Non-adiabatic quantum dynamics of the electronic quenching OH(A2Σ+) + Kr

Abstract

We present the dynamics of the electronic quenching OH(A²Σ⁺) + Kr(¹S) → OH(X²Π) + Kr(¹S), with OH(A²Σ⁺) in the ground ro-vibrational state. This study relies on a new non-adiabatic quantum theory that uses three diabatic electronic states Σ⁺, Π′, and Π′′, coupled by one conical-intersection and nine Renner–Teller matrix elements, all of which are explicitly considered in the equation of the motion. The time-dependent mechanism and initial-state-resolved quenching probabilities, integral cross sections, thermal rate constants, and thermally-averaged cross sections are calculated via the real wavepacket method. The results point out a competition among three non-adiabatic pathways: Σ⁺ ↔ Π′, Σ⁺ ↔ Π′′, and Π′ ↔ Π′′. In particular, the conical-intersection effects Σ⁺–Π′ are more important than the Renner–Teller couplings Σ⁺–Π′, Σ⁺–Π′′, and Π′–Π′′. Therefore, Π′ is the preferred product channel. The quenching occurs via an indirect insertion mechanism, opening many collision complexes, and the probabilities thus present many oscillations. Some resonances are still observable in the cross sections, which are in good agreement with previous experimental and quasi-classical findings. We also discuss the validity of more approximate quantum methods.