Stimulated desorption of atoms from rare-gas monolayers on metal surfaces: Dependence of yields and energy distributions on primary excitations

Kinetic energy distributions of Ar and Kr atoms desorbed by electron impact from saturated and dilute monolayers on Ru(001) have been measured by a time-of-flight technique. Both the most-probable kinetic energies and the desorption yields are found to increase for electron energies above the thresholds for multiple ionization. This effect is particularly pronounced for Kr. Using gas-phase ionization cross sections, relative escape probabilities for single and multiple primary ionization are derived. The data can form the basis for a quantitative theory of the desorption process.