Charge exchange, surface-induced dissociation and reactions of doubly charged molecular ions SF42+ upon impact on a stainless steel surface:: A comparison with surface-induced dissociation of singly charged SF4+ molecular ions

Collisions of SF42+ and SF4+ ions with hydrocarbon-covered stainless steel surface at room temperature were investigated. The projectile ions were mass selected by a two-sector-field mass spectrometer and decelerated to incident energies of 60 to a few eV. Product ions were measured with the use of a time-of-flight spectrometer and their relative abundances determined as a function of the incident energy of the projectile ions (collision-energy-resolved mass spectra, CERMS curves). The mass spectra of product ions were dominated by fragment ions SF3+, SF2+, and SF+ at incident energies below 40 eV, while sputtering of contaminant adsorbates prevailed at higher energies. The results indicate that the likely major reaction sequence responsible for the observed CERMS curves of product ions from SF42+ collisions is charge exchange to form singly charged projectile ions followed by subsequent unimolecular fragmentation. In chemical reactions between projectile ions and hydrocarbon adsorbates were observed leading addition. to SF2CH3+, SFCH2+, and SCH+ ions. (C) 2008 Elsevier B.V. All rights reserved.