Atoms

12 pages, 819 KiB

Open AccessArticle

Ionization of CF₃CH₂F by Protons and Photons

by Carlos E. Ferreira, Jorge A. de Souza-Corrêa, Alexandre B. Rocha and Antônio C. F. Santos

Atoms 2025, 13(6), 58; https://doi.org/10.3390/atoms13060058 - 18 Jun 2025

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(1) Background: Ionizing radiation in the Earth’s atmosphere drives key chemical transformations affecting atmospheric composition. Despite their environmental relevance, experimental data on proton collisions with hydrofluorocarbons remain limited, and theoretical models for total cross-sections and stopping power are still underdeveloped. (2) Methods: This [...] Read more.

(1) Background: Ionizing radiation in the Earth’s atmosphere drives key chemical transformations affecting atmospheric composition. Despite their environmental relevance, experimental data on proton collisions with hydrofluorocarbons remain limited, and theoretical models for total cross-sections and stopping power are still underdeveloped. (2) Methods: This study applies Rudd’s semiempirical model to calculate proton impact ionization cross-sections for the CF₃CH₂F molecule, considering contributions from both outer and inner electron shells. The model enables the estimation of differential cross-sections and the average energy of secondary electrons. In addition, we calculate the photoionization cross-sections using a discretized representation of the continuum—the so-called pseudo-spectrum—obtained through TDDFT with PBE0 as an exchange–correlation functional and compare it with the cross-section obtained for proton impact in the high-energy limit. (3) Results: The Rudd model proves highly adaptable and suitable for numerical applications. However, its validation is hindered by the scarcity of experimental data. Existing models, such as SRIM and Bethe–Bloch, show significant discrepancies due to their limited applicability at intermediate energies and lack of molecular structure consideration. (4) Conclusions: A comparison between the Rudd and BEB models reveals strong agreement in the analyzed energy range. This consistency stems from both models accounting for the molecular structure of the target, as well as from the fact that protons and electrons possess charges of the same magnitude, supporting a coherent description of ionization processes at these energies. Full article

(This article belongs to the Special Issue Electronic, Photonic and Ionic Interactions with Atoms and Molecules)

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19 pages, 857 KiB

Open AccessArticle

An Explicit Numerical Scheme for Milne’s Phase–Amplitude Equations

by Robin Piron and Mikael Tacu

Atoms 2025, 13(6), 57; https://doi.org/10.3390/atoms13060057 - 18 Jun 2025

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Abstract

We present an explicit numerical method to solve Milne’s phase–amplitude equations. Existing methods directly solve Milne’s nonlinear equation for amplitude. For that reason, they exhibit high sensitivity to errors and are prone to instability through the growth of a spurious, rapidly varying component [...] Read more.

We present an explicit numerical method to solve Milne’s phase–amplitude equations. Existing methods directly solve Milne’s nonlinear equation for amplitude. For that reason, they exhibit high sensitivity to errors and are prone to instability through the growth of a spurious, rapidly varying component of the amplitude. This makes the systematic use of these methods difficult. On the contrary, the present method is based on solving a linear third-order equation which is equivalent to the nonlinear amplitude equation. This linear equation was derived by Kiyokawa, who used it to obtain analytical results on Coulomb wavefunctions. The present method uses this linear equation for numerical computation, thus resolving the problem of the growth of a rapidly varying component. Full article

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14 pages, 2874 KiB

Open AccessArticle

Quantitative Analysis of Lithium in Natural Brines from the Lithium Triangle by Laser-Induced Breakdown Spectroscopy

by Juan Molina M., Carisa Sarchi, Alvaro Y. Tesio, César Costa-Vera and Diego M. Díaz Pace

Atoms 2025, 13(6), 56; https://doi.org/10.3390/atoms13060056 - 17 Jun 2025

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Abstract

Lithium (Li)-rich continental brines found in the Lithium Triangle region in South America are a natural resource of paramount importance. In the present research, the analytical performance of laser-induced breakdown spectroscopy (LIBS) technology was assessed for the quantitative analysis of Li in natural [...] Read more.

