-01

    We consider whether Broad Absorption Line Quasars (BAL QSOs) and Narrow Line Seyfert 1 galaxies (NLS1s) are similar, as suggested by Brandt & Gallagher (2000) and Boroson (2002). For this purpose we constructed a sample of 11 BAL QSOs from existing Chandra and Swift observations. We found that BAL QSOs and NLS1s both operate at high Eddington ratios L/Ledd, although BAL QSOs have slightly lower L/Ledd. BAL QSOs and NLS1s in general have high FeII/H$\\beta$ and low [OIII]/H$\\beta$ ratios following the classic 'Boroson \\& Green' eigenvector 1 relation. We also found that the mass accretion rates $\\dot{M}$ of BAL QSOs and NLS1s are more similar than previously thought, although some BAL QSOs exhibit extreme mass accretion rates of more than 10 \\msun/year. These extreme mass accretion rates may suggest that the black holes in BAL QSOs are relativistically spinning. Black hole masses in BAL QSOs are a factor of 100 larger than NLS1s. From their location on a M-$\\sigma$ plot, we find that BAL QSOs contain fu...

  8. Is there a connection between broad absorption line quasars and narrow-line Seyfert 1 galaxies?

    Grupe, Dirk [Space Science Center, Morehead State University, 235 Martindale Dr., Morehead, KY 40351 (United States); Nousek, John A., E-mail: d.grupe@moreheadstate.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)

    2015-02-01

    We consider whether broad absorption line quasars (BAL QSOs) and narrow-line Seyfert 1 galaxies (NLS1s) are similar, as suggested by Brandt and Gallagher and Boroson. For this purpose, we constructed a sample of 11 BAL QSOs from existing Chandra and Swift observations. We found that BAL QSOs and NLS1s both operate at high Eddington ratios L/L{sub Edd}, although BAL QSOs have slightly lower L/L{sub Edd}. BAL QSOs and NLS1s in general have high Fe ii/Hβ and low [O iii]/Hβ ratios following the classic “Boroson and Green” eigenvector 1 relation. We also found that the mass accretion rates M-dot of BAL QSOs and NLS1s are more similar than previously thought, although some BAL QSOs exhibit extreme mass accretion rates of more than 10 M{sub ⊙} yr{sup −1}. These extreme mass accretion rates may suggest that the black holes in BAL QSOs are relativistically spinning. Black hole masses in BAL QSOs are a factor of 100 larger than NLS1s. From their location on a M−σ plot, we find that BAL QSOs contain fully developed black holes. Applying a principal component analysis to our sample, we find eigenvector 1 to correspond to the Eddington ratio L/L{sub Edd}, and eigenvector 2 to black hole mass.

  9. Self-absorption of x-ray spectral lines in an expanding laser plasma

    Results are presented of new experimental investigations of asymmetry of spectral line profiles as a result of the self-absorption of x-ray lines of multiply charged ions in an expanding laser plasma. A theoretical interpretation is based on the solution of the one-dimensional radiation transport equation. Narrowing of the resonance line of the Mg XI ion caused by self-absorption in an inhomogeneous plasma was measured experimentally. The behavior of the profiles of trapped and optically thin spectral lines during gasdynamic expansion of a laser plasma was compared. Narrowing of the resonance line of the Mg XI ion by a factor exceeding 2 was observed

  10. Self-absorption of x-ray spectral lines in an expanding laser plasma

    Boiko, V.A.; Vinogradov, A.V.; Ilyukhin, A.A.; Katulin, V.A.; Maiorov, S.A.; Nosach, V.Y.; Peregudov, G.V.; Petrov, A.L.; Pikuz, S.A.; Skobelev, I.Y.; Faenov, A.Y.; Chirkov, V.A.; Shilov, K.A.

    1981-01-01

    Results are presented of new experimental investigations of asymmetry of spectral line profiles as a result of the self-absorption of x-ray lines of multiply charged ions in an expanding laser plasma. A theoretical interpretation is based on the solution of the one-dimensional radiation transport equation. Narrowing of the resonance line of the Mg XI ion caused by self-absorption in an inhomogeneous plasma was measured experimentally. The behavior of the profiles of trapped and optically thin spectral lines during gasdynamic expansion of a laser plasma was compared. Narrowing of the resonance line of the Mg XI ion by a factor exceeding 2 was observed.

