LIF MEASUREMENTS OF RADIATIVE LIFETIMES OF THE C2(B'(1)SIGMA-G+) STATE

The 193 nm photolysis of acetylene has been used as a source of C2(B'1 SIGMA(g)+) radicals, which are subsequently detected by laser-induced fluorescence technique. The pressure-dependent collisional lifetimes o f this radical are experimentally determined by delaying the probe las er with respect to the photolysis laser, thus allowing extraction of t he pseudo-first-order rate constants. Stem-Volmer plots of these rate constants versus pressure yield the natural radiative lifetimes of the state. Three different rotational levels of the C2(B'SIGMA(g)+) state were studied. The natural radiative lifetimes were 11.6 +/- 1.4 mus a nd 10.4 +/- 1.9 mus for the nu' = 0, J' = 8 and J' = 14 levels, respec tively, and 8.3 +/- 1.9 mus for the nu' = 1, J' = 8 level. These value s are in reasonable agreement with the recent theoretical calculations . In addition, the second-order rate constants for the excited state q uenching by Ar have also been calculated from the data.