Some remarks on the photodynamics of NO2

We review the literature concerning the electronic structure and spectroscopy of nitrogen dioxide for excitation energies up to 20 eV. Our aim is not to be exhaustive but rather to summarize important results and observations which we have found useful in the interpretation of recent experiments in both the frequency and time domain in which competing and often multiphoton excitation paths access high lying Rydberg and valence states. The photodynamics in NO2 are particularly fascinating and complicated by numerous non-adiabatic couplings between the various electronic states which, despite the molecule’s apparent simplicity as a triatomic species, leads to a very rich photochemistry that exemplifies many features occurring in the photochemistry of much larger molecules.