In this project in the Physical Chemistry program of the Chemistry Division, Professor Marsha I. Lester of the University of Pennsylvania will study the spectroscopy and reaction dynamics of open shell complexes in order to: 1) map out the intermolecular potential energy surfaces between a free radical and a collision partner by accessing intermolecular vibrations via stimulated emission pumping and infrared overtone excitation; 2) examine the change in the intermolecular interaction between a free radical and a collision partner due to the orientation of the orbital containing an unpaired electron; and 3) induce chemical reaction within a complex composed of a hydroxyl radical and a molecular partner by surmounting the activation barrier to reaction via infrared overtone excitation of that radical. Detailed understanding of reaction chemistry at the molecular level requires knowledge of the behavior of the reaction partners during the short duration of the reaction process. Free radicals, i.e., atoms or molecules with an unpaired electron, play an essential part in reaction processes but because of their short lived existence are difficult to study in themselves and, especially, in a reaction process. The present research will provide fundamental knowledge and insight into the process of chemical reactions taking place in the gaseous state.
