Extreme Parametric Sensitivity in the Steady-State Photoisomerization of Model Retinal

TL;DR

This study reveals that the steady-state quantum yield of retinal photoisomerization is extremely sensitive to small parameter changes, likely due to quantum chaos, with implications for biological light sensing and photochemistry.

Contribution

It demonstrates the extreme parametric sensitivity of steady-state quantum yields in retinal photoisomerization and links it to quantum chaos phenomena.

Findings

Steady-state quantum yields differ significantly from transient values.

Quantum yield sensitivity is highly dependent on system parameters.

Sensitivity correlates with nonadiabatic vibronic system level spacing statistics.

Abstract

The photoisomerization reaction of the retinal chromophore in rhodopsin was computationally studied using a two-state two-mode model coupled to thermal baths. Reaction quantum yields at the steady state (10 ps and beyond) were found to be considerably different than their transient values, suggesting a weak correlation between transient and steady-state dynamics in these systems. Significantly, the steady-state quantum yield was highly sensitive to minute changes in system parameters, while transient dynamics was nearly unaffected. Correlation of such sensitivity with standard level spacing statistics of the nonadiabatic vibronic system suggests a possible origin in quantum chaos. The feasibility of experimental observation of this phenomenon and its implications in condensed-phase photochemistry and biological light sensing are discussed.