  11. Fraunhofer-type absorption line splitting and polarization in confocal double-pulse laser induced plasma

    Strong line splitting and polarization are observed in Fraunhofer-type absorption lines in Pb, Sn, Si, Cd, In, and Zn in confocal double-pulse laser induced plasma (DP-LIP) experiments. This effect is detectable using medium laser power densities: (∼ 1–2) × 1013 W/m2 for the first laser pulse and 1 × 1014 W/m2 for the second laser pulse. Polarization and splitting effects exist only during the second laser pulse (∼ 7 ns). Absorption line polarization and splitting phenomena may be explained by a high overall magnetic field and motional Stark effect caused by the second laser pulse inside the laser plasma created by the first pulse. - Highlights: • Certain Fraunhofer absorption lines in DP LIBS are polarized. • Certain Fraunhofer absorption lines in DP LIBS are split. • Those effects exist during laser pulse. • Effects take place in elements with ns2np2 and ns2 electron ground state

  12. Non-Voigt Lyman-alpha absorption line profiles

    Outram, P. J.; Carswell, R.F.; Theuns, T.

    1999-01-01

    Recent numerical simulations have lead to a paradigm shift in our understanding of the intergalactic medium, and the loss of a physical justification for Voigt profile fitting of the Lyman-alpha forest. Many individual lines seen in simulated spectra have significant departures from the Voigt profile, yet could be well fitted by a blend of two or more such lines. We discuss the expected effect on the line profiles due to ongoing gravitational structure formation and Hubble expansion. We devel...

  13. Depths of formation of magnetically sensitive absorption lines

    Sheminova, V A

    2012-01-01

    Characteristics of the depression contribution functions are studied for the Stokes line profiles formed in a magnetic field. The form of the depression functions depends mainly on the strength of splitting and the Zeeman component intensity, and is of a complicated character with a distinctly pronounces asymmetry. The depths of formation of magnetically sensitive lines are found by means of these contribution functions. The calculations reveal that the steep section of the line profile is formed higher than the profile center when a strong longitudinal magnetic field is present. The Stokes profiles that describe the polarization characteristics are formed only several kilometers higher than the Stokes profile that specifies the general depression of the unpolarized and polarized radiation. The averaged depth of formation of the whole line profile is practically independent of the magnetic field strength. The depths of formation of 17 photospheric lines usually used in magnetospectroscopic observations are ca...

  14. Fiber-distributed multi-channel open-path H2S sensor based on tunable diode laser absorption spectroscopy

    Dong Chen; Wenqing Liu; Yujun Zhang; Jianguo Liu; Ruifeng Kan; Min Wang; Xi Fang; Yiben Cui

    2007-01-01

    Tunable diode laser based gas detectors are now being used in a wide variety of applications for safety and environmental interest. A fiber-distributed multi-channel open-path H2S sensor based on tunable diode laser absorption spectroscopy (TDLAS) is developed, the laser used is a telecommunication near infrared distributed feed-back (DFB) tunable diode laser, combining with wavelength modulation specby combining optical fiber technique. An on-board reference cell provides on-line sensor calibration and almost maintenance-free operation. The sensor is suitable for large area field H2S monitoring application.

  15. A heated chamber burner for atomic absorption spectroscopy.

    Venghiattis, A A

    1968-07-01

    A new heated chamber burner is described. The burner is of the premixed type, and burner heads of the types conventionally used in atomic absorption may be readily adapted to it. This new sampling system has been tested for Ag, Al, Ca, Cu, Fe, Mg, Mn, Ni, Pb, Si, Ti, and Zn in aqueous solutions. An improvement of the order of ten times has been obtained in sensitivity, and in detection limits as well, for the elements determined. Interferences controllable are somewhat more severe than in conventional burners but are controllable. PMID:20068792

  16. [Retrieval of tropospheric NO2 by multi axis differential optical absorption spectroscopy].

    Xu, Jin; Xie, Pin-hua; Si, Fu-qi; Dou, Ke; Li, Ang; Liu, Yu; Liu, Wen-qing

    2010-09-01

    A method of retrieving NO2 in troposphere based on multi axis differential optical absorption spectroscopy (MAX-DOAS) was introduced. The differential slant column density (dSCD) of NO2 was evaluated by differential optical absorption spectroscopy (DOAS), removing the Fraunhofer structure and Ring effect. Combining the results of different observing directions, the tropospheric NO2 differential slant column density (deltaSCD) was evaluated, and the air mass factor (AMF) was calculated with the radiative transfer model SCIATRAN and the tropospheric NO2 vertical column density (VCD) was retrieved. To ensure the accuracy of the results, it was compared with the results of long path differential optical absorption spectroscopy (LP-DOAS), a good accordance was shown with the correlation coefficients of 0.94027 and 0.96924. PMID:21105419

  17. On-line laser spectroscopy with thermal atomic beams

    Thibault, C; De Saint-Simon, M; Duong, H T; Guimbal, P; Huber, G; Jacquinot, P; Juncar, P; Klapisch, Robert; Liberman, S; Pesnelle, A; Pillet, P; Pinard, J; Serre, J M; Touchard, F; Vialle, J L

    1981-01-01

    On-line high resolution laser spectroscopy experiments have been performed in which the light from a CW tunable dye laser interacts at right angles with a thermal atomic beam. /sup 76-98/Rb, /sup 118-145 /Cs and /sup 208-213/Fr have been studied using the ionic beam delivered by the ISOLDE on-line mass separator at CERN while /sup 30-31/Na and /sup 38-47/K have been studied by setting the apparatus directly on-line with the PS 20 GeV proton beam. The principle of the method is briefly explained and some results concerning nuclear structure are given. The hyperfine structure, spins and isotope shifts of the alkali isotopes and isomers are measured. (8 refs).

