The effect of collision energy in polyatomic ion/neutral target collisions over a range of 10–6000 eV

Abstract

Mass spectra resulting from superthermal collisions between polyatomic ions and atomic or diatomic targets have been acquired as a function of the collision energy over a range of 10–6000 eV for the t-butyl cation and the molecular ions of methane, propane and n-butylbenzene. Changes in relative fragment ion abundances with systematic variation of the collision energy have been monitored in order to assess the effect of this experimental variable on the degree to which the polyatomic ion is excited by collision. The data for the t-butyl cation and the methane molecular ion show an apparent monotonic increase in energy deposition into the ion with increasing collision energy over the entire range investigated. The data for the molecular ions of propane and n-butylbenzene, on the other hand, indicate that maxima in energy deposition into these ions occur at laboratory collision energies of 140 and 70 eV, respectively. The results are interpreted as being due to changes in the relative importance of direct vibrational excitation and electronic excitation with increasing collision energy.