The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform

W. H. Parkinson - One of the best experts on this subject based on the ideXlab platform.

  • High resolution absorption cross-section measurements of the Schumann–Runge Bands of O2 by VUV Fourier transform spectroscopy
    Journal of Molecular Spectroscopy, 2003
    Co-Authors: T. Matsui, K. Yoshino, W. H. Parkinson, A.s.-c. Cheung, Anne P. Thorne, J. E. Murray, K. S. Leung, T. Imajo
    Abstract:

    Abstract The photoabsorption spectrum of the O 2 Schumann–Runge Bands was measured with resolution comparable to the Doppler widths by using the VUV Fourier transform spectrometer from Imperial College, London, combined with synchrotron radiation as a continuum light source at the Photon Factory, KEK, Japan. The analysis of the (12,0)–(17,0) Bands of the Schumann–Runge system provides accurate rotational line positions as well as the line intensities from 185 to 175 nm. Molecular constants of the v ′ =12 to 17 levels of the B 3 Σ u − state have been determined. The ( v ′ ,0) band oscillator strengths were determined as 2.38, 2.62, 2.70, 2.66, 2.40, and 2.12×10 −5 for the Bands from v ′ =12 to 17, respectively.

  • Isotopic dependence of predissociation linewidths in the Schumann-Runge Bands of oxygen
    Journal of Chemical Physics, 1995
    Co-Authors: A. S‐c. Cheung, K. Yoshino, W. H. Parkinson, M. J. Jamieson, A. Dalgarno, M. S. Child
    Abstract:

    It is demonstrated that, according to semi‐classical theory, the isotopic dependence of the predissociation linewidths in the Schumann‐Runge Bands of oxygen cannot be removed by simple scaling of the reduced mass. This is in contrast to the isotopic dependence of the predissociated vibrational energy levels.

  • Rotational dependence of the predissociation linewidths of the Schumann–Runge Bands of O2
    Journal of Chemical Physics, 1993
    Co-Authors: A.s.-c. Cheung, K. Yoshino, M. J. Jamieson, A. Dalgarno, M. Finch, W. H. Parkinson
    Abstract:

    The predissociation linewidths of vibrational levels v=0 –12 for 16O2, 16O18O, and 18O2 molecules in the B 3Σu− state with rotational quantum numbers N≤20 have been calculated taking into account the spin–orbit interactions of the B 3Σu− state with the 5Πu, 3Σu+, 3Πu, and 1Πu states, and the rotational coupling with the 3Πu state. The predissociation linewidths exhibit systematic variations with rotational quantum number for different vibrational levels. Good agreement between most of the calculated and experimental linewidths has been obtained for all three isotopic molecules, with the exception of the set of linewidths of 16O2 for v=0 and 2. The agreement can be improved by adjustment of the 1Πu potential and the strength of the spin–orbit interaction between the B 3Σu− and 1Πu states.

  • High resolution absorption cross sections in the transmission window region of the Schumann-Runge Bands and Herzberg continuum of O2
    Planetary and Space Science, 1992
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    Abstract The absorption cross sections of the Schumann-Runge Bands in the window region between the rotational lines have been measured in the wavelength region 180–195 nm. The measurements have been done with many different pressures of oxygen, 2.5−760 torr, so that the pressure-dependent absorption can be separated from the main cross sections. The published cross sections [Yoshino et al.. Planet. Space Sci. 31, 339 (1983)] in the window region are superseded by the present cross sections. The combined cross sections are presented graphically here and are available at wavenumber intervals of 0.1 cm−1 as numerical compilations stored on magnetic tape, from the National Space Science Data Center, NASA/ Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. The Herzberg continuum cross sections are derived after subtracting calculated contributions from the Schumann-Runge Bands and are significantly smaller than any previous measurements.

  • Band oscillator strengths of the (2, 1)–(12, 1) Schumann‐Runge Bands of O2 from absolute absorption cross‐section measurements at room temperature
    Journal of Geophysical Research, 1990
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    The absolute absorption cross sections of the (2, 1)–(12, 1) Schumann-Runge Bands of O2 at room temperature have been obtained from measurements of the total absolute absorption cross sections arising from transitions from the ground-state levels with υ″ = 0 and 1 by subtraction of the υ″ = 0 contributions, which have been synthesized from our previous determinations of the band oscillator strengths, line center positions and predissociation line widths of the (υ′, 0) Schumann-Runge Bands of O2. The resultant absolute absorption cross sections of the (2, 1)–(12, 1) Bands have been integrated numerically to obtain the band oscillator strengths. Our experimental band oscillator strengths are somewhat lower than the experimental values of Lewis et al.(1986) but are in good agreement with the recently calculated values of Friedman (1990).