  18. Self-corrected sensors based on atomic absorption spectroscopy for atom flux measurements in molecular beam epitaxy

    A high sensitivity atom flux sensor based on atomic absorption spectroscopy has been designed and implemented to control electron beam evaporators and effusion cells in a molecular beam epitaxy system. Using a high-resolution spectrometer and a two-dimensional charge coupled device detector in a double-beam configuration, we employ either a non-resonant line or a resonant line with low cross section from the same hollow cathode lamp as the reference for nearly perfect background correction and baseline drift removal. This setup also significantly shortens the warm-up time needed compared to other sensor technologies and drastically reduces the noise coming from the surrounding environment. In addition, the high-resolution spectrometer allows the most sensitive resonant line to be isolated and used to provide excellent signal-to-noise ratio

  19. Surface and ultrathin-layer absorptance spectroscopy for solar cells

    Holovský, Jakub; Remeš, Zdeněk; De Wolf, S.; Ballif, C.

    Vol. 60. Amsterdam: Elsevier Ltd, 2014 - (Gordon, I.; Valenta, J.; Turan, R.; Atwater, H.; Mirabella, S.), s. 57-62 ISSN 1876-6102. [E- MRS Spring Meeting 2014. Lille (FR), 26.05.2014-30.05.2014] R&D Projects: GA MŠk 7E12029; GA ČR(CZ) GA14-05053S EU Projects: European Commission(XE) 283501 - FAST TRACK Institutional support: RVO:68378271 Keywords : surface states * thin-film limit * ATR-FTIR * photothermal deflection spectrscopy * photocurrent spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism

  20. Alternative method for concentration retrieval in differential optical absorption spectroscopy atmospheric gas pollutant measurements

    Videla, Fabián; Schinca, Daniel Carlos; Tocho, Jorge O.

    2003-01-01

    Differential optical absorption spectroscopy is a widely used technique for open-column atmospheric-gas pollution monitoring. The concentration retrieval is based on the fitting of the measured differential absorbance through the Lambert-Beer law. We present an alternative method for calculating the gas concentration on the basis of the proportionality between differential absorbance and differential absorption cross section of the gas under study. The method can be used on its own for single...

  1. Optical-Feedback Cavity-Enhanced Absorption Spectroscopy with a Quantum Cascade Laser.

    Maisons, G.; Gorrotxategi Carbajo, P.; Carras, M.; Romanini, D.

    2010-01-01

    Optical{feedback cavity{enhanced absorption spectroscopy is demonstrated in the mid{IR using a quantum cascade laser (emitting at 4.46 ¹m). The laser linewidth reduction and frequency locking by selective optical feedback from the resonant cavity ¯eld turns out to be particularly important in this spectral range: It allows strong cavity transmission which compensates for low light sensitivity, especially when using room temperature detectors. We obtain a noise equivalent absorption coe±cient ...

  2. Absorption spectroscopy in the ultraviolet and visible spectral range of hexavalent chromium aqueous solutions

    Mignani, Anna G.; Spadoni, Lorenzo

    1999-09-01

    In order to demonstrate the possibility of performing direct absorption spectroscopy of Hexavalent Chromium aqueous solutions, absorption measurements were performed at the dual- beam spectrophotometer in the 250 - 850 nm spectral range, with 10 mm and 100 mm path lengths. Low concentration (26 - 520 (mu) g/l) (and high concentration (2.6 - 52 mg/l) solutions were analyzed, showing that it is possible to implement a basic instrumentation for risk condition monitoring and a more advanced instrumentation for quantitative measurements.

  3. Polarization dependent interface properties of ferroelectric Schottky barriers studied by soft X-ray absorption spectroscopy

    Kohlstedt, H.; Petraru, A.; Denlinger, M. Meier J.; Guo, J.; Wanli, Y.; A. Scholl; Freelon, B.; Schneller, T.; Waser, R.; Yu, P; Ramesh, R.; Learmonth, T.; Glans, P.-A.; Smith, K. E.

