Atoms

26 pages, 4050 KiB

Open AccessArticle

Vibrational Excitation of HDO Molecule by Electron Impact

by Mehdi Adrien Ayouz, Alexandre Faure, Ioan F. Schneider, János Zsolt Mezei and Viatcheslav Kokoouline

Atoms 2025, 13(4), 32; https://doi.org/10.3390/atoms13040032 - 8 Apr 2025

Abstract

Cross sections and thermally averaged rate coefficients for the vibrational excitation and de-excitation by electron impact on the HDO molecule are computed using a theoretical approach based entirely on first principles. This approach combines scattering matrices obtained from the UK R-matrix codes for [...] Read more.

Cross sections and thermally averaged rate coefficients for the vibrational excitation and de-excitation by electron impact on the HDO molecule are computed using a theoretical approach based entirely on first principles. This approach combines scattering matrices obtained from the UK R-matrix codes for various geometries of the target molecule, three-dimensional vibrational states of HDO, and the vibrational frame transformation. The vibrational states of the molecule are evaluated by solving the Schrödinger equation numerically, without relying on the normal-mode approximation, which is known to be inaccurate for water molecules. As a result, couplings and transitions between the vibrational states of HDO are accurately accounted for. From the calculated cross sections, thermally averaged rate coefficients and their analytical fits are provided. Significant differences between the results for HDO and H₂O are observed. Additionally, an uncertainty assessment of the obtained data is performed for potential use in modeling non-local thermodynamic equilibrium (non-LTE) spectra of water in various astrophysical environments. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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10 pages, 2805 KiB

Open AccessArticle

Photoionization of Trans-Fe Ions: Se IV, Se V, and Se VI

by Brendan M. McLaughlin, Joern Wilms and James F. Babb

Atoms 2025, 13(4), 31; https://doi.org/10.3390/atoms13040031 - 8 Apr 2025

Abstract

In the present study, the photoionization cross-sections are calculated for the trans-Fe ions Se IV, Se V, and Se VI over a wide energy region for ground and meta-stable states within the Dirac Atomic R-matrix approach (darc). Our cross-section results, [...] Read more.

In the present study, the photoionization cross-sections are calculated for the trans-Fe ions Se IV, Se V, and Se VI over a wide energy region for ground and meta-stable states within the Dirac Atomic R-matrix approach (darc). Our cross-section results, when benchmarked against the available high-resolution measurements taken at the Advanced Light Source (ALS) for Se IV (Ga-like) and Se VI (Cu-like) selenium ions, show good agreement over the entire photon energy investigated. The present high quality cross-section data are suitable for use in many applications in astrophysics. Full article

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9 pages, 2679 KiB

Open AccessArticle

Forced Atom Interferometers in Optical Harmonic Potentials

by Mingjie Xin, Wui Seng Leong, Zilong Chen and Shau-Yu Lan

Atoms 2025, 13(4), 30; https://doi.org/10.3390/atoms13040030 - 3 Apr 2025

Abstract

We present a study of Doppler-sensitive light-pulse atom interferometers operating within optical dipole potentials, where atomic trajectories are manipulated using momentum transfer from light pulses and optical forces from the trap. Efficient methods are introduced to minimize the inhomogeneous broadening of oscillation frequencies [...] Read more.

We present a study of Doppler-sensitive light-pulse atom interferometers operating within optical dipole potentials, where atomic trajectories are manipulated using momentum transfer from light pulses and optical forces from the trap. Efficient methods are introduced to minimize the inhomogeneous broadening of oscillation frequencies in atoms confined within a three-dimensional optical lattice trap. These techniques enable the preparation of various quantum states, including vacuum, thermal, and squeezed states, for atom interferometry. Additionally, we demonstrate a two-dimensional atom interferometer using a single optical dipole trap, where transverse motion is activated by offsetting the trap position. Our work provides insights into controlling the mechanical motion of neutral atoms in optical harmonic potentials and contributes to advancing applications in quantum sensing and quantum computing. Full article

(This article belongs to the Special Issue Advances in and Prospects for Matter Wave Interferometry)

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13 pages, 375 KiB

Open AccessArticle

Electron Scattering from Sevoflurane

by Savinder Kaur, Ajay Kumar Arora, Kasturi Lal Baluja and Anand Bharadvaja

Atoms 2025, 13(4), 29; https://doi.org/10.3390/atoms13040029 - 1 Apr 2025

Abstract

Various electron impact scattering cross sections of Sevoflurane are reported up to 5 keV. The elastic cross sections (differential and integral) are computed using the single-centre-expansion formalism within a molecular framework. The ground state target wavefunction is determined at the Hartree–Fock (HF) level. [...] Read more.

