Exploring Strong Field Molecular and Electron Dynamics, and Oxidation of Bio-Organic Systems

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H. Bernhard Schlegel of Wayne State University is supported by an award from the Theory, Models and Computational Methods program within the Chemistry Division for research to further our understanding of the way lasers reveal details about chemical reactions. The work supported is theoretical and computational in nature, but is being carried out in close collaboration with experimental scientists who are testing the predictions of these theories in laser laboratories. The investigations provide information on how light delivered in short, intense pulses can be used to follow minute details of atoms and molecules as chemical reactions are taking place. In a second portion of the project, the investigators are studying how damage to DNA by oxidizing species occurs at the molecular level. This process is thought to be at the core of a number of health problems, including cancer and aging. The work is promoting the progress of science by developing new tools and methods that will have application in many other areas of science. The work is also helping to train the next generation of scientists in projects that involve a high degree of collaboration between computational scientists and experimental scientists.The research has three main categories: (1) a study of strong field molecular dynamics; (2) electron dynamics in strong fields; and (3) oxidation in bio-organic systems. In (1), the investigators are studying isomerization and fragmentation of molecules in intense mid-IR (infrared) laser fields using molecular dynamics calculations. In some cases that go beyond the Born-Oppenheimer approximation, the investigators are using Ehrenfest dynamics and extended Lagrangian dynamics. In (2), time-dependent Hartree-Fock, density functional and configuration interaction methods with real space complex absorbing potentials are being used to investigate electron dynamics and ionization processes in strong laser fields. Topics under investigation include angle-resolved ionization rates in conjugated molecules, electron dynamics in ions during and after ionization, and changes in ionization rates during isomerization and fragmentation reactions. In (3), oxidation of G-quadruplexes, guanine-lysine adduct formation during oxidative degradation of guanine, and oxidation of ascorbic acid are being investigated. Continuum solvation models with cavity scaling are being used to obtain reliable pKas, redox potentials and energetics along reaction paths.