Dresden 2011 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 5: Collisions, Energy Transfer
MO 5.3: Vortrag
Montag, 14. März 2011, 15:00–15:15, MER 02
Rotational dependence of the proton-transfer reaction HBr+ + CO2 → HOCO+ + Br — •Lisa Paetow, Franziska Unger, Bernd Beutel, and Karl-Michael Weitzel — Philipps-Universität Marburg, Fachbereich Chemie, 35032 Marburg
The effects of reactant ion rotational excitation on the proton-transfer reactions of HBr+ and DBr+ with CO2 were studied in a guided ion beam apparatus. State selected HBr+ (DBr+) ions in the 2Π3/2(v+=0) and the 2Π1/2(v+=0) state were prepared by resonance enhanced multiphoton ionization (REMPI). This process, which results in ions with narrow rotational state distributions, was used to vary the mean rotational energy of the ions from 1 to 66 meV. Cross sections are presented for collision energies Ec.m. in the center of mass system in the range of 0.23 to 1.90 eV. Ab initio calculations were performed to obtain energetic information about reactants, intermediates, and products [1]. For certain values of Ec.m., a comparison between the experimental results for HBr+ and DBr+ indicates that the cross section is dominated by effects of rotational energy rather than angular momentum. While the proton transfer is slightly endothermic for HBr+(2Π3/2), it is exothermic for HBr+(2Π1/2). This allows us to compare the cross sections for an endothermic and an exothermic reaction within the same reaction system [2]. Our results provide information on the relevant bottleneck of the reactions.
[1] L.Paetow, F.Unger, W.Beichel, G.Frenking, K.-M.Weitzel, JCP 132, 174305(2010)
[2] L.Paetow, F.Unger, B.Beutel, K.-M.Weitzel, JCP, in press