Experimental and theoretical studies of the doubly charged NO/sup 2+/2 ion

Six features observed in the energy distribution of H- ions arising from the single collision double charge transfer of 3--5 keV protons on nitrogen dioxide are interpreted as vertical double ionization energies of NO2 of 35.1, 38.1, 39.5, 41.0, 43.2, and 46.8 eV to form doublet states. Theoretical energies of the first 13 doublet and quartet electronic states of NO/sup 2+/2 have been calculated by the ab initio CIPSI method at a fixed N--O distance and for several O--N--O bending angles. Thresholds and kinetic energy releases observed in dissociative double photoionization of NO2 are interpreted by comparison with the calculations and charge transfer results. The N- and O-Auger spectra of NO2 have been recorded and some of the 40 features observed have been assigned, confirming and improving the spectrum of NO/sup 2+/2