Atomic, Molecular and Optical Physics

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Fig. 1: Sketch of the resonant-Auger process in a laser-dressed atom. The optical field couples core-excited states and produces sidebands on the ejected electron energies.

The AMO Physics program seeks quantitative understanding of x-ray interactions with atoms and molecules from the weak-field limit explored at Argonne's Advanced Photon Source (APS) to the strong-field regime accessible at the Linac Coherent Light Source (LCLS) and other x-ray light sources around the world. We perform experimental and theoretical research on x-ray and inner-shell processes, laser control of atomic and molecular motions, laser-pump/x-ray-probe studies of molecular and chemical dynamics, and x-ray diffractive imaging of optically trapped nanoparticles. Theory is a key element of our program by predicting phenomena that motivate experiments and by simulating measured results. The AMO group is particularly active at APS beamline 7-ID where we use high-repetition-rate lasers for pump-probe measurements on the photodynamics of solvated molecules and x-ray/ion coincidence measurements on core-hole decay dynamics of gas-phase molecules. Topics of LCLS experiments include multiple-photon ionization, femtosecond pulse characterization, and x-ray-pump/x-ray-probe studies of molecular dynamics. Theoretical studies include laser-dressed atoms in weak and strong x-ray fields and intense x-ray interactions with atoms, clusters, and nanoparticles. See "Current Research" for further details.