Ion–molecule reactions in SiH4–D2 mixtures

Abstract

The ion–molecule reactions characteristic of SiH4–D2 mixtures have been elucidated and the reaction cross sections measured as a function of relative kinetic energy. D2+ reacts with SiH4 to yield SiH3+, SiH2+, SiH+, and Si+ by exothermic processes that proceed with a total cross section near the Langevin orbiting value. D3+ reacts with SiH4 to form only SiH3+ with a cross section also near the Langevin value. The absence of SiH2D+ suggests direct H− transfer from SiH4 rather than the intermediate formation of SiH4D+. All reactions of Si-containing ions in their ground states with D2 are endothermic. Energy thresholds for the deuterium atom pickup reactions of Si+ and SiH2+ yield thermochemical results in satisfactory agreement with values obtained by other methods. SiH3+ reacts with D2 to form SiH2D+ solely, a result indicating that only HD is eliminated from an SiH3D2+ intermediate and showing the nonequivalence of D and H in the silanium ion.