Neutralization of slow multicharged ions at a clean gold surface: Total electron yields.

Abstract

Total slow-electron (${\mathit{E}}_{\mathit{e}}$\ensuremath{\le}60 eV) yields as derived from measured electron-emission statistics are presented for impact of various slow (${\mathit{v}}_{\mathit{p}}$\ensuremath{\le}${10}^{5}$ m/s) multicharged ions (${\mathrm{N}}^{5+}$,${\mathrm{N}}^{6+}$,${\mathrm{Ne}}^{5+}$--${\mathrm{Ne}}^{10+}$, ${\mathrm{Ar}}^{5+}$--${\mathrm{Ar}}^{16+}$, ${\mathrm{Kr}}^{5+}$--${\mathrm{Kr}}^{10+}$, ${\mathrm{Xe}}^{6+}$,${\mathrm{Xe}}^{8+}$,${\mathrm{Xe}}^{10+}$, and ${\mathrm{I}}^{16+}$,${\mathrm{I}}^{20+}$,${\mathrm{I}}^{23+}$,${\mathrm{I}}^{25+}$) on atomically clean polycrystalline gold. The experimental data can successfully be modeled by classical over-barrier-type calculations, in which way three different electron-emission processes have been identified, i.e., autoionization of the transiently neutralized projectile (``hollow atom'') on its approach toward the surface, promotion into vacuum of electrons captured by the projectile, and ``peeling off'' of electrons remaining bound in highly excited states until projectile impact on the surface. The relative importance of these three processes depends strongly both on projectile species and impact velocity.