An experimental study of the valence shell photoelectron spectrum of the NO2 molecule Original Research Article

The complete valence shell photoelectron spectrum of the NO2 molecule has been studied in the binding energy range between 10 and 50 eV. HeI and HeII resonance radiation as well as monochromated synchrotron radiation have been used for the ionisation. Assignments have been made for most of the photoelectron bands by comparison with previous theoretical predictions. Photoelectron angular distributions and branching ratios for the bands associated with the outer valence shell have been determined for photon energies between 18 and 120 eV. The HeI and HeII excited spectra have allowed detailed studies to be made of the vibrational fine structure. For the X 1Σ+g ground ionic state, close lying vibrational lines associated with combined excitations of the symmetric ν1 and the bending ν2 modes have been observed for the first time. Excitation of the asymmetric stretch ν3 mode, in one quantum, is found in the A 1A2 photoelectron band, and its presence is explained in terms of vibronic coupling.