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Ab-initio calculation of electron impact ionization cross sections for atoms in exotic electron configurations
John Jasper Bekx, Sang-Kil Son, Robin Santra, and Beata ZiajaDPG Spring Meeting of the Condensed Matter Section
(German Physical Society, Berlin, Germany, March 11-16, 2018)
Coherent diffraction imaging uses intense femtosecond pulses of hard X-rays. When such pulses interact with the imaged sample, photoelectrons from atomic inner shells are ionized. In light elements, the core holes formed relax predominantly through Auger decay, whose characteristic lifetime is usually between 1 and 10 fs. During this time interval, due to the presence of many energetic electrons excited by X-rays, the ions with core holes may also undergo impact ionization. In this study, we investigate the impact ionization cross sections of ions with such exotic electron configurations and compare them to those of ground state atoms and ions. For calculating the doubly differential cross section, both energy- and angle-resolved, we extend the ab-initio toolkit XATOM . We use the Born approximation for the impact electron, and apply the Hartree-Fock-Slater model for the description of the complex many-electron system under consideration. Our predictions have important implications for understanding radiation damage in X-ray free-electron laser experiments. We also expect applications in the area of electron diffraction, where similar bound-electron configurations could arise.  Z. Jurek et al., J. Appl. Crystallogr. 49, 1048-1056 (2016).
Tags: XATOM, impact ionization, XFEL, CFEL, DESY
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