Development of new light scattering spectroscopy for the investigation of mode coupling molecular

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Soft condensed materials are characterized by their various kinds of internal degrees of freedom. The degrees interact each other and the coupling phenomena between them play important role in determining the complex function of the soft materials. The purpose of this study is to establish the experimental scheme to reveal the physical mechanism of the coupling phenomenon among these internal degrees of freedom.First, we successfully developed the light scattering relaxation spectroscopy technique to directly observe dynamic interaction between the shear motion of fluid and the orientational order parameter in liquid crystals. The role of the dye molecules in enhancing the optical Kerr effect is revealed. The idea of the Brownian motor was applied oanalyze the enhancing mechanism. The wideband spectra showing the rotational relaxation can be now available for various kinds of soft complex systems.Second, We applied the optical beating Brillouin spectroscopy technique to the direct observation of the molecular relaxation. Phonons excited by the thermal fluctuation propagate interacting the other internal degrees of freedom such as the molecular association. The phonon spectrum is then modulated by their motion and the new quasi-elastic component appears. We successfully observed this Mountain component for some organic liquid. The Brillouin spectroscopy is further improved in the study and we can observe the phonon resonance phenomenon giving 0.01 % accuracy in determining the phonon velocity. Te rapid measurement with FFT technique was also realized.Finally, we carried out the quantitative estimation of the coupling viscosity in liquids. Combination of the Brillouin scattering technique and the capillary wave birefringence method enables us to uniquely determine the coupling viscosity as well as the shear and rotational parameters.