Coherent Phase Control in Isolated Molecules and Condensed Phases

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This research investigates the application of the phase of laser light to understand and manipulate the behavior of electrons and/or nuclei in isolated molecules and in condensed matter. By varying the relative phase of two electromagnetic fields, it is possible to control the interference between two competing excitation paths and thereby to alter the branching ratio of a chemical reaction or the direction of a photocurrent. Moreover, from the laser-phase dependence of the observable, it is possible to obtain fundamentally new information about continuum structure. Three new initiatives are designed to deepen our understanding of such interference effects. The first is the application of coherent control to bond-selective chemistry of complex molecules. Specifically, the interference between one- and three-photon excitation will be used to control the product distribution in the photodissociation of vinyl chloride. Second, coherent control will be used to manipulate the photodissociation of hydrogen molecules in selected vibrational and rotational levels. The phase lag spectrum for this process will then be compared with theoretical predictions. Finally, the theory of phase-lag spectroscopy will be extended to deal with surface resonances, thereby providing a tool for understanding a variety of decay and decoherence mechanisms relevant to photon- and electron-triggered surface chemistry and to electron transport in molecular devices. This project is jointly funded by the AMOP program in the Physics Division and the EPC program in the Chemistry Division.