Collisions of metastable He-like C4+ions on He and H2targets

Single and double electron transfer collisions into metastable C 4+ (1s2s) 3 S have been studied. With He as a target, both single and double electron capture take place dominantly in the n=2 shell and the decay from there on is mostly through autoionization, whereas with H 2 single electron capture populates C 3+ (1s2s3l) states which stabilize both by autoionization and radiation. The discussion is focused on the influence of the 2s metastable electron on the capture mechanism.