FORMATION OF THE NITROGEN SHAPE RESONANCE IN N-2(-2(ASTERISK) (A(3)SIGMA(+)(U)) COLLISIONS WITH METALLIC SURFACES() AND N)

Electron energy spectra from collisions of slow (50 eV) N-2(+) ions an d thermal N-2(A(3) Sigma(u)(+)) molecules with W(110) surfaces are re ported. The surface work function was varied by exposure to alkali ato ms. From the comparison of the respective spectra it is concluded that an appreciable part of the electron emission is due to the fast autod etachment of N-2(-)(X-2 Pi(g)) temporary negative ions. N-2(-)(X-2 Pi( g)) is formed through the resonant capture of a surface electron by ex cited A(3) Sigma(u)(+) molecules (for N-2 collisions), and by B-3 Pi( g) and a(1) Pi(g) (for N-2(+) collisions). The results suggest that th is sequence of processes leads to fast (within about 5 x 10(-15) s) an d efficient neutralization of N-2(+) ions into the nitrogen X-1 Sigma( g)(+) ground state at metal surfaces. Some consequences of this fast c onversion process are discussed. (C) 1998 Elsevier Science B.V.