Evidence for the formation of N-*(1D) ions in ion-surface collisions

Slow N+, N2+, NO+ and N2O+ 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 N-* (1D) is formed in a two-step capture process: in the first step neutral nitrogen atoms are formed in excited multiplet states of the N 2p3 configuration. In the second step an additional surface electron is attached to the excited parent neutral atoms. The excitation energy of N-* (1D) with respect to the nitrogen ground state would be 1.4 eV; its lifetime must be shorter than 200 ns. (author)