Experimental study of configuration mixing effects on the lifetimes of 1s(2)2s6l levels in Be-like O

The lifetimes of 11 levels in the 2s6d, 6f and 6g configurations in O V hav e been determined using the beam-foil technique. The new CCD detection syst em is described and its advantages for atomic lifetime measurements are dis cussed. The experimental results are compared with ab initio theoretical an d semiempirical values calculated by the superposition-of-configurations me thod. Configuration interactions between 2s6f and 2p4d and between 2s6g and 2p4f are found to have a significant influence on the lifetimes and an acc urate treatment of this level mixing is necessary to bring theory and exper iment into agreement.