Theoretical line shapes for rotational spectra of HCl in Ar

摘要

An interaction potential for HClndash;Ar recently derived from spectra of van der Waals complexes lsqb;J. M. Hutson, J. Chem. Phys.89, 4550 (1988)rsqb; has been used to obtain converged closehyphen;coupling scatteringSmatrices from which pressure broadening (linewidth, line shift, and line coupling) cross sections have been computed within the Fanondash;Benhyphen;Reuven formalism. Linewidths agree well with experimental data with the exception of the 0ndash;1 line at low temperatures (an error of about 15percnt; at 125 K). Line shifts, especially the largest, for the 0ndash;1 line, are also in reasonable accord with experimental data. Line coupling is predicted to be quite small. The coupledhyphen;states molecular scattering approximation is found to be accurate except at very low collision energies. The infinitehyphen;order sudden approximations, on the other hand, is not reliable for this system. Inelastic scattering out of the spectroscopic levels accounts for only a fraction of the linewidth at thermal energies, especially in the lower rotational levels.