Quantum Dynamics Predicts Coherent Oscillatory Behavior in the Early-times of a Photoisomerization Reaction

TL;DR

This study uses quantum dynamics modeling to reveal coherent oscillations during early photoisomerization in a specific molecular system, highlighting challenges in computational convergence and the role of vibrational energy.

Contribution

It introduces a detailed quantum dynamical approach to simulate early-time photoisomerization, emphasizing convergence issues and the emergence of coherent oscillations.

Findings

Reliable convergence captures large amplitude torsional motion

Coherent oscillations are observed in the formation of trans isomer

Vibrational energy plays a key role in photoisomerization dynamics

Abstract

In this work, we study the quantum dynamics of a photoisomerization reaction employing a two-electronic-state three-vibrational-mode model of the 2-cis-penta-2,4-dieniminium cation (cis-PSB3). In particular, we address two main issues: the challenges encountered in properly converging quantum dynamics calculations, even when a reduced-dimensionality molecular model is used; the emergence of a coherent oscillatory behavior in the formation of the trans isomer upon photoexcitation of cis-PSB3. The two issues are strictly related, since only upon reliable convergence, the simulated dynamics is able to capture the large amplitude motion associated to the torsion around the reactive bond, typical of photoisomerizations, which is due to the large amount of kinetic energy acquired by the vibrational modes after light excitation.