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The formation of OH(A) and OD(A) in the 193-nm photolyses of HONO and DONO with a low quantum yield of about 10/sup -5/ is reported. The rotational population of OH(A) can be approximated by a Boltzmann distribution with a temperature of 650 K. It is compared with the predictions of the impulsive and statistical models and is found to be close to the latter. A reinvestigation of the absorption spectrum for HONO between 185 and 270 nm and a comparison of the OH(A-X) fluorescence intensities excited in the 193-nm photolyses of nitric acids are also reported.

The fluorescence lifetime of NH(c,v,J) has been investigated for v = 0, J = 2-9 and v = 1, J = 1, 4. Rate constants for quenching of NH(c, v = O) in thermal equilibrium at 298 K have been measured for 15 collision partners and for NH(c, v = O) in nonequilibrium for 8 partners. Most rate constants are near gas kinetic and decrease as the energy of the colliding pair increases. Comparison with NH(A) shows in many cases roughly a factor of 2 difference in the cross sections while there is near quantitative agreement with the cross sections for OH(A). Comparisons with the cross sections for the quenching of O({sup 1}D) show a linear relationship with nonpolar and polar collision partners falling on separate parallel lines. Both the well-depth model and the complex-formation model show reasonable correlations with the data.

The involvement of an intermediate species in the excitation of OH(A) emission in the 193-nm photolysis of nitric acid is demonstrated by using two excimer lasers in a pump-probe experiment. The intermediate species is characterized both through analysis of the resulting OH(A) emission and by measurements of its collisional and lifetime properties. After careful consideration of all reasonable candidates, it is proposed that the intermediate is HONO - probably in its lowest triplet state. 37 references, 5 figures, 1 table.