EVIDENCE FOR THE FORMATION OF N--ASTERISK(D-1) IONS IN ION-SURFACE COLLISIONS

Slow N+, N-2(+), NO+ and N2O+ ions are scattered from partially caesia ted W(110) surfaces under grazing incidence. The collision-induced emi ssion of electrons (due to inter- and intra-atomic Auger processes) is studied. We provide evidence that the metastable negative nitrogen io n state N-(D-1) is formed in a two-step capture process: in the first step neutral nitrogen atoms are formed in excited multiplet states of the N 2p(3) configuration. In the second step an additional surface e lectron is attached to the excited parent neutral atoms. The excitatio n energy of N-(D-1) with respect to the nitrogen neutral ground state would be 1.4 eV; its lifetime must be shorter than 200 ns.