Angular and energy distributions of D2 molecules desorbing from sulfur and oxygen modified V(111) surfaces

The energy and angular distribution of deuterium molecules desorbing from a vanadium (111) surface modified either by oxygen or by sulfur has been studied, using time-of-flight spectroscopy. It has been shown that the desorption flux contains two contributions, a thermal and a hyperthermal contribution. The mean translational energy of the hyperthermal part can be described by [E]=8.3.kT(s) and 5.8.kT(s) for the sulfur and oxygen covered V(111) surface, respectively. Interestingly, the mean translational energy of the hyperthermal contribution is independent of the desorption angle. The angular distribution of the hyperthermal desorption flux is forward focused and can be described by cos(3.3) theta and cos(4.3) theta functions for the sulfur and oxygen modified surface, respectively. From the angular flux distribution and the angle independent mean translational energy of the hyperthermal contribution one can conclude that normal energy scaling does not exist for this adsorption/desorption channel. This is mainly due to the strong geometric corrugation of the modified V(111) surfaces. (C) 2002 American Institute of Physics.