title: Reactions of Th(+) + H2, D2, and HD Studied by Guided Ion Beam Tandem Mass Spectrometry and Quantum Chemical Calculations.
abstract: 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 (3)Δ1 ground level with a low-lying (1)Σ(+) excited state. Theory also provides the reaction potential energy surfaces and BDEs that are in reasonable agreement with experiment.
authors.affiliation: Department of Chemistry, University of Utah , Salt Lake City, Utah 84112-0850 United States.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Cox
authors.affiliation: Department of Chemistry, University of Utah , Salt Lake City, Utah 84112-0850 United States.
authors.forename: P B
authors.initials: PB
authors.lastname: Armentrout
authors.affiliation: Lawrence Berkeley National Laboratory , One Cyclotron Road, Berkeley, California 94720, United States.
authors.forename: Wibe A
authors.initials: WA
authors.lastname: de Jong