The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
R Volkamer - One of the best experts on this subject based on the ideXlab platform.
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rayleigh Scattering Cross section measurements of nitrogen argon oxygen and air
Journal of Quantitative Spectroscopy & Radiative Transfer, 2014Co-Authors: Ryan Thalman, Kyle J Zarzana, R Volkamer, Margaret A. TolbertAbstract:Abstract Knowledge about Rayleigh Scattering Cross sections is relevant to predictions about radiative transfer in the atmosphere, and needed to calibrate the reflectivity of mirrors that are used in high-finesse optical cavities to measure atmospheric trace gases and aerosols. In this work we have measured the absolute Rayleigh Scattering Cross-section of nitrogen at 405.8 and 532.2 nm using cavity ring-down spectroscopy (CRDS). Further, multi-spectral measurements of the Scattering Cross-sections of argon, oxygen and air are presented relative to that of nitrogen from 350 to 660 nm using Broadband Cavity Enhanced Spectroscopy (BBCES). The reported measurements agree with refractive index based theory within 0.2±0.4%, and have an absolute accuracy of better than 1.3%. Our measurements expand the spectral range over which Rayleigh Scattering Cross section measurements of argon, oxygen and air are available at near-ultraviolet wavelengths. The expressions used to represent the Rayleigh Scattering Cross-section in the literature are evaluated to assess how uncertainties affect quantities measured by cavity enhanced absorption spectroscopic (CEAS) techniques. We conclude that Rayleigh Scattering Cross sections calculated from theory provide accurate data within very low error bounds, and are suited well to calibrate CEAS measurements of atmospheric trace gases and aerosols.
Ryan Thalman - One of the best experts on this subject based on the ideXlab platform.
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rayleigh Scattering Cross section measurements of nitrogen argon oxygen and air
Journal of Quantitative Spectroscopy & Radiative Transfer, 2014Co-Authors: Ryan Thalman, Kyle J Zarzana, R Volkamer, Margaret A. TolbertAbstract:Abstract Knowledge about Rayleigh Scattering Cross sections is relevant to predictions about radiative transfer in the atmosphere, and needed to calibrate the reflectivity of mirrors that are used in high-finesse optical cavities to measure atmospheric trace gases and aerosols. In this work we have measured the absolute Rayleigh Scattering Cross-section of nitrogen at 405.8 and 532.2 nm using cavity ring-down spectroscopy (CRDS). Further, multi-spectral measurements of the Scattering Cross-sections of argon, oxygen and air are presented relative to that of nitrogen from 350 to 660 nm using Broadband Cavity Enhanced Spectroscopy (BBCES). The reported measurements agree with refractive index based theory within 0.2±0.4%, and have an absolute accuracy of better than 1.3%. Our measurements expand the spectral range over which Rayleigh Scattering Cross section measurements of argon, oxygen and air are available at near-ultraviolet wavelengths. The expressions used to represent the Rayleigh Scattering Cross-section in the literature are evaluated to assess how uncertainties affect quantities measured by cavity enhanced absorption spectroscopic (CEAS) techniques. We conclude that Rayleigh Scattering Cross sections calculated from theory provide accurate data within very low error bounds, and are suited well to calibrate CEAS measurements of atmospheric trace gases and aerosols.
Woon Yong Baek - One of the best experts on this subject based on the ideXlab platform.
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Total electron-Scattering Cross sections of pyrimidine
Physical Review A, 2013Co-Authors: Woon Yong Baek, A. Arndt, Hans Rabus, Mingjie WangAbstract:Total electron-Scattering Cross sections of pyrimidine, the basic component for the nucleic bases cytosine and thymine, were measured for electron energies from 5 eV to 1 keV using the linear transmission method. The measured results were compared to semiempirical data obtained by means of the additivity rule and to experimental data for benzene since it has a similar ring structure and the same number of valence electrons as pyrimidine. Furthermore, integral elastic and inelastic electron-Scattering Cross sections of pyrimidine were calculated by applying the spherical complex optical potential model. The sum of both Cross sections agrees reasonably well with the experimental total electron-Scattering Cross sections of pyrimidine in the energy range from 20 eV to 1 keV. The experimental data are, however, significantly lower than the theoretical Cross sections when including the contribution of rotational excitations to the electron Scattering.
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Differential elastic and total electron Scattering Cross sections of tetrahydrofuran
Physical Review A, 2012Co-Authors: Woon Yong Baek, Hans Rabus, Marion U. Bug, E. Gargioni, B. GrosswendtAbstract:Differential elastic Scattering Cross sections of tetrahydrofuran for electrons were measured absolutely in the energy range from 20 eV to 1 keV at Scattering angles between 5\ifmmode^\circ\else\textdegree\fi{} and 135\ifmmode^\circ\else\textdegree\fi{}. The measurements were carried out using a Crossed-beam arrangement without the application of the widely used relative flow technique. The experimental differential Scattering Cross sections could be put on an absolute scale by means of the total electron Scattering Cross sections of tetrahydrofuran and of the current loss of the primary electron beam in the forward direction arising due to the Scattering by the molecular beam. The total Scattering Cross sections were determined for electron energies between 6 eV and 1 keV using a separate linear transmission experiment. The differential Cross sections of tetrahydrofuran for the elastic Scattering of electrons were also calculated in the energy range between 60 eV and 1 keV by applying the modified independent-atom model. A comparison with the experimental results showed a satisfactory agreement, indicating that the selected theoretical model is adequate for these calculations.
John H. Moore - One of the best experts on this subject based on the ideXlab platform.
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Total electron Scattering Cross section for Cl2
The Journal of Chemical Physics, 1999Co-Authors: Gary D. Cooper, John H. Moore, Jason E. Sanabia, James K. Olthoff, Loucas G. ChristophorouAbstract:Absolute measurements of the total electron Scattering Cross section, σsc,t(e), for chlorine, Cl2, are reported for electron energies, e, ranging from 0.3 to 23 eV. The present data are in reasonable agreement with previous measurements of the Cross sections for total electron Scattering and total rotational excitation, and indicate significant indirect vibrational excitation due to negative ion resonances.
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LOW-ENERGY ELECTRON Scattering Cross SECTIONS OF HALOFLUOROCARBONS
Journal of Chemical Physics, 1994Co-Authors: Theresa Underwood‐lemons, Dennis C. Winkler, John A. Tossell, John H. MooreAbstract:The interaction of low‐energy electrons with halogenated methanes is important in both their atmospheric and plasma‐processing chemistry. In this work, the total electron Scattering Cross sections of mixed fluorohalomethanes (CFnX4−n) were measured for incident electrons in the energy range of 0.3–12 eV using electron transmission spectroscopy. Resonances in the Scattering Cross sections may be interpreted as the capture of low‐energy electrons into unoccupied molecular orbitals. To aid in the assignments of the resulting negative ion states, we performed quantum‐mechanical calculations of the electron attachment energies. The effect of halogen substitution on the orbitals participating in electron capture are examined.
Loucas G. Christophorou - One of the best experts on this subject based on the ideXlab platform.
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Total electron Scattering Cross section for Cl2
The Journal of Chemical Physics, 1999Co-Authors: Gary D. Cooper, John H. Moore, Jason E. Sanabia, James K. Olthoff, Loucas G. ChristophorouAbstract:Absolute measurements of the total electron Scattering Cross section, σsc,t(e), for chlorine, Cl2, are reported for electron energies, e, ranging from 0.3 to 23 eV. The present data are in reasonable agreement with previous measurements of the Cross sections for total electron Scattering and total rotational excitation, and indicate significant indirect vibrational excitation due to negative ion resonances.