A High-Resolution Reaction Microscope for Storage Rings

Reaction Microscopes (REMI) [1] enable kinematically complete experiments on atomic and molecular fragmentation processes by coincident and momentum resolved detection of recoiling target ions and emitted electrons. Thus, these devices represent the ideal tool to study with highest possible detail the many-particle dynamics in collisions of fast highly-charged ions with atoms or molecules. The implementation of Reaction Microscopes into ion storage rings like the ESR at GSI or the TSR at the MPI in Heidelberg (MPIK), which provide ion beams of unprecedented quality with respect to beam intensity, ion temperature, and emittance, offers completely new and unique possibilities. The combination of both techniques will, for the very first time, enable highly differential measurements of reaction channels with very small cross-sections. In spring 2009 a Reaction Microscope equipped with a supersonic gas-jet target a setup that has been operated before inside the ESR will be inserted into the TSR and first experiments will be performed. Here, in particular the dynamics of electron-transfer reactions in ion-atom collisions will be of interest. The goal is to obtain first data on radiative electron capture (REC) differential in the projectile deflection angle. In addition, the kinematics of non-radiative capture shall be measured in coincidence with characteristic photons emitted from the outgoing, generally highly excited projectile in order to obtain spectroscopic information of highly-charged ions. Furthermore, a new Emmy-Noether Junior Research Group the ’PRIOC’ group (’PRecision studies of IOn Collisions’) headed by D. Fischer will be launched at the MPIK, the University of Heidelberg, and the GSI in 2009. The work of this group will be devoted to the physics of ion-atom collisions and to electronic structure studies of highly charged ions in highest possible detail. To achieve that goal it is planned to install a Reaction Microscope equipped a laser-cooled, ultra-cold lithium target, provided by means of a magneto-optical trap (MOT), into the ESR storage ring. This will lead to an improvement in the momentum resolution of up to a factor of 10 compared to previous experiments using conventional supersonic gastargets. In the planned experiments, fully differential cross sections for singly ionizing ion-atom collisions shall be obtained. The high quality of the target, as well as its electronic structure, very much mimicking a H-like system, will help to unambiguously disentangle previously troubling discrepancies between experiment and theory. These issues have been prevalent in the past several years, and were partly traced back to electronic correlation in the ini-