Rare gas dependence of vibration–vibration energy transfer processes: A diagnostic technique. Applications to CH2D2 and CH3F

Abstract

The rare gas dependence of V–V rates can be used as a diagnostic technique to identify different mechanisms of vibrational energy transfer and determine the rate constants for individual kinetic steps. The method is especially useful for the identification and measurement of rates of resonant vibrational energy transfer processes. Analytical and numerical solutions of pertinent model equations are presented and their range of applicability is discussed. The technique is applied to CH₂D₂ and CH₃F. In CH₂D₂ results of studies on ν₉, [ν₁, ν₆] and states in the 2000 cm⁻¹ region are presented where the application of the technique has made it possible to identify the pathways leading to population of these states and to assign rate constants to some of the steps involved. In CH₃F, by studying the Ar dependence of the V–V rates of the [ν₂, ν₅] and [ν₁, ν₄] states it has been possible to construct a complete map of energy transfer pathways which can explain all experimental observations for this system, to date. The general applicability of the technique and its potential application to other systems is also considered.