Ultrasonic Measurements Near Transitions

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Dr. Garland will apply experimental methods, refined in his laboratory, to study in formation and behavior of structural glasses and the commensurate phases, important research areas in low temperature physics and chemistry. Ultrasonic measurements provide an excellent method to enhance the basic understanding of these challenging problems by providing an important tool for characterizing the glass "freezing" temperature and for monitoring prefreezing dynamics in the megahertz frequency range. In addition, these experimental measurements provide the data essential to testing modern theories of critical dynamics in pure fluids and to point the directions for the development of new theory. Ultrasonic studies are also advantageous since both the static and dynamic response of a system can be determined from simultaneous measurements of velocity and attenuation of acoustic waves as a function of frequency. Such measurements will be made as a function of temperature and composition in 1) alkali cyanide structural glasses, 2) dipolar ferro/antiferroelectric structural glasses, and 3) crystals exhibiting incommensurate phases.