A fresh computational approach to atomic structures, processes and cascades

Fritzsche, S.

doi:10.1016/j.cpc.2019.01.012

Cited by 91 publications

(87 citation statements)

References 42 publications

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“…Cascade repopulation of intermediate levels is also common to atoms and multi-charged ions in laboratory plasmas [1,2], as well as astrophysical plasmas encountered in solar coronas, gas nebulae and active galactic nuclei (AGN) [1,3,4]. The complex character of the stepwise cascade process, an inherent, but usually unwanted side effect in most investigations, has received considerable attention, studied primarily by simulations [5][6][7][8]. Such studies have focused on mostly radiative cascades related to recombination in He-like ions [9], emission of polarized X-rays [10], X-ray fusion diagnostics [11], shake-off effects [12], solar wind [13] and electron capture in H-like ions [14][15][16], just to mention a few.…”

Section: Introductionmentioning

confidence: 99%

Radiative Cascade Repopulation of 1s2s2p 4P States Formed by Single Electron Capture in 2–18 MeV Collisions of C4+ (1s2s 3S) with He

Zouros

Nikolaou

Madesis

et al. 2020

Atoms

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This study focuses on the details of cascade repopulation of doubly excited triply open-shell C3+(1s2s2p)4P and 2P± states produced in 2–18 MeV collisions of C4+(1s2s3S) with He. Such cascade calculations are necessary for the correct determination of the ratio R of their cross sections, used as a measure of spin statistics [Madesis et al. PRL 124 (2020) 113401]. Here, we present the details of our cascade calculations within a new matrix formulation based on the well-known diagrammatic cascade approach [Curtis, Am. J. Phys. 36 (1968) 1123], extended to also include Auger depopulation. The initial populations of the 1s2snℓ4L and 1s2snℓ2L levels included in our analysis are obtained from the direct nℓ single electron capture (SEC) cross sections, calculated using the novel three-electron close-coupling (3eAOCC) approach. All relevant radiative branching ratios (RBR) for n≤4 were computed using the COWAN code. While doublet RBRs are found to be very small, quartet RBRs are found to be large, indicating cascade feeding to be important only for quartets, consistent with previous findings. Calculations including up to third order cascades, extended to n→∞ using an n−3 SEC model, showed a ∼60% increase of the 1s2s2p4P populations due to cascades, resulting, for the first time, in R values in good overall agreement with experiment.

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Section: Introductionmentioning

confidence: 99%

Radiative Cascade Repopulation of 1s2s2p 4P States Formed by Single Electron Capture in 2–18 MeV Collisions of C4+ (1s2s 3S) with He

Zouros

Nikolaou

Madesis

et al. 2020

Atoms

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“…Acknowledgments: I would like to thank the organizers as well as the participants of the Helmholtz International Summer School (HISS) -Dubna International Advanced School of Theoretical Physics (DIAS-TH) "Quantum Field Theory at the Limits: from Strong Fields to Heavy Quarks" for making the 2019 edition of the summer school in Dubna a very inspiring and enjoyable event. Moreover, I am grateful to Elena Mosman for a careful and critical reading of the manuscript, as well as to Stephan Fritzsche for interesting discussions and a fresh beer [94] to atomic structures, processes and cascades.…”

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confidence: 99%

Probing Vacuum Polarization Effects with High-Intensity Lasers

Karbstein

2020

Particles

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These notes provide a pedagogical introduction to the theoretical study of vacuum polarization effects in strong electromagnetic fields as provided by state-of-the-art high-intensity lasers. Quantum vacuum fluctuations give rise to effective couplings between electromagnetic fields, thereby supplementing Maxwell's linear theory of classical electrodynamics with nonlinearities. Resorting to a simplified laser pulse model allowing for explicit analytical insights, we demonstrate how to efficiently analyze all-optical signatures of these effective interactions in high-intensity laser experiments. Moreover, we highlight several key features relevant for the accurate planning and quantitative theoretical analysis of quantum vacuum nonlinearities in the collision of high-intensity laser pulses.

