Collision-induced intra-shell transitions in He-like ions

We report collision-induced intra-shell transitions for the first time. It has been observed between two close by levels 1s2s 3S1 and 1s2p3Po2 in He-like Ti ions by the beam-two-foil time-of-flight technique. The mean collision-induced transition probability between these two levels is found to be quite large (0.72 ± 0.05/collision), which is attributable to the small energy splittings (32 eV) between them. (fast track communication)