State-resolved distribution of OH X 2Pi products arising from electronic quenching of OH A 2Sigma+ by N2.

The nascent OH X (2)Pi product state distribution arising from collisional quenching of electronically excited OH A (2)Sigma(+) by N(2) has been determined using a pump-probe technique. 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 (v(")=0) products are generated with a substantial degree of rotational excitation, peaking around N(")=18, with an average rotational energy of approximately 6500 cm(-1). A preference is found for the OH Pi(A(')) Lambda-doublet, indicating some degree of ppi orbital alignment. The branching fraction into OH X (2)Pi product states demonstrates that nonreactive quenching is the dominant decay pathway for quenching of OH A (2)Sigma(+) by N(2). The topography of the conical intersection region that couples the electronically excited and ground state potential energy surfaces is also examined theoretically. The rotational excitation of the OH X (2)Pi products and branching fraction are found to be dynamical signatures of nonadiabatic passage through the conical intersection region.