Collision-induced intersystem crossing NH(c 1Π)→NH(A 3Π)

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Abstract
The kinetics and the specific products of the collision‐induced intersystem crossing NH(c 1Π,v=0)+M→NH(A 3Π,v)+M were investigated in the ArF laser photolysis of HN3 for various M. The efficiency of the intersystem crossing process was monitored time and spectrally resolved by the enhancement of the NH(A→X) emission. The efficiencies for M=O2, NO, Xe, and N2O are 0.95±0.05, 0.95±0.05, ≤0.15, 2, various vibrational NH(A,v=0, 1, and 2) states are formed with the detailed efficiencies of 0.64, 0.12, and 0.24. We propose that these vibrational states are generated together with O2(a 1Δ,v=4, 2, and 0), respectively. The rotational temperatures for the NH(A,v) products are much colder for M=O2 than for M=NO. For M=Xe, the enhancement of NH(A,v=0) is much larger than that predicted for an efficiency of one and, in the presence of Ar, it is markedly reduced. This large enhancement might be due to a second intersystem crossing process such as NH(b 1Σ+,v≥3)+Xe→NH(A,v=0,1)+Xe. A similar quenchable, but much weaker, additional triplet emission was observed for M=N2O. Absolute rate constants for the quenching of NH(c,v=0) by M=O2, NO, Xe, and N2O were determined at room temperature. Similarly, a value was measured for NH(A,v=2)+O2.