DETERMINATION OF RADIATIVE LIFETIMES OF NEUTRAL SULFUR BY TIME-RESOLVED 3-PHOTON VUV LASER SPECTROSCOPY

Radiative lifetimes of the highly exited states 3p(3)8s S-3(1)0 and 3p (3)6d D-3(1,2,3)0 of neutral sulphur have been measured using time-res olved laser-induced fluorescence. The sulphur atoms were generated in a laser-produced plasma. The investigated states were populated throug h a two-step process involving a two-photon excitation to the lowest e xcited tripler state of even parity 3p(4) P-3(0,1,2), followed by a on e-photon excitation to the investigated state. We obtained tau(8s(3)S( 1)(0)) = 40 +/- 5 ns and tau(6d(3)D(1,2,3)(0)) = 75 +/- 7 ns. These va lues are much longer than theoretically predicted ones and much shorte r than those indirectely inferred from astronomical data.