Abstract:We theoretically study orbital alignment in x-ray-ionized atoms and ions, based on improved electronicstructure calculations starting from the Hartree-Fock-Slater model. We employ first-order many-body perturbation theory to improve the Hartree-Fock-Slater calculations and show that the use of first-order-corrected energies yields significantly better transition energies than originally obtained. The improved electronic-structure calculations enable us also to compute individual state-to-state cross sections a… Show more
“…The discrepancies between theory and experiment might be due to higher-order many-body processes 46 , 47 , the chaoticity of self-amplified spontaneous emission (SASE) pulses 48 , and coherence effects 28 , 49 , 50 , which are not included in the model. The resonance positions are expected to profit from improved electronic structure theory 51 , which affects resonant ionisation dynamics 52 . Fig.…”
Understanding the interaction of intense, femtosecond X-ray pulses with heavy atoms is crucial for gaining insights into the structure and dynamics of matter. One key aspect of nonlinear light–matter interaction was, so far, not studied systematically at free-electron lasers—its dependence on the photon energy. Here, we use resonant ion spectroscopy to map out the transient electronic structures occurring during the complex charge-up pathways of xenon. Massively hollow atoms featuring up to six simultaneous core holes determine the spectra at specific photon energies and charge states. We also illustrate how different X-ray pulse parameters, which are usually intertwined, can be partially disentangled. The extraction of resonance spectra is facilitated by the possibility of working with a constant number of photons per X-ray pulse at all photon energies and the fact that the ion yields become independent of the peak fluence beyond a saturation point. Our study lays the groundwork for spectroscopic investigations of transient atomic species in exotic, multiple-core-hole states that have not been explored previously.
“…The discrepancies between theory and experiment might be due to higher-order many-body processes 46 , 47 , the chaoticity of self-amplified spontaneous emission (SASE) pulses 48 , and coherence effects 28 , 49 , 50 , which are not included in the model. The resonance positions are expected to profit from improved electronic structure theory 51 , which affects resonant ionisation dynamics 52 . Fig.…”
Understanding the interaction of intense, femtosecond X-ray pulses with heavy atoms is crucial for gaining insights into the structure and dynamics of matter. One key aspect of nonlinear light–matter interaction was, so far, not studied systematically at free-electron lasers—its dependence on the photon energy. Here, we use resonant ion spectroscopy to map out the transient electronic structures occurring during the complex charge-up pathways of xenon. Massively hollow atoms featuring up to six simultaneous core holes determine the spectra at specific photon energies and charge states. We also illustrate how different X-ray pulse parameters, which are usually intertwined, can be partially disentangled. The extraction of resonance spectra is facilitated by the possibility of working with a constant number of photons per X-ray pulse at all photon energies and the fact that the ion yields become independent of the peak fluence beyond a saturation point. Our study lays the groundwork for spectroscopic investigations of transient atomic species in exotic, multiple-core-hole states that have not been explored previously.
“…First, as shown in Ref. [43], the first-order-corrected energies, delivered by the improved electronic-structure calculations, often provide better transition energies. Second, individual states associated with a configuration generally do not behave the same during ionization dynamics.…”
Section: Introductionmentioning
confidence: 94%
“…For more details, the reader is referred to Ref. [43]. XATOM is based on the Hartree-Fock-Slater (HFS) approach [32,44], in order to keep the calculations feasible and efficient for heavy atoms also and the inclusion of resonant excitations (see Sec.…”
Section: A Improved Electronic-structure Calculationsmentioning
confidence: 99%
“…In this work, we investigate x-ray multiphoton ionization dynamics of neon atoms based on individual electronic states by extending the ab initio electronic-structure and ionization-dynamics toolkit XATOM [32,41,42]. Recently, a state-resolved electronic-structure framework, based on firstorder many-body perturbation theory, has been introduced in XATOM [43]. As a follow-up study, we here embed these improved electronic-structure calculations into the Monte Carlo on-the-fly rate-equation method for describing ionization dynamics [9,27].…”
Section: Introductionmentioning
confidence: 99%
“…Additionally, individual state-to-state resonant photoabsorption cross sections, which are missing in Ref. [43], are addressed. A comparison with a configuration-based Monte Carlo calculation is the topic of Sec.…”
We present a theoretical framework to describe state-resolved ionization dynamics of neon atoms driven by ultraintense x-ray free-electron-laser pulses. In general, x-ray multiphoton ionization dynamics of atoms have been described by time-dependent populations of the electronic configurations visited during the ionization dynamics, neglecting individual state-to-state transition rates and energies. Combining a state-resolved electronic-structure calculation, based on first-order many-body perturbation theory, with a Monte Carlo rate-equation method enables us to study state-resolved dynamics based on time-dependent state populations. Our results demonstrate that configuration-based and state-resolved calculations provide similar charge-state distributions, but the differences are visible when resonant excitations are involved, which are also reflected in calculated time-integrated electron and photon spectra. In addition, time-resolved spectra of ions, electrons, and photons are analyzed for different pulse durations to explore how frustrated absorption manifests itself during the ionization dynamics of neon atoms.
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