ELECTRON-EMISSION AND IMAGE-CHARGE ACCELERATION FOR THE IMPACT OF VERY HIGHLY-CHARGED IONS

We present total yields for emission of slow (E(e) less-than-or-equal-to 50 eV) electrons due to the impact of slow (v(p) less-than-or-equal-to 5 X 10(5) m/s) highly charged ions [Ar(q+) (q less-than-or-equal-to 18), Xe(q+) (q less-than-or-equal-to 51), and Th(q+) (q less-than-or-equal-to 80)] on clean polycrystalline gold. The highly charged ions were produced in the Lawrence Livermore National Laboratory electron-beam ion trap; electron yields have been derived from the respective measured electron emission statistics. The experimental data support a currently accepted scenario for multicharged ion-induced electron emission, which is largely based on a classical over-barrier model. In particular, we are able to distinguish different processes contributing to the total above-surface electron emission. In addition, an ultimate low-impact-energy limit due to projectile self-acceleration toward the metal surface, as a result of the projectile image charge, has been demonstrated and evaluated.