Penning Collision Processes

Abstract

A review is presented of experimental investigations dealing with the ionization of various atoms and molecules in collisions with metastable rare gas atoms. The methods for determining de-excitation (Penning ionization) rate constants or cross sections; a W-value measurement, a static-afterglow, a flowing-afterglow, a beam and a pulse-radiolysis methods, are reviewed. Our results obtained by a pulse-radiolysis method are compared with those obtained by other methods. For theoretical investigations such as those based on a gas-kinetic collision model and an electron exchange model, the formalism and calculations for Penning ionization cross sections in collisions with atoms in metastable and resonance states are also reviewed, and our recent results are discussed from the viewpoint of a gas-kinetic collision model. Some aspects of the application of Penning ionization processes to gas lasers and the production of polarized electrons and ions are also presented.