Studies of negative ion spectroscopy and dynamics using time resolved photoelectron imaging

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In this project, funded by the Experimental Physical Chemistry Program of the Chemistry Division, Daniel Neumark of the University of California at Berkeley will engage in spectroscopic and dynamical studies of negative ions and negative ion clusters by means of time-resolved photoelectron imaging (TRPEI) based on femtosecond pump-probe techniques. The approach is based on the successful work done under the previous grant, which is now extended into the domain of time resolution. Specifically, femtosecond-stimulated emission pumping will be used to coherently excite clustered negative I2 ions, and TRPEI will be used to track the resulting vibrational relaxation and solvent evaporation dynamics. Time-resolved pump-probe experiments on halide-water clusters will probe the dynamics of electron solvation in clusters. Time-resolved studies of bimolecular ion-molecule reactions, in particular gas-phase SN2 reactions, by photoinitiating a reaction with a femtosecond pump pulse and monitoring the subsequent dynamics by time-resolved photoelectron spectroscopy are also planned. The focus of the work is to understand the processes of photodetachment dynamics and cluster dynamics. This research will be conducted with postdoctoral research associates and graduate students, as well as undergraduates, who, through their participation in a forefront, cutting-edge research topic, will receive training in advanced research techniques in preparation for employment in the industrial, academic, or governmental sectors of the American economy.