    2008-01-01

    We applied soft X-ray absorption spectroscopy to study the Ti L-edge in ferroelectric capacitors using a modified total electron yield method. The inner photo currents and the X-ray absorption spectra were polarization state dependent. The results are explained on the basis of photo electric effects and the inner potential in the ferroelectric capacitors as a result of back-to-back Schottky barriers superimposed by the potential due to the depolarization field. In general, the presented metho...

  4. Broadband Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) – applicability and corrections

    U. Platt; J. Meinen; D. Pöhler; T. Leisner

    2008-01-01

    Atmospheric trace gas measurements by cavity assisted long-path absorption spectroscopy are an emerging technology. An interesting approach is the combination of CEAS with broadband light sources, the broadband CEAS (BB-CEAS). BB-CEAS lends itself to the application of the DOAS technique to analyse the derived absorption spectra. While the DOAS approach has enormous advantages in terms of sensitivity and specificity of the measurement, an important implication is the reduction of the light pa...

  5. Non-intrusive sensing of air velocity, humidity, and temperature using tunable diode laser absorption spectroscopy

    Park, Suhyeon

    2015-01-01

    This work will report the non-intrusive sensing of air velocity, humidity, and temperature using tunable diode laser absorption spectroscopy (TDLAS), and discuss the potential applications of such sensors for in situ monitoring and active control for wind energy. The sensing technique utilizes the absorption features of water vapor in ambient air to monitor multiple flow parameters including velocity, humidity, and temperature simultaneously and non-intrusively [1-3]. The TDLAS technique does...

  6. Measuring changes in the fundamental constants with redshifted radio absorption lines

    Curran, SJ; Kanekar, N; Darling, JK

    2004-01-01

    Strong evidence has recently emerged for a variation in the fine structure constant, alpha equivalent to e(2)/hc, over the history of the Universe. This was concluded from a detailed study of the relative positions of redshifted optical quasar absorption spectra. However, radio absorption lines at h

  7. Observing broad-absorption line quasars with Spectrum-Rontgen-Gamma

    Singh, K.P.; Schnopper, H.W.; Westergaard, Niels Jørgen Stenfeldt

    Broad-absorption line quasars are found to have extremely weak soft X-ray emission when compared with other optically selected quasars. In the only example of PHL 5200 for which a detailed X-ray spectrum has been obtained with ASCA, strong absorption in the source appears to be responsible for the...

  8. Total absorption spectroscopy of N = 51 nucleus 85Se

    Goetz, K. C.; Grzywacz, R. K.; Rykaczewski, K. P.; Karny, M.; Fialkowska, A.; Wolinska-Cichocka, M.; Rasco, B. C.; Zganjar, E. F.; Johnson, J. W.; Gross, C. J.

    2014-09-01

    An experimental campaign utilizing the Modular Total Absorption Spectrometer (MTAS) was conducted at the HRIBF facility in January of 2012. The campaign studied 22 isotopes, many of which were identified as the highest priority for decay heat analysis during a nuclear fuel cycle, see the report by the OECD-IAEA Nuclear Energy Agency in 2007. The case of 85Se will be discussed. 85Se is a Z = 34, N = 51 nucleus with the valence neutron located in the positive parity sd single particle state. Therefore, its decay properties are determined by interplay between first forbidden decays of the valence neutron and Gamow-Teller decay of a 78Ni core. Analysis of the data obtained during the January 2012 run indicates a significant increase of the beta strength function when compared with previous measurements, see Ref..

  9. Thyroid lesions diagnosis by Fourier transformed infrared absorption spectroscopy (FTIR)

    Thyroid nodules are a common disorder, with 4-7% of incidence in the Brazilian population. Although the fine needle aspiration (FNA) is an accurate method for thyroid tumors diagnosis, the discrimination between benign and malignant neoplasm is currently not possible in some cases with high incidence of false negative diagnosis, leading to a surgical intervention due to the risk of carcinomas. The aim of this study was to verify if the Fourier Transform infrared spectroscopy (FTIR) can contribute to the diagnosis of thyroid carcinomas and goiters, using samples of tissue and aspirates. Samples of FNA, homogenates and tissues of thyroid nodules with histopathological diagnosis were obtained and prepared for FTIR spectroscopy analysis. The FNA and homogenates samples were measured by μ-FTIR (between 950 . 1750 cm-1), at a nominal resolution of 4 cm-1 and 120 scans). Tissue samples were analyzed directly by ATR-FTIR technique, at a resolution 2 cm-1, with 60 scans in the same region. All spectra were corrected by the baseline and normalized by amides area (1550-1640 cm-1) in order to minimize variations of sample homogeneity. Then, spectra were converted into second derivatives using the Savitzk-Golay algorithm with a 13 points window. The Ward's minimum variance algorithm and Euclidean distances among the points were used for cluster analysis. Some FNA samples showed complex spectral pattern. All samples showed some cell pellets and large amount of hormone, represented by the bands of 1545 and 1655 cm-1. Bands in 1409, 1412, 1414, 1578 and 1579 cm-1 were also found, indicating possible presence of sugar, DNA, citric acid or metabolic products. In this study, it was obtained an excellent separation between goiter and malign lesion for the samples of tissues, with 100% of specificity in specific cluster and 67% sensibility and 50 of specificity. In homogenate and FNA samples this sensibility and specificity were lower, because among these samples, it were included

