Excitation transfer into bound and continuum states investigated by optical and electron spectroscopy

Abstract

We have investigated the reaction of metastable helium He(2¹ S, 2³ S) with the homogeneous halogens Br₂ and I₂ and with the heterogeneous molecules ICl and IBr. Further, we have taken fluorescence spectra from these reactions. For reasons of comparison, we have taken the same set of data with HeI photons as projectiles. This rather complete set of data reveals several general trends concerning the reaction of metastable helium atoms with halogen molecules. One result consists in very direct support for the previously published statement that the process of Penning ionization is very stereospecific with respect to the involved target orbital. Further, we find interesting hints as for the dynamics of the reaction which proceeds via formation of an intermediate ion-pair channel.