Modeling the Evolution of Laser-Induced Electronic Coherences with Trajectory Surface Hopping.

Current attosecond XUV/X-ray pulses and few-fs UV pulses, with bandwidths up to several eV, can excite molecules in a coherent superposition of electronic states. Theoretical modeling of the ensuing dynamics requires accounting for the coupled motion of electrons and nuclei to capture the subtle interplay between the initial electronic coherence, decoherence induced by nuclear motion, and additional coherences that may emerge at conical intersections. In this work, we introduce Trajectory Surface Hopping with Projected Forces and Momenta (TSH-PFM), which accounts for these effects in a numerically inexpensive way and, therefore, is particularly suited to describe molecular dynamics arising from an initial coherent superposition of electronic states. We demonstrate its performance by comparing with previously reported quantum mechanical results for the BMA[5,5], para-xylene, and fulvene molecules by working in full dimensionality. Application of the TSH-PFM method to the glycine molecule shows that the initial electronic coherences can have a dramatic impact in the charge distribution over the molecule at the very early stages of the dynamics.