RADIATIVE LIFETIME OF THE HCO(B)OVERTILDE(2)A' STATE

The fragment HCO, produced from acetaldehyde by photolysis at 300 nm, was detected by laser-induced fluorescence of B2A'-X2A' transitions. T he fluorescence lifetimes of the HCO B state decrease rapidly as the p hotolysis energy increases, indicating strong predissociation of the B state. The radiative lifetimes of B are in the range 70-90 ns for (0, 0, 0) K = 0 states and 42-50 ns for K' = 1 states. For all measured v ibrational levels, the K' = 1 states have smaller average lifetimes th an the K' = 0 states. Correction over individual lifetimes is necessar y to obtain the state population if the B state is excited. The state B (0, 1, 0) has a shorter average lifetime than the states (1, 0, 0) a nd (0, 0, 2), despite having a lower energy.