Electron Excitation and Positron Emission in Quasi-Molecular Collisions of very Heavy Ions

Abstract

In collisions of very heavy ions superheavy quasiatomic systems are created, where the electrons experience for a period T ~ 10⁻²⁰S the combined nuclear charge Z = Z_p + Z_t of the projectile and the target. This offers us the possibility to extend our knowledge on atomic physics by about a factor of two concerning the nuclear charge number and by an order of magnitude concerning the binding energy of the strongest bound electron^1–4). For Z > 173 the binding energy of the 1s-electron exceeds the pair production threshold of 2 mc² ~ 1 MeV, which allows for a spontaneous emission of positrons. In heavy-ion collisions close to or slightly above the nuclear Coulomb barrier superheavy nuclear compound systems may be formed. The spectroscopy of the emitted 6-electrons and positrons in such scattering experiments is a sensitive tool for the investigation of the nuclear reaction mechanism and for the determination of the reaction time.

This work was supported by the Bundesministerium für Forschung und Technologie (BMFT) and the Deutsche Forschungsgemeinschaft (DFG). One of us (G.S.) acknowledges the support of the DFG-Heisenberg Program.