****NON-TECHNICAL ABSTRACT**** Since Einstein?s original work on Brownian motion 100 years ago, random walks and diffusion have stood as paradigms for how scientists understand the motions of microscopic particles. Recently it has emerged that in highly viscous fluids, ordinary diffusion is superceded by a previously unrecognized and still incompletely characterized process, in which the particles move further than expected on the basis of diffusion. Such motion is therefore described as superdiffusive. This project will systematically elucidate superdiffusive particle motions of collections of particles as well as at the single particle level using state-of-the-art x-ray and optical techniques. The proposed experiments will create new knowledge and motivate new theoretical descriptions of the dynamics of particles and particle suspensions in highly viscous fluids. This will transform our understanding of highly viscous fluids, whose properties give rise to superdiffusion in a way that is not currently understood. The research will also inform programmatic and technical decisions to be made about the next generation of national x-ray facilities, and it will support the education PhD students, who will learn how to do the best possible science at these facilities, fulfilling a vital national need for such trained individuals.
Brownian motion, random walks and diffusion are paradigms of how we understand the dynamics of condensed matter systems. Recently it has emerged that in highly viscous fluids, ordinary diffusion is superceded by a previously unrecognized and still incompletely characterized process, for which the particle's mean-square displacement varies, not linearly in time, as it does for diffusion, but faster than linearly in time. Such motion is therefore described as superdiffusive. This project will systematically elucidate superdiffusive particle dynamics at the ensemble level using x-ray photon correlation spectroscopy, and at the single particle level by using back-focal-plane interferometry. The proposed experiments will create new knowledge and motivate new theoretical descriptions of the dynamics of particles and particle suspensions in highly viscous fluids. This will be transformative to our understanding of highly viscous fluids, whose properties give rise to superdiffusion in a way that currently is not understood. This research will also inform programmatic and technical decisions to be made about the next generation of national x-ray facilities, and it will support the education PhD students, who will learn how to do the best possible science at these facilities, fulfilling a vital national need for such trained individuals.
