The ionndash;molecule reactions characteristic of SiH4ndash;D2mixtures have been elucidated and the reaction cross sections measured as a function of relative kinetic energy. D2+reacts with SiH4to yield SiH3+, SiH2+, SiH+, and Si+by exothermic processes that proceed with a total cross section near the Langevin orbiting value. D3+reacts with SiH4to form only SiH3+with a cross section also near the Langevin value. The absence of SiH2D+suggests direct Hminus;transfer from SiH4rather than the intermediate formation of SiH4D+. All reactions of Sihyphen;containing ions in their ground states with D2are 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 D2to 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.
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