Observation of Partial Wave Resonances in Low-Energy O2-H2 Inelastic Collisions

Partial wave resonances predicted to occur in bimolecular collision processes have proven challenging to observe experimentally. Here, we report crossed-beam experiments and quantum-scattering calculations on inelastic collisions between ground-state O-2 and H-2 molecules that provide state-to-state cross sections for rotational excitation of O-2 (rotational state N = 1, j = 0) to O-2 (N = 1, j = 1) in the vicinity of the thermodynamic threshold at 3.96 centimeter(-1). The close agreement between experimental and theoretical results confirms the classically forbidden character of this collision-induced transition, which occurs exclusively in a purely quantum mechanical regime via shape and Feshbach resonances arising from partial waves with total angular momentum (J) = 2 to 4.