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Atoms, Volume 11, Issue 1 (January 2023) – 13 articles

Cover Story (view full-size image): Orbitals resulting from MCDHF calculations describing core–core correlation and other effects may be inadequate for building CSFs which account for correlation effects that are energetically unimportant but decisive for computed properties, e.g., hyperfine structures. This inadequacy can be traced in irregular or oscillating convergence patterns of the computed properties as functions of the increasing orbital set. We propose an efficient procedure to lower the energy and adequately account for the correlation effects that are important for the property. The old (red) and new methods (blue) of determining the convergence of the hyperfine structure constants in Li as functions of orbital sets of increasing size are depicted on the cover page. View this paper
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8 pages, 1480 KiB  
Article
X-ray Spectroscopy Based on Micro-Calorimeters at Internal Targets of Storage Rings
by Marc Oliver Herdrich, Daniel Hengstler, Andreas Fleischmann, Christian Enss, Alexandre Gumberidze, Pierre-Michel Hillenbrand, Paul Indelicato, Stephan Fritzsche and Thomas Stöhlker
Atoms 2023, 11(1), 13; https://doi.org/10.3390/atoms11010013 - 14 Jan 2023
Cited by 2 | Viewed by 1118
Abstract
With metallic-magnetic calorimeters (MMCs), promising detectors for high-precision X-ray spectrometry in atomic and fundamental physics experiments are available. In this work, we present a pilot experiment based on a maXs-30 type MMC-spectrometer for recording X-rays emitted in collisions of lithium-like uranium ions with [...] Read more.
With metallic-magnetic calorimeters (MMCs), promising detectors for high-precision X-ray spectrometry in atomic and fundamental physics experiments are available. In this work, we present a pilot experiment based on a maXs-30 type MMC-spectrometer for recording X-rays emitted in collisions of lithium-like uranium ions with a molecular nitrogen gas jet in the internal target of the ESR storage ring of the GSI. Sample spectra have been measured, and a multitude of X-ray transitions have been unambiguously identified. As a first test and for comparison with data recorded at an EBIT, the 2s Lamb shift in lithium-like uranium was estimated. Full article
(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)
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25 pages, 761 KiB  
Article
Performance Tests and Improvements on the rmcdhf and rci Programs of GRASP
by Yanting Li, Jinqing Li, Changxian Song, Chunyu Zhang, Ran Si, Kai Wang, Michel Godefroid, Gediminas Gaigalas, Per Jönsson and Chongyang Chen
Atoms 2023, 11(1), 12; https://doi.org/10.3390/atoms11010012 - 13 Jan 2023
Cited by 5 | Viewed by 1638
Abstract
The latest published version of GRASP (General-purpose Relativistic Atomic Structure Package), i.e., GRASP2018, retains a few suboptimal subroutines/algorithms, which reflect the limited memory and file storage of computers available in the 1980s. Here we show how the efficiency of the relativistic self-consistent-field (SCF) [...] Read more.
The latest published version of GRASP (General-purpose Relativistic Atomic Structure Package), i.e., GRASP2018, retains a few suboptimal subroutines/algorithms, which reflect the limited memory and file storage of computers available in the 1980s. Here we show how the efficiency of the relativistic self-consistent-field (SCF) procedure of the multiconfiguration-Dirac–Hartree–Fock (MCDHF) method and the relativistic configuration-interaction (RCI) calculations can be improved significantly. Compared with the original GRASP codes, the present modified version reduces the CPU times by factors of a few tens or more. The MPI performances for all the original and modified codes are carefully analyzed. Except for diagonalization, all computational processes show good MPI scaling. Full article
(This article belongs to the Special Issue The General Relativistic Atomic Structure Package—GRASP)
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10 pages, 6728 KiB  
Article
Collinear Laser Spectroscopy of Helium-like 11B3+
by Konstantin Mohr, Axel Buß, Zoran Andelkovic, Volker Hannen, Max Horst, Phillip Imgram, Kristian König, Bernhard Maaß, Wilfried Nörtershäuser, Simon Rausch, Rodolfo Sánchez and Christian Weinheimer
Atoms 2023, 11(1), 11; https://doi.org/10.3390/atoms11010011 - 11 Jan 2023
Cited by 2 | Viewed by 1320
Abstract
Collinear laser spectroscopy in the 1s2s3S11s2p3P0,2 transitions of helium-like 11B3+ was performed using the HITRAP beamline at the GSI Helmholtz Centre. The ions were [...] Read more.
