Transition probabilities and electronic transition moments of the A (2)Sigma(+)-X (2)Pi and D (2)Sigma(+)-X (2)Pi systems of nitric oxide

Dispersed fluorescence scans of the A-X(4,upsilon ") and D-X(0,upsilon ") p rogressions of nitric oxide, after two-photon excitation, are used to deter mine the electronic transition moments of these band systems. The measured collision free lifetimes of 206 +/- 7 ns for A (2)Sigma(+), upsilon' = 0, a nd 18 +/- 1 ns for D (2)Sigma(+), upsilon' = 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. Th e 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, upsilon' = 0 is larger th an from A, upsilon' = 4 at 375 nm. Also, the two-photon excitation of A-X(4 ,0) has an unusual intensity distribution, probably due either to interfere nce between intermediate states in the excitation or to anomalies in the ph otoionization step. (C) 1999 American Institute of Physics. [S0021-9606(99) 01140-X].