Lithium (Li)-rich continental brines found in the Lithium Triangle region in South America are a natural resource of paramount importance. In the present research, the analytical performance of laser-induced breakdown spectroscopy (LIBS) technology was assessed for the quantitative analysis of Li in natural brines aimed at enhancing the efficient exploration of salt flats (called salars). Brine samples were collected from different salars located in the Puna plateau (Northwest Argentina) and analyzed by LIBS in the form of solid pressed pellets. Broadband emission spectra (180–900 nm) were recorded and spectrally analyzed by specially designed computational algorithms. The laser-induced plasmas were characterized by calculating the electron density and the temperature. The Li elemental concentrations in the brines were determined through univariate calibration with the Li I emission line at 670.77 nm by using a suitable set of standards with Li concentrations up to 1300

μ

g/g. The calculated limit of detection was LoD = 0.2 ± 0.1

μ

g/g. The Li content in the brines determined with LIBS showed a good agreement (normalized standard deviation: σ_N = 25%) with the concentrations measured with atomic absorption spectroscopy. The results demonstrated the feasibility of the LIBS technique for the quantitative analysis of Li in natural brines, thus contributing to advancing the exploration of Li-rich resources. Full article

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Graphical abstract

8 pages, 360 KiB

Open AccessObituary

Nigel R. Badnell (1958–2024): A Legacy in Atomic Astrophysics

by Giulio Del Zanna, Helen E. Mason, Peter J. Storey, Stefan Kuhr, Chunyu Zhang, Junjie Mao, Gary J. Ferland, Alessandra Giunta and Roger P. Dufresne

Atoms 2025, 13(6), 55; https://doi.org/10.3390/atoms13060055 - 17 Jun 2025

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Abstract

Nigel Robert Badnell was born on the 27th of October 1958 and grew up in Swindon where he lived with his parents, Dave and Patricia, and his wee sister, Hilary [...] Full article

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

15 pages, 875 KiB

Open AccessArticle

Multi-Configuration Dirac–Hartree–Fock Calculations of Pr⁹⁺ and Nd¹⁰⁺: Configuration Resolution and Probing Fine-Structure Constant Variation

by Songya Zhang, Cunqiang Wu, Chenzhong Dong and Xiaobin Ding

Atoms 2025, 13(6), 54; https://doi.org/10.3390/atoms13060054 - 16 Jun 2025

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Abstract

We present high-precision multi-configuration Dirac–Hartree–Fock (MCDHF) calculations for the metastable states of

\Pr^{9 +}

and

{Nd}^{10 +}

ions, systematically investigating their energy levels, transition properties, Landé

g_{J}

factors, and hyperfine interaction constants. Our results show excellent agreement with available experimental [...] Read more.

We present high-precision multi-configuration Dirac–Hartree–Fock (MCDHF) calculations for the metastable states of

\Pr^{9 +}

and

{Nd}^{10 +}

ions, systematically investigating their energy levels, transition properties, Landé

g_{J}

factors, and hyperfine interaction constants. Our results show excellent agreement with available experimental data and theoretical benchmarks, while resolving critical configuration assignment discrepancies through detailed angular momentum coupling analysis. The calculations highlight the significant role of Breit interaction and provide the first theoretical predictions of electric quadrupole hyperfine constants (

B_{hfs}

). These findings deliver essential atomic data for the development of next-generation optical clocks and establish lanthanide highly charged ions as exceptional candidates for precision tests of fundamental physics. Full article

(This article belongs to the Special Issue Atomic and Molecular Data and Their Applications: ICAMDATA 2024)

