Picosecond Rotational Diffusion Studies Using Time-Resolved and Phase-Resolved Spectroscopy

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This project is in the general area of analytical and surface chemistry and in the subfields of spectroscopy and separation science. Electronic spectroscopy affords a sensitive means of quantifying solutes. Because faster time scales are now accessible to electronic spectroscopy, this tool can be more readily used to obtain structural information. In particular, the size and shape of a solute determine its rotational diffusion behavior. Rotational diffusion studies of medium-sized organic molecules in common solvents require both picosecond spectroscopy and the resolution of multiple exponentially decreasing response signals. Professor Wirth and her students will measure the three components of the rotational diffusion constant of the solute tetracene which will enable an assessment of the extent to which structural information can be derived from this approach. However, if the solvent has short-range structural order, the presence of the solvent could potentially limit the solute information that is obtained. To address this issue, Professor Wirth will also study the effect of solvent structure on solute rotational diffusion. The results of these studies are expected to be valuable both to analytical spectroscopy and to an enhanced fundamental understanding of liquids.