Inelastic scattering of NO(A 2 Σ + ) + CO 2 : rotation-rotation pair-correlated differential cross sections.

A crossed beam velocity-map ion-imaging apparatus has been used to determine differential cross sections (DCSs) for the rotationally inelastic scattering of NO(A 2 Σ + , v = 0, j = 0.5) with CO 2 , as a function of both NO(A, v = 0, N ') final state and the coincident final rotational energy of the CO 2 . The DCSs are dominated by forward-peaked scattering for all N ', with significant rotational excitation of CO 2 , and a small backward scattered peak is also observed for all final N '. However, no rotational rainbow scattering is observed and there is no evidence for significant product rotational angular momentum polarization. New ab initio potential energy surface calculations at the PNO-CCSD(T)-F12b level of theory report strong attractive forces at long ranges with significant anisotropy relative to both NO and CO 2 . The absence of rotational rainbow scattering is consistent with removal of low-impact-parameter collisions via electronic quenching, in agreement with the literature quenching rates of NO(A) by CO 2 and recent electronic structure calculations. We propose that high-impact-parameter collisions, that do not lead to quenching, experience strong anisotropic attractive forces that lead to significant rotational excitation in both NO and CO 2 , depolarizing product angular momentum while leading to forward and backward glory scattering.