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Energy corrected sudden calculations of linewidths and line shapes based on coupled states cross sections : the test case of CO2–argon.

Thibault, F. and Boissoles, J. and Boulet, C. and Ozanne, L. and Bouanich, J.P. and Roche, C.F. and Hutson, J.M. (1998) 'Energy corrected sudden calculations of linewidths and line shapes based on coupled states cross sections : the test case of CO2–argon.', Journal of chemical physics., 109 (15). pp. 6338-6345.


The accuracy of the energy-corrected sudden (ECS) formalism for line shape calculations is investigated, using coupled states calculation for CO2–Ar collisions on the recently developed “single repulsion” potential of Hutson et al. [J. Chem. Phys. 107, 1824 (1997); 105, 9130 (1996)]. Inelastic cross sections σ0(L→0,E)≡Q′L(E) are calculated using the MOLSCAT program, and then averaged over Maxwell–Boltzmann kinetic energy distributions to give the thermally averaged “basic rates” Q′L(T) needed in the ECS formalism. The ECS linewidths for low initial J, Ji⩽16, are sensitive only to the low-L basic rates, for which the CS calculations are converged; comparing them with directly calculated CS linewidths thus gives a stringent test of the ECS model, and it works well (within 10%). However, for higher Ji lines and for band shape calculations, basic rates for higher L are needed for convergence. These are obtained by an extrapolation procedure based on experimental data, using an exponential power law and the adiabaticity factor recently suggested by Bonamy et al. [J. Chem. Phys. 95, 3361 (1991)] ECS calculations using the resulting basic rates are designated “extrapolated CS-ECS calculations,” and are found to give accurate results for high-Jlinewidths, for near-wing absorption and for band profiles over a very wide range of perturber pressures (up to 1000 atm).

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Publisher statement:© 1998 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in The Journal of Chemical Physics 109, 6338 (1998) and may be found at
Date accepted:10 July 1998
Date deposited:19 August 2015
Date of first online publication:October 1998
Date first made open access:No date available

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