Emission of Negative Ions from Metal Surfaces Bombarded by Positive Cesium Ions

Abstract

High yields (>1%) of negative metal ions, usually including clusters of metal atoms and oxides, have been observed from targets of Cu, Ag, Au, Be, Cd, Al, Sn, Ta, W, and Ni bombarded by a beam of positive cesium ions. The increase observed in the negative-ion yields when an auxiliary beam of neutral cesium was directed at a copper target indicates that the presence of cesium on the target was an important factor in the production of large numbers of negative ions. From targets of aluminum and tin, respectively, the Al2− and Sn2− yields were an order of magnitude greater than the corresponding single-atom yields.