Emission of Non-Metallic Ions from a Metal Surface under Heavy-Ion Bombardment

Abstract

At the GSI in Darmstadt/FRG thin foils of Al, Sc, Y and Ta were bombarded with 58Ni, 132Xe and 238U ions having velocities between 0.2 and 1.4 cm ns−1. Secondary ions emerging from the metal surface of these foils were investigated by TOF techniques under UHV conditions. Apart from metal ions also ions of a few impurities were observed being residues of an ion-etching-cleaning procedure. Comparing ion yields as function of projectile velocity and also shapes of mass lines, the emission of metal ions is obviously induced by atomic collision cascades and that of impurity ions by processes related to electronic excitation. Therefore, ion emission related to electronic energy loss is not restricted to dielectric material as has been concluded from earlier experiments.