Kinetic energy release distributions in the Coulomb explosion ofN2molecules induced by fast, highly-charged-ion impact

Abstract

The dissociation of molecular ions $({\mathrm{N}}_{2}{)}^{q+}$ produced by 4.7 MeV/amu ${\mathrm{Bi}}^{57+,25+}$ and 5.9 MeV/amu ${\mathrm{Xe}}^{43+,18+}$ ion impact on ${\mathrm{N}}_{2}$ has been studied using the coincidence technique with a position- and time-sensitive multiparticle detector. The kinetic energy release distributions for all observed ion pairs ${\mathrm{N}}^{{q}_{1}+}+{\mathrm{N}}^{{q}_{2}+}$ are measured. Analysis of the distributions is made with emphasis on the highly charged-molecular ions, $q>3.$ In these cases the most probable total kinetic energy of the two fragments is quite well described by the Coulomb explosion model for point charges, while the measured width of the distributions is much larger than that predicted by this simplified model. We therefore suggest a more elaborate model of Coulomb fragmentation based on a statistical description of the individual potential energy curves of the molecular ion. This enables us to describe both the position and the width of the kinetic energy release distributions. We suggest that the main cause of the large width of the distributions for the high q values is the spread of the potential energy curves at the equilibrium internuclear distance; this is mainly due to the dispersion interaction arising from the mutual polarization of the atomic ions.