Nonadiabatic ab initio molecular dynamics including spin-orbit coupling and laser fields

TL;DR

This paper introduces a novel nonadiabatic ab initio molecular dynamics method that incorporates spin-orbit coupling and laser fields, enabling detailed studies of excited-state processes in large molecular systems.

Contribution

The work develops a general framework for including spin-orbit coupling and non-perturbative laser interactions in ab initio MD, allowing treatment of triplet states and nonlinear laser effects.

Findings

SOC significantly affects potential curves and dynamics in IBr.

Nonresonant Stark effect can control reaction barriers.

Method enables simulation of large systems with complex excited-state interactions.

Abstract

Nonadiabatic ab initio molecular dynamics (MD) including spin-orbit coupling (SOC) and laser fields is investigated as a general tool for studies of excited-state processes. Up to now, SOCs are not included in standard ab initio MD packages. Therefore, transitions to triplet states cannot be treated in a straightforward way. Nevertheless, triplet states play an important role in a large variety of systems and can now be treated within the given framework. The laser interaction is treated on a non-perturbative level that allows nonlinear effects like strong Stark shifts to be considered. As MD allows for the handling of many atoms, the interplay between triplet and singlet states of large molecular systems will be accessible. In order to test the method, IBr is taken as a model system, where SOC plays a crucial role for the shape of the potential curves and thus the dynamics. Moreover, the influence of the nonresonant dynamic Stark effect is considered. The latter is capable of controlling reaction barriers by electric fields in timereversible conditions, and thus a control laser using this effect acts like a photonic catalyst. In the IBr molecule, the branching ratio at an avoided crossing, which arises from SOC, can be influenced.