K. Yoshino - One of the best experts on this subject based on the ideXlab platform.

  • High resolution absorption cross-section measurements of the Schumann–Runge Bands of O2 by VUV Fourier transform spectroscopy
    Journal of Molecular Spectroscopy, 2003
    Co-Authors: T. Matsui, K. Yoshino, W. H. Parkinson, A.s.-c. Cheung, Anne P. Thorne, J. E. Murray, K. S. Leung, T. Imajo
    Abstract:

    Abstract The photoabsorption spectrum of the O 2 Schumann–Runge Bands was measured with resolution comparable to the Doppler widths by using the VUV Fourier transform spectrometer from Imperial College, London, combined with synchrotron radiation as a continuum light source at the Photon Factory, KEK, Japan. The analysis of the (12,0)–(17,0) Bands of the Schumann–Runge system provides accurate rotational line positions as well as the line intensities from 185 to 175 nm. Molecular constants of the v ′ =12 to 17 levels of the B 3 Σ u − state have been determined. The ( v ′ ,0) band oscillator strengths were determined as 2.38, 2.62, 2.70, 2.66, 2.40, and 2.12×10 −5 for the Bands from v ′ =12 to 17, respectively.

  • Isotopic dependence of predissociation linewidths in the Schumann-Runge Bands of oxygen
    Journal of Chemical Physics, 1995
    Co-Authors: A. S‐c. Cheung, K. Yoshino, W. H. Parkinson, M. J. Jamieson, A. Dalgarno, M. S. Child
    Abstract:

    It is demonstrated that, according to semi‐classical theory, the isotopic dependence of the predissociation linewidths in the Schumann‐Runge Bands of oxygen cannot be removed by simple scaling of the reduced mass. This is in contrast to the isotopic dependence of the predissociated vibrational energy levels.

  • Rotational dependence of the predissociation linewidths of the Schumann–Runge Bands of O2
    Journal of Chemical Physics, 1993
    Co-Authors: A.s.-c. Cheung, K. Yoshino, M. J. Jamieson, A. Dalgarno, M. Finch, W. H. Parkinson
    Abstract:

    The predissociation linewidths of vibrational levels v=0 –12 for 16O2, 16O18O, and 18O2 molecules in the B 3Σu− state with rotational quantum numbers N≤20 have been calculated taking into account the spin–orbit interactions of the B 3Σu− state with the 5Πu, 3Σu+, 3Πu, and 1Πu states, and the rotational coupling with the 3Πu state. The predissociation linewidths exhibit systematic variations with rotational quantum number for different vibrational levels. Good agreement between most of the calculated and experimental linewidths has been obtained for all three isotopic molecules, with the exception of the set of linewidths of 16O2 for v=0 and 2. The agreement can be improved by adjustment of the 1Πu potential and the strength of the spin–orbit interaction between the B 3Σu− and 1Πu states.

  • High resolution absorption cross sections in the transmission window region of the Schumann-Runge Bands and Herzberg continuum of O2
    Planetary and Space Science, 1992
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    Abstract The absorption cross sections of the Schumann-Runge Bands in the window region between the rotational lines have been measured in the wavelength region 180–195 nm. The measurements have been done with many different pressures of oxygen, 2.5−760 torr, so that the pressure-dependent absorption can be separated from the main cross sections. The published cross sections [Yoshino et al.. Planet. Space Sci. 31, 339 (1983)] in the window region are superseded by the present cross sections. The combined cross sections are presented graphically here and are available at wavenumber intervals of 0.1 cm−1 as numerical compilations stored on magnetic tape, from the National Space Science Data Center, NASA/ Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. The Herzberg continuum cross sections are derived after subtracting calculated contributions from the Schumann-Runge Bands and are significantly smaller than any previous measurements.

  • Band oscillator strengths of the (2, 1)–(12, 1) Schumann‐Runge Bands of O2 from absolute absorption cross‐section measurements at room temperature
    Journal of Geophysical Research, 1990
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    The absolute absorption cross sections of the (2, 1)–(12, 1) Schumann-Runge Bands of O2 at room temperature have been obtained from measurements of the total absolute absorption cross sections arising from transitions from the ground-state levels with υ″ = 0 and 1 by subtraction of the υ″ = 0 contributions, which have been synthesized from our previous determinations of the band oscillator strengths, line center positions and predissociation line widths of the (υ′, 0) Schumann-Runge Bands of O2. The resultant absolute absorption cross sections of the (2, 1)–(12, 1) Bands have been integrated numerically to obtain the band oscillator strengths. Our experimental band oscillator strengths are somewhat lower than the experimental values of Lewis et al.(1986) but are in good agreement with the recently calculated values of Friedman (1990).

