Dynamics in the condensed phase

We sometimes describe this hy saying that the solvent motions cause the barrier to fluctuate. When we discuss charge transfer in Section 11.1.2, the solvent motion is the reaction coordinate. 

The time scale is a factor in another way. A polyatomic solvent has a range of frequencies with which it can respond because the solvent s intramolecular vibrations can be coupled, even if indirectly, to the solute. The translations and 

For special materials or if we can manage a fast probe, we can have trouble deciding between a solid and a liquid. Toy stores sell plastic balls that are as malleable as plasticine and can be shaped by a gentle slow pressure but that rebound as a new tennis ball when thrown hard at the floor. The same situation is familiar to a diver who jumps from a board into a pool too high a jump and the water responds rather rigidly. The limit of a fast perturbation corresponds to the sudden regime of Chapter 9. 

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In order to discuss various aspects of a mixed quantum-classical treatment of photoinduced nonadiabatic dynamics, we consider five different kinds of molecular models, each representing a specihc challenge for a mixed quantum-classical modeling. Here, we introduce the specifics of these models and discuss the characteristics of their nonadiabatic dynamics. The molecular parameters of the few-mode models (Model I-IV) describing intramolecular nonadiabatic dynamics are collected in Tables I-V. The parameters of Model V describing various aspects of nonadiabatic dynamics in the condensed phase will be given in the text. 

Electron attachment to O2 has been investigated in supercritical hydrocarbon fluids at densities up to about 10 molecules/cm using the pulsed electric conductivity technique [110], and the results have been explained in terms of the effect of the change in the electron potential energy and the polarization energy of 2 in the medium fluids. In general, electron attachment to O2 is considered to be a convenient probe to explore electron dynamics in the condensed phase. 

Abstract. In this chapter we discuss approaches to solving quantum dynamics in the condensed phase based on the quantum-classical Liouville method. Several representations of the quantum-classical Liouville equation (QCLE) of motion have been investigated and subsequently simulated. We discuss the benefits and limitations of these approaches. By making further approximations to the QCLE, we show that standard approaches to this problem, i.e., mean-field and surface-hopping methods, can be derived. The computation of transport coefficients, such as chemical rate constants, represent an important class of problems where the QCL method is applicable. We present a general quantum-classical expression for a time-dependent transport coefficient which incorporates the full system s initial quantum equilibrium structure. As an example of the formalism, the computation of a reaction rate coefficient for a simple reactive model is presented. These results are compared to illuminate the similarities and differences between various approaches discussed in this chapter. 

Thus the principal feature distinguishing this kinetic theory of chemical reactions from earlier theories is the inclusion of the correlated collision events contained in the R collision operators. These terms are crucial for a description of the dynamics in the condensed phase. 

In order to treat these observations and hypotheses in a theoretical framework as successfully as the case of electron localization in helium, we must first probe the dynamical properties of the IR absorptions in the subpicosecond regime. What perhaps is surprising and stimulating for future studies is the wealth of microscopic details that can be obtained on intermolecular interactions and electron transfer in liquids through picosecond spectroscopy, information of fundamental interest to chemical dynamics in the condensed phase. In this vein, we will conclude this chapter by an example of photoselective chemistiy in electron transfer processes that occur following laser excitation of e in the cluster. 

We conclude this article on a note of optimistic speculation. Clearly the above results on solvated electrons establish the potential of ultrashort laser pulses to probe the fundamental details of the dynamics of electron transfer reactions, which will be the cornerstone for the development of microscopic theories of electron dynamics in the condensed phase. Electrons are ubiquitous species, and the practical reflection of this appears in research areas such as photosynthesis, dielectric breakdown, fast optical... 

Nuemberger P, Vogt G, Brixner T, Gerber G (2007) Femtosecond quantum control of molecular dynamics in the condensed phase. Phys Chem Chem Phys 9 2470... 

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