Time Resolved Electron Energy Loss Spectroscopy of Surface Kinetics

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The main goal of this research project is to obtain a detailed understanding at the molecular level the kinetics and mechanisms of gas - surface interactions. Changes in the nature of the adsorbate chemical bond are studied by time resolved electron energy loss spectroscopy (TREELS) coupled with fast temperature and pressure perturbations. A wide range of surface processes can be studied by this excite - and - probe technique, including adsorption/desorption, dissociation, and reaction of adsorbate. More specifically, the proposed project will address problems in the following areas: 1. alkali-promoted dissociations and reactions, 2. effects of impurities on surface kinetics, 3. synthesis reactions, and 4. electron and photon induced reactions. Extension of the experimental time resolution from millisecond to microsecond range will be undertaken. In addition to improvise a faster 96-channel multidector and data acquisition electronics for TREELS, the more rapid pressure and temperature perturbations will be achieved by the addition of a chopper to the pulsed molecular beam and direct heating with a microsecond pulsed laser, respectively. A pulsed electron source will be generated from a negative electron affinity GaAs photocathode.