Excitation of Molecular Vibration on Collision. I. Preferential Orientations for Vibrational Transitions

Abstract

The problem of preferential orientations in vibrational transitions has been investigated for collision systems involving two diatomic molecules or a molecule and an atom. Orientation‐ and temperature‐dependent transition probabilities were obtained for such systems. Applications of the final formulas to O₂–Ar, O₂–O₂, HBr–Ar, and HBr–HBr show that the vibrational transition (0 → 1) is most effective for colinear configurations in the collisions involving homonuclear molecules, while such configuration is either most effective or least effective when the molecule is asymmetric. In HBr–HBr the colinear configuration in which two H atoms are in head‐on interaction is most effective, while the Br···Br head‐on colinear collision is least effective. In HBr–Ar the Br–H···Ar colinear configuration is most effective and the H–Br···Ar is least effective. In O₂–O₂ the parallel configuration is least effective, but in HBr–HBr the efficiency of such configuration is intermediate between the two extreme colinear configurations.