ELECTRONS FROM INTRAATOMIC AND INTERATOMIC AUGER PROCESSES IN LOW-ENERGY GRAZING COLLISIONS OF H+ AND H-2(+) WITH W(110) PARTIALLY COVERED BY ALKALI ATOMS

Electron energy spectra from slow H+ and H-2+ ions (below 100 eV, typically) colliding under grazing incidence with W(110) surfaces are reported. The surface work function was varied by the exposure to alkali (Li, Na, Cs) atoms. The electron emission spectra can be interpreted in terms of various inter- and intra-atomic Auger processes: for clean W(110) Auger capture involving two electrons of the surface dominates both for H+ and H-2+ collisions. For sufficiently large coverages by alkali atoms resonant capture of one or two surface electrons leads to the formation of excited states of the neutralized projectile and to the formation of core excited states with two electrons occupying outer-shell orbitals (H-(2121') and possibly H-2- (1s2l2l')), respectively. These states manifest themselves by their decay via Auger deexcitation and, in particular, by autodetachment. For H-2+ projectiles the implications of these electronic processes for the molecular survival probability are discussed.