Lifetimes of some O II levels by beam-foil experiments

Using the beam-foil technique and rather low beam energies tin the range 21 6 296 keV) in order to reduce cascade corrections, we have determined lifet imes for the 3p(4)D(0), 3p' D-2(0) and 3d(4)D terms of O II and compared th em with predictions from various theoretical and experimental approaches. O ur results support the claim for a short 3d(4)D average lifetime. Experimen tal lifetimes for 4s' D-2(3/2), 4s(4)P and 2s2p(3)(S-5)4s S-6(5/2)0 have be en determined for the first time. The first two compare well with the opaci ty project results, whereas the experimental lifetime of 2s2p(3)(S-5)4s S-6 (5/2)0 level, a pseudo-five-electron system lying above the O II ionization limit, is a factor of four smaller.