LIF measurements of radiative lifetimes of the C 2(B' 1Σ +g) state

Abstract

The 193 nm photolysis of acetylene has been used as a source of C 2(B' 1Σ + g) radicals, which are subsequently detected by laser-induced fluorescence technique. The pressure-dependent collisional lifetimes of this radical are experimentally determined by delaying the probe laser with respect to the photolysis laser, thus allowing extraction of the pseudo-first-order rate constants. Stern—Volmer plots of these rate constants versus pressure yield the natural radiative lifetimes of the state. Three different rotational levels of the C 2(B' 1Σ + g) state were studied. The natural radiative lifetimes were 11.6±1.4 μs and 10.4±1.9 μs for the ν'=0, J'=8 and J'=14 levels, respectively, and 8.3±1.9 μs for the ν'=1, J'=8 level. These values are in reasonable agreement with the recent theoretical calculations. In addition, the second-order rate constants for the excited state quenching by Ar have also been calculated from the data.