Quantitative techniques, nonlinear optics

Motivating the research is the need for systematic, quantitative information about how different surfaces and solvents affect the structure, orientation, and reactivity of adsorbed solutes. In particular, the question of how the anisotropy imposed by surfaces alters solvent-solute interactions from their bulk solution limit will be explored. Answers to this question promise to affect our understanding of broad classes of interfacial phenomena including electron transfer, molecular recognition, and macromolecular self assembly. By combining surface sensitive, nonlinear optical techniques with methods developed for bulk solution studies, experiments will examine how the interfacial environment experienced by a solute changes as a function of solvent properties and surface composition. 

The Kurtz powder technique developed by S. W. Kurtz and T. T. Perry in 1968 offered the first possibility for the determination of nonlinear optical properties of crystalline organic componnds. In comparison with a standard such as quartz or urea, the capability of materials to generate the second harmonic is detected. The pulverized sample is irradiated by a laser and the intensity of frequency-doubled light is measured. As this method is influenced by many factors, such as particle size, it is only semi-quantitative. The results give no precise values for the hyperpolarizability p. A further disadvantage is that the method is limited to molecules that crystallize in noncentrosynunetric space groups. 

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