Ionization processes in ground-state alkali-noble gas collisions. I Na-Ne

Abstract

The authors report the results of an experimental study of ionization processes in collisions between fast sodium atoms and thermal neon atoms in a crossed-beam experiment (250, 289 and 392 eV laboratory collision energies). Energy loss spectra of scattered ions at selected scattering angles as well as differential cross sections for some specific ionization channels have been measured. Observed structures in the energy loss spectra are ascribed to scattered Na+ ions and recoiled Ne+ ions. The results are interpreted qualitatively using a molecular orbital (MO) correlation diagram. Most of the Ne+ structures are ascribed to ion pair exit channels of the type Na-(*)+Ne+(*) and to autoionization of doubly excited Ne** states. These exit channels arise from a single or double electron promotion along the 4f sigma MO, correlating with 2pNe in the separated atom limit. Na+ production is believed to arise from an L-vacancy-sharing mechanism following a double 4f sigma promotion.