Non-adiabatic Processes of Energy Transfer in Gases

The present review examines general methods for constructing the adiabatic electronic functions of molecular systems produced by binary collisions of atoms and molecules in gases. Mechanisms of energy transfer accompanying the collision of electronically excited atoms and molecules are discussed on the basis of the selection rules for non-adiabatic interactions and models of non-adiabatic coupling. These mechanisms are classified according to the amounts of electronic energy transferred on collision and according to the distances at which transfer takes place between the electronic states of the colliding species. The quenching of the electronically excited states of the atoms is brought about by close approach of the colliding species, and the probability of transitions and the corresponding cross-section depend in decisive fashion on the characteristics of the electronic functions of the system of two interacting species. Transitions between the components of the fine structure of the atomic terms take place at large distances, and the cross-section can be interpreted in terms of the characteristics of the non-excited functions for the interacting species. Transitions between the vibrational levels of molecules with incomplete electronic sub-levels are determined by vibronic or spin-orbital interaction in a given electronic configuration. The bibliography contains 62 references.