Showing papers by "P. B. Armentrout published in 1985"

Translational energy dependence of Ar++XY→ArX++Y (XY=H2,D2,HD) from thermal to 30 eV c.m.

Abstract: Cross sections for the reactions of Ar+ with H2, D2, and HD to form ArH+ and ArD+ are measured using a new guided ion beam tandem mass spectrometer which affords an experimental energy range from 0.05 to 500 eV laboratory. The apparatus and experimental techniques are described in detail. Cross sections for H2 and D2 are found to be nearly identical over this entire energy range when compared at the same barycentric energy. The total HD cross section is the same as H2 and D2 at low energies, but differs significantly above 4 eV c.m., where product dissociation becomes important. The intramolecular isotope effect for reaction with HD exhibits a reversal at low energy, favoring the deuteride product below ∼0.14 eV c.m., and surprising nonmonotonic behavior at energies above 5 eV c.m. In all these systems, a new feature at higher energies is observed. This is interpreted as the onset of a product channel having an energy barrier of 8±1 eV. The room temperature rate constant derived from the data for the reac...

Effect of kinetic and electronic energy on the reaction of V+ with H2, HD, and D2

Abstract: Guided ion beam mass spectrometry has been used to examine the kinetic energy dependence of the reactions of vanadium ions with H/sub 2/, D/sub 2/ and HD. Results for a number of electronic states of V/sup +/ are obtained and show remarkably different behavior. While kinetic energy and electronic energy display no striking differences in their ability to promote reaction, different electronic states (corresponding to different electron configurations) are found to react by different mechanisms. An analysis of this behavior is used to infer a detailed picture of the dynamics of the reactions and a general view of how transition metals interact with molecular hydrogen. Analysis of the threshold behavior of these reactions is used to deduce the VH/sup +/ bond energy of 2.05 +/- 0.06 eV (47.3 +/- 1.4 kcal/mol). This assumes reaction occurs with no activation barrier. 54 references, 8 figures, 3 tables.