A new facility for capture-state resolved measurements of angular distributions in very slow collisions between highly charged ions and atoms

We have constructed, and performed the first experiments with, a new facility for studies of charge exchange in very slow collisions between highly charged ions and neutral atoms. State-selective angular differential cross sections for single-electron capture have been measured for laboratory collision energies down to 4.75q eV, where q is the charge state of the projectile. A very slow beam, with an energy spread of ≅ 0.2q eV, is collimated to a maximum angular divergence of ±0.5deg before it interacts with a gas-jet target. The post-collisional energy-, charge-, and angular-distributions are then analysed by means of a cylindrical energy analyzer and a two-dimensional position-sensitive detector. The relative energy resolution is measured to be 1.6% and the angular acceptance is ±9deg. In the first experiment, we determined the dominating electron transfer mechanisms for single-electron capture, transfer ionization, and true double capture in 0.5-20 eV/amu Ar4+-Ar collisions by means of comparisons with multichannel Landau-Zener angular differential cross sections. (orig.)