Evidence for the formation of ions in ion - surface collisions

Abstract

Slow and ions are scattered from partially caesiated W(110) surfaces under grazing incidence. The collision-induced emission of electrons (due to inter- and intra-atomic Auger processes) is studied. We provide evidence that the metastable negative nitrogen ion state is formed in a two-step capture process: in the first step neutral nitrogen atoms are formed in excited multiplet states of the configuration. In the second step an additional surface electron is attached to the excited parent neutral atoms. The excitation energy of with respect to the nitrogen neutral ground state would be 1.4 eV; its lifetime must be shorter than 200 ns.