Dynamics in Complex Molecular Condensed Matter Systems

Stanford University, Stanford CA

Investigators

Abstract

This project aims to use a variety of ultrafast nonlinear optical and infrared experiments and theory to increase understanding of glasses and complex liquids, such as supercooled liquids, liquid crystals, and hydrogen bonding liquids (water and alcohols). Ultrafast infrared vibrational echoes, spectrally resolved vibrational echoes, and vibrational echo correlation spectroscopy will be used to study the dynamics of hydrogen bonded systems, such as glycerol, as normal liquids, supercooled liquids and glasses. The vibrational echo experiments provide a direct probe of hydrogen bond network dynamics. Ultrafast (< 100 fs) to slow (ms) optical heterodyne detected optical Kerr effect experiments will be used to study supercooled liquids, the approach to the glass transition, liquid crystals, and ionic organic liquids. Comparisons among the liquids and to Mode Coupling Theory will provide insights into the connection between dynamics, intermolecular interactions, and structure. New tools and experimental methods using ultrafast pulse sequences of visible and infrared light, are being developed and applied to gain understanding of such systems. The methods permit examination of changing molecular structures on the time scales on which the important events occur. Graduate students and postdoctoral students participating in all aspects of the research will train the next generation of first-rate scientists. %%% Disordered molecular materials, such as liquids and glasses, play important roles in a wide range of scientific fields from astronomy to zoology, as well as in chemistry, materials science and biology. Crystals are ordered solids. Their structures are fixed. Using x-ray crystallography, the arrangement of the molecules and atoms is well known. Liquids, particularly complex liquids, for example, liquid crystals, alcohols, and water, and glasses (amorphous solids), are very different from crystals. They do not have a regular structure and the structure is constantly changing. Even glasses, which are solids, do not have fixed structures. The structures evolve with time. The macroscopic properties of complex liquids and glasses are determined by details of the relationship between their microscopic structure and dynamics. Explication of complex molecular systems can lead to their control and utilization. Participation of graduate students and postdoctoral students in all aspects of the research trains the next generation of first-rate scientists. Liquids and glasses are materials of high importance to industry, and students trained in these areas will compete extremely well in the high-technology job market. ***