Structure of very heavy few-electron ions—new results from the heavy ion storage ring, ESR

Abstract

The heavy ion synchrotron/storage ring facility at GSI, SIS/ESR, provides intense beams of cooled, highly-charged ions up to naked uranium (U92+). By electron capture during ion-atom collisions in the gas target of the ESR or by recombination at ion-electron encounters in the "electron cooler" excited states are populated. The detailed structure of very heavy one-, two-and three-electron ions is studied. The different mechanisms leading to the excited states are described, as well as the new experimental tools now available for a detailed spectroscopy of these interesting systems. Special emphasis is given to x-ray transitions to the groundstates in H- and He-like systems. For the heaviest species the groundstate Lambshift can now be probed on an accuracy level of better than 10% using solid-state x-ray detectors. Applying dispersive x-ray analysing techniques, this accuracy will certainly be improved in future. However, utilizing the dielectronic recombination resonances for a spectroscopy, the structure in Li-like heavy ions can already be probed now on the sub eV level.