Collisional broadening and shifting of Raman lines, and the potential energy surface for H2-Ar

Quantum mechanical close-coupling calculations of pressure broadened and pressure shifting coefficients for polarized vibrational Raman Q(1)(j) and pure rotational SO(j) Raman transitions of H-2-Ar and D-2-Ar have been performed using the empirically determined three-dimensional 'XC(fit)' potential energy surface. While the calculated Q(1)(j) vibrational line shifting coefficients, and both the shifting and broadening coefficients for the pure rotational S-0(j) lines agree well with experiment, broadening coefficients calculated for the Q(1)(j) transitions are substantially smaller than the measured values. Test calculations using ad hoc modifications of the XC(fit) potential indicate that the diatom stretching dependence of that potential energy surface needs further refinement. (C) 2002 Elsevier Science B.V. All rights reserved.