Radiative lifetimes and collisional deactivation cross sections of the 5d6p states of laser-ablated Ba in He gas

We have measured radiative lifetimes and collisional deactivation cross sections of the 5d6p excited states of Ba atoms in He buffer gas. Barium atoms are produced by laser ablation of a solid Ba sample, whereby populating the 6s5d D-3(J) metastable states about 0.1-1% of the total population. The 5d6p P-1.3 degrees, D-1.3 degrees, and F-1.3 degrees states, most of which are not accessible from the ground state by single-photon transition, are excited from the metastable states by a laser, and radiative lifetimes as well as collisional deactivation cross sections are determined from the decay rates of the laser-induced fluorescence. Radiative lifetimes of the 5d6p (3)P(J)degrees, (3)D(J)degrees, and 3F(J)degrees states do not depend on J, indicating the validity of LS coupling scheme. Collisional deactivation cross sections by He are in the range of 5-20 Angstrom(2) for the 5d6p (3)D(J)degrees, (1)D(2)degrees, and (3)F(3,4)degrees states, whereas those for the 5d6p 3P(J)degrees, (1)P(1)degrees, (3)F(2)degrees and (1)F(3)degrees states are less than 1.5 Angstrom(2) in the He pressure range of 60-400 Pa. Among 5d6p manifolds, the 5d(2) P-3(2) State is populated, by the collisional deactivation from the laser-excited 5d6p (3)D(1)degrees state, leading to the sensitized fluorescence from 5d(2) P-3(2). Radiative lifetime and collisional deactivation cross section of the 5d2 P-3(2) State are also determined from the decay rates of the sensitized fluorescence. [S1050-2947(99)09403-2].