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XATOM: an integrated toolkit for X-ray and atomic physics
Sang-Kil Son and Robin Santra
The 3rd CQSE International Workshop on Atomic, Molecular, and Ultrafast Science and Technology
(National Taiwan University, Taipei, Taiwan, January 7-8, 2012) [poster]
X-ray free-electron lasers (XFEL) open a new era in science and technology, offering many unique opportunities that have not been conceivable with conventional light sources. Because XFELs produce ultrashort pulses with a very high x-ray photon fluence, materials interacting with XFEL pulses undergo significant radiation damage and possibly become highly ionized. To understand the underlying physics, it is crucial to describe detailed ionization and relaxation dynamics in individual atoms during XFEL pulses. Here we present an integrated toolkit to investigate x-ray-induced atomic processes and to simulate electronic damage dynamics. This XATOM toolkit can handle all possible electronic configurations of all atom/ion species, and calculate physical observables during/after intense x-ray pulses. Based on nonrelativistic quantum electrodynamics and perturbation theory within the Hartree-Fock-Slater model, the toolkit can compute subshell photoionization cross sections, Auger and Coster-Kronig decay rates, fluorescence rates, shake-off branching ratios, and elastic x-ray scattering form factors including dispersion corrections. For electronic dynamics during intense x-ray pulses, XATOM employs the rate equation approach with all computed cross sections and rates, and then produces charge state distributions, electron and fluorescence spectra, scattering signals, and so on. By use of XATOM, we can explore many exciting XFEL-related phenomena. Several applications of XATOM will be presented.