  10. A upper limit for water dimer absorption in the 750 nm spectral region and a revised water line list

    A. J. L. Shillings

    2010-10-01

    Full Text Available The absorption of solar radiation by water dimer molecules in the Earth's atmosphere can potentially act as a positive feedback effect for climate change. There seems little doubt from the results of previous laboratory and theoretical studies that significant concentrations of the water dimer should be present in the atmosphere, yet attempts to detect water dimer absorption signatures in atmospheric field studies have so far yielded inconclusive results. Here we report spectral measurements in the near-infrared in the expected region of the third overtone of the water dimer hydrogen-bonded OHb stretching vibration around 750 nm. The results were obtained using broadband cavity ringdown spectroscopy (BBCRDS, a methodology that allows absorption measurements to be made under controlled laboratory conditions but over absorption path lengths representative of atmospheric conditions. In order to account correctly and completely for overlapping absorption of monomer molecules in the same spectral region, we have also constructed a new list of spectral data (UCL08 for the water monomer in the 750–20 000 cm−1 (13 μm–500 nm range.

    Our results show that the additional lines included in the UCL08 spectral database provide a substantially improved representation of the measured water monomer absorption in the 750 nm region, particularly at wavelengths dominated by weak monomer absorption features. No absorption features which could not be attributed to the water monomer were detected in the BBCRDS experiments up to water mixing ratios more than an order of magnitude greater than those in the ambient atmosphere. The absence of detectable water dimer features leads us to conclude that, in the absence of significant errors in calculated dimer oscillator strengths or monomer/dimer equilibrium constants, the widths of water dimer features present around 750 nm must be substantially greater (~100 cm−1 HWHM than

  11. Absorption spectroscopy of powdered materials using time-resolved diffuse optical methods.

    D'Andrea, Cosimo; Obraztsova, Ekaterina A; Farina, Andrea; Taroni, Paola; Lanzani, Guglielmo; Pifferi, Antonio

    2012-11-10

    In this paper a novel method, based on time-resolved diffuse optical spectroscopy, is proposed to measure the absorption of small amounts of nanostructured powder materials independent of scattering. Experimental validation, in the visible and near-infrared spectral range, has been carried out on India Inkparticles. The effectiveness of the technique to measure scattering-free absorption is demonstrated on carbon nanotubes. The comparison between the absorption spectra acquired by the proposed method and conventional measurements performed with a commercial spectrophotometer is discussed. PMID:23142900

  12. Tomographic multiaxis-differential optical absorption spectroscopy observations of Sun-illuminated targets: a technique providing well-defined absorption paths in the boundary layer.

    Frins, Erna; Bobrowski, Nicole; Platt, Ulrich; Wagner, Thomas

    2006-08-20

    A novel experimental procedure to measure the near-surface distribution of atmospheric trace gases by using passive multiaxis differential absorption optical spectroscopy (MAX-DOAS) is proposed. The procedure consists of pointing the receiving telescope of the spectrometer to nonreflecting surfaces or to bright targets placed at known distances from the measuring device, which are illuminated by sunlight. We show that the partial trace gas absorptions between the top of the atmosphere and the target can be easily removed from the measured total absorption. Thus it is possible to derive the average concentration of trace gases such as NO(2), HCHO, SO(2), H(2)O, Glyoxal, BrO, and others along the line of sight between the instrument and the target similar to the well-known long-path DOAS observations (but with much less expense). If tomographic arrangements are used, even two- or three-dimensional trace gas distributions can be retrieved. The basic assumptions of the proposed method are confirmed by test measurements taken across the city of Heidelberg. PMID:16892129

  13. Quartz crystal microbalance and infrared reflection absorption spectroscopy characterization of bisphenol A absorption in the poly(acrylate) thin films.

