Electron Emission from Ion Bombarded Solid Argon

Abstract

Rare gas solids (RGS) are good model systems to study ionization effects in insulators. Their electronic states are relatively well known[l]; they are monoatomic and bound by weak Van der Waals forces which allow them to be treated as dense gases with generally negligible chemical changes. The interaction of ionizing radiation with RGS produces lattice damage and desorption by the conversion of energy deposited as electronic excitation into kinetic energy. This conversion occurs by transitions involving repulsive potential energy curves and is generally known as desorption induced by electronic transition (DIET). We are studying the DIET mechanism in solid argon as described by Johnson and Inokuti[2], which also accounts for the bright luminescence observed during bombardment with ionizing particles. Previous studies have correlated sputter yields with luminescence yields in solid argon excited by MeV ions [3], low energy electrons[4], and photons[5, 6]. In order to determine the importance of this DIET mechanism in the decay pathways of electronic excitation, however, absolute correlation must be made. Furthermore, because this mechanism begins with an ionization event, the secondary electron emission processes during bombardment must also be understood and accounted for by any model for desorption and luminescence. In this paper we look at the beginning of this DIET mechanism by focusing on the secondary electron emission from bombarded solid argon.