QUASI-CLASSICAL TRAJECTORY STUDY OF COLLISIONAL ENERGY-TRANSFER IN TOLUENE SYSTEMS .1. ARGON BATH GAS - ENERGY-DEPENDENCE AND ISOTOPE EFFECTS

Experimental studies of collisional energy transfer from highly vibrationally excited toluene to various bath gases have recently been reported [Toselli and Barker, J. Chem. Phys. 97, 1809 (1992), and references therein]. A quasiclassical trajectory investigation for toluene in argon bath gas at 300 K for initial internal energies E'=41 000, 30 000, and 15 000 cm(-1) is reported here. Collisional energy transfer is almost linearly dependent on E'. Predictions of energy transfer quantities are very sensitive to the average well depth of the assumed individual pairwise potentials, but is less sensitive to the detailed shape. Qualitative and quantitative agreement with experiment is obtained where the overall well depth is physically realistic. Isotope studies using Ar-40 and pseudohelium (Ar-4) bath gases indicate that energy transfer is independent of the mass of the bath-gas collider, but perdeuteration increases (Delta E(2))(1/2) by 13% over the undeuterated values.