Rotationally inelastic collisions of a molecule in a 1Δ electronic state: NH(a 1Δ)

The general theory for inelastic scattering of molecules ¹Δ electronic states is outlined and applied to the specific case of ¹Δ states arising from a π² electron occupancy, e.g., NH(a ¹Δ). Integral cross sections for rotational transitions out of the lowest rotational level (J=2) of NH(a ¹Δ) v=0 are reported for several targets. A pulsed beam of rotationally cold NH(a ¹Δ) was produced by 193 nm photolysis of a dilute mixture of hydrazoic acid in nitrogen seed gas at the tip of a nozzle. The target beam was also prepared as a pulsed supersonic beam. The final rotational state distribution was measured in the collision zone by laser fluorescence excitation. The state-to-state cross sections were found to decrease significantly with increasing final rotational quantum number J'. The magnitude of the J=2→J'=3 cross sections were compared for the different targets. Isotopic scrambling in NH(a ¹Δ)-D₂ collisions was also searched for but not observed.