Inelastic scattering of NO(A2Σ+) + CO2: rotation–rotation pair-correlated differential cross sections

Abstract

A crossed beam velocity-map ion-imaging apparatus has been used to determine differential cross sections (DCSs) for the rotationally inelastic scattering of NO(A²Σ⁺, v = 0, j = 0.5) with CO₂, as a function of both NO(A, v = 0, N′) final state and the coincident final rotational energy of the CO₂. The DCSs are dominated by forward-peaked scattering for all N′, with significant rotational excitation of CO₂, 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 CO₂. 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 CO₂ 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 CO₂, depolarizing product angular momentum while leading to forward and backward glory scattering.