Complexity Management in Strong Field-Molecule Interactions: Lessons from Evolution and Dimensionality Reduction Manipulation and control of the molecular Hamiltonian is possible using amplified, femtosecond laser radiation because the electric field strength approaches that binding valence electrons. The interaction of such strong fields with a molecule leads to highly nonlinear excitation, resulting in processes such as tunnel ionization, high harmonic generation, selective bond dissociation, and laser filamentation. The product space is large with dimension ranging up to 50 using mass spectral detection, for example. Phase, amplitude and polarization shaping of the incident laser pulse results in an excitation space of even higher dimension (up to 2000). Thus, an astronomic number of excitation pulses and detection states are in play. Understanding the mapping of shaped, strong field laser pulses onto the product state space is one goal of our research. This seminar will present our current understanding of strong field excitation ranging from simple models (nonadiabatic excitation) to time-dependent density functional theory for attosecond electronic dynamics. Methods for managing these complex systems will be discussed including diffusion mapping, adaptive searching, and correlation analysis. Applications of the resulting strong field phenomena will be discussed including photonic reagents for chemical reactions, control of laser filamentation, and novel molecular sensing paradigms.
Levis pioneered the area of strong field chemistry, which is the use of ultrafast and intense lasers to modify, manipulate and detect molecular systems. This work involves experimental and theoretical investigations of lasers having electric field strength of magnitude equal to the forces binding electrons to molecules. Recent work combines strong laser fields with condensed phase systems to induce intact vaporization of biological macromolecules and explosives, the development of filament-based impulsive Raman spectroscopy for gas phase detection and the discovery of the dynamic Rabi oscillation in strong fields. The Levis laboratory has demonstrated the use of intense lasers to produce new molecular signatures for mass spectrometry and the use of pulse shaping to modify these signatures.
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