Dissociative double photoionization of N2 using synchrotron radiation: appearance energy of the N2+ dication.
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 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 N2+(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 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 N(2)2+ 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.
Franceschi
Pietro
P
Dipartimento di Fisica, Università di Trento, via Sommarive 14, 38050 Povo (TN), Italy. pfranc@science.unitn.it
Ascenzi
Daniela
D
Tosi
Paolo
P
Thissen
Roland
R
Zabka
Ján
J
Roithová
Jana
J
Ricketts
Claire L
CL
De Simone
Monica
M
Coreno
Marcello
M