Atoms

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10 pages, 816 KiB

Open AccessArticle

Theoretical Investigation on Vortex Electron Impact Excitation of a Mg Atom Confined in a Solid-State Environment

by Sophia Strnat, Aloka K. Sahoo, Lalita Sharma, Jonas Sommerfeldt, Daesung Park, Christian Bick and Andrey Surzhykov

Atoms 2025, 13(3), 23; https://doi.org/10.3390/atoms13030023 - 24 Feb 2025

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Abstract

We present a theoretical investigation of the inelastic scattering of vortex electrons by many-electron atoms embedded in a solid-state environment. Special emphasis is placed on the probability of exciting a target atom and on the relative population of its magnetic substates as described [...] Read more.

We present a theoretical investigation of the inelastic scattering of vortex electrons by many-electron atoms embedded in a solid-state environment. Special emphasis is placed on the probability of exciting a target atom and on the relative population of its magnetic substates as described by the set of alignment parameters. These parameters are directly related to the angular distribution of the subsequent radiative decay. To demonstrate the application of the developed theoretical approach, we present calculations for the

3 s^{2} {}^{1}S_{0} \to 3 s 3 p {}^{3}P_{1}

excitation of a Mg atom and its subsequent

3 s 3 p {}^{3}P_{1} \to 3 s^{2} {}^{1}S_{0}

radiative decay. Our results highlight the significance of the orbital angular momentum (OAM) projection as well as the relative position of the vortex electron with respect to the target atom. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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10 pages, 659 KiB

Open AccessArticle

Stopping Power of Iron for Protons: Theoretical Calculations from Very Low to High Energies

by Jesica P. Peralta, Alejandra M. P. Mendez, Dario M. Mitnik and Claudia C. Montanari

Atoms 2025, 13(3), 22; https://doi.org/10.3390/atoms13030022 - 20 Feb 2025

Viewed by 535

Abstract

The energy loss in iron can serve as valuable knowledge due to its extended use in technological applications and open topics in fundamental physics. The electronic structure of solid Fe is challenging, given that it is the first of the groups of transition [...] Read more.

The energy loss in iron can serve as valuable knowledge due to its extended use in technological applications and open topics in fundamental physics. The electronic structure of solid Fe is challenging, given that it is the first of the groups of transition metals with some of the d-electrons promoted to the conduction band while others remain bound. The low energy description, the deviation from velocity proportionality at low impact energies, and the contribution of the loosely bound d-electrons to the energy loss are active featured fields when it comes to the stopping in Fe. Very recent TDDFT calculations have been compared with the first stopping measurements in steel, showing surprisingly good agreement. In the present work, we applied a recent model based on the momentum distribution function of the d-electrons to the case of Fe. A comparison with other models is discussed, as well as with experimental data. We also highlight discrepancies among datasets regarding the stopping maximum and the need for new experimental efforts. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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10 pages, 4991 KiB

Open AccessArticle

Interaction Between Atoms and Structured Light Fields

by Shreyas Ramakrishna and Stephan Fritzsche

Atoms 2025, 13(2), 20; https://doi.org/10.3390/atoms13020020 - 13 Feb 2025

Viewed by 554

Abstract

Structured light encompasses a vast variety of light fields. It has unique properties such as non-uniform transverse intensity and a polarization pattern across their beam cross-sections. In this contribution, we discuss the photoexcitation of a single ionic target system driven by different sets [...] Read more.