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20 pages, 2231 KiB

Open AccessArticle

Comparative DFT Study of K₂AgSbBr₆ and K₂NaScBr₆: Exploring the Role of B^′B^″ Cation Substitution on Material Properties

by Abdelkebir Ejjabli, Mohamed Karouchi, Hamza Errahoui, Abdelmounaim Laassouli, Aymane El haji, Youssef Lachtioui and Omar Bajjou

Atoms 2025, 13(6), 53; https://doi.org/10.3390/atoms13060053 - 13 Jun 2025

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Abstract

The effects of cation substitution are the main emphasis of this investigation into the structural, mechanical, electronic, and optical properties of double perovskites K₂AgSbBr₆ and K₂NaScBr₆. Outwardly favorable tolerance and octahedral factors and negative formation energy [...] Read more.

The effects of cation substitution are the main emphasis of this investigation into the structural, mechanical, electronic, and optical properties of double perovskites K₂AgSbBr₆ and K₂NaScBr₆. Outwardly favorable tolerance and octahedral factors and negative formation energy confirmed structural stability and thermodynamic feasibility. Mechanical analysis showed that K₂AgSbBr₆ possesses greater volumetric stability and rigidity, while K₂NaScBr₆ exhibits greater ductility and isotropic characteristics. The electronic properties determined based on density functional theory (DFT) calculations indicate that K₂AgSbBr₆ has an indirect bandgap of 0.857 eV, making it suitable for applications using visible light, and K₂NaScBr₆ has a direct bandgap of 3.107 eV, making it ideal for UV-specific technologies. Optical analyses demonstrate complementary characteristics, particularly in terms of the dielectric function, absorption, reflectivity, energy loss function, refractive index, extinction coefficient, and optical conductivity. K₂AgSbBr₆ exhibits strong visible light absorptivity. 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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12 pages, 532 KiB

Open AccessArticle

g-Factor Isotopic Shifts: Theoretical Limits on New Physics Search

by Dmitry S. Akulov, Rinat R. Abdullin, Dmitry V. Chubukov, Dmitry A. Glazov and Andrey V. Volotka

Atoms 2025, 13(6), 52; https://doi.org/10.3390/atoms13060052 - 13 Jun 2025

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Abstract

The isotopic shift of the bound-electron g factor in highly charged ions (HCI) provides a sensitive probe for testing physics beyond the Standard Model, particularly through interactions mediated by a hypothetical scalar boson. In this study, we analyze the sensitivity of this method [...] Read more.

The isotopic shift of the bound-electron g factor in highly charged ions (HCI) provides a sensitive probe for testing physics beyond the Standard Model, particularly through interactions mediated by a hypothetical scalar boson. In this study, we analyze the sensitivity of this method within the Higgs portal framework, focusing on the uncertainties introduced by quantum electrodynamics corrections, including finite nuclear size, nuclear recoil, and nuclear polarization effects. All calculations are performed for the ground-state

1 s

configuration of hydrogen-like HCI, where theoretical predictions are most accurate. Using selected isotope pairs (e.g.,

{He}^{4 / 6}

,

{Ne}^{20 / 22}

,

{Ca}^{40 / 48}

,

{Sn}^{120 / 132}

,

{Th}^{230 / 232}

), we demonstrate that the dominant source of uncertainty arises from finite nuclear size corrections, which currently limit the precision of new physics searches. Our results indicate that the sensitivity of this method decreases with increasing atomic number. These findings highlight the necessity of improved nuclear radius measurements and the development of alternative approaches, such as the special differences method, to enable virtually the detection of fifth-force interactions. Full article

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

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12 pages, 1058 KiB

Open AccessArticle

The Influence of External Radiation on the Emission Properties of H- and He-like Argon Ions in High Temperature Plasma

by Roman K. Kulikov, Igor Yu. Skobelev and Evgeny D. Filippov

Atoms 2025, 13(6), 51; https://doi.org/10.3390/atoms13060051 - 11 Jun 2025

Viewed by 208

Abstract

In the present work, the influence of external X-ray radiation on the kinetics of multicharged ions in high-temperature plasma is investigated. A generalized diagnostic approach is proposed for the electron density and temperature measurements of photo-pumped plasma based on the relative intensity of [...] Read more.

