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Bimolecular Reactions |
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 Our
research focuses on the reactions of vibrationally excited molecules. We
use lasers to prepare molecules in specific rovibrational states and allow
them to react with atoms (H,O,Cl) that are produced by laser photolysis
of an appropriate precursor (NO2, Cl2). The next step
is to spectroscopically monitor (by LIF, REMPI) not only the identity of
the products, but the nascent quantum states that are populated in the reactive
encounter.Full State Resolution In favorable cases we can determine the amount of energy that is channeled into every product degree of freedom. Since the reactants are state-selected, the experiment is fully quantum state resolved. The removal of averaging over the initial and final states in the reaction provides detailed information about the dynamics of the system and facilitates comparisons to cutting-edge theoretical models. Control Reactions It's not all about quantum mechanics and theoretical models, though - our experiments appeal to one's sense of chemical intuition as well. The goal is to understand how different vibrational motions of the molecule can affect the outcome of a reaction. Take, for an example, the partially deuterated water molecule, HOD. It can react with H atoms to produce either H2 + OD or HD + OH. We have demonstrated that it is possible to control the path the reaction takes by judiciously choosing the initial vibrational state of the HOD. States that are predominantly OH-stretching produce H2 + OD, while OD-stretching states react to produce HD + OH. In essence, the initially excited bond is the one that breaks in the reaction. This is the first ever example of bond-selected chemistry. Future Directions We are currently trying to extend this idea to larger molecules where vibrational excitations are much less localized. We are also striving to widen our detection capabilities which will enable us to study a greater number of reactions. |
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