Nuclear Magnetic Resonance Spectroscopy and Spin Relaxation in Amphiphilic Liquid Crystals
Sammanfattning: Spin relaxation theory and nuclear magnetic resonance spectroscopy in amphiphilic liquid crystals are presented. Group theory is used to determine the information content and the orientation dependence in spin relaxation experiments, and to investigate the combined effect of crystal and local symmetries and the effect of symmetry on multiple timescales. From lineshapes of a deuterated decanol and SdS molecules the distribution within and aspect ratio of rodlike aggregates in the rectangular phase of the system SdS/decanol/water are determined. The results reveal the importance of electrostatic interactions in stabilisation of the rectangular phase. A geometry independent theory is developed for spin relaxation by diffusion on a biaxial rod. The most striking result of this theory is the strong geometry dependence of the spinrelaxation functions. A theoretical investigation of spinrelaxation in coupled membrane system are presented. The coupled membrane theory reveals a strong dependence of spectral density functions on membrane coupling. The second and fourth order spectral density functions are calculated. The effective diffusion coefficient for a particle diffusing on a random surface is related to the degree of roughness of the surface. An exact result for the diffusion coefficient is obtained in the limit of fast surface fluctuations, for a static surface upper and lower bounds and an effective medium approximation are derived. From diffusion measurements the surface configuration can then be determined. For particle diffusion in one dimensional random geometry an exact results for the diffusion coefficient is obtained for rapidly fluctuating geometry, a static geometry and in the general case.
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