The Behavior of Solvated Electrons in the Presence of Electrolytes: Using Simulation and Experiment to Determine the Hydrated Electron's Structure from Competitive Ion Pairing

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With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Professor Benjamin Schwartz of the University of California-Los Angeles is using a combination of theoretical and experimental techniques to investigate the behavior of hydrated electrons in the presence of salts. Hydrated electrons play a critical role in radiation chemistry and electron transfer reactions. Despite the importance of hydrated electrons in chemical reactivity, their structure is uncertain given current limitations in experimental measurements and variations in results from theoretical models. Professor Schwartz and his group will investigate hydrated electrons in the presence of salts to examine how hydrated electrons pair with different salt cations using ultrafast spectroscopic measurements. These results will be directly compared using first-principles simulations to better understand the chemical reactivity of hydrated electrons. Professor Schwartz works with secondary-school teachers and students through an outreach program to help bring modern science to local area high schools. Both experimental and computational studies will be employed to reveal the structure of hydrated electrons. Both mixed quantum/classical simulations, where only the hydrated electron is treated quantum mechanically, and ab initio simulations, where the entire system is treated by density functional theory (DFT), will be used to understand the thermodynamics of simulated hydrated electrons paired with different cations. Ultrafast spectroscopy experiments will be used to measure the absorption spectrum of hydrated electrons in the presence of different salts thereby providing a direct measure of the degree of ion pairing that can be compared with the different simulation models. Additional measurements of photoexcited hydrated electrons have the potential to provide a detailed understanding of how the presence of salts alters the dynamics and thus the structure of hydrated electrons paired with different cations. By using both experiments and simulations, the reactive chemistry of pairs of hydrated electrons and a direct connection between structure and reactivity will be developed.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.