Photoionization cross sections for the production of the doubly charged ion N2+ from N2 have been measured by means of synchrotron radiation in the photon energy range from 50to110eV. The appearance energy for N2+ has been determined as 55.2±0.2eV, i.e., about 1.3eV higher than the spectroscopic dissociation limit leading to the charge asymmetric dissociation channel N2+(P2)+N(S4) at 53.9eV. The onset of a second threshold at 59.9±0.2eV is detected and the energy dependence of photoion intensities near the threshold regions is interpreted in terms of the Wannier theory. The production of the N2+ dication is discussed in terms of direct and indirect mechanisms for dissociative charge asymmetric photoionization and by comparison with the potential energy curves of the intermediate N22+ dication. Experimental evidences for the opening of the Coulomb explosion channel N2++N+ at high photon energies are provided by measuring the kinetic energy release spectra of N2+ fragments at selected photon energies.

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