Structure and predissociation dynamics of electronically excited nitrogen dioxide: A resonance Raman study

Abstract

Resonance Raman spectra of NO2 have been recorded as a function of excitation frequency in the range 0–8000 cm− 1 above the predissociation threshold. These spectra are interpreted using the time‐dependent formulation of resonant Raman scattering, to elucidate the shape of the excited electronic statepotential energy surface, and the dynamics which occur on it immediately following photoexcitation. Our results show that the dominant optical transition in this spectral range is 2 B 2–2 A 1. Our Raman spectra reveal a marked decrease in the dynamical time scale of the predissociation of the 2 B 2 state as excitation frequency increases. At excitation frequencies approximately 4850 cm− 1 above the dissociation threshold, the 2 B 2 predissociative lifetime becomes comparable to a vibrational period. We have analyzed the resonance Raman spectra, along with the absorptionspectrum, to determine the magnitudes of the slopes of the potential surface along the symmetric stretch and bending normal coordinates for the 2 B 2excited state in the Frank–Condon region.