Vibrational Enhancement of the Charge Transfer Reaction Rate of N2+(v=0-4) with Kr at Thermal Energies

Published

October 12, 2021

Author(s)

S Kato, J A. de Gouw, C D. Lin, V M. Bierbaum, S R. Leone

Abstract

The charge transfer reaction of N₂⁺(v=0-4) + KR->N₂ + Kr⁺ is studied at thermal energy as a function of vibrational excitation in the reactant ion. A selected-ion flow tube technique coupled with laser-induced fluorescence detection is used to measure the vibrationally specific rate constants. A dramatic vibrational enhancement is observed; measured rate constants are 1.0 ( O.6) x 10-¹², 2.8 ( O.3) x 10^-12, 2.1 ( O.2) x 10^-11, 5.1 ( O.2) x 10^-11 and 8.3 ( O.4) x 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, N₂⁺(v) + Kr->N₂⁺(v'2(v'=O) + Kr⁺(²P₁) 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 (< <1 eV). The model assumes that only the most enerL7v-resonant exothermic transitions, N₂⁺(v) + Kr->N₂(v+3) + Kr⁺ (-P₁), occur within the duration of the ion-molecule collision complex and that the charge transfer takes place at probabilities governed by the corresponding Franck-Condon factors. However, the Franck-Condon factors are modified by a trial displacement of 0.02 A to accountfor the changes in vibrational wave functions of N₂⁺ and N₂ during a close approach of the (N₂-Kr)⁺ pair; this method gives an excellent description of the experimental results.

Citation

Journal of Chemical Physics

Pub Type

Journals

Keywords

charge transfer, ion-molecule reaction, krpton, laser fluorescence, nitrogen

Citation

Kato, S. , de Gouw, J. , Lin, C. , Bierbaum, V. and Leone, S. (2021), Vibrational Enhancement of the Charge Transfer Reaction Rate of N₂⁺(v=0-4) with Kr at Thermal Energies, Journal of Chemical Physics (Accessed April 18, 2024)