Fragmentation of allene dications induced by electron loss collisions of 3 MeV He⁺ ions

The fragmentation dynamics of allene dications induced by electron loss collisions of 3 MeV He + ions is studied. Utilizing cold target recoil ion momentum spectroscopy, the momenta of ionic fragments are measured and the kinetic energy release (KER) distributions for two complete and six incomplete fragmentation channels are obtained. For two complete two-body channels, the fragmentation mechanisms are analyzed by comparing the experimental KER distributions with available results of ab initio reaction path calculations. We analyze the fragmentation mechanisms of incomplete channels, with one undetected hydrogen atom, using the island slope in ion-ion coincidence time-of-flight maps and Newton diagrams. The data indicate that initial charge separation [s(i)] is the dominant mechanism. In particular, the KER peak values for the channels considered are found to be lower than those reported in previous experiments involving 50 keV/u Ne 8+ ion impact and intense laser ionization. This may suggest that the e-e process dominates simultaneous projectile-target ionization in the present experiment. This process predominates at large impact parameters.