Dissociative double photoionization of N2 using synchrotron radiation: Appearance energy of the N2+ dication

Bibliographic citation D. Ascenzi, P. Franceschi, P. Tosi, R. Thissen, J. Zabka, J. Roithova, C.L. Ricketts, M. De Simone, M. Coreno, "Dissociative double photoionization of N2 using synchrotron radiation: Appearance energy of the N2+ dication" in THE JOURNAL OF CHEMICAL PHYSICS, v. 126, n. 13 (2007), p. 134310-1-134310-9. - DOI: 10.1063/1.2714521

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Abstract: Photoionization cross sections for the production of the doubly charged ion N++ from N2 have been measured by means of synchrotron radiation in the photon energy range from 50 to 110 eV. The appearance energy for N2+ has been determined as 55.2±0.2 eV, i.e., about 1.3 eV higher than the spectroscopic dissociation limit leading to the charge asymmetric dissociation channel N++(2P) +N(4S) at 53.9 eV. The onset of a second threshold at 59.9±0.2 eV 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 N++ 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 N2++ dication. Experimental evidences for the opening of the Coulomb explosion channel N++ plus N+ at high photon energies are provided by measuring the kinetic energy release spectra of N++ fragments at selected photon energies.