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“…Apart from the resonance at ∼282 eV, we observed a number of additional photodetachment resonances with a variety of line shapes as well as a clear signature for multiple detachment by direct double K-hole production. To better understand these observations, detailed atomic-structure calculations were performed by using the GRASP [10] and RATIP [11] codes as well as the Jena Atomic Calculator (JAC) [12]. To the best of our knowledge, there is only one other theoretical study of highly excited resonances in C − which, however, is focussed exclusively on high-spin states [13].The experiments were carried out employing the photon-ion merged-beams technique (see [14] for a recent review) at the PIPE end-station [15] of beamline P04 [16] of the synchrotron radiation source PETRA III operated by DESY in Hamburg, Germany.…”

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confidence: 99%

Multiple Photodetachment of Carbon Anions via Single and Double Core-Hole Creation

Perry‐Sassmannshausen

Buhr

Borovik

et al. 2020

Phys. Rev. Lett.

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We report on new measurements of m-fold photodetachment (m = 2 − 5) of carbon anions via K-shell excitation and ionization. The experiments were carried out employing the photon-ion merged-beams technique at a synchrotron light source. While previous measurements were restricted to double detachment (m = 2) and to just the lowest-energy K-shell resonance at about 282 eV, our absolute experimental m-fold detachment cross sections at photon energies of up to 1000 eV exhibit a wealth of new thresholds and resonances. We tentatively identify these features with the aid of detailed atomic-structure calculations. In particular, we find unambiguous evidence for fivefold detachment via double K-hole production.Atomic anions are highly correlated systems where the extra electron is weakly bound to an overall neutral charge distribution. Consequently, the number of excited states of atomic anions is quite limited [1] and some atomic species such as nitrogen do not form anions at all. A thorough treatment of the correlation effects in negative atomic ions still poses a formidable challenge to atomic theory, and this becomes even greater for innershell vacancies, since the valence electrons are then subject to strong many-electron relaxation effects following the creation of core holes [2, 3]. On the experimental side, core holes can be readily created by exciting or ionizing an inner-shell electron by a photon. For light ions, the core-hole state will subsequently decay via Auger transitions such that electrons are emitted with the net effect of photoionization. For negative ions, the entire process is termed (multiple) photodetachment.So far, photodetachment via the initial creation of a single K-hole has been experimentally studied only for a limited number of light anions up to F − [3-9]. For C − ions especially, previous measurements were carried out by Gibson et al. [7] and by Walter et al. [8] who studied double photodetachment in a very narrow photon energy range just covering the 1s 2 2s 2 2p 3 4 S → 1s 2s 2 2p 4 4 P resonance at about 282 eV. This scarcity of data is due to the fact that sufficiently high photon fluxes for more comprehensive studies were not available. Here, we present absolute cross sections, σ m , for m-fold photodetachment of C − ions by a single photon,with m = 2, 3, 4, 5 and photon energies from below the K-edge up to ∼1000 eV. These cross sections provide a view of the photodetachment dynamics of a highly correlated atomic system in unprecedented detail. Apart from the resonance at ∼282 eV, we observed a number of additional photodetachment resonances with a variety of line shapes as well as a clear signature for multiple detachment by direct double K-hole production. To better understand these observations, detailed atomic-structure calculations were performed by using the GRASP [10] and RATIP [11] codes as well as the Jena Atomic Calculator (JAC) [12]. To the best of our knowledge, there is only one other theoretical study of highly excited resonances in C − which, however, is focussed exc...

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A fresh computational approach to atomic structures, processes and cascades

Cited by 91 publications

References 42 publications

Radiative Cascade Repopulation of 1s2s2p 4P States Formed by Single Electron Capture in 2–18 MeV Collisions of C4+ (1s2s 3S) with He

Radiative Cascade Repopulation of 1s2s2p 4P States Formed by Single Electron Capture in 2–18 MeV Collisions of C4+ (1s2s 3S) with He

Probing Vacuum Polarization Effects with High-Intensity Lasers

Multiple Photodetachment of Carbon Anions via Single and Double Core-Hole Creation

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