A study of nitrogen dioxide (22B2) photodecomposition to O(1D) and NO(2Π) in its second predissociation region 2500−2139 Å

Publisher Website
Google Scholar
Abstract
A photochemical decomposition study of NO2(22B2) from specified vibronic states is reported. The yields of excited oxygen atoms O(1D), below and abovce the 2440 Å dissociation limit (40973 cm−1), were measured in the presence of neopentane through the C−H insertion product neopentyl alcohol. The sharp onset of O(1D) formation below 2450 Å suggests a change in the predissociation mechanism probably involving a vibrational energy redistribution mechanism at energies above this limit. Vibrational mode specificty is vibrational energy redistribution mechanism at energies above this limit. Vibrational mode specificity is examined, and the asymmetric stretch vibration (ν3′) is considered important in the O(1D) formation. It is apparent from the O(1D) quantum yield of 0.5±0.1 at high energies that the formation of O(3P) products is equally competitive. The electronic symmetry correlations of various NO2 species with different possible dissociation products are clarified. The assistance of the ground state rotationl energy is affecting the predissociation by supplementing tyhe photon energy is less apparent with the 22B2 state than at the lower 3979 Å predissociation limit [E.K.C. Lee and W. M. Uselman, Faraday Discuss. Chem. Soc. 53, 125, (1972)] due to the larger rotational barriers resulting from the shallower potential well depth of the 22B2 state.