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Reactions of Th+ + H2, D2, and HD Studied by Guided Ion Beam Tandem Mass Spectrometry and Quantum Chemical Calculations

  • Author(s): Cox, RM
  • Armentrout, PB
  • De Jong, WA
  • et al.
Abstract

© 2015 American Chemical Society. Kinetic energy dependent reactions of Th+ with H2, D2, and HD were studied using a guided ion beam tandem mass spectrometer. Formation of ThH+ and ThD+ is endothermic in all cases with similar thresholds. Branching ratio results for the reaction with HD indicate that Th+ reacts via a statistical mechanism, similar to Hf+. The kinetic energy dependent cross sections for formation of ThH+ and ThD+ were evaluated to determine a 0 K bond dissociation energy (BDE) of D0(Th+-H) = 2.45 ± 0.07 eV. This value is in good agreement with a previous result obtained from analysis of the Th+ + CH4 reaction. D0(Th+-H) is observed to be larger than its transition metal congeners, TiH+, ZrH+, and HfH+, believed to be a result of lanthanide contraction. The reactions with H2 were also explored using quantum chemical calculations that include a semiempirical estimation and explicit calculation of spin-orbit contributions. These calculations agree nicely and indicate that ThH+ most likely has a 3Δ1 ground level with a low-lying 1Σ+ excited state. Theory also provides the reaction potential energy surfaces and BDEs that are in reasonable agreement with experiment.

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