Molecular Cluster Calculations for the Analysis of Laser Induced Emission of Electrons and Ions from the (111) Surface of BaF2

Abstract

The subject of this presentation is to show how molecular cluster calculations can lead to a deeper understanding of laser induced processes at surfaces of ionic crystals. Molecular cluster calculations were performed for bulk BaF2 and for different clusters modelling the (111) surface of BaF2. The effect of the surrounding crystal ions have been included by an embedding crystal potential. Calculations for a stoichiometric surface give an electronic structure similar to the bulk, while calculations for a local non-stoichiometric surface show the existence of occupied surface states in the upper half of the bandgap, followed by unoccupied states extending above the ionization limit. These calculations give a qualitative understanding of the experimentally observed resonantly enhanced multiphoton processes of electron and ion emission from the (111) surface of BaF2.