Quantum-classical model of the rhodopsin retinal chromophore cis–trans photoisomerization with modified inter-subsystem coupling

Abstract A modified model of the rhodopsin retinal chromophore cis–trans photoisomerization is developed, where the electron-vibration coupling constant depends exponentially on displacements of mass points. The quantum subsystem of the model includes three electronic states for rhodopsin: (i) the ground state, (ii) the excited state, (iii) the primary photoproduct in the ground state. The classical subsystem includes three mass points. The modifications give sufficient improvement of agreement between computational data and experiments, with all parameters of the model being very close to the most physically realistic values. In particular, improvements concern with data on residual coherent oscillations after photoisomerization is complete.