Ultrafast Photodynamics of Glucose

TL;DR

This study uses advanced simulations to explore how glucose molecules rapidly return to their ground state after UV excitation, revealing nonradiative decay pathways involving conical intersections within 200 femtoseconds.

Contribution

It introduces a field-induced surface hopping method (FISH) to simulate coupled electron-nuclear dynamics of glucose, capturing nonadiabatic effects and light-induced excitation explicitly.

Findings

Glucose returns to ground state within 200 fs via conical intersections.

Excitation populates multiple electronic states nearly equally.

Decay proceeds predominantly through the S1 state involving specific CIs.

Abstract

We have investigated the photodynamics of $\beta$-D-glucose employing our field-induced surface hopping method (FISH), which allows us to simulate the coupled electron-nuclear dynamics, including explicitly nonadiabatic effects and light-induced excitation. Our results reveal that from the initially populated S$_{1}$ and S$_{2}$ states, glucose returns nonradiatively to the ground state within about 200 fs. This takes place mainly via conical intersections (CIs) whose geometries in most cases involve the elongation of a single O-H bond, while in some instances ring-opening due to dissociation of a C-O bond is observed. Experimentally, excitation to a distinct excited electronic state is improbable due to the presence of a dense manifold of states bearing similar oscillator strengths. Our FISH simulations explicitly including a UV laser pulse of 6.43 eV photon energy reveals that after initial excitation the population is almost equally spread over several close-lying electronic states. This is followed by a fast nonradiative decay on the time scale of 100-200 fs, with the final return to the ground state proceeding via the S$_{1}$ state through the same types of CIs as observed in the field-free simulations.