    Li, Guifeng; Morita, Shigeaki; Ye, Shen; Tanaka, Masaru; Osawa, Masatoshi

    2004-02-01

    The absorption process of bisphenol A (BPA) in a number of poly(acrylate) thin films, such as poly(2-methoxyethyl acrylate) (PMEA), poly(ethyl acrylate) (PEA), poly(n-butyl methacrylate) (PBMA), and poly(methyl methacrylate) (PMMA), has been investigated by quartz crystal microbalance (QCM) and infrared reflection absorption spectroscopy (IRRAS) measurements. Both QCM and IRRAS measurements show that the BPA molecules absorb in PMEA, PEA, and PBMA thin films but not in PMMA thin film. The differences in the BPA absorption behavior are mainly attributed to the difference in the glass transition temperature (T(g)) between these polymers. This absorption behavior also depends on the BPA concentration and polymer film thickness. Furthermore, IRRAS characterization demonstrates that the hydrogen bonding is formed between the hydroxyl group in BPA and the carbonyl group in the poly(acrylate) thin films. BPA molecule absorbed in these polymer thin films can be removed by ethanol rinse treatment. By optimizing experimental conditions for the QCM electrode modified by PMEA thin film, detection limitation of approximately 1 ppb for BPA can be realized by the in situ QCM measurement. This method is expected to be a sensitive in situ detection way for trace BPA in the environmental study. PMID:14750877

  14. On-Line Wavelength Calibration of Pulsed Laser for CO2 Differential Absorption LIDAR

    Xiang, Chengzhi; Ma, Xin; Han, Ge; Liang, Ailin; Gong, Wei

    2016-06-01

    Differential absorption lidar (DIAL) remote sensing is a promising technology for atmospheric CO2 detection. However, stringent wavelength accuracy and stability are required in DIAL system. Accurate on-line wavelength calibration is a crucial procedure for retrieving atmospheric CO2 concentration using the DIAL, particularly when pulsed lasers are adopted in the system. Large fluctuations in the intensities of a pulsed laser pose a great challenge for accurate on-line wavelength calibration. In this paper, a wavelength calibration strategy based on multi-wavelength scanning (MWS) was proposed for accurate on-line wavelength calibration of a pulsed laser for CO2 detection. The MWS conducted segmented sampling across the CO2 absorption line with appropriate number of points and range of widths by using a tunable laser. Complete absorption line of CO2 can be obtained through a curve fitting. Then, the on-line wavelength can be easily found at the peak of the absorption line. Furthermore, another algorithm called the energy matching was introduced in the MWS to eliminate the backlash error of tunable lasers during the process of on-line wavelength calibration. Finally, a series of tests was conducted to elevate the calibration precision of MWS. Analysis of tests demonstrated that the MWS proposed in this paper could calibrate the on-line wavelength of pulsed laser accurately and steadily.

  15. Evidence for ultra-fast outflows in radio-quiet AGNs: II - detailed photo-ionization modeling of Fe K-shell absorption lines

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G.G.C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blueshifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and direct...

  16. Assessment of the performance of a compact concentric spectrometer system for Atmospheric Differential Optical Absorption Spectroscopy

    Whyte, C.; Leigh, R. J.; Lobb, D.; Williams, T.; Remedios, J. J.; Cutter, M.; Monks, P. S.

    2009-12-01

    A breadboard demonstrator of a novel UV/VIS grating spectrometer has been developed based upon a concentric arrangement of a spherical meniscus lens, concave spherical mirror and curved diffraction grating suitable for a range of atmospheric remote sensing applications from the ground or space. The spectrometer is compact and provides high optical efficiency and performance benefits over traditional instruments. The concentric design is capable of handling high relative apertures, owing to spherical aberration and comma being near zero at all surfaces. The design also provides correction for transverse chromatic aberration and distortion, in addition to correcting for the distortion called "smile", the curvature of the slit image formed at each wavelength. These properties render this design capable of superior spectral and spatial performance with size and weight budgets significantly lower than standard configurations. This form of spectrometer design offers the potential for exceptionally compact instrument for differential optical absorption spectroscopy (DOAS) applications from LEO, GEO, HAP or ground-based platforms. The breadboard demonstrator has been shown to offer high throughput and a stable Gaussian line shape with a spectral range from 300 to 450 nm at 0.5 nm resolution, suitable for a number of typical DOAS applications.

  17. Accurate measurement of the HI column density from HI 21cm absorption-emission spectroscopy

    Chengalur, Jayaram N; Roy, Nirupam

    2013-01-01

    We present a detailed study of an estimator of the HI column density, based on a combination of HI 21cm absorption and HI 21cm emission spectroscopy. This "isothermal" estimate is given by $N_{\\rm HI,ISO} = 1.823 \\times 10^{18} \\int \\left[ \\tau_{\\rm tot} \\times {\\rm T_B} \\right] / \\left[ 1 - e^{-\\tau_{\\rm tot}} \\right] {\\rm dV}$, where $\\tau_{\\rm tot}$ is the total HI 21cm optical depth along the sightline and ${\\rm T_B}$ is the measured brightness temperature. We have used a Monte Carlo simulation to quantify the accuracy of the isothermal estimate by comparing the derived $N_{\\rm HI,ISO}$ with the true HI column density $N_{\\rm HI}$. The simulation was carried out for a wide range of sightlines, including gas in different temperature phases and random locations along the path. We find that the results are statistically insensitive to the assumed gas temperature distribution and the positions of different phases along the line of sight. The median value of the ratio of the true H{\\sc i} column density to the...

