Charge exchange processes which occur in collisions either between atoms and a surface or between atoms and molecular ions have been extensively studied since they act as precursors of any chemical reactions. The first studies in the field of atom-surface interaction were initiated by Taylor and Langmuir in 1933 for cesium adsorption on tungsten. As the ionization potential of cesium is less than the work function of tungsten, cesium atom transfers its electron to tungsten leading to positive ion which interacts with the metal through image potential . More recently charge transfer in scattering atoms, molecules or ions from surface have been the subject of numerous theoretical and experimental studies for surface analysis and for local probe. The general approach in describing charge transfer in scattering atoms from a metal surface assumes that the metal electrons are free electrons in a potential box and that the atom is a one-electron hydrogen like atom. When the atom is brought close to the metal surface the originally sharp valence level shifts and broadens into a band of finite width making resonant electron tunneling through the potential barrier between the atom and the metal possible [2,3]. However if the atomic level still stay off resonance from the fermi level of the metal surface, an increase of incident velocity parallel to the surface can shift the fermi sphere into resonance with the atomic state as clearly illustrated in . The influence of the velocity component of the colliding particle parallel to the surface is already known for a long time in atomic collisions, where one studies electron transfer during the collision as a function of relative velocity between the two particles.
KeywordsCharge Exchange Collisional Induce Dissociation Heterogeneous Cluster Neutral Product Cesium Vapor
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