NEAR-THRESHOLD ELECTRON-EMISSION FROM IMPACT OF SLOW VAN-DER-WAALS CLUSTERS AND FULLERENE IONS ON CLEAN GOLD

Atomically clean polycrystalline gold has been bombarded by slow clust er ions (N2)n+ (n less-than-or-equal-to 120), Ne(n)+ (n less-than-or-e qual-to 100), and C-60,70q+ (q = 1-4) at kinetic energies from the app arent, electron emission thresholds up to 6 kV times the cluster charg e (qe). The resulting electron yields have been derived from the corre sponding electron emission statistics. Grossly different electron yiel ds were found for different cluster species of about equal masses and velocities, which is attributed to different partitions of the initial cluster kinetic energy among (a) inelastic binary collision processes involving cluster constituents and surface atoms, and (b) intramolecu lar vibrational excitation in the cluster ions (where possible). We fo und emission threshold velocities of approximately 1 X 10(4) m/s, whic h is a lower velocity than where emission was observed in most other s tudies previously conducted. For (N2)n+ cluster ions, clear evidence f or a nonlinear behavior (i.e., increasing electron emission per cluste r constituent with increasing cluster size) has been found.