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.