Electronic excitation effects on secondary ion emission in highly charged ion-solid interaction

In order to investigate the secondary ion emission from the surface of conductive materials bombarded by highly charged heavy ions, we have done two types of experiments. First, we have measured the yield of the sputtered ions from the surface of solid targets of conductive materials (Al, Si, Ni, Cu) bombarded by Xeq+ (q=15-44) at 300 keV (vp=0.30 a.u) and at 1.0 MeV (vp=0.54 a.u). In view of the secondary ion yields as a function of the potential energy of the projectile, the increase rates below q=35, where the potential energy amounts to 25.5 keV, were rather moderate and showed a prominent increase above q=35. These phenomena were rather strong in the case of the metal targets. Second, we have measured the energy dependence of the yield of the sputtered ions from the surface of solid targets of conductive materials (C, Al) bombarded by Xeq+ (q=30,36,44) between 76 keV (vp=0.15 a.u) and 6.0 MeV (vp=1.3 a.u). A broad enhancement of the secondary ion yield has been found for Al target bombarded by Xe44+. From these experimental results, the electronic excitation effects in conductive materials for impact of slow highly charged heavy ions bearing high potential energy is discussed