Collinear laser spectroscopy in the 1s2s3S11s2p3P0,2 transitions of helium-like 11B3+ was performed using the HITRAP beamline at the GSI Helmholtz Centre. The ions were produced in an electron beam ion source, extracted, and accelerated to a beam energy of 4 keV/q. Results agree with previous measurements within uncertainty. Thus, it was demonstrated that the metastable state in He-like ions is sufficiently populated to carry out collinear laser spectroscopy. The measurement is a pilot experiment for a series of measurements that will be performed at a dedicated collinear laser spectroscopy setup at TU Darmstadt with light helium-like ions. Full article
(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)
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17 pages, 433 KiB  
Article
Quantum Electrodynamics of Dicke States: Resonant One-Photon Exchange Energy and Entangled Decay Rate
by Ulrich D. Jentschura and Chandra M. Adhikari
Atoms 2023, 11(1), 10; https://doi.org/10.3390/atoms11010010 - 10 Jan 2023
Cited by 2 | Viewed by 1417
Abstract
We calculate the fully retarded one-photon exchange interaction potential between electrically neutral, identical atoms, one of which is assumed to be in an excited state, by matching the scattering matrix (S matrix) element with the effective Hamiltonian. Based on the Feynman prescription, [...] Read more.
We calculate the fully retarded one-photon exchange interaction potential between electrically neutral, identical atoms, one of which is assumed to be in an excited state, by matching the scattering matrix (S matrix) element with the effective Hamiltonian. Based on the Feynman prescription, we obtain the imaginary part of the interaction energy. Our results lead to precise formulas for the distance-dependent enhancement and suppression of the decay rates of entangled superradiant and subradiant Dicke states (Bell states), as a function of the interatomic distance. The formulas include a long-range tail due to entanglement. We apply the result to an example calculation involving two hydrogen atoms, one of which is in an excited P state. Full article
(This article belongs to the Section Atom Based Quantum Technology)
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12 pages, 348 KiB  
Article
Many-Body and Single-Body Low-Energy Elastic Positron Scattering by Beryllium Atoms: From Ab Initio to Semiempirical Approaches
by Marcos V. Barp, Wagner Tenfen and Felipe Arretche
Atoms 2023, 11(1), 8; https://doi.org/10.3390/atoms11010008 - 04 Jan 2023
Cited by 2 | Viewed by 1833
Abstract
Positron scattering by beryllium atoms in the low-energy range (≤4.0 eV) was studied within ab initio and semiempirical frameworks. When interpreting the static dipole polarizability and the scattering length as representative quantities of the target and positron–atom correlations, the scattering observables obtained in [...] Read more.
Positron scattering by beryllium atoms in the low-energy range (≤4.0 eV) was studied within ab initio and semiempirical frameworks. When interpreting the static dipole polarizability and the scattering length as representative quantities of the target and positron–atom correlations, the scattering observables obtained in the ab initio calculation were extrapolated by applying a semiempirical approach. Our results ratify previous ones, since no Ramsauer minimum structures or shape resonances were found in the cross sections. The presence of a (e+,Be) bound state was also identified as a function of the dipole polarizability. Full article
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15 pages, 386 KiB  
Article
Electronic Structure Calculations with the Exact Pseudopotential and Interpolating Wavelet Basis
by Tommi Höynälänmaa and Tapio T. Rantala
Atoms 2023, 11(1), 9; https://doi.org/10.3390/atoms11010009 - 01 Jan 2023
Cited by 1 | Viewed by 1012
Abstract
Electronic structure calculations are mostly carried out with Coulomb potential singularity adapted basis sets such as STO or contracted GTO. With another basis or for heavy elements, the pseudopotentials may appear as a practical alternative. Here, we introduce the exact pseudopotential (EPP) to [...] Read more.
