Near-resonant vibrational energy exchange between the stretching levels of H 2O

Abstract

The probabilities of vibrational energy exchange between the two stretching levels of H 2O have been calculated from 200 to 3000 K by use of a semiclassical procedure. Probabilities of the exothermic process (001 → 100) take a near-constant value of 0.35 over the entire temperature range, while the endothermic probabilities closely follow a 1/ T dependence. Probabilities exhibit a strong orientation dependence; large values are found when one of the H atoms is interacting with the incident atom in close proximity producing strong stretch-stretch couplings. Various intramolecular couplings during vibration are discussed. The effects of stretch-bend couplings and displacement of the O atom from the center-of-mass on the energy exchange is found to be unimportant.