Transfer of electronic excitation in collisions of metastable argon atoms with nitrogen molecules

Abstract

Measurements have been made of the product vibrational and rotational state distributions for the process Ar^*(³P_2,0)+N₂(X) →Ar(¹S₀)+N₂^*(C,³Π_u) by spectrometric observation of the C→B fluorescence at the intersection of supersonic beams of the reactant species over the relative kinetic energy range 0.06–0.41 eV. The results are compared with the predictions of a ’’golden rule’’ model which gives the transition probabilities in the highly impulsive limit as the product of Franck–Condon and density of states factors. Below 0.17 eV, the model fits the experimentally determined v′=0/v′=1 population ratio reasonably well. At higher energies the experimental ratio rises, however, and reaches a maximum at 0.3 eV. A statistical population of rotational levels for v′=0 corresponding to rotational temperatures of 1300 °K and 1100 °K at 0.161 and 0.089 eV relative energy, respectively, is observed, while the ’’golden rule’’ predicts considerably higher rotational excitation in each case.