Electron Excitation Processes and Quantum Electrodynamics in High-Z Systems

Abstract

Collisions of very heavy ions with bombarding energies close to the Coulomb barrier offer us the possibility to perform a spectroscopy of electronic states in transient superheavy systems within a charge range of 100⩽Z⩽190 (₉₂U+₉₈Cf). The pivotal question to answer is whether the binding energy of the strongest bound electronic state can reach or exceed twice the electron rest mass. An important task in this connection is the investigation of electron excitation processes in superheavy systems. Two possible excitation mechanisms are visualized in Fig. 1. As an example we consider the schematic level structure for a head-on collision of Pb + Cm with a total charge Z = 178 at 5.9 MeV/u bombarding energy. Binding energies of the adiabatic 1 saσ — and 2sσ- states¹) are displayed versus the internuclear separation R. The turning point between incoming and outgoing trajectroy is given by R_min = 17 fm.

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 Programm.