Fundamental Interactions
Since its inception Argonne has been involved in long-term fundamental
research that addresses problems in the chemical sciences that are related to
the mission-oriented activities of the Department of Energy. Our programs in
this area are directed to basic research in atomic, molecular and optical
science; chemical physics; photochemistry; and physical chemistry. Our research
seeks to understand chemical reactivity through studies of the interactions of
atoms, molecules, and ions with photons and electrons; the making and breaking
of chemical bonds in the gas phase; and energy transfer processes within and
between molecules.
Ultimately, this research leads to the development of such advances as
efficient combustion systems with reduced emissions of pollutants, new solar
photoconversion processes, and improved development and application of novel
x-ray light sources at current and planned DOE user facilities.
This program combines experiment and theory in developing a quantitative
understanding of x-ray interactions with atoms and molecules from the weak-field
limit to the strong-field regime. Research thrusts are in x-ray probes of
optical strong-field processes, inner-shell processes with intense ultrafast
x-rays, theory and the development of synchrotron-based 1 ps x-ray source at the
Advanced Photon Source. Experimental results are used to challenge and calibrate
some of the most detailed theoretical models in atomic physics.
This program merges theoretical and experimental work on the energetics,
kinetics, and dynamics of chemical reactions in the gas phase with particular
emphasis on combustion reactions. Shock tube, flow tube, and photo-ionization
techniques provide fundamental measurements on the high- and low-temperature
kinetics of radical-radical and radical-molecule reactions, on the
thermochemistry of radicals, and on vibrational/rotational selected
photodissociation of small molecules. A comparable theoretical effort maps out
potential energy surfaces by electronic structure techniques; follows the
dynamics and kinetics on surfaces with trajectories, wave packets, and
statistical models; and couples multiple processes together in kinetics
simulations. The synergism between comparable experimental and theoretical
efforts is a hallmark of this effort.
Researchers are defining the basic principles in solar energy conversion that
govern charge separation in molecules via the study of electron transfer
reactions within natural and biomimetic photosynthetic structures. Work on the
mechanism of charge separation in natural photosystems is being extended to
construct novel artificial systems to mimic the natural process. The program
approach features the resolution of structural dynamics linked to ET reactions
by the application of a suite of advanced, multi-frequency, pulsed magnetic
resonance, transient optical, and x-ray techniques to follow light-activated
structural dynamics across multiple time (10-13 s to 1 s) and length
(1 Å to 500 Å) scales. The research develops a fundamental understanding of
structure-function relationships in biological photosynthesis and establishes
principles for the design of biomimetic systems for solar energy conversion.
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