Various electron impact scattering cross sections of Sevoflurane are reported up to 5 keV. The elastic cross sections (differential and integral) are computed using the single-centre-expansion formalism within a molecular framework. The ground state target wavefunction is determined at the Hartree–Fock (HF) level. Post-HF corrections are incorporated to make a scattering realistic model. The total interacting potential is defined as the sum of static, correlation–polarization and exchange potentials. These potentials are numerically computed using their local forms. The long-range effects affecting the scattering due to the polar nature of the molecule are incorporated using the Born Top-up approach. The ionization cross sections are obtained from the semi-empirical binary-encounter-Bethe model. The total cross sections are estimated from the incoherent sum of Born-corrected elastic integral and ionization cross sections. The computed results show fairly good agreement with the experimental reported cross sections. Full article

(This article belongs to the Special Issue Many-Particle Dynamics in Collisions of Electrons, Positrons and Photons, 2nd Edition)

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13 pages, 2840 KiB

Open AccessArticle

Electron Spin Resonance Study on Hydrogen Abstraction Reactions of Radiation-Induced Radicals in Synthetic Silica Clathrate with Ethylamine and Ethanol

by Shusuke Isogai, Kazuhiko Masuda, Kazuma Dan, Atsushi Tani and Sachiko Tojo

Atoms 2025, 13(4), 28; https://doi.org/10.3390/atoms13040028 - 31 Mar 2025

Abstract

Intermolecular hydrogen abstraction reactions of radiation-induced radicals from guest molecules in adjacent cages, as observed in clathrate hydrates, were investigated in synthetic silica clathrate (clathrasil) with ethylamine and ethanol. ESR observation of the silica clathrate after γ-ray irradiation at 77 K confirmed the [...] Read more.

Intermolecular hydrogen abstraction reactions of radiation-induced radicals from guest molecules in adjacent cages, as observed in clathrate hydrates, were investigated in synthetic silica clathrate (clathrasil) with ethylamine and ethanol. ESR observation of the silica clathrate after γ-ray irradiation at 77 K confirmed the formation of 1-aminoethyl radical (CH₃)(CH·)(NH₂), 1-hydroxyethyl radical (CH₃)(CH·)(OH), and hydrogen atom at 225 K. In isothermal annealing experiments, the amount of hydrogen atoms decreased at around 225 K following first-order kinetics, while the amount of 1-aminoethyl radical simultaneously increased by a similar amount. The amount of 1-hydroxyethyl radical decreased at temperatures around 280 K with first-order kinetics, while the amount of 1-aminoethyl radical increased at these temperatures. These results suggest that hydrogen abstraction reactions occur not only between the hydrogen atom and ethylamine at around 225 K but may also occur between 1-hydroxyethyl radical and ethylamine at around 280 K. Furthermore, observation of 1-hydroxyethyl radical in silica clathrate with only a small amount of ethanol indicated that ESR measurements could be used to detect traces of guest molecules in clathrates if the radicals derived from them are stably stored in the cages. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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5 pages, 278 KiB

Open AccessArticle

Benchmark Calculations for Near-Threshold Electron-Impact Excitation of the (1s3s)^3,1S States of Helium

by Klaus Bartschat, Igor Bray and Dmitry V. Fursa

Atoms 2025, 13(4), 27; https://doi.org/10.3390/atoms13040027 - 31 Mar 2025

Abstract

We revisit the current status of high-precision calculations for electron-impact excitation of the

{(1 s 3 s)}^{3, 1} S

states in helium in the low-energy near-threshold regime that is characterized by a large number of resonance features. Having noticed [...] Read more.

We revisit the current status of high-precision calculations for electron-impact excitation of the

{(1 s 3 s)}^{3, 1} S

states in helium in the low-energy near-threshold regime that is characterized by a large number of resonance features. Having noticed discrepancies between predictions from two previous large-scale calculations for this problem, we report new results and make recommendations regarding the absolute cross-sections that should be used in modeling applications. Full article

(This article belongs to the Special Issue Ab Initio Calculations in Atomic, Molecular, and Optical Physics: A Tribute to Barry Irwin Schneider)

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11 pages, 2964 KiB

Open AccessArticle

Spatially Resolved Precision Measurement of Magnetic Field Using Ultracold Cesium Atoms as Sensors

by Anjali Bisht, Manoj Das and Poonam Arora

Atoms 2025, 13(4), 26; https://doi.org/10.3390/atoms13040026 - 27 Mar 2025

Abstract

Sub-Doppler laser-cooled cesium-133 atoms are utilized as quantum sensors to achieve precise mapping of magnetic fields across a region in ultra-high vacuum (UHV), with a spatial resolution of 1 cm and a sensitivity of approximately 550 pT/√Hz, enabling accurate measurements within the nanotesla [...] Read more.

