Nonlinear optical solvent effects

There have been some attempts to compute nonlinear optical properties in solution. These studies have shown that very small variations in the solvent cavity can give very large deviations in the computed hyperpolarizability. The valence bond charge transfer (VB-CT) method created by Goddard and coworkers has had some success in reproducing solvent effect trends and polymer results (the VB-CT-S and VB-CTE forms, respectively). 

The homogeneous and hetergeneous models for solvent effects are generic for nonlinear optical properties and cover a great number of processes emerging from strong matter-light interaction. These are of considerable fundamental interest, and also possess... 

An analytical structure-(hyper)polarizability relationship based on a two-state description has also been derived [49]. In this model a parameter MIX is introduced that describes the mixture between the neutral and charge-separated resonance forms of donor-acceptor substituted conjugated molecules. This parameter can be directly related to BLA and can explain solvent effects on the molecular hyperpolarizabilities. NMR studies in solution (e.g. in CDCl3) can give an estimate of the BLA and therefore allow a direct correlation with the nonlinear optical experiments. A similar model introducing a resonance parameter c that can be related to the MIX parameter was also introduced to classify nonlinear optical molecular systems [50,51]. 

Tabei, H. Kurihara, T. and Kaino, T. (1987). Recrystallization solvent effects on second-order nonlinear optical organic materials. Appl Phys. Lett., 50, 1855-7. [213]... 

It is also important to realize that the nonlinear optical properties of a molecule in solution or in the solid state will differ from that of the isolated molecule due to polarization effects caused by the surrounding molecules. In theoretical calculations of molecules in die liquid phase, these effects may be modeled using for instance dielectric continuum models [33, 41, 42, 52, 56]. The use of such schemes for estimating the polarization of the solute by the solvent does not resolve the issue of local field factors. 

Bartkowiak, W., Lipifiski, J. Solvent effect on the nonlinear optical properties of para-nitroaniline studied by Langevin dipoles-Monte Carlo (LD/MC) approach. Computers Chem. 22, 31-37 (1998)... 

Dehu, C., Meyers, F., Hendrickx. E.. Clays, K., Persoons, A., Marder, S.R., Bredas, J.L. Solvent effects on the second-order nonlinear optical response of tr-conjugated molecules A combined evaluation through self-consistent reaction field calculations and hyper-Rayleigh scaterring measurements. J. Am. Chem. Soc. 117, 10127-10128 (1995)... 

The term solvatochromism is used to describe the change of position, intensity and shape of the UV-Vis absorption band of the chromophore in solvents of different polarity [1, 2], This phenomenon can be explained on the basis of the theory of intermolecular solute-solvent Interactions in the ground g) and the Franck-Condon excited state e). We will consider only the effect of the solute-solvent interaction on the electronic absorption and nonlinear optical response of a dilute solution of the solute. This way we avoid the explicit discussion of the solute-solute interaction, which significantly obscures the picture of the solvatochromism phenomenon. 

The understanding and reliable prediction of the influence of the solute-solvent interactions on the nonlinear optical properties of molecular systems is a significant issue for a width range of theoretical and experimental areas of studies. In this review, it was shown that the simple two-state approximations combined with tlie solvatochromic methods are an effective tools in prediction tlie direction of tlie changes of molecular nonlinear responses as a function of solvent polarity. This methodology based on the description of the solvent effects at the molecular level should be treated as a supporting for the most sophisticated quantum chemical approaches. 

Bhat, M.N., Dharmaprakash, S.M. Effect of solvents on the growth morphology and physical characteristics of nonlinear optical y-glycine crystals, J. Crystal Growth 242 (1-2) (2002) 245-252. 

In this section we shall present and discuss some numerical results regarding structures of two series of noncentrosymmetric polyenes NH2(CH=CH)nR (n=l,2), with R=CHO (series I) and with R=N02 (series II). These results have been extracted from a study we have published on the Journal of the American Chemical Society about solvent effects on electronic and vibrational components of linear cUid nonlinear optical properties of Donor-Acceptor polyenes. 

I. D. L. Albert, S. di Bella, D. R. Kanis, T. J. Marks, and M. A. Ratner, in Polymers for Second-Order Nonlinear Optics, American Chemical Society, Washington, DC, 1995, pp. 57-65. Solvent Effects on the Molecular Quadratic Hyperpolarizabilities. 

By analogy ivith SHG described above, if two light beams of fixed visible frequency cOvis and tunable IR frequency cOir are focused onto a surface then due to nonlinear optical effects reflected light of sum-frequency cOsf = cOvis-I-(Uir may be detected, hence the name sum-frequency generation. The selection rules demand that only bands that are both IR and Raman active are observed. Unfortunately, sum frequency generation (SFG) suffers from the disadvantage of strong IR absorption by solvent, so irradiation from the back of the electrode is sometimes used. 

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