  18. The high-resolution absorption spectroscopy branch on the VUV beamline DESIRS at SOLEIL.

    de Oliveira, Nelson; Joyeux, Denis; Roudjane, Mourad; Gil, Jean François; Pilette, Bertrand; Archer, Lucy; Ito, Kenji; Nahon, Laurent

    2016-07-01

    A VUV absorption spectroscopy facility designed for ultra-high spectral resolution is in operation as a dedicated branch on the DESIRS beamline at Synchrotron SOLEIL. This branch includes a unique VUV Fourier transform spectrometer (FTS) and a dedicated versatile gas sample chamber. The FTS instrument can cover a large UV-VUV spectral range from 4 to 30 eV, with an ultimate line width of 0.08 cm(-1) on a large spectral window, ΔE/E = 7%, over which all spectral features can be acquired in a multiplex way. The performance can be considered to be a middle ground between broadband moderate-resolution spectrometers based on gratings and ultra-high-spectral-resolution VUV tunable-laser-based techniques over very narrow spectral windows. The various available gaseous-sample-handling setups, which function over a wide range of pressures and temperatures, and the acquisition methodology are described. A selection of experimental results illustrates the performance and limitations of the FTS-based facility. PMID:27359137

  19. Vibration-rotational overtones absorption of solid hydrogens using optoacoustic spectroscopy technique

    Vibrational-rotational overtones absorption solid hydrogens (H2, D2, HD) is studied using pulsed laser piezoeletric transducer (PULPIT) optoacoustic spectroscopy is studied. A general downward shift in energy from isolated molecular energies is observed. Studying normal-hydrogen it was observed that the phonon excitations associated with double-molecular transitions are predominantly transverse-optical phonons, whereas the excitations associated with single-molecular transitions are predominantly longitudinal - optical phonons. Multiplet structures were observed for certain double transitions in parahydrogen and orthodeuterium. The HD spectrum, besides presenting the sharp zero-phonon lines and the associated phonon side bands, like H2 and D2, showed also two different features. This observation was common to all the transitions involving pure rotational excitation in H2 and D2, which showed broad linewidths. This, together with some other facts (fluorescence lifetime *approx*105 sec; weak internal vibration and lattice coupling), led to the proposition of a mechanism for the fast nonradiative relaxation in solid hydrogens, implied from some observed experimental evidences. This relaxation, due to strong coupling, would happen in two steps: the internal vibration modes would relax to the rotational modes of the molecules, and then this rotational modes would relax to the lattice vibration modes. (Author)

  20. Assessment of the performance of a compact concentric spectrometer system for Atmospheric Differential Optical Absorption Spectroscopy

    C. Whyte

    2009-08-01

    Full Text Available A breadboard demonstrator of a novel UV/VIS grating spectrometer for atmospheric research has been developed based upon a concentric arrangement of a spherical meniscus lens, concave spherical mirror and curved diffraction grating suitable for a range of remote sensing applications from the ground or space. The spectrometer is compact and provides high optical efficiency and performance benefits over traditional instruments. The concentric design is capable of handling high relative apertures, owing to spherical aberration and coma being near zero at all surfaces. The design also provides correction for transverse chromatic aberration and distortion, in addition to correcting for the distortion called "smile", the curvature of the slit image formed at each wavelength. These properties render this design capable of superior spectral and spatial performance with size and weight budgets significantly lower than standard configurations. This form of spectrometer design offers the potential for an exceptionally compact instrument for differential optical absorption spectroscopy (DOAS applications particularly from space (LEO, GEO orbits and from HAPs or ground-based platforms. The breadboard demonstrator has been shown to offer high throughput and a stable Gaussian line shape with a spectral range from 300 to 450 nm at better than 0.5 nm resolution, suitable for a number of typical DOAS applications.

  1. Assessment of the performance of a compact concentric spectrometer system for Atmospheric Differential Optical Absorption Spectroscopy

    C. Whyte

    2009-12-01

    Full Text Available A breadboard demonstrator of a novel UV/VIS grating spectrometer has been developed based upon a concentric arrangement of a spherical meniscus lens, concave spherical mirror and curved diffraction grating suitable for a range of atmospheric remote sensing applications from the ground or space. The spectrometer is compact and provides high optical efficiency and performance benefits over traditional instruments. The concentric design is capable of handling high relative apertures, owing to spherical aberration and comma being near zero at all surfaces. The design also provides correction for transverse chromatic aberration and distortion, in addition to correcting for the distortion called "smile", the curvature of the slit image formed at each wavelength. These properties render this design capable of superior spectral and spatial performance with size and weight budgets significantly lower than standard configurations. This form of spectrometer design offers the potential for exceptionally compact instrument for differential optical absorption spectroscopy (DOAS applications from LEO, GEO, HAP or ground-based platforms. The breadboard demonstrator has been shown to offer high throughput and a stable Gaussian line shape with a spectral range from 300 to 450 nm at 0.5 nm resolution, suitable for a number of typical DOAS applications.

