Superheavy nuclei and quasi-atoms produced in collisions of transuranium ions

Abstract

Low energy collisions of very heavy nuclei ($^{238}\mathrm{U}+^{238}\mathrm{U}$, $^{232}\mathrm{Th}+^{250}\mathrm{Cf}$, and $^{238}\mathrm{U}+^{248}\mathrm{Cm}$) have been studied within the realistic dynamical model based on multidimensional Langevin equations. Large charge and mass transfer was found to result from the ``inverse quasi-fission'' process leading to the formation of the surviving superheavy long-lived neutron-rich nuclei. In many events, the lifetime of the composite system consisting of two touching nuclei turns out to be rather long; sufficiently long for the spontaneous formation of positrons to occur from a super-strong electric field---a fundamental QED process.