Ultrafast laser spectroscopy: A probe of the photodynamics of chemical intermediates

The effect of the solute–solvent coupling on the dynamics of adiabatic charge transfer reactions is examined. A two-state description of the solute electronic configuration is implemented to adequately treat the gradual transfer of charge from the donor to acceptor as the reaction progresses. A formalism is developed for separating the solute and solvent contributions to the reaction coordinate (defined here as the difference in energy between the reactant and product states) and equations of motion are derived for these coordinates. It is found that these equations of motion are far more elaborate than the ones considered in the diabatic case (weak coupling between solute electronic states). In particular, they must reflect the effect of the solvent polarization on the solute polarization. The corresponding coupling term is missing in most treatments of charge transfer processes. To explore the coupled dynamics of the reactive trajectories we use both direct downhill simulations and a new approach which evaluates the average solvent coordinate using the linear response approximation. Our study indicates that the reactive fluctuations are characterized by both the polarization time of the solute dipole and the relaxation time (or times) of the solvent. The nature of the relevant solvent relaxation time is explored on a microscopic level for different charge configurations and different solute radii. The results demonstrate that the autocorrelation function of the solvent coordinate (which is proportional to the solvent reaction field) reflects saturation effects and depends on the solute size and charge distribution. Thus we conclude that the microscopic dynamics of the solvent can deviate from the corresponding macroscopic estimate.

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Ultrafast laser spectroscopy: A probe of the photodynamics of chemical intermediates

Cited by 2 publications

References 73 publications

Femtosecond Laser Spectroscopy and Dynamics in Dense Media

Femtosecond Laser Spectroscopy and Dynamics in Dense Media

Effects of solute–solvent coupling and solvent saturation on solvation dynamics of charge transfer reactions

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