Dissociative Photodetachment Dynamics of Multiply Charged Anions

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With this award, the Chemical Structure, Dynamics, and Mechanism (CSDM-A) Program in the Division of Chemistry supports Dr. Robert Continetti at the University of California-San Diego in his studies of isolated multiply charged anions. These molecules with extra electrons play an important role in a wide range of chemistry, including biological systems, catalysts and as building blocks in ionic solids. However, they are very difficult to study experimentally in an isolated state. This research program involves novel measurements of the stability and chemistry of isolated multiply charged anions, with the information gained providing new insights and guiding the development of an improved theoretical understanding of these important chemical building blocks. Students involved in this project are learning about the design, construction and chemical application of a unique apparatus. The PI also uses contacts with local industry in San Diego (Cymer, Illumina, Air Products and others) to arrange quarterly tours of industrial labs and seminars by industrial scientists to enhance the career development of underrepresented minority and women graduate students across the Dept. of Chemistry and Biochemistry at UCSD.On a more technical level, this award enables experimental studies of the energetics, photochemistry and dissociation dynamics of multiply charged anions (MCAs) with a particular focus on dissociative photodetachment. Isolated MCAs are challenging systems for study theoretically and experimentally, but important progress has been made using photoelectron and photodissociation spectroscopies. However, many MCAs can undergo complex multiple photodetachment and dissociation processes. These studies use an electrospray ionization source coupled with a cryogenic accumulator ion trap prior to injection into a high-energy electrostatic ion beam trap where the photoelectron and photofragment measurements are made. Time- and position-sensitive detectors are used to make three-dimensional, kinematically complete measurements of the photodetachment, multiple photodetachment, photodissociation and dissociative photodetachment processes observed. In addition, the lifetimes of metastable polyanions and photofragment anions are measured in the electrostatic ion beam trap. The first focus of the project is on the stable dianions formed from dicarboxylic acids, later to be extended to phthalocyanines and biologically relevant sulfonates. In a collaboration with the synthetic inorganic laboratory of Figueroa at UCSD, novel metal carbonyl and isocyanide complexes synthesized for applications in catalysis are also under study. For these systems, there is no prior experimental information available on the ligand dissociation processes and electron-capture energetics that this project is providing. This information is essential for guiding the design of future catalysts and the development of an improved theory of MCAs.