Abstract
Field-cycling nuclear magnetic resonance relaxometry was used to study the spin-lattice relaxation dispersion of selected standard nematic liquid crystals at different temperatures, in presence and absence of a monochromatic ultrasonic field. It was found that sonication changes the relaxation dispersion and, in some cases, it shortens the spin-lattice relaxation time on a broad frequency range. The theoretical interpretation is based on the interaction between the ultrasound and the nematic director field. A model previously developed and tested in preliminary experiments, is now successfully applied in a broader temperature range for different compounds. We found a remarkably good agreement with earlier experiments in pentylcyanobiphenyl (5CB). Nonetheless, new interesting features and stronger effects were observed in p-azoxyanysole (PAA). The analysis of our results clearly suggests a sound-induced enhancement of order director modes.
Published Version
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