Electronic structure calculations are mostly carried out with Coulomb potential singularity adapted basis sets such as STO or contracted GTO. With another basis or for heavy elements, the pseudopotentials may appear as a practical alternative. Here, we introduce the exact pseudopotential (EPP) to remove the Coulomb singularity and test it for orbitals of small atoms with the interpolating wavelet basis set. We apply EPP to the Galerkin method with a basis set consisting of Deslauriers–Dubuc scaling functions on the half-infinite real interval. We demonstrate the EPP–Galerkin method by computing the hydrogen atom 1s, 2s, and 2p orbitals and helium atom configurations He1s2, He1s2s1S, and He1s2s3S. We compare the method to the ordinary interpolating wavelet Galerkin method (OIW–Galerkin), handling the singularity at the nucleus by excluding the scaling function located at the origin from the basis. We also compare the performance of our approach to that of finite-difference approach, which is another practical method for spherical atoms. We find the accuracy of the EPP–Galerkin method to be better than both of the above-mentioned methods. Full article
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44 pages, 978 KiB  
Article
An Introduction to Relativistic Theory as Implemented in GRASP
by Per Jönsson, Michel Godefroid, Gediminas Gaigalas, Jörgen Ekman, Jon Grumer, Wenxian Li, Jiguang Li , Tomas Brage, Ian P. Grant, Jacek Bieroń and Charlotte Froese Fischer
Atoms 2023, 11(1), 7; https://doi.org/10.3390/atoms11010007 - 31 Dec 2022
Cited by 18 | Viewed by 4035
Abstract
Computational atomic physics continues to play a crucial role in both increasing the understanding of fundamental physics (e.g., quantum electrodynamics and correlation) and producing atomic data for interpreting observations from large-scale research facilities ranging from fusion reactors to high-power laser systems, space-based telescopes [...] Read more.
Computational atomic physics continues to play a crucial role in both increasing the understanding of fundamental physics (e.g., quantum electrodynamics and correlation) and producing atomic data for interpreting observations from large-scale research facilities ranging from fusion reactors to high-power laser systems, space-based telescopes and isotope separators. A number of different computational methods, each with their own strengths and weaknesses, is available to meet these tasks. Here, we review the relativistic multiconfiguration method as it applies to the General Relativistic Atomic Structure Package [grasp2018, C. Froese Fischer, G. Gaigalas, P. Jönsson, J. Bieroń, Comput. Phys. Commun. (2018). DOI: 10.1016/j.cpc.2018.10.032]. To illustrate the capacity of the package, examples of calculations of relevance for nuclear physics and astrophysics are presented. Full article
(This article belongs to the Special Issue The General Relativistic Atomic Structure Package—GRASP)
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7 pages, 450 KiB  
Article
Preliminary Results for Observation of Radiative Double-Electron Capture by F9+,8+ on Graphene
by D. S. La Mantia, A. Kayani, K. Bhatt and J. A. Tanis
Atoms 2023, 11(1), 6; https://doi.org/10.3390/atoms11010006 - 31 Dec 2022
Viewed by 1165
Abstract
Radiative double-electron capture, which can be considered the inverse of double photoionization, has been investigated for 2.11 MeV/u F9+ and F8+ projectiles colliding with the two-dimensional target single-layer graphene. Preliminary results for the cross sections are obtained and presented [...] Read more.
