Spectral lineshape parameters revisited for HF in a bath of argon - I. widths and shifts in the (0-0), (0-1), and (0-2) bands

The test of an interaction potential for HF-argon recently determined from the spectroscopy of the Van der Waals complex requires accurate experimenta l widths and shifts cross sections. Since inconsistencies existed between p revious measurements, collisional lineshapes were studied at T = 296 K by h igh-resolution Fourier transform spectroscopy for the 0-0, 0-1, and 0-2 ban ds. The accurate close-coupling molecular scattering calculations of Green and Hutson (1994. J. Chem. Phys. 100, 891) were extended to a complementary set of kinetic energies in order to check the thermal averaging procedure. Agreement between measured and computed room temperature cross sections is excellent for the three vibrational bands. This confirms the accuracy of t he HF-argon surface and particularly its dependence on the HF vibrational l evel, which is sensitively probed both by the widths and by the shifts cros s sections at high j(i) values. (C) 1999 Academic Press.