Steric asymmetry in rotationally inelastic state-resolved NOAr collisions

The first direct experimental evidence is reported of large orientation (head-tail) effects in rotationally inelastic collisions, for the specific case of NO and Ar. NO is selected in the 2Π12 j = 12− state and oriented in an electric field. The steric effect, measured for collisions to three distinct final rotational states, appears to depend on the j′ value and the parity of the final state. This behaviour also follows from quantum-mechanical scattering calculations, but the calculated values do not coincide with the corresponding experimental ones.