Beyond MGR: Wave packet squeezing

Abstract

The MGR scenario for Electron-Stimulated Desorption proved to be a very fruitful model allowing for theoretical interpretation for a broader class of desorption experiments than originally intended. New experimental tools and techniques require, however, considering alternative scenarios to interpret the results. Depending on one's preferences, almost all of them can either be considered as genuinely new ones or merely an MGR in disguise. I am concentrating here on one such scenario, the Wave Packet Squeezing model, which was invoked recently to account for the experimental features of ESD of physisorbed atoms from metal surfaces which the Antoniewicz version of the MGR model cannot deal with. Time evolution of the wave packet shape rather than that of its position is seen as the most important feature of the desorption process. It is shown that wave packet squeezing in three dimensions may affect drastically the angular as well as the kinetic energy distributions of particles desorbing in the direction of the surface normal. Several examples of the wave packet spreading/squeezing scenarios, invoked recently by other researchers in the context of rotational distributions of desorbing molecules, are also briefly discussed. © 1995.