Thermal, Photo- and Radiation-Induced Reactions in Condensed Media
This program examines fundamental chemistry underlying production and efficient use of energy stored in chemical forms, with focuses on chemistry of transient species and catalysis.
The complementary techniques of excitation by photons or fast electrons are used to 1) Provide basic knowledge relevant to the capture and storage of light energy in useful chemical forms, and 2) Elucidate the chemistry of radicals and ions on fast time scales. Subjects investigated include electron transfer reactions, motions of charges in condensed media (including fluids, ionic liquids, glasses and supercritical fluids), fast molecular dissociation reactions, dipole-moment changes in charge transfer transitions, formation of excited states of molecules, transition metal complexes, and chemical and physical transformations of excited and highly reactive species are investigated. The Laser-Electron Accelerator Facility (LEAF) is a powerful tool for these studies.
The development of new experimental techniques and detection systems at LEAF is an integral part of our effort to produce ground-breaking science. Theoretical and experimental efforts are elucidating the factors that control excited-state lifetimes and electron transfer rates; the roles of nuclear-configuration and free-energy changes, electronic configuration, orbital symmetry, donor/acceptor separation, bridging groups and solvent dynamics for a wide range of donor/acceptor systems.
The long-term storage of solar energy as fuels or valuable chemicals requires efficient coupling of light absorption and chemical transformations. Mechanistic studies of transition-metal complexes and metal clusters which couple photo-induced electron transfer processes to the bond-forming reactions required in the photogeneration of dihydrogen and the photoreduction of carbon dioxide to carbon monoxide or methanol are a major focus. Since M-H bond cleavage is a requisite step in both catalytic and stoichiometric reactions of metal hydrides, a goal is an improved understanding of the factors that influence the rates and mechanisms for rupture of M-H bonds. This information contributes to the rational design of new homogeneous catalysts and catalytic reactions that are environmentally friendly, through use of alternative renewable feedstocks, readily recycled catalysts, aqueous solvents, or solvent-free processes.
The Thermal, Photo- and Radiation-Induced Reactions in Condensed Media Group is supported by the Photochemistry and Radiation Research Program of the Division of Chemical Sciences, Geosciences, and Biosciences of the Office of Basic Energy Sciences of the Office of Science under contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Last Modified: September 24, 2014