Transient negative ions in the Spectroscopy and dynamics of molecules on surfaces: orientational effects

Abstract

We discuss the role of short-lived molecular negative ions in a variety of surface spectroscopies and dynamical processes occurring on surfaces. Results obtained from electron scattering experiments with physisorbed O 2 and CO monolayers on graphite show the important role of molecular orientation in the cross-section for creating a transient negative ion. In the case of O 2, two different negative ions states with orthogonal symmetries can be selectively populated by orienting the molecule in two different alignments on the graphite surface. Distinctive, anisotropic cross-sections are also seen in the case of CO. The implications of these spectroscopic results for the dynamical processes are addressed.