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

Publisher Website
Google Scholar
Abstract
The accuracy of the energy-corrected sudden (ECS) formalism for line shape calculations is investigated, using coupled states calculation for CO 2 –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 σ 0 (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, J i ⩽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 J i 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).

This publication has 39 references indexed in Scilit: