In this project in the Physical Chemistry Program of the Chemistry Division, Professor Michael Topp of the University of Pennsylvania will use picosecond-resolution polarization spectroscopy in cooled jet expansions to study structure and dynamics in molecular clusters. Using the time-domain rotational coherence technique, Topp proposes to obtain structural information on clusters in order to understand energy transfer and related processes in these organized systems. Such information is difficult to obtain by more normal frequency resolved spectroscopic techniques. The aromatic molecule perylene will be used in much of the structural work, involving the complexation of different alkanes and various polar and unsaturated molecules with large electrostatic interactions. %%% The nucleation of small clusters of atoms or molecules by large organic molecules which absorb and emit visible light presents valuable opportunities to study intermolecular forces of the kind found on a larger scale in solutions and in the adsorption of molecules onto extended surfaces. Lasers can be used to excite these large organic molecules, and then the time evolution of the associated cluster can be followed on very fast time scales in order to be able to determine the structure and dynamics of these microscopic organized systems. Such information can have a bearing on many fields, including catalysis and the chemistry of life processes.