Radiative double-electron capture, which can be considered the inverse of double photoionization, has been investigated for 2.11 MeV/u F9+ and F8+ projectiles colliding with the two-dimensional target single-layer graphene. Preliminary results for the cross sections are obtained and presented and compared with our previous measurements for the one-dimensional gas targets N2 and Ne, with the three-dimensional target thin-foil C, and with the most accurate theoretical results that currently exist. The graphene results reported here are reasonable when compared with the F9++N2, Ne results given the thicknesses of the respective targets, being larger by about a factor of four. Full article
(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)
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7 pages, 433 KiB  
Article
Exploitation of the Timing Capabilities of Metallic Magnetic Calorimeters for a Coincidence Measurement Scheme
by Philip Pfäfflein, Günter Weber, Steffen Allgeier, Sonja Bernitt, Andreas Fleischmann, Marvin Friedrich, Christoph Hahn, Daniel Hengstler, Marc Oliver Herdrich, Anton Kalinin, Felix Martin Kröger, Patricia Kuntz, Michael Lestinsky, Bastian Löher, Esther Babette Menz, Uwe Spillmann, Binghui Zhu, Christian Enss and Thomas Stöhlker
Atoms 2023, 11(1), 5; https://doi.org/10.3390/atoms11010005 - 31 Dec 2022
Cited by 1 | Viewed by 1217
Abstract
In this report, we compare two filter algorithms for extracting timing information using novel metallic magnetic calorimeter detectors, applied to the precision X-ray spectroscopy of highly charged ions in a storage ring. Accurate timing information is crucial when exploiting coincidence conditions for background [...] Read more.
In this report, we compare two filter algorithms for extracting timing information using novel metallic magnetic calorimeter detectors, applied to the precision X-ray spectroscopy of highly charged ions in a storage ring. Accurate timing information is crucial when exploiting coincidence conditions for background suppression to obtain clean spectra. For X-rays emitted by charge-changing interactions between ions and a target, this is a well-established technique when relying on conventional semiconductor detectors that offer a good temporal resolution. However, until recently, such a coincidence scheme had never been realized with metallic magnetic calorimeters, which typically feature much longer signal rise times. In this report, we present optimized timing filter algorithms for this type of detector. Their application to experimental data recently obtained at the electron cooler of CRYRING@ESR at GSI, Darmstadt is discussed. Full article
(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)
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12 pages, 452 KiB  
Article
Independently Optimized Orbital Sets in GRASP—The Case of Hyperfine Structure in Li I
by Yanting Li, Per Jönsson, Michel Godefroid, Gediminas Gaigalas, Jacek Bieroń, José Pires Marques, Paul Indelicato and Chongyang Chen
Atoms 2023, 11(1), 4; https://doi.org/10.3390/atoms11010004 - 30 Dec 2022
Cited by 3 | Viewed by 1635
Abstract
In multiconfiguration Dirac–Hartree–Fock (MCDHF) calculations, there is a strong coupling between the localization of the orbital set and the configuration state function (CSF) expansion used to determine it. Furthermore, it is well known that an orbital set resulting from calculations, including CSFs describing [...] Read more.
In multiconfiguration Dirac–Hartree–Fock (MCDHF) calculations, there is a strong coupling between the localization of the orbital set and the configuration state function (CSF) expansion used to determine it. Furthermore, it is well known that an orbital set resulting from calculations, including CSFs describing core–core correlation and other effects, which aims to lower the weighted energies of a number of targeted states as much as possible, may be inadequate for building CSFs that account for correlation effects that are energetically unimportant but decisive for computed properties, e.g., hyperfine structures or transition rates. This inadequacy can be traced in irregular or oscillating convergence patterns of the computed properties as functions of the increasing orbital set. In order to alleviate the above problems, we propose a procedure in which the orbital set is obtained by merging several separately optimized, and mutually non-orthogonal, orbital sets. This computational strategy preserves the advantages of capturing electron correlation on the total energy through the variational MCDHF method and allows to target efficiently the correlation effects on the considered property. The orbital sets that are merged are successively orthogonalized against each other to retain orthonormality. The merged orbital set is used to build CSFs that efficiently lower the energy and also adequately account for the correlation effects that are important for the property. We apply the procedure to compute the hyperfine structure constants for the 1s22s2S1/2 and 1s22p2P1/2,3/2o states in 7Li and show that it leads to considerably improved convergence patterns with respect to the increasing orbital set compared to standard calculations based on a single orbital set, energy-optimized in the variational procedure. The perspectives of the new procedure are discussed in a broader context in the summary. Full article
(This article belongs to the Special Issue The General Relativistic Atomic Structure Package—GRASP)
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16 pages, 1612 KiB  
Article
Strongly Interacting Bose Polarons in Two-Dimensional Atomic Gases and Quantum Fluids of Polaritons
by Luis Fernando Cárdenas-Castillo and Arturo Camacho-Guardian
Atoms 2023, 11(1), 3; https://doi.org/10.3390/atoms11010003 - 29 Dec 2022
Cited by 4 | Viewed by 1762 | Correction
Abstract
Polarons are quasiparticles relevant across many fields in physics: from condensed matter to atomic physics. Here, we study the quasiparticle properties of two-dimensional strongly interacting Bose polarons in atomic Bose–Einstein condensates and polariton gases. Our studies are based on the non-self consistent T-matrix [...] Read more.
