Threshold photoelectron spectroscopy on inner-valence ionic states of NO

The N O+ states lying in the ionization region of 20-40 eV have been investigated by high-resolution threshold photoelectron spectroscopy and a configuration interaction calculation. Substantial agreement between the structures on the present experimental and theoretical spectra in the 21-27 eV range enables us to assign the relevant inner-valence ionic states unambiguously. The dissociation products from the ion states are measured with threshold photoelectron-photoion coincidence spectroscopy, and the dissociation processes are discussed with reference to the potential energy curves calculated. Sharp peaks are observed in the ionization region of 27.5-35 eV, which are allocated to ionic Rydberg states converging to N O2+.