X˜2A′/Ã2A′ conical intersection effects on the fluorescence of NO2

 We have analyzed the effect of the X˜2A′/Ã2A′ conical intersection between the first two electronic surfaces of NO2 on the fluorescence of the molecule. Our computations are based on diabatic potentials obtained by a transformation of ab initio adiabatic potentials. We have computed time- and frequency-resolved fluorescence spectra from stationary and nonstationary states, showing the effects of the conical intersection, which slows down the fluorescence, shifts the emitted frequencies, redistributes the intensities, and increases the density of the lines. Furthermore, we have explained the low fluorescence yield observed by Dulcey et al. after optical excitation.