EXCITATION TRANSFER IN BARIUM BY COLLISIONS WITH NOBLE-GASES

We present a time-resolved study of excitation transfer processes betw een the low-lying excited states of barium (6s6p(3)P(J), 6s5d(1)D(2), 6s5d(3)D(J)) induced by collisions with noble gases. The transient exc ited-state populations have been measured by means of fluorescence and absorption spectroscopy. Cross sections for spin-changing collisions from P-3(1) to D-1(2) and from D-1(2) to D-3(3) as well as for fine-st ructure mixing within the D-3 multiplet were obtained by fitting the n umerical solution of a seven-state system of rate equations including diffusion to the experimental data. We compare our results to experime ntal findings for other alkaline earth metals add report an improved v alue of the lifetime of the 6s6p(3)P(1) state of barium.