Ground-state intermolecular spectroscopy and pendular states in benzene-argon

The results of nonlinear Raman spectroscopy at 0.03 cm(-1) resolution on the intermolecular transitions of the perprotonated and perdeuterated isotopomers of benzene-Ar are reported. Five bands were observed for each species. For each, band-contour measurements were performed. These, when compared to simulated contours, allow for the unambiguous assignment of the bands in terms of the two intermolecular fundamentals, the two components of the first bending overtone, and the bend-stretch combination band. Further, it is shown that the measured contours are ''pendular'' contours arising from species in optical-held-induced pendular states. The results are discussed in terms of (a) prior experiments on and calculations of the intermolecular level structure of benzene-Ar, (b) the mechanisms giving rise to the Raman intensities of intermolecular transitions, and (c) their implications regarding the prevalence of pendular behavior in nonlinear Raman experiments on jet-cooled species. (C) 1997 American Institute of Physics.