In the present work, the influence of external X-ray radiation on the kinetics of multicharged ions in high-temperature plasma is investigated. A generalized diagnostic approach is proposed for the electron density and temperature measurements of photo-pumped plasma based on the relative intensity of the H-like ion resonance line and its dielectronic satellites. Based on detailed kinetic calculations performed for argon plasma, the conditions under which these techniques can be applied without modification to the photo-pumped plasma are determined, and the relative intensities of these lines are calculated for cases where the external influence significantly alters the kinetics of their excitation. The development of such diagnostic methods is of particular importance for the experiments with powerful X-ray free-electron lasers and thermonuclear laser plasma. Full article

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

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1 pages, 128 KiB

Open AccessCorrection

Correction: Nishimura et al. Charge Exchange Spectroscopy of Multiply Charged Erbium Ions. Atoms 2023, 11, 40

by Yuki Nishimura, Saki Imaizumi, Hajime Tanuma, Nobuyuki Nakamura, Yuichiro Sekiguchi, Shinya Wanajo, Hiroyuki A. Sakaue, Daiji Kato, Izumi Murakami, Masaomi Tanaka and Gediminas Gaigalas

Atoms 2025, 13(6), 50; https://doi.org/10.3390/atoms13060050 - 9 Jun 2025

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Abstract

The journal’s Editorial Office and Editorial Board are jointly issuing a resolution and removal of the Journal Notice linked to this article [...] Full article

10 pages, 509 KiB

Open AccessArticle

Energy Levels, Lifetimes, and Transition Properties for N iii – v

by Meichun Li, Juan Du, Kaijian Huang and Wenxian Li

Atoms 2025, 13(6), 49; https://doi.org/10.3390/atoms13060049 - 6 Jun 2025

Viewed by 613

Abstract

We present excitation energies, transition wavelengths, electric dipole (E1) transition rates, oscillator strengths, line strengths, and lifetimes for the 86 lowest states up to and including

1 s^{2} 2 s^{2} 7 f

in N iii, the 125 lowest states up [...] Read more.

We present excitation energies, transition wavelengths, electric dipole (E1) transition rates, oscillator strengths, line strengths, and lifetimes for the 86 lowest states up to and including

1 s^{2} 2 s^{2} 7 f

in N iii, the 125 lowest states up to and including

1 s^{2} 2 s 7 f

in N iv, and the 53 lowest states up to

1 s^{2} 8 g

in N v using the multiconfiguration Dirac–Hartree–Fock (MCDHF) and relativistic configuration interaction (RCI) methods. The computed results are then compared with data from the Atomic Spectra Database of the National Institute of Standards and Technology (NIST-ASD), experimental results, and other theoretical studies. For all levels in N iii – v, the root mean square energy differences from the NIST values are 130, 103, and 6 cm⁻¹, respectively. Compared to previous multiconfiguration Hartree–Fock and the Breit–Pauli (MCHF-BP) calculations, 89.3%, 98.5%, and 100% of the

log (g f)

values for N iii – v agree within 5%, respectively. Full article

(This article belongs to the Special Issue Atomic and Molecular Data and Their Applications: ICAMDATA 2024)

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13 pages, 1934 KiB

Open AccessArticle

Collision Kinematics for Fast Positron Impact Ionization of Argon

by Robert D. DuBois and Károly Tőkési

Atoms 2025, 13(6), 48; https://doi.org/10.3390/atoms13060048 - 4 Jun 2025

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Abstract

Classical trajectory Monte Carlo calculations for 1 keV positron impact ionization of argon are presented. A combination of energy-weighted triple differential cross-sections is shown to provide good to excellent agreement compared with experimental data, depending on the ejected electron azimuthal angular acceptance range [...] Read more.

Classical trajectory Monte