Effect of the Electromagnetic Field on the Photoisomerization of the Rhodopsin Molecule
Molecular photoisomerization is a process of configurational rearrangement induced by the action of electromagnetic radiation and whose efficiency can be controlled via the manipulation of the electric field that triggers the reaction. In the present work, we introduce a theoretical model for the isomerization process that incorporates the essential features of this phenomenon at the microscopic level. Two potential energy surfaces and two degrees of freedom are used to represent the active center of the molecule. The effect of the electric field on the overall dynamics is studied by considering different widths and shapes of the exciting field, within the electric dipole approximation. The rest of the system is modeled as a set of classical harmonic oscillators. The model reproduces previously reported experimental results on the isomerization yield upon instantaneous excitation and it predicts the behavior of the system under the action of laser pulses of finite duration.