Exploring Strong Field Electronic and Molecular Dynamics

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Professor H. Bernhard Schlegel of Wayne State University is supported by an award from the Theory, Models and Computational Methods program within the Chemistry Division. He studies the interaction of intense laser light pulses with molecules to investigate chemical reactions that occur over a very short time scale (attoseconds, or quadrillionths of a second). The research is theoretical and computational in nature and is being carried out in close collaboration with experimental scientists who are testing the predictions of these theories in laser laboratories. Dr. Schlegel's investigations are revealing how light delivered in short, intense pulses can be used to follow the movement of electrons in molecules during chemical reactions, called electron dynamics. Results of this fundamental study can provide details about the individual steps involved in a chemical reaction, its mechanism, which can aid in making chemical processes more efficient. He conducts workshops to instruct student researchers on how to utilize computational chemistry software. The computer software developed during the project is available to the scientific community through Dr. Schlegel's website and is incorporated into general-purpose quantum chemistry computer codes. The response of molecules to intense laser fields involves electron dynamics on a time scale as short as few hundreds of attoseconds and molecular dynamics at times of a few femtoseconds and longer. Methodologies to simulate these interactions are being developed for both time scales. Time-dependent configuration interaction methods with real space complex absorbing potentials (TDCI-CAP) and real-time integration of time-dependent density functional theory (rt-TDDFT) are used to investigate electron dynamics and ionization of molecules in strong laser fields. Machine learning is being tested for predicting the angular dependence of strong field ionization from orbital energies, ionization potentials and the shapes of molecular orbitals, electrostatic potentials and electric field gradients. Born-Oppenheimer, extended Lagrangian and Ehrenfest dynamics are being used to simulate isomerization and fragmentation in cations by ultra-short, intense mid-infrared laser pulses. The involvement of excited states in strong field isomerization and fragmentation reactions is to be investigated with non-adiabatic molecular dynamics.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.