Structured light encompasses a vast variety of light fields. It has unique properties such as non-uniform transverse intensity and a polarization pattern across their beam cross-sections. In this contribution, we discuss the photoexcitation of a single ionic target system driven by different sets of structured light modes. Specifically, we provide a compilation of transition amplitudes for various structured light modes interacting with atomic systems based on the first-order perturbation theory. To illustrate this, we will choose an electric quadrupole transition (

4 s {}^{2}{S_{1 / 2}} \to 3 d {}^{2}{D_{5 / 2}}

) in the target Ca⁺ ion driven by a structured light field. For this particular interaction, we examine how the beam parameters affect the population of magnetic sub-levels in the atomic excited state. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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5 pages, 363 KiB

Open AccessCommunication

Bound–Free and Free–Free Pair Production Channels in Forward Delbrück Scattering

by Jonas Sommerfeldt, Vladimir A. Yerokhin and Andrey Surzhykov

Atoms 2025, 13(2), 19; https://doi.org/10.3390/atoms13020019 - 12 Feb 2025

Viewed by 569

Abstract

We present a theoretical study of forward-angle Delbrück scattering of light by the Coulomb field of a target nucleus. Special attention is paid to the Coulomb corrections, which take into account the interaction of the emerging virtual electron–positron pairs with the nucleus to [...] Read more.

We present a theoretical study of forward-angle Delbrück scattering of light by the Coulomb field of a target nucleus. Special attention is paid to the Coulomb corrections, which take into account the interaction of the emerging virtual electron–positron pairs with the nucleus to higher orders of

α Z

. We compare the results from three different computation methods: the direct all-order evaluation of the Delbrück amplitude, the computation from the pair production cross section with the optical theorem and the low-energy limit. We find that the values obtained from the optical theorem are in very good agreement with the all-order calculations and can be used as benchmark data. Moreover, both methods agree with the low-energy limit for photon energies

ω < < m_{e} c^{2}

when correctly accounting for the bound–free pair production cross section in the optical theorem calculations, and the discrepancy found in the literature originates from neglecting this contribution. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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9 pages, 900 KiB

Open AccessArticle

Visible Light Spectroscopy of W¹⁴⁺ Ions in an Electron Beam Ion Trap

by Ben Niu, Zhaoying Chen, Jihui Chen, Yanting Li, Fangshi Jia, Bingli Li, Zhencen He, Jun Xiao, Yaming Zou and Ke Yao

Atoms 2025, 13(2), 17; https://doi.org/10.3390/atoms13020017 - 8 Feb 2025

Viewed by 572

Abstract

In this work, the visible lines of

W^{14 +}

ions in the wavelength range of 400–650 nm are investigated experimentally and theoretically. The experiments were performed in a low-energy electron beam ion trap. The simulated spectra of

W^{14 +}

ions (Nd-like) [...] Read more.

In this work, the visible lines of

W^{14 +}

ions in the wavelength range of 400–650 nm are investigated experimentally and theoretically. The experiments were performed in a low-energy electron beam ion trap. The simulated spectra of

W^{14 +}

ions (Nd-like) were obtained from atomic structure computations in combination with a collisional–radiative model. Overall, there is a reasonable similarity between the measurements and the results of the simulations, and most of the twelve observed spectral lines associated with

W^{14 +}

were tentatively identified. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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8 pages, 490 KiB

Open AccessArticle

Diagnostics of Spin-Polarized Ions at Storage Rings

by Anna Maiorova, Stephan Fritzsche, Andrey Surzhykov and Thomas Stöhlker

Atoms 2025, 13(2), 15; https://doi.org/10.3390/atoms13020015 - 4 Feb 2025

Viewed by 558

Abstract

Polarized heavy ions in storage rings are seen as a valuable tool for a wide range of research, from the study of spin effects in relativistic atomic collisions to the tests of the Standard Model. For forthcoming experiments, several important challenges need to [...] Read more.