Sub-Doppler laser-cooled cesium-133 atoms are utilized as quantum sensors to achieve precise mapping of magnetic fields across a region in ultra-high vacuum (UHV), with a spatial resolution of 1 cm and a sensitivity of approximately 550 pT/√Hz, enabling accurate measurements within the nanotesla [nT] range. The cold cesium-133 atoms used for magnetic field measurements in this paper are a key component of the cesium fountain frequency standard at CSIR-NPL, which contributes to both timekeeping and magnetic sensing. The results show magnetic field fluctuations within 1 nT with a spatial resolution of 1 cm. The uncertainty in these measurements is of the order of 1.24 × 10⁻¹⁶, ensuring reliable and precise spatially resolved magnetic field mapping. Full article

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26 pages, 414 KiB

Open AccessArticle

Statistics of Quantum Numbers for Non-Equivalent Fermions in Single-j Shells

by Jean-Christophe Pain

Atoms 2025, 13(4), 25; https://doi.org/10.3390/atoms13040025 - 25 Mar 2025

Abstract

This work addresses closed-form expressions for the distributions

P (M)

of the magnetic quantum numbers M and

Q (J)

of total angular momentum J for non-equivalent fermions in single-j orbits. Such quantities play an important role in both [...] Read more.

This work addresses closed-form expressions for the distributions

P (M)

of the magnetic quantum numbers M and

Q (J)

of total angular momentum J for non-equivalent fermions in single-j orbits. Such quantities play an important role in both nuclear and atomic physics, through the shell models. Using irreducible representations of the rotation group, different kinds of formulas are presented, involving multinomial coefficients, generalized Pascal triangle coefficients, or hypergeometric functions. Special cases are discussed, and the connections between

P (M)

(and therefore

Q (J)

) and mathematical functions such as elementary symmetric, cyclotomic, and Jacobi polynomials are outlined. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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12 pages, 1538 KiB

Open AccessArticle

Properties of a Static Dipolar Impurity in a 2D Dipolar BEC

by Neelam Shukla and Jeremy R. Armstrong

Atoms 2025, 13(3), 24; https://doi.org/10.3390/atoms13030024 - 10 Mar 2025

Abstract

We study a system of ultra-cold dipolar Bose gas atoms confined in a two-dimensional (2D) harmonic trap with a dipolar impurity implanted at the center of the trap. Due to recent experimental progress in dipolar condensates, we focused on calculating properties of dipolar [...] Read more.

We study a system of ultra-cold dipolar Bose gas atoms confined in a two-dimensional (2D) harmonic trap with a dipolar impurity implanted at the center of the trap. Due to recent experimental progress in dipolar condensates, we focused on calculating properties of dipolar impurity systems that might guide experimentalists if they choose to study impurities in dipolar gases. We used the Gross–Pitaevskii formalism solved numerically via the split-step Crank–Nicolson method. We chose parameters of the background gas to be consistent with dysprosium (Dy), one of the strongest magnetic dipoles and of current experimental interest, and used chromium (Cr), erbium (Er), terbium (Tb), and Dy for the impurity. The dipole moments were aligned by an external field along what was chosen to be the z-axis, and we studied 2D confinements that were perpendicular or parallel to the external field. We show density contour plots for the two confinements, 1D cross-sections of the densities, calculated self-energies of the impurities while varying both number of atoms in the condensate and the symmetry of the trap. We also calculated the time evolution of the density of an initially pure system where an impurity is introduced. Our results show that while the self-energy increases in magnitude with increasing number of particles, it is reduced when the trap anisotropy follows the natural anisotropy of the gas, i.e., elongated along the z-axis in the case of parallel confinement. This work builds upon work conducted in Bose gases with zero-range interactions and demonstrates some of the features that could be found when exploring dipolar impurities in 2D Bose gases. Full article

(This article belongs to the Section Cold Atoms, Quantum Gases and Bose-Einstein Condensation)

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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

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

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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13 pages, 6452 KiB

Open AccessArticle

Evaluation of Spatial Profile of Local Emissions from W¹⁷⁺–W²³⁺ Unresolved Transition Array Spectra

by Ryota Nishimura, Tetsutarou Oishi, Izumi Murakami, Daiji Kato, Hiroyuki A. Sakaue, Hayato Ohashi, Shivam Gupta, Chihiro Suzuki, Motoshi Goto, Yasuko Kawamoto, Tomoko Kawate, Hiroyuki Takahashi and Kenji Tobita

Atoms 2025, 13(2), 21; https://doi.org/10.3390/atoms13020021 - 18 Feb 2025

Abstract

Tungsten (W) spectroscopy has attracted significant attention because W is one of the major impurities in ITER and future DEMO reactors. W²²⁺–W³³⁺ spectra at 15–45 Å have been useful for impurity diagnostics. Unresolved Transition Array (UTA) spectra around 200 Å, [...] Read more.

