Quantum State Distribution of the OH X²Π Products from Collisional Quenching of OH A²Σ⁺ by O₂ and CO₂

Abstract

The OH X(2)Pi product state distribution arising from quenching of electronically excited OH A(2)Sigma(+) by O(2) and CO(2) under single collision conditions has been determined using a pump-probe technique. For both collision partners, the majority of OH X(2)Pi products are observed in their lowest vibrational level, v'' = 0, with significantly less population in v'' = 1. The OH products from quenching by O(2) are generated with a substantial degree of rotational excitation, peaking around N'' approximately = 17, with an average rotational energy of approximately 4800 cm(-1), whereas OH products from quenching by CO(2) exhibit a moderate degree of rotational excitation, peaking around N'' approximately = 5, with an average rotational energy of approximately 1800 cm(-1). The branching fraction into OH X(2)Pi products states reveals that nonreactive quenching is a significant decay pathway for both systems, accounting for at least 40(1)% of the quenched products with O(2) and 64(5)% with CO(2).