ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The charge transfer reaction of N+2(v=0–4)+Kr→N2+Kr+ is studied at thermal energy as a function of vibrational excitation in the reactant ion. The selected-ion flow tube technique coupled with laser-induced fluorescence detection is used to measure the vibrationally state specific rate constants. A dramatic vibrational enhancement is observed; measured rate constants are 1.0 (±0.6)×10−12, 2.8 (±0.3)×10−12, 2.1 (±0.2)×10−11, 5.1 (±0.2)×10−11, and 8.3 (±0.4)×10−11 cm3 molecule−1 s−1 for v=0, 1, 2, 3 and 4, respectively. Mass spectrometric kinetics experiments are also performed to confirm that vibrational relaxation, N+2(v)+Kr→N+2(v′〈v)+Kr, is a negligible process. The charge transfer for v=0 is extremely slow in spite of the large exothermicity (e.g., 0.915 eV for the production of N2(v′=0)+Kr+(2P1/2) states), yet the reaction is enhanced when the apparent energy mismatch is greater for the vibrationally excited reactant. A simple model is proposed to explain the experimental results at thermal energies ((very-much-less-than)1 eV). The model assumes that only the most energy-resonant exothermic transitions, N+2(v)+Kr→N2(v+3)+Kr+(2P1/2), occur within the duration of the ion–molecule collision complex and that the charge transfer takes place with probabilities governed by the corresponding Franck–Condon factors. However, the Franck–Condon factors are modified by a trial displacement of 0.02 A(ring) to account for the changes in vibrational wave functions of N+2 and N2 during a close approach of the (N2–Kr)+ pair; this method gives an excellent description of the experimental results. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.472386
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