NEUTRALIZATION OF SLOW MULTICHARGED IONS AT A CLEAN GOLD SURFACE - ELECTRON-EMISSION STATISTICS

Emission of slow electrons (E(e) less-than-or-equal-to 60 eV) induced by impact of slow multicharged ions (impact velocity v(p) less-than-or-equal-to 2 X 10(5) m/s) onto an atomically clean, polycrystalline gold surface has been studied both experimentally and by numerical simulation, based on the resulting electron-emission statistics. The projectile ions (N(q+), q=5,6; Ne(q+), q=5-10; Ar(q), q=5-16; Kr(q+), q=5-10; Xe(q+), q=6,8,10; I(q+), q=16,20,23,25) have been extracted from a recoil ion source pumped by the GSI UNILAC heavy-ion accelerator in Darmstadt, Germany. We discuss the shape of the experimentally obtained electron-emission statistics and, by means of numerical simulation based on the classical over-the-barrier model put forward recently by Burgdorfer, Lerner, and Meyer [Phys. Rev. A 44, 5674 (199 1)], identify the various processes contributing to the ''above-surface'' electron emission, i.e., taking place until projectile impact on the surface. In particular, for impact of slow (E greater-than-or-equal-to 50 eV) Ar12+ we show that most of the emitted electrons have energies below 50 eV, with the above-surface-produced fast Auger electrons being a small minority of less than 1%.