Solvation dynamics nonlinear response

K. Ando and S. Kato, Dielectric relaxation dynamics of water and methanol solutions associated with the ionization of /V,/V-dimcltiylanilinc theoretical analyses, J. Chem. Phys., 95 (1991) 5966-82 D. K. Phelps, M. J. Weaver and B. M. Ladanyi, Solvent dynamic effects in electron transfer molecular dynamics simulations of reactions in methanol, Chem. Phys., 176 (1993) 575-88 M. S. Skaf and B. M. Ladanyi, Molecular dynamics simulation of solvation dynamics in methanol-water mixtures, J. Phys. Chem., 100 (1996) 18258-68 D. Aheme, V. Tran and B. J. Schwartz, Nonlinear, nonpolar solvation dynamics in water the roles of elec-trostriction and solvent translation in the breakdown of linear response, J. Phys. Chem. B, 104 (2000) 5382-94. 

Simulation of Solvation Dynamics Using a Nonlinear Response Approach. 

The nonlinear Smoluchowski-Vlasov equation is calculated to investigate nonlinear effects on solvation dynamics. While a linear response has been assumed for free energy in equilibrium solvent, the equation includes dynamical nonlinear terms. The solvent density function is expanded in terms of spherical harmonics for orientation of solvent molecules, and then only terms for =0 and 1, and m=0 are taken. The calculated results agree qualitatively with that obtained by many molecular dynamics simulations. In the long-term region, solvent relaxation for a change from a neutral solute to a charged one is slower than that obtained by the linearized equation. Further, in the model, the nonlinear terms lessen effects of acceleration by the translational diffusion on solvent relaxation. 

The recent femtosecond experimental data on electron solvation in water (Gaudel et al., 1984, 1987) and observations in a mass spectroscopy on the formation of electrons stabilized in molecular beam clusters (Arbruster et al., 1984) has rekindled extensive interest on the microscopic details of the dynamics and structure of e in particular. Since the appearance of the visible spectrum of e has now been observed from the two photon photoionization of pure water (e.g., no dopant molecules or ions were present) we must focus on what responses can be Induced from the medium on this timescale. From our present databank, it is evident that following the instantaneous electronic polarizability (linear and nonlinear) response to the moving charge and/or field, it is the librational responses that must be the key motion. We assume, for the moment, that the lifetime of the autoionizing level in H2O is not a significant factor. As we have discussed elsewhere (Kenney-Wallace,... 

In this chapter I have presented the basics of SD and described several approaches that can be used to uncover the molecular mechanisms contributing to SD both within the LRA and when the response is nonlinear. Within the LRA, I discussed INM and time-domain methods for analyzing the solvation TCP and the related solvation velocity time correlation, G(f). The methods were illustrated by showing how they can determine the relative contributions to SD from different molecules, types of molecular motion, and correlations among solvent molecules. I also discussed how they can be used relate SD to other observable dynamics in liquids and to explore the similarities and differences between SD in... 

Given this brief summary of the electron solvation data, the reader is urged to consult the references cited for the more extensive arguments that lie behind the points made above. In order to examine the microscopic response of the molecules in the liquid to the electron, we designed a series of ultrafast nonlinear optical experiments (in the absence of e ) in which we would specifically investigate the rotation, libration, vibration, and other (as then unknown) dynamical responses of a molecule suddenly polarized in a strong, transient laser field. This naturally led to the field of nonlinear optical phenomena and quantum electronics, which we will briefly discuss in the following section. 

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