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.
Highlights
Whereas quenching cross sections for He, Ne, and Ar are almost negligible when compared with rotational energy transfer on the excited potential energy surface (PES), for Kr and Xe quenching cross sections are similar or larger than those with H2, O2, or N2.18,21,23 As such, adiabatic calculations carried out on the 2A0 excited PES for Kr and Xe cannot account for rotational initial state depopulation.[21,22,23]
We use a new non-adiabatic quantum theory based on three diabatic electronic states, S+(1), P0(2), and P00(3), coupled by nine conical-intersection (CI) and Renner–Teller (RT) matrix elements
Using a triatomic Hamiltonian H, all the matrix elements of the electronic Hamiltonian Hel and of the total electronic angular momentum Lare taken into account and ab initio calculated in three dimensions
Summary
Previous calculations for the Kr + OH(A2S+) system using quasiclassical trajectories (QCT) and surface hopping (SH) on ab initio PESs21,22 demonstrated that the sole consideration of 2-PES transition (2A0–1A0) could not reproduced the magnitude of the quenching cross section dependence on the initial rotational state of OH(A2S+). Extending the previous studies,[21,22] the present work reports time-dependent wavepacket (WP) quantum dynamics of the electronic quenching OH(A2S+) + Kr(1S) - OH(X2P) + Kr(1S), including three 3D PESs and all the non-adiabatic interactions (i.e., one CI and nine RT coupling surfaces) all of them at multireference configuration-interaction (MRCI) level.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
