SLOW-ELECTRON EMISSION FROM SLOW HOLLOW ATOMS PRODUCED NEAR A CLEAN METAL-SURFACE

Statistics of electron emission have been measured for bombardment of a clean polycrystalline gold surface by slow (impact velocities 1- 15 X 10(4) m/s) highly charged recoil ions N(q+) (q less-than-or-equal-to 6), Ne(q+) (q less-than-or-equal-to 10), Ar(q+) (q less-than-or-equal-to 16), Kr(q+) (q less-than-or-equal-to 10) and I(q+) (q less-than-or-equal-to 25) produced with the GSI UNILAC heavy ion accelerator, from which precise absolute total electron yields have been derived. As an example, with 150 eV I25+ a total electron yield of 70 with about 1% probability for emission of greater-than-or-equal-to 85 electrons/ion was observed. A semi-classical over-barrier approach recently introduced by Burgdorfer et al. 1991 has been further extended and successfully applied for modelling the impact-velocity dependences of measured total electron yields. In this way, new insights could be achieved on the neutralization and electron emission taking place during conversion of slow multicharged ions into hollow atoms and their subsequent rapid de-excitation in front of a metal surface.