Studies of laser-induced fluorescence in fast beams of Sr+ and Ba+ ions

Studies of the LIF radiation from beams of Sr+ and Br+ ions have been used to measure the lifetimes of the 4f and 5p levels of Sr II, and of the 4f, 6p and 7p levels of Ba II. The lifetimes obtained for the 5p levels of Sr II and the 6p levels of Ba II are in good agreement with previous LIF measurements. The fine structure of the 4f2F degrees term in Sr II has been resolved for the first time, the observed splitting being -1.30+or-0.06 cm-1. The energies of the two 4f levels have been measured as 60991.3 cm-1 (j=5/2) and 60990.0 cm-1 (j=7/2). The LIF decay curves recorded using a detector sensitive in the visible region for the 7p levels in Ba II showed very strong growing-in cascading, demonstrating that LIF decay curves are not necessarily single-exponential for high-lying levels. The lifetime results are compared with Coulomb approximation and RHF calculations where available, the latter including semi-empirical polarization corrections.