Internal and Translational Energies of Molecules Desorbed by Electronic Transitions

Abstract

Atoms and monatomic ions ejected from surfaces following electronic transitions clearly possess translational kinetic energy, and often electronic excitation as well [1]. Several mechanisms have been proposed [2] to describe both how the initial state excitation could arise, and then survive for sufficient time for particle ejection to be a competitive de-excitation channel. These mechanisms are system specific, but all convert an initially bound system into a repulsive neutral, ionized, or excited configuration, the properties of which essentially define the kinetic energy and angular distribution, and electronic excitation of the ejected product. Several successful calculations of the translational energy distributions and angular distributions (or spot patterns) have been reported [3,4] and confirm the belief, derived from experimental evidence, that to first order the observed distributions reflect the initial system bond length and orientation distributions [5].