Anomalous signal formation in secondary ion mass spectrometry of palladium

Cesium ions bombarding a high-purity palladium (Pd) target are shown to spu tter out negative ions incompatible with stable isotopes of Pd. These unusu al ions possess a mass of(Pd + 1), and they may possibly arise from the Pd- H reaction occurring in the ion-bombarded area. It is also shown that dimer s of Pd are emitted exclusively as negative ions, with positive dimers virt ually undetectable. The process whereby the dimer emission occurs in such a selective manner is still unclear. (Int J Mass Spectrom 189 (1999) 173-179 ) (C) 1999 Elsevier Science B.V.