This project is a unified study of reactions in liquids and gases with the goal of comparing the influence of vibrational excitation on bimolecular reactions in the two settings and of understanding the role played by the surroundings. In gases, bimolecular reactions can be promoted and controlled using laser pulses to generate a reactive radical, to excite a reactant vibrationally, and to detect the reaction products. The same conceptual approach, using different technology, will be applied in liquids. Gas-phase studies rely on relatively high spectral resolution lasers to prepare and probe individual quantum states of the reactants and products. Because of the frequent encounters in liquids, studies in solution need short time resolution, with the consequence that the spectral resolution of the laser pulses is poorer. Nonetheless, it is possible to excite and probe individual vibrations in liquids by a judicious choice of time and spectral resolution in the excitation and interrogation steps. This project will use bromine in vibrational-mode selective single collision reactions and compare gas-phase reactions with those in solution. The high time resolution in the solution-phase experiments will allow the direct observation of the evolution of a photolytically generated bromine atom as it forms complexes and reacts with vibrationally excited solvent molecules. Single collision studies of the same reactions in a molecular beam will provide a point of comparison by observing the influence of vibrational excitation without the complication of the surrounding solvent. The fundamental science in this project will provide valuable experience and skills to graduate students, as well as opportunities designed to integrate research, teaching, and learning at the University of Wisconsin/Madison. The principal investigator will participate in education and policy related activities, and reach out to beginning scientists about the research enterprise.
