Dynamics of desorption induced by electronic transitions: Desorption of neutrals from physisorbed layers

The dynamical theory of desorption from physisorbed layers irradiated by electrons or photons is presented. The basic steps of the microscopic mechanism are: ionization to a more strongly bound state, acceleration towards the surface, reneutralization, and finally, desorption. Desorption yields and the kinetic energy distributions of desorbing neutrals obtained in the classical and in the fully quantum-mechanical approach are numerically compared. Comparison with the existing experimental data is also made. Next, the classical trajectory approximation is applied to study the metal — adsorbate charge transfer process. The neutralization rate obtained is compared with the one following from the conventional perturbation theory. Viene presentata la teoria dinamica di desorbimento da strati fisisorbiti irraggiati da elettroni o fotoni. Le fasi basilari del meccanismo microscopico sono: ionizzazione ad uno stato più fortemente legato, accelerazione verso la superficie, rineutralizzazione ed infine, desorbimento. Vengono confrontati numericamente i rendimenti di desorbimento e le distribuzioni di energia cinetica delle specie neutre desorbite, ottenute nello schema classico e in quello totalmente quanto-mccanico. Si confrontano inoltre i dati sperimentali esistenti.