Direct measurement of the radiative lifetimes of the A2Σ+ (V′ = 0) states of OH and OD

The fluorescent decay of the A 2Σ+ (V′ = 0) state of OH and OD has been measured for N′ ? 8 for OH and N′ ? 9 for OD using pulsed dye laser excitation and at total gas pressures ? 1 mtorr. For the rotationless molecule, a radiative lifetime of 0.688 ± 0.021 μsec for OH and 0.692 ±0.021 μsec for OD was obtained, where the error bars are three standard deviations. In addition, OH exhibited a 8 ± 2% lengthening of the radiative lifetime between N′ = 1 and N′ = 8.