Verification of the insertion mechanism of N(2 2D) into H-H bonds by the vibrational state distribution measurement of NH(X 3Σ-,0≤ v≤3)

The nascent vibrational state distribution of NH(X (3)Sigma(-)) radicals produced in the reaction of N(D-2) with H-2 was determined by employing a pulsed laser technique. N(D-2) was produced by two-photon dissociation of NO, while NH(X (3)Sigma(-)) was detected by laser-induced fluorescence. Off-diagonal transitions of the A-X system were employed to probe NH(X (3)Sigma(-),v greater than or equal to 2) because of the predissociative nature of the upper state. The vibrational distribution was determined to be 10.0(v = 0): 8.0 +/- 1.0(v = 1): 5.0 +/- 0.7(v = 2): 2.5 +/- 0.5(v = 3). This distribution is much cooler than that obtained by infrared emission measurements, but is similar to that of recent quasiclassical trajectory calculations as well as that of three dimensional quantum calculations based on an ab initio potential energy surface. The agreement with theoretical results suggests that the reaction proceeds via an insertive process. (C) 2000 American Institute of Physics. [S0021-9606(00)00813-8].