Energy transfer according to a multi-dimensional harmonic oscillator model: Application to methane

Abstract

A semiclassical theory for the collision of two harmonic oscillators of variable dimension is developed to take into account the degeneracy of vibrational modes. The intermolecular potential used is an angle-dependent exponential potential which takes into consideration the tetrahedral symmetry of CH 4. Transition probabilities for VV and VT processes in CH 4 have been calculated. Better agreement with experimental data is obtained than for breathing sphere theory. For degenerate modes like v 2 or v 4 in CH 4 the second order vibrational matrix elements have similar values as the first order matrix elements. Therefore, efficient energy exchange with these overtone levels is to be expected.