Measurement of absolute state-to-state rate constants for collision-induced transitions between spin-orbit and rotational states of NO(X 2Π, v = 2)

Abstract

Using a pulsed, time resolved IR–UV double resonance technique, we have measured initial and final state specific rates for collision‐induced rotational and spin‐orbit transitions in NO in its (X 2Π, v = 2) vibronic state. A systematic study of the rates was done for initial and final rotational states with J between 1/2 and 35/2, for both Ω = 1/2 and the Ω = 3/2 spin‐orbit components of the X 2Π state. Collision partners were room temperature NO, He, Ar, N2, CO, and SF6. No propensity rules favoring ΔΩ = 0 or ΔJ = 0,±1 were observed, except in NO–He collisions, where ΔΩ = 0 was favored. The state‐to‐state rates do not vary much with initial state and fall off slowly with increasing ΔJ. Total cross sections for collision‐induced rotational transitions were found to be tens of Å2, insensitive to initial state, and correlated with the size of the collision partner.