A.s.-c. Cheung - One of the best experts on this subject based on the ideXlab platform.

  • High resolution absorption cross-section measurements of the Schumann–Runge Bands of O2 by VUV Fourier transform spectroscopy
    Journal of Molecular Spectroscopy, 2003
    Co-Authors: T. Matsui, K. Yoshino, W. H. Parkinson, A.s.-c. Cheung, Anne P. Thorne, J. E. Murray, K. S. Leung, T. Imajo
    Abstract:

    Abstract The photoabsorption spectrum of the O 2 Schumann–Runge Bands was measured with resolution comparable to the Doppler widths by using the VUV Fourier transform spectrometer from Imperial College, London, combined with synchrotron radiation as a continuum light source at the Photon Factory, KEK, Japan. The analysis of the (12,0)–(17,0) Bands of the Schumann–Runge system provides accurate rotational line positions as well as the line intensities from 185 to 175 nm. Molecular constants of the v ′ =12 to 17 levels of the B 3 Σ u − state have been determined. The ( v ′ ,0) band oscillator strengths were determined as 2.38, 2.62, 2.70, 2.66, 2.40, and 2.12×10 −5 for the Bands from v ′ =12 to 17, respectively.

  • Predicted predissociation linewidths in the Schumann–Runge Bands of O2 compared with recent high resolution measurements
    Journal of Chemical Physics, 2001
    Co-Authors: G. S. M. Tong, A.s.-c. Cheung, M. J. Jamieson
    Abstract:

    We derive and use new parameters to quantify the semiempirical expressions of Julienne and Krauss [J. Mol. Spectrosc. 56, 270 (1975)] for the 5Πu, 3Σu+, 3Πu, and 1Πu potentials that predissociate the rovibrational levels of the B 3Σu− state of O2. Using the new parameters in the model of Julienne and Krauss we evaluate fine-structure predissociation linewidths for the Schumann–Runge Bands that terminate on the v=13,14 rovibrational levels of the B 3Σu− state. We compare these linewidths and those calculated with several existing sets of parameters with the measurements of Dooley et al. [J. Chem. Phys. 109, 3856 (1998)]. We also show the deperturbing effect of the level shifts, calculated with the new parameters, on the energies of the rotationless v=0–17 vibrational levels of the B 3Σu− state.

  • Rotational dependence of the predissociation linewidths of the Schumann–Runge Bands of O2
    Journal of Chemical Physics, 1993
    Co-Authors: A.s.-c. Cheung, K. Yoshino, M. J. Jamieson, A. Dalgarno, M. Finch, W. H. Parkinson
    Abstract:

    The predissociation linewidths of vibrational levels v=0 –12 for 16O2, 16O18O, and 18O2 molecules in the B 3Σu− state with rotational quantum numbers N≤20 have been calculated taking into account the spin–orbit interactions of the B 3Σu− state with the 5Πu, 3Σu+, 3Πu, and 1Πu states, and the rotational coupling with the 3Πu state. The predissociation linewidths exhibit systematic variations with rotational quantum number for different vibrational levels. Good agreement between most of the calculated and experimental linewidths has been obtained for all three isotopic molecules, with the exception of the set of linewidths of 16O2 for v=0 and 2. The agreement can be improved by adjustment of the 1Πu potential and the strength of the spin–orbit interaction between the B 3Σu− and 1Πu states.

  • High resolution absorption cross sections in the transmission window region of the Schumann-Runge Bands and Herzberg continuum of O2
    Planetary and Space Science, 1992
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    Abstract The absorption cross sections of the Schumann-Runge Bands in the window region between the rotational lines have been measured in the wavelength region 180–195 nm. The measurements have been done with many different pressures of oxygen, 2.5−760 torr, so that the pressure-dependent absorption can be separated from the main cross sections. The published cross sections [Yoshino et al.. Planet. Space Sci. 31, 339 (1983)] in the window region are superseded by the present cross sections. The combined cross sections are presented graphically here and are available at wavenumber intervals of 0.1 cm−1 as numerical compilations stored on magnetic tape, from the National Space Science Data Center, NASA/ Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. The Herzberg continuum cross sections are derived after subtracting calculated contributions from the Schumann-Runge Bands and are significantly smaller than any previous measurements.

