SPUTTERED PROTONS DURING SURFACE-INDUCED DISSOCIATION (SID) TANDEM MASS-SPECTROMETRY (MS MS)/

A new tandem mass spectrometer has been constructed for the study of i on/surface interactions and the study of surface induced dissociation processes. During the development and initial testing of this new inst rument, experiments have been carried out using a stainless steel surf ace under high vacuum(10(-7)-10(-8) Torr) conditions where hydrocarbon s (pump oil) would be expected to be adsorbed onto the surface. A surp rising result of these experiments has been the observation of sputter ed protons. The yield of sputtered protons remains relatively constant with varying incident ion kinetic energy (over the 20-100 eV range) a nd appears to have little or no dependence on momentum transfer from t he incident ions. These findings provide direct evidence (via observat ion of an excess of the charged intermediate protons) for a charge exc hange mechanism for associative ion/surface reactions involving proton ation. However, the yield of protonated products (protonated pyridazin e ions) due to associative ion/surface reactions is dependent on incid ent ion kinetic energy. These results suggest that the protonation of pyridazine may depend on interaction times at the surface which, in tu rn, depend on the depth of penetration of the incident species into th e hydrocarbon overlayer. In addition, the observation of sputtered pro tons as the likely intermediates to associative ion/surface protonatio n reactions may have implications for the proposed mechanisms of ion/s urface reactions where alkylation of incident ions occurs.