Steady State Photoisomerization Quantum Yield of Model Rhodopsin: Insights from Wavepacket Dynamics?

TL;DR

This study uses wavepacket dynamics to analyze the steady state quantum yield of retinal photoisomerization in rhodopsin, revealing the importance of energy redistribution and environment effects beyond initial dynamics.

Contribution

It demonstrates that steady state quantum yield depends on energy redistribution influenced by environment interactions, extending beyond traditional transient wavepacket models.

Findings

Quantum yield correlates with excess energy above crossing point.

Environment-induced energy redistribution affects reaction efficiency.

Pure dynamical models are insufficient for accurate yield prediction.

Abstract

We simulate the nonequilibrium steady state \textit{cis-trans} photoisomerization of retinal chromophore in rhodopsin based on a two-state-two-mode model coupled to a thermal environment. By analyzing the systematic trends within an inhomogeneously broadened ensemble of systems, we find that the steady state reaction quantum yield (QY) correlates strongly with the excess energy above the crossing point of the system, in agreement with the prediction of the short time dynamical wavepacket picture. However, the nontrivial dependence of the QY on the system-environment interaction indicates that a pure dynamical picture is insufficient and that environment-induced partial internal energy redistribution takes place before the reaction concludes. These results imply that a proper treatment of the photoisomerization reaction, particularly its high QY, must account for the redistribution and dissipation of energy beyond the dynamical wavepacket motion that is typically employed in the literature and that is appropriate only in the transient regime.