Selective product channels in the reactions of NH(a 1Δ) and NH(X 3Σ−) with NO

Abstract

Reactions of imidogen, NH, in the electronically excited a 1Δ and ground X 3Σ− states with NO have been studied at 300±2 K and at 20 Torr (Ar). NH(a 1Δ) and NH(X 3Σ−) 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(2σ)]×10−11 cm3 molecule−1 s−1 for NH(a 1Δ)+NO; [4.7±0.6(2σ)]×10−11 cm3 molecule−1 s−1 for NH(X 3Σ−)+NO. The ratio of electronic quenching, NH(a 1Δ)+NO→NH(X 3Σ−) +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(X 3Σ−)+NO produces OH+N2 exclusively, while NH(a 1Δ)+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 1Δ)+NO but not in the reaction NH(X 3Σ−)+NO.

Product branching fractions in the reactions of NH(a 1Δ) and NH(X 3Σ−) with NO

“…It is concluded that Reaction (2b) is a minor process in Reaction (2). Also, Oe P) was found to be a direct product of Reaction (1). The time lag for OH(v =0) production [which was ascribed to the exclusive production of OH in Reaction (2) in the previous study] was clearly explained by the formation of OH(v;;'I) and successive vibrational relaxation mainly by collisions with NO.…”

“…However, the conclusion contradicted the other experimental estimates of the branching fraction for Reaction (2b)8,1l,IZ and the prediction 13 based on the potential energy surface calculation. 14 Also, Hack et al 3 measured OH in the NH + NO reaction system controlling the contribution of Reactions (1) and (2) with Xe or N 2 , and suggested that the branching ratio between H and OH production is similar for both Reactions (1) and (2).…”

“…In the present study, in order to resolve the contradiction, we have reinvestigated the branching fractions in Reactions (1) and (2) by measuring the yields of H, 0, and OH to the initial concentration of NH(a '.6.) by comparing the LIF intensities.…”

Kinetics of the NH reaction with H2 and reassessment of HNO formation from NH + CO2, H2O

“…The method developed here is based on the observation, by Kenner et al [16], that 193 nm two-photon photolysis of NH3 proceeds in part as NH3 + hυ → NH2* + H followed by NH2* + hυ → NH( [18]. The a state has been shown to be quenched by N2 [19], kQ (300 K) = (6-9) × 10 -14 cm 3 molecule -1 s -1 , which was therefore used as the bath gas and as the NH3 diluent. The highest NH fluorescence intensities were obtained by slightly defocusing the photolysis laser beam.…”

Infrared Emission from the Reaction of CHF (X̃A‘) with NO

“…30 If it contributes to the F atom yield, then by the same arguments as presented above, it must form N 2 O with little internal excitation, a surprising result for this exothermic process.…”