Quantum control of photo-chemical isomerization

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We have proposed control scenarios for isomerizations that play an important role in photochemical reactions. The basic idea of the quantum control originates from an optimal control theory that was developed in our group. We have applied the control theory to two types of photochemical reactions; IR pulse-induced isomerization of difluorobenzo[c]phenanthrene, and visible laser induced trans-cis isomerization of the retinal chromophore in bacteriorhodopsin.1. Difluorobenzo[c]phenanthrene has herical, molecular chirality. Most of control theories of molecular chirality were restricted to simple systems such as one-dimensional systems with axial chirality. The initial system was assumed to be in an equal mixture of M- and P-forms (racemic mixture). Pure M-form chiral molecules are formed from a racemic mixture by designed two linearly polarized IR laser pulses. These components are p-phase-shifted when the representative points of the isomerization is transferred to the target position a … More long the intrinsic reaction path, while the other representative point remains in its initial potential regime. This results in one-way isomerization control. The research of the molecular chirality control reported here is the first step toward the establishment of a method for controlling herical changes in biomolecules such as DNA.2. A trans-cis isomerization of retinal is a typical example of the potential crossing between the ground and excited states, in which non-adiabatic couplings play an essential role. We have clarified the effects of non-adiabatic couplings on an optimal pathway for the photoisomerization to obtain the control scenario. For this purpose, we considered two cases, strong- and medium-coupling cases. In the former case, most of the initial population of the Franck-Condon packet adiabatically switches to another diabatic potential after initially passing the crossing point. In the latter case, on the other hand, the half of the initial population remains in the original diabatic potential, which is due to non-adiabatic couplings. Less