The Non-Linear Erosion Yield of Condensed Gas Solids Electronically Excited by Fast Light Ions

Abstract

The erosion of rare gas and simple molecular gas solid films (i.e., H₂O [1–4], Xe [5], Ar [6], CO₂ [3], SO₂ [7,8], CO) by fast ions is a special case of desorption due to electronic excitationo It is special in several respects. First, the films studied are not monolayers as in most desorption work, but are typically ~1000 Å thick, essentially bulk materialo Second, the surface binding energies of the condensed gas species are low (≲0.5 eV), characteristic of VanderWaals bonded atoms and molecules or, in the case of water, hydrogen bonded molecules. Third, all of the films are insulators. Fourth, the use of MeV ions allows large changes in the density of electronic excitation along well-defined linear paths by choosing the nuclear charge and velocity of the incident ions. Fifth, the erosion or desorption yields are large, from 0.1 to 1000 molecules desorbed per incident ion even for H and He ions.