  • Band oscillator strengths of the (2, 1)–(12, 1) Schumann‐Runge Bands of O2 from absolute absorption cross‐section measurements at room temperature
    Journal of Geophysical Research, 1990
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    The absolute absorption cross sections of the (2, 1)–(12, 1) Schumann-Runge Bands of O2 at room temperature have been obtained from measurements of the total absolute absorption cross sections arising from transitions from the ground-state levels with υ″ = 0 and 1 by subtraction of the υ″ = 0 contributions, which have been synthesized from our previous determinations of the band oscillator strengths, line center positions and predissociation line widths of the (υ′, 0) Schumann-Runge Bands of O2. The resultant absolute absorption cross sections of the (2, 1)–(12, 1) Bands have been integrated numerically to obtain the band oscillator strengths. Our experimental band oscillator strengths are somewhat lower than the experimental values of Lewis et al.(1986) but are in good agreement with the recently calculated values of Friedman (1990).

Brenton Lewis - One of the best experts on this subject based on the ideXlab platform.

  • A new model for the Schumann-Runge Bands of O2
    Physics and Chemistry of The Earth Part C-solar-terrestial and Planetary Science, 2020
    Co-Authors: Brenton Lewis, Stephen Gibson, F Hawes, L. W. Torop
    Abstract:

    Abstract A new quantum-mechanical model is presented of photoabsorption and photodissociation in the discrete and continuous Schumann-Runge regions of the molecular oxygen spectrum, based on the coupled-channel Schrodinger-equations method. The ability of the model to predict accurately temperature-dependent photoabsorption cross sections and photodissociation branching ratios is demonstrated, suggesting applications in the areas of atmospheric vacuum-ultraviolet opacity and photochemistry.

  • Assignment of the excess absorption underlying the Schumann–Runge Bands of molecular oxygen
    Journal of Chemical Physics, 2001
    Co-Authors: Brenton Lewis, Stephen Gibson, E. H. Roberts
    Abstract:

    A long-standing problem, pertaining to the origin of the excess absorption found experimentally to underlie the high-vibrational Schumann–Runge Bands of molecular oxygen, is resolved. Through new calculations, with parameter sets based on recently obtained experimental information, it is shown that the excess absorption arises from transitions into the lowest valence states of 3Πu and 3Πg symmetry.

  • A comparative high-resolution study of predissociation linewidths in the Schumann-Runge Bands of O2
    Journal of Chemical Physics, 1998
    Co-Authors: P. M. Dooley, Brenton Lewis, Stephen Gibson, Kenneth Baldwin, Philip C. Cosby, J. L. Price, Richard A. Copeland, Tom G. Slanger, Anne P. Thorne, J. E. Murray
    Abstract:

    Results are presented of a comparative study in which three distinct high-resolution experimental techniques (vacuum-ultraviolet laser spectroscopy, laser-induced fluorescence spectroscopy and vacuum-ultraviolet Fourier-transform spectroscopy) were used to study predissociation in the Schumann-Runge Bands of O2 B 3Σu−(v′)←X 3Σg−(v″) with v′=13 and 14. Our measurements are the first to be performed at high resolution for these levels and represent a significant advance on previous knowledge, characterizing completely the fine-structure and rotation dependencies of the B 3Σu−(v=13 and 14)-state predissociation for the first time. The measured fine-structurespecific linewidths will result in significant improvements in the parameterization of models describing predissociation of the B-state and will have an impact on the development of realistic photochemical models of the terrestrial atmosphere. Good agreement was found between linewidths measured using vacuum-ultraviolet laser spectroscopy and laser-induce...

  • Quantum interference in the Schumann-Runge Bands of molecular oxygen
    Geophysical Research Letters, 1998
    Co-Authors: Brenton Lewis, Stephen Gibson, L. W. Torop, D.g. Mccoy
    Abstract:

    The photoabsorption cross section of O2 in the Schumann-Runge Bands is investigated theoretically using the coupled-channel Schrodinger-equations method. It is found that quantum interference between vibrational Bands leads to significant asymmetry in the far line wings, a result supported by experimental evidence. Thus, Schumann-Runge cross sections calculated with the usual band models based on Voigt line shapes may be in error in regions of weak absorption between vibrational band heads, suggesting the need to re-evaluate aspects of atmospheric photochemistry sensitive to those regions.

  • Fine-structure-resolved collisional broadening in the Schumann-Runge Bands of O2
    Journal of Quantitative Spectroscopy & Radiative Transfer, 1997
    Co-Authors: P. M. Dooley, Brenton Lewis, Stephen Gibson, K. Waring, Kenneth Baldwin
    Abstract:

    Abstract Collisional self-broadening and shift coefficients are presented for selected fine-structure-resolved rotational lines from the B3∑u− ← X3∑g−(ν′,1) Bands of O2. The coefficients were derived from high-resolution photoabsorption cross-sections measured using the tuneable, narrow-bandwidth, vacuum-ultraviolet radiation generated by the two-photon-resonant difference-frequency four-wave mixing of excimer-pumped dye-laser radiation in Xe. The results, obtained at room temperature and at pressures of less than 800 torr, are consistent with previous results derived from medium-resolution measurements of the (ν′,0) Bands at much higher pressures.

