Nitrogen-broadened lineshapes in the oxygen A-band: Experimental results and theoretical calculations

Abstract:

We report measurements for N2-broadening, pressure-shift and line mixing coefficients for 55 oxygen transitions in the A-bandretrieved using a multispectrum fitting technique. Nineteen laboratory absorption spectra were recorded at 0.02 cm1 resolution usinga multi-pass absorption cell with path length of 1636.9 cm and the IFS 120 Fourier transform spectrometer located at Justus-Liebig-Uni-versity in Giessen, Germany. The total sample pressures ranged from 8.8 to 3004.5 Torr with oxygen volume mixing ratios in nitrogenranging between 0.057 and 0.62. An Exponential Power Gap (EPG) scaling law was used to calculate the N2-broadening and N2-linemixing coefficients.The line broadening and shift coefficients for the A-band of oxygen self-perturbed and perturbed by N2 are modeled using semiclas-sical calculations based on the Robert–Bonamy formalism and two intermolecular potentials. These potentials involve electrostatic con-tributions including the hexadecapole moment of the molecules and (a) a simple dispersion contribution with one adjustable parameter tofit the broadening coefficients or (b) the atom–atom Lennard-Jones model without such adjustable parameters. The first potential leadsto very weak broadening coefficients for high J transitions whereas the second potential gives much more improved results at mediumand large J values, in reasonable agreement with the experimental data. For the line shifts which mainly arise in our calculation from theelectronic state dependence of the isotropic potential, their general trends with increasing J values can be well predicted, especially fromthe first potential. From the theoretical results, we have derived air-broadening and air-induced shift coefficients with an agreement com-parable to that obtained for O2–O2 and O2–N2. 2008 Elsevier Inc. All rights reserved.

Notes:

n/a