Tungsten (W) spectroscopy has attracted significant attention because W is one of the major impurities in ITER and future DEMO reactors. W²²⁺–W³³⁺ spectra at 15–45 Å have been useful for impurity diagnostics. Unresolved Transition Array (UTA) spectra around 200 Å, which contain W¹⁷⁺–W²³⁺, have potential for diagnostics tungsten ions in even lower charge states. Because multiple charge states overlap with very similar wavelengths, it is challenging to evaluate impurity spatial profiles from UTA spectra around 200 Å. In this study, we conducted tungsten pellet injection experiments in Large Helical Device (LHD) and attempted to evaluate the spatial profiles of UTA spectra around 200 Å, observed at 0.3–0.8 keV of central electron temperature. The results indicated that tungsten ions around W²⁰⁺ were locally profiled in a radial region, r_eff = 0.38 m, where the local electron temperature decreases by 30% to 40% with respect to more central and outer temperatures. These results suggested that the UTA spectrum around 200 Å would be useful for diagnostics of tungsten impurities in lower charge states than the charge states contained in UTA spectra around 15–45 Å. Full article

(This article belongs to the Section Atomic, Molecular and Nuclear Spectroscopy and Collisions)

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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

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

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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14 pages, 749 KiB

Open AccessArticle

Modelling of X-Ray Spectra Originating from the He- and Li-like Ni Ions for Plasma Electron Temperature Diagnostics Purposes

by Karol Kozioł, Andrzej Brosławski and Jacek Rzadkiewicz

Atoms 2025, 13(2), 18; https://doi.org/10.3390/atoms13020018 - 9 Feb 2025

Abstract

The multi-configurational Dirac–Hartree–Fock method has been used to examine the electron correlation effect on wavelengths and transition rates for

L \to K

transitions occurring in He- and Li-like nickel ions. The collisional-radiative modelling approach has been used to simulate the X-ray spectra, in [...] Read more.

The multi-configurational Dirac–Hartree–Fock method has been used to examine the electron correlation effect on wavelengths and transition rates for

L \to K

transitions occurring in He- and Li-like nickel ions. The collisional-radiative modelling approach has been used to simulate the X-ray spectra, in a 1.585–1.620 Å wavelength range, originating from the He-like nickel ions and their dielectronic Li-, Be-, and B-like satellites for various electron temperature values in the 2 keV to 8 keV range. The presented results may be useful in improving the plasma electron temperature diagnostics based on nickel spectra. Full article

(This article belongs to the Special Issue Atom and Plasma Spectroscopy)

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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

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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13 pages, 807 KiB

Open AccessArticle

High-Resolution Fourier Transform Spectra of Atomic Sulfur: Testing of Modified Quantum Defect Theory

by Vladislav E. Chernov, Nikolai L. Manakov, Alexei V. Meremianin, Alexander V. Naskidashvili, Svatopluk Civiš, Martin Ferus, Petr Kubelík, Ekaterina M. Zanozina and Oxana V. Zetkina

Atoms 2025, 13(2), 16; https://doi.org/10.3390/atoms13020016 - 8 Feb 2025

Abstract

QDT (quantum defect theory) is an effective technique for calculating processes involving highly excited (Rydberg) states of atoms, ions, and molecules with one valence electron outside filled shells, whose spectrum generally resembles a hydrogen-like atom’s spectrum. At the expense of some modification of [...] Read more.

QDT (quantum defect theory) is an effective technique for calculating processes involving highly excited (Rydberg) states of atoms, ions, and molecules with one valence electron outside filled shells, whose spectrum generally resembles a hydrogen-like atom’s spectrum. At the expense of some modification of QDT, in this paper, we extend its applicability to describe low- and intermediate-excited levels of atoms with more complex spectra (on the example of atomic sulfur S I). Transitions between just such states are responsible for the infrared (IR) spectra of atoms. While the quantum defects (QDs) of the highly excited Rydberg levels are determined by the energies of individual levels near the ionization threshold, the radial wave functions of low excited electronic states, in the framework of our modification of QDT, include the QD dependence on energy over a wide energy range; this dependence is determined from the whole spectral series. We show that, outside the atomic core domain, the electron radial functions calculated using modified semi-phenomenological QDT agree well with ab initio calculations. As another assessment of QDT accuracy, we show satisfactory agreement of the probabilities of dipole transitions in S I, taken from the NIST Atomic Spectra Database, with our QDT calculations. We perform an indirect experimental verification of QDT on the basis of spectra of S I in gas-discharge plasma measured by time-resolved high-resolution Fourier transfer spectroscopy (FTS). The Boltzmann plot built from our measured spectra demonstrates that QDT provides a satisfactory approximation for calculating the experimental lines’ intensities. Full article

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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

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

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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