Increase of true double-electron-capture cross sections in slow Xeq+-(Xe,He) collisions at very high q

We have measured cross sections for true double-electron capture (DC) and transfer ionization (TI) in slow Xeq+-(Xe,He) collisions in the charge-state regime 15≤q≤42. We find that the probabilities for radiative stabilization Prad=σDC/(σDC+σTI) increase rapidly with q for q≥28 and are very similar for two-electron transfer from Xe and He. This surprising similarity indicates that the core structure of the projectile, rather than the initially populated capture state, is decisive for the electronic relaxation process