Transition probabilities and electronic transition moments of the A 2Σ+–X 2Π and D 2Σ+–X 2Π systems of nitric oxide

Dispersed fluorescence scans of the A–X(4,v″) and D–X(0,v″) progressions of nitric oxide, after two-photon excitation, are used to determine the electronic transition moments of these band systems. The measured collision free lifetimes of 206±7 ns for A 2Σ+, v′=0, and 18±1 ns for D 2Σ+, v′=0 are used to place transition probabilities on an absolute basis. The branching ratio for D→X is 3.0±0.3 times that for D→A and more than 30 times that for D→C. The ratio of two-photon absorption cross sections for D–X(0,0)/A–X(4,0) is 6±2 and the photoionization probability from D, v′=0 is larger than from A, v′=4 at 375 nm. Also, the two-photon excitation of A–X(4,0) has an unusual intensity distribution, probably due either to interference between intermediate states in the excitation or to anomalies in the photoionization step.