SELECTIVE PRODUCT CHANNELS IN THE REACTIONS OF NH(A1-DELTA) AND NH(X3-SIGMA-) WITH NO

Reactions of imidogen, NH, in the electronically excited a 1-DELTA and ground X3-SIGMA- states with NO have been studied at 300 +/- 2 K and at 20 Torr (Ar).NH(a 1-DELTA) and NH (X3-SIGMA-) were produced in the 193 nm photolysis of HNCO and CHBr3/NO, respectively, and detected by the laser-induced fluorescence (LIF) technique. Rate constants have been measured under pseudo-first-order conditions by scanning the time delay between the photolysis and probe laser pulses. Overall rate constants were determined: [4.8 +/- 0.1(2-sigma)] x 10(-11) cm3 molecule-1 s-1 for NH (a 1-DELTA) + NO; [4.7 +/- 0.6(2-sigma)] x 10(-11) cm3 molecule-1 s-1 for NH(X3-SIGMA-) + NO. The ratio of electronic quenching, NH(a 1-DELTA) + NO --> NH(X3-SIGMA-) + NO, to the overall reaction has been obtained to be 0.53 +/- 0.1. An interesting specificity for the products from different spin states of the reactants has been found from observation of OH concentration profiles. NH(X3-SIGMA-) + NO produces OH + N2 exclusively, while NH(a 1-DELTA) + NO is over five times less effective in producing OH + N2. Profiles of H atoms detected by the vuv LIF technique indicated that H atoms are directly produced in the reaction NH(a 1-DELTA) + NO but not in the reaction NH(X3-SIGMA-) + NO.