  2. Submegahertz frequency stabilization of a terahertz quantum cascade laser to a molecular absorption line

    Richter, Heiko; Pavlov, Sergei G.; Semenov, A. D.; Mahler, L.; Tredicucci, A.; Beere, H.E.; Ritchie, D. A.; Hübers, H. -W.

    2010-01-01

    The frequency of a terahertz quantum-cascade laser is stabilized to the absorption line of methanol gas at a frequency of 2.55 THz. The method is based on frequency modulation of the laser emissionm across the absorption line. The resulting derivativelike signal is used as an error signal for a control loop that keeps the laser frequency at maximum absorption. The unstabilized laser that is operated in a pulse tube cooler has frequency fluctuations of 15 MHz, which are reduced to 300 kHz with...

  3. High bandwidth absorption spectroscopy with a dispersed supercontinuum source.

    Hult, Johan; Watt, Rosalynne S; Kaminski, Clemens F

    2007-09-01

    An optical gas sensor is presented, making use of a dispersed supercontinuum source, capable of acquiring broad bandwidth spectra at ultrahigh wavelength sweep and repetition rates. Wavelength sweeps from 1100 nm to 1700 nm can be performed in 800 ns at a spectral resolution of 40 pm. This is comparable to line-widths of molecular spectra at atmospheric pressure. Quantitative measurements are presented of CH(4) employing 80 nm wide sweeps over the P- Q- and R-branches of the 2nu(3) transition near 1665 nm, at rates exceeding 100 kHz. The effective acquisition rate is determined by the amount of averaging required, and the effect of this averaging on observed precision is investigated. PMID:19547496

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

    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.

  5. Oxidation of plutonium dioxide: an X-ray absorption spectroscopy study

    X-ray absorption spectroscopy experiments were conducted in order to characterise plutonium dioxide oxidation. It is shown that the sample preparation adopted does not enable elaboration of hyperstoichiometric plutonium dioxide. These results could mean that plutonium dioxide oxidation only occurs under very specific conditions

  6. Determination of atmospheric corrosion of coated steel surfaces by in situ infrared reflection absorption spectroscopy (IRRAS)

    Full text: Infrared reflection absorption spectroscopy (IRRAS) is a sensitive technique for measuring thin layers on metallic surfaces. The principal goal of this IRRAS study was the development of a reproducible and reliable in situ measurement procedure for the determination of corrosion of coated steel surfaces. (author)

  7. Absorption spectroscopy of Al XIII Ly-ŕ radiation by an Fe XXIV plasma

    Gouveia, A.; Al'miev, I. R.; Hawreliak, J.; Chambers, D. M.; Liang, T.; Marjoribanks, R.; Pinto, O.; Renner, Oldřich; Zhang, J.; Wark, J. S.

    2003-01-01

    Roč. 81, - (2003), s. 199-207. ISSN 0022-4073 Institutional research plan: CEZ:AV0Z1010921 Keywords : XUV laser * radiative transfer * X-ray absorption spectroscopy Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.382, year: 2003

  8. The interstellar absorption-line spectrum of Mu Ophiuchi

    Cardelli, J.; Boehm-Vitense, E.

    1982-01-01

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

  9. Experimental design and methodology for a new Moessbauer scan experiment: absorption line tracking

    A new experimental setup and methodology that allows the automatic tracking of a Moessbauer absorption line as its energy position varies during the experiment is introduced. As a test the sixth spectral line of FeSn2 was tracked while temperature was varied between room temperature and a value slightly above its Neel temperature.

  10. PKS 0119-46 and the origin of infalling absorption-line systems in quasars

    It is proposed that the infalling (z/sub abs/>z/sub em/) absorption-line systems in the quasar PKS 0119--046 are due to a blueshifting of the broad emission lines with respect to the rest frame of the underlying galaxy in which the quasar is located rather than being due to a real high-velocity infall. The spectrum of PKS 0119-046 shows a narrow emission-line spike at 3610 A. This is interpreted as Lyman-α emission from the narrow-line region of the quasar. The emission is at a redshift very close to that of the highest redshift absorption-line systems. The spectrum of PKS 0119-046 is consistent with it having a lightly reddened narrow-line region similar to that which might be seen in a typical low-redshift quasar. The physical parameters deduced for one of the absorption-line systems are completely compatible with that system being caused by a narrow emission-line cloud seen in absorption