Lifetimes of Rydberg levels in the perturbed 6snd1,3D2series of barium I

Using two-step laser excitation in an atomic beam and time-delayed field ionisation detection, we have measured the lifetimes of the Rydberg levels of Ba I belonging to the perturbed series 6snd 1 D 2 (n = 17-35) and 6snd 3 D 2 (n = 17-28) and also the lifetime of the perturbing 5d7d 1 D 2 level. The expected shortening has been observed for the lifetimes of those levels which are strongly mixed with the perturber. The measured values have been satisfactorily interpreted by a parametric method based upon the wavefunctions previously obtained from a multichannel quantum defect analysis of the energies.