Spontaneous electron emission from slow atomic collisions

Abstract

An overview is given of the physics connected with processes of spontaneous electron emission occuring in slow (<10 keV) collisions of two atomic particles. First, the general theoretical concepts, the quantum mechanical description, and the semiclassical approximations currently used are outlined, and their applicability to the description of the various possible spontaneous ionization processes is discussed. In the following sections, experimental results from the recent literature - electron spectra and energy gain spectra - are discussed. For this discussion simple “prototype” systems are selected that allow a detailed theoretical analysis. Three types of qualitatively different processes are distinguished: (i) spontaneous molecular ionization during the collision, (ii) atomic auto-ionization after the collision, and (iii) atomic auto-ionization in the long range Coulomb field of the collision partner. The special possibilities of employing spontaneously emitted electrons as a medium to obtain information on the dynamics of atomic collisions are emphasized.