Ultrafast dynamics control mechanisms

As most chemical and virtually all biochemical processes occur in liquid state, solvation of the reaction partners is one of the most prominent topics for the determination of chemical reactivity and reaction mechanisms and for the control of reaction conditions and resulting materials. Besides an exhaustive investigation by various experimental methods [1,2,3], theoretical approaches have gained an increasing importance in the treatment of solvation effects [4,5,6,7,8], The reason for this is not only the need for sufficiently accurate models for a physically correct interpretation of the experimental data (Theory determines, what we observe ), but also the limitation of experimental methods in dealing with ultrafast reaction dynamics in the pico- or even subpicosecond regime. These processes have become more and more the domain of computational simulations and a critical evaluation of the accuracy of simulation methods covering experimentally inaccessible systems is of utmost importance, therefore. 

The flavor of the diversity in current ET research can be appreciated by noting a number of recent advances which serve to broaden perspectives about underlying electron-transfer mechanisms. These developments have benefited especially from ultrafast laser pump/probe experiments [1,2, 23, 24, 39-42], which have opened up a broader and better-controlled dynamic range, thus forcing the community to address a number of new issues related to the nature of the interacting states and the dynamics of their evolution. 

Other prominent examples are theoretical proposals for different optical control schemes using laser field parameters for the manipulation of ultrafast process pioneered by Rice and Tannor, Shapiro and Brumer, and Peirce, Dahleh, and Rabitz [2, 56-61]. They stimulated control experiments that were carried out first on simple systems such as metallic dimers and trimers [62-84], and later on more complex systems [23-25, 43, 85-89], confirming theoretically proposed concepts. Since tailored laser pulses have the ability to select pathways that optimally lead to the chosen target, their analysis should allow one to determine the mechanism of the processes and to provide the information about the selected pathways (inversion problem). Therefore, theoretical approaches are needed, which are capable of designing interpretable optimal laser pulses for complex systems (e.g., clusters or biomolecules) by establishing the connection between the underlying dynamical processes and their shapes. In this case, the optimal control can be used as a tool for the analysis. 

Abstract We present a general theoretical approach for the simulation and control of ultrafast processes in complex molecular systems. It is based on the combination of quantum chemical nonadiabatic dynamics on the fly with the Wigner distribution approach for simulation and control of laser-induced ultrafast processes. Specifically, we have developed a procedure for the nonadiabatic dynamics in the framework of time-dependent density functional theory using localized basis sets, which is applicable to a large class of molecules and clusters. This has been combined with our general approach for the simulation of time-resolved photoelectron spectra that represents a powerful tool to identify the mechanism of nonadiabatic processes, which has been illustrated on the example of ultrafast photodynamics of furan. Furthermore, we present our field-induced surface hopping (FISH) method which allows to include laser fields directly into the nonadiabatic... 

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