The influence of angular momentum on double electron capture by highly charged ions

Double electron capture during collisions of highly charged ions with H-2 or He is studied by measuring and analysing energy spectra of the resulting autoionization electrons and by comparing the experimentally determined population probabilities for the various states with those calculated from a simple classical model. This model is based on the extended classical over-barrier model (ECBM), modified by taking additionally the angular momenta of the exchanged electrons into account. Reasonable agreement between measured and calculated population probabilities for the highly correlated two-electron states is obtained especially for the cases of fully stripped projectiles, although correlation during the exchange process is neglected in the theoretical description. The success of the model implies that highly oriented doubly excited states result from the capture process.