Photoinitiated H- and D-Atom Reactions With N2O in the Gas Phase and in N2O-HIand N2O-DI Complexes

摘要

Reactions of H atoms with N2O have two product channels yielding NH + NO and OH +N2. Both channels were observed via NH A 3 II yields X 3 sigma and OH A 2 sigma yields X 2 II laser-induced fluorescence spectra. Photoinitiated reactions with N20-HI complexes yield a much lower NH /OH ratio than under the corresponding bulk conditions at the same photolysis wavelength. For hot D-atom reactions with N20, this effect is somewhat more pronounced. These results can be interpreted in terms of entrance channel geometric specificity, namely, biasing hydrogen attack toward the oxygen. Another striking observation is that the OH and OD rotational level distributions (RLD) obtained under bulk conditions differ markedly from those obtained under complexed conditions, while the NH as well as the ND RLD are similar for the two environments. In addition, OH Doppler profiles change considerably in going from bulk to complexed conditions, while such an effect is not observed for NH. The changes observed with the OH RLD are most likely due to OH-halogen interactions and/or entrance channel specificity. Under bulk conditions, the Doppler shift measurements indicate a large amount of N, internal excitation (i.e., approx. 25 000 cm-1) for the OH (v = 0) levels monitored. This is consistent with a reaction mechanism involving an HNNO intermediate.