Polarons are quasiparticles relevant across many fields in physics: from condensed matter to atomic physics. Here, we study the quasiparticle properties of two-dimensional strongly interacting Bose polarons in atomic Bose–Einstein condensates and polariton gases. Our studies are based on the non-self consistent T-matrix approximation adapted to these physical systems. For the atomic case, we study the spectral and quasiparticle properties of the polaron in the presence of a magnetic Feshbach resonance. We show the presence of two polaron branches: an attractive polaron, a low-lying state that appears as a well-defined quasiparticle for weak attractive interactions, and a repulsive polaron, a metastable state that becomes the dominant branch at weak repulsive interactions. In addition, we study a polaron arising from the dressing of a single itinerant electron by a quantum fluid of polaritons in a semiconductor microcavity. We demonstrate the persistence of the two polaron branches whose properties can be controlled over a wide range of parameters by tuning the cavity mode. Full article
(This article belongs to the Special Issue Recent Trends on Quantum Fluctuations in Ultra-Cold Quantum Gases)
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7 pages, 1373 KiB  
Article
Radiative Recombination Studies for Bare Lead Ions Interacting with Low-Energy Electrons
by Binghui Zhu and Thomas Stöhlker
Atoms 2023, 11(1), 2; https://doi.org/10.3390/atoms11010002 - 21 Dec 2022
Cited by 1 | Viewed by 1179
Abstract
X-ray emission as a result of radiative recombination (RR) at threshold energies in the electron cooler of CRYRING@ESR was investigated for decelerated bare lead ions at a beam energy of 10 MeV/u. The recorded spectra are dominated by characteristic transitions in Pb [...] Read more.
X-ray emission as a result of radiative recombination (RR) at threshold energies in the electron cooler of CRYRING@ESR was investigated for decelerated bare lead ions at a beam energy of 10 MeV/u. The recorded spectra are dominated by characteristic transitions in Pb81+, namely, the Lyman, Balmer and Paschen series, as a result of decay cascades from high-n states that are preferentially populated by the RR processes. In addition, a rigorous theoretical model is applied for the interpretation of measured X-ray spectra, and shows good agreement. Full article
(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)
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7 pages, 2305 KiB  
Article
Higher-Order Recombination Processes in Argon Ions Observed via X-ray Emission in an EBIT
by Weronika Biela-Nowaczyk, Pedro Amaro, Filipe Grilo and Andrzej Warczak
Atoms 2023, 11(1), 1; https://doi.org/10.3390/atoms11010001 - 21 Dec 2022
Cited by 2 | Viewed by 1370
Abstract
In electron–ion collisions, recombination processes play a very important role. Recently, multielectron recombination processes have been highly investigated, as they carry information about electron–electron interaction. Among them, the most basic process is dielectronic recombination (DR). The research presented here was conducted using an [...] Read more.
In electron–ion collisions, recombination processes play a very important role. Recently, multielectron recombination processes have been highly investigated, as they carry information about electron–electron interaction. Among them, the most basic process is dielectronic recombination (DR). The research presented here was conducted using an EBIT at Jagiellonian University. Using X-ray spectroscopy, we conducted research into K-LL, K-LM, K-LN, K-LO and K-MM resonances. The aim of this study was to investigate the contribution of the intershell higher-order recombination processes in collected spectra. A good resolution for the K-LL DR spectrum made it possible to distinguish structures for He- up to C-like Ar ions. Full article
(This article belongs to the Special Issue 20th International Conference on the Physics of Highly Charged Ions)
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