D. E. Freeman - One of the best experts on this subject based on the ideXlab platform.

  • High resolution absorption cross sections in the transmission window region of the Schumann-Runge Bands and Herzberg continuum of O2
    Planetary and Space Science, 1992
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    Abstract The absorption cross sections of the Schumann-Runge Bands in the window region between the rotational lines have been measured in the wavelength region 180–195 nm. The measurements have been done with many different pressures of oxygen, 2.5−760 torr, so that the pressure-dependent absorption can be separated from the main cross sections. The published cross sections [Yoshino et al.. Planet. Space Sci. 31, 339 (1983)] in the window region are superseded by the present cross sections. The combined cross sections are presented graphically here and are available at wavenumber intervals of 0.1 cm−1 as numerical compilations stored on magnetic tape, from the National Space Science Data Center, NASA/ Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A. The Herzberg continuum cross sections are derived after subtracting calculated contributions from the Schumann-Runge Bands and are significantly smaller than any previous measurements.

  • Band oscillator strengths of the (2, 1)–(12, 1) Schumann‐Runge Bands of O2 from absolute absorption cross‐section measurements at room temperature
    Journal of Geophysical Research, 1990
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    The absolute absorption cross sections of the (2, 1)–(12, 1) Schumann-Runge Bands of O2 at room temperature have been obtained from measurements of the total absolute absorption cross sections arising from transitions from the ground-state levels with υ″ = 0 and 1 by subtraction of the υ″ = 0 contributions, which have been synthesized from our previous determinations of the band oscillator strengths, line center positions and predissociation line widths of the (υ′, 0) Schumann-Runge Bands of O2. The resultant absolute absorption cross sections of the (2, 1)–(12, 1) Bands have been integrated numerically to obtain the band oscillator strengths. Our experimental band oscillator strengths are somewhat lower than the experimental values of Lewis et al.(1986) but are in good agreement with the recently calculated values of Friedman (1990).

  • Band oscillator strengths of the (2, 1)–(12, 1) Schumann-Runge Bands of O2from absolute absorption cross-section measurements at room temperature
    Journal of Geophysical Research, 1990
    Co-Authors: K. Yoshino, J. R. Esmond, A.s.-c. Cheung, D. E. Freeman, W. H. Parkinson
    Abstract:

    The absolute absorption cross sections of the (2, 1)-(12, 1) Schumann-Runge Bands of O 2 at room temperature have been obtained from measurements of the total absolute absorption cross sections arising from transitions from the ground-state level with v″=0 and 1 by subtraction of the v″=0 contributions, which have been synthesized from our previous determinations of the band oscillator strengths, line center positions and predissociation line widths of the (v′, 0) Schumann-Runge band of O 2. The resultant absolute absorption cross sections of the (2, 1)-(12, 1) Bands have been integrated numerically to obtain the band oscillator strengths. Our experimental band oscillator strengths are somewhat lower than the experimental values of Lewis et al (1986) but are in good agreement with the recently calculated values of Friedman (1990). -Authorslink_to_subscribed_fulltex

  • Predissociation linewidths of the (1,0)-(12,0) Schumann-Runge absorption Bands of O2 in the wavelength region 179-202 nm
    Journal of Chemical Physics, 1990
    Co-Authors: A.s.-c. Cheung, K. Yoshino, J. R. Esmond, D. E. Freeman, S. S. L. Chiu, W. H. Parkinson
    Abstract:

    A nonlinear least‐squares method of retrieving predissociation linewidths from the experimental absolute absorption cross sections of Yoshino et al. [Planet. Space Sci. 31, 339 (1983)] has been applied to the (1,0)–(12,0) Schumann–Runge Bands of oxygen. Predissociation linewidths deduced for the Schumann–Runge Bands are larger than the theoretical predictions of Julienne [J. Mol. Spectrosc. 63, 60 (1976)] and the latest measurements of Lewis et al. [J. Quant. Spectrosc. Radiat. Transfer 36, 187 (1986)]. The larger linewidths found will have an impact on calculations of solar flux penetration into the Earth’s atmosphere and of the photodissociation rates of trace species in the upper atmosphere. Systematic variation of predissociation linewidths with rotational quantum number is observed in the Bands (v’,0) with v’=6, 8, 9, 11, and 12.