Polarized heavy ions in storage rings are seen as a valuable tool for a wide range of research, from the study of spin effects in relativistic atomic collisions to the tests of the Standard Model. For forthcoming experiments, several important challenges need to be addressed to work efficiently with such ions. Apart from the production and preservation of ion polarization in storage rings, its measurement is an extremely important issue. In this contribution, we employ the radiative recombination (RR) of polarized electrons into the ground state of initially hydrogen-like, finally helium-like, ions as a probe process for beam diagnostics. Our theoretical study clearly demonstrates that the RR cross section, integrated over photon emission angles, is highly sensitive to both the degree and the direction of ion polarization. Since the (integrated) cross-section measurements are well established, the proposed method offers promising prospects for ion spin tomography at storage rings. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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9 pages, 521 KiB

Open AccessArticle

Experimental Cross Sections for Electron-Impact Single, Double, and Triple Ionization of La⁺

by B. Michel Döhring, Alexander Borovik, Jr., Florian Gocht, Kurt Huber and Stefan Schippers

Atoms 2025, 13(2), 14; https://doi.org/10.3390/atoms13020014 - 28 Jan 2025

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Abstract

We report on new measurements of absolute cross sections for single, double, and triple electron-impact ionization of singly charged lanthanum ions. The resulting single and double ionization cross sections are in fair agreement with results from previous experimental work. In the present work, [...] Read more.

We report on new measurements of absolute cross sections for single, double, and triple electron-impact ionization of singly charged lanthanum ions. The resulting single and double ionization cross sections are in fair agreement with results from previous experimental work. In the present work, we extended the experimental range by a factor of two to approx. 2000 eV. To the best of our knowledge, there have been no previous measurements of triple ionization. The present work in progress aims to provide vitally needed atomic data for the astrophysical modeling of kilonovae. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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9 pages, 799 KiB

Open AccessArticle

Single and Double Electron Capture by 1–16 keV Sn⁴⁺ Ions Colliding on H₂

by Emiel de Wit, Lennart Tinge, Klaas Bijlsma and Ronnie Hoekstra

Atoms 2025, 13(2), 12; https://doi.org/10.3390/atoms13020012 - 24 Jan 2025

Viewed by 618

Abstract

Single and double electron capture cross-sections for collisions of ¹¹⁸Sn⁴⁺ with molecular hydrogen have been measured in an energy range of 1 keV to 16 keV using a crossed-beam setup. The cross-sections are determined from measurements of charge-state-resolved ion currents obtained [...] Read more.

Single and double electron capture cross-sections for collisions of ¹¹⁸Sn⁴⁺ with molecular hydrogen have been measured in an energy range of 1 keV to 16 keV using a crossed-beam setup. The cross-sections are determined from measurements of charge-state-resolved ion currents obtained through a retarding field analyser. Remarkably, the single electron capture cross-sections for Sn⁴⁺ are more than a factor 3 smaller than the previously determined single electron capture cross-sections for Sn³+–H₂ collisions and the double electron capture cross-sections are only about 20% smaller than the single electron capture cross-sections. These results are understood on the basis of potential energy curve crossings. The first active curve crossings for the Sn⁴⁺–H₂ system happen at a relatively small internuclear distance of about 5.5 a.u., which should be compared to 8 a.u. for Sn³+ ions. Multi-channel Landau–Zener calculations have been performed for single electron capture and confirm these low cross-sections. The curve crossing for double electron capture by Sn⁴⁺ lies very close to the one for single electron capture, which may explain the single and double electron capture cross-sections being of similar magnitude. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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6 pages, 259 KiB

Open AccessCommunication

Lithium-like O⁵⁺ Emission near 19 Å

by Jaan K. Lepson, Gregory V. Brown, Joel H. T. Clementson, Alexander J. Fairchild, Ming Feng Gu, Natalie Hell, Elmar Träbert and Peter Beiersdorfer

Atoms 2025, 13(2), 10; https://doi.org/10.3390/atoms13020010 - 21 Jan 2025

Viewed by 551

Abstract

Using a high-resolution grating spectrometer on the Livermore EBIT-I electron beam ion trap, we have measured three

n = 3, 4 \to n = 1

K-shell emission lines in lithium-like O

5^{+}

, which are situated near the O VIII Lyman- [...] Read more.

Using a high-resolution grating spectrometer on the Livermore EBIT-I electron beam ion trap, we have measured three

n = 3, 4 \to n = 1

K-shell emission lines in lithium-like O

5^{+}

, which are situated near the O VIII Lyman-

α

lines at 19 Å. Two of the resulting wavelengths agree well with the wavelengths of these lines we reported earlier, but the wavelength of the third line does not. In contrast, our new wavelengths now fully agree with those from resonant photo-absorption experiments on the PETRA III synchrotron facility. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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11 pages, 260 KiB

Open AccessArticle

Nuclear Hyperfine Mixing Effect in Highly Charged ²⁰⁵Pb Ions

by Wu Wang, Yong Li and Xu Wang

Atoms 2025, 13(1), 2; https://doi.org/10.3390/atoms13010002 - 3 Jan 2025

Viewed by 662

Abstract

In highly charged ions, significant nuclear hyperfine mixing (NHM) effects can arise when the electromagnetic field generated by the electrons interacts strongly with the nucleus, leading to mixing of nuclear states. While previous studies have primarily attributed the NHM effect to unpaired valence [...] Read more.

In highly charged ions, significant nuclear hyperfine mixing (NHM) effects can arise when the electromagnetic field generated by the electrons interacts strongly with the nucleus, leading to mixing of nuclear states. While previous studies have primarily attributed the NHM effect to unpaired valence electrons, we present a reformulation of the theoretical framework using dressed hyperfine states and investigate the NHM effect in ²⁰⁵Pb⁷⁶⁺, ²⁰⁵Pb⁷⁵⁺, ²⁰⁵Pb⁷⁴⁺, and ²⁰⁵Pb⁷³⁺ ions. Our numerical results show that significant NHM effects occurred in all of the studied ions, even in the absence of unpaired valence electrons in ²⁰⁵Pb⁷⁶⁺ and ²⁰⁵Pb⁷⁴⁺. We found that the lifetime of the isomeric state was reduced by 2–4 orders of magnitude compared with the bare ²⁰⁵Pb nucleus, depending on the charge state of the ion. These results indicate that it is the active valence electrons rather than unpaired electrons which play a key role in the NHM effect, thereby deepening our understanding of this phenomenon. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

5 pages, 196 KiB

Open AccessArticle

Measurement and Flexible Atomic Code (FAC) Computation of Extreme Ultraviolet (EUV) Spectra of Eu

by Joel H. T. Clementson, Peter Beiersdorfer, Gregory V. Brown, Natalie Hell and Elmar Träbert

Atoms 2024, 12(10), 48; https://doi.org/10.3390/atoms12100048 - 27 Sep 2024

Viewed by 1175

Abstract

A group of EUV lines of H- and He-like ions of C provides excellent wavelength calibrations for a position-sensitive multichannel detector at a high-resolution spectrograph. We have exploited this setting for a series of spectra of highly charged Eu ions recorded at the [...] Read more.

A group of EUV lines of H- and He-like ions of C provides excellent wavelength calibrations for a position-sensitive multichannel detector at a high-resolution spectrograph. We have exploited this setting for a series of spectra of highly charged Eu ions recorded at the Livermore SuperEBIT electron beam ion trap. A variation in the electron beam energy results in spectra with correspondingly staggered highest Eu ion charge states ranging from Na- through to Ni-like Eu ions. A number of spectral features can be identified from the literature, but the majority of line identifications need guidance from computations of simulated spectra on the basis of collisional-radiative models. For ions with more than two electrons in the valence shell, the typical computational results are of a markedly lower accuracy. We have applied the Flexible Atomic Code (FAC), which is capable of handling all our measured ions with reasonable accuracy. We look into the systematics of the deviation of the computed transition energies from the measured ones as a function of the electron number. Full article

(This article belongs to the Special Issue 21st International Conference on the Physics of Highly Charged Ions)

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