Regular Article – Plasma Physics
Tracing X-ray-induced formation of warm dense gold with Boltzmann kinetic equations
Center for Free-Electron Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607, Hamburg, Germany
2 Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342, Krakow, Poland
3 Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 182 21, Prague 8, Czech Republic
4 Institute of Plasma Physics, Czech Academy of Sciences, Za Slovankou 3, 182 00, Prague 8, Czech Republic
5 Department of Physics, Indian Institute of Technology Delhi, 110016, New Delhi, India
6 Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607, Hamburg, Germany
Accepted: 21 July 2021
Published online: 16 August 2021
In this paper, we report on the Boltzmann kinetic equation approach adapted for simulations of warm dense matter created by irradiation of bulk gold with intense ultrashort X-ray pulses. X-rays can excite inner-shell electrons, which triggers creation of deep-lying core holes. Their relaxation, especially in heavier elements such as gold (atomic number ) takes complicated pathways, involving collisional processes, and leading through a large number of active configurations. This number can be so high that solving a set of evolution equations for each configuration becomes computationally inefficient, and another modeling approach should be used instead. Here, we use the earlier introduced ’predominant excitation and relaxation path’ approach. It still uses true atomic configurations but limits their number by restricting material relaxation to a selected set of predominant pathways for material excitation and relaxation. With that, we obtain time-resolved predictions for excitation and relaxation in X-ray irradiated bulk of gold, including the respective change of gold optical properties. We compare the predictions with the available data from high-energy-density experiments. Their good agreement indicates ability of the Boltzmann kinetic equation approach to describe warm dense matter created from high-Z materials after their irradiation with X rays, which can be validated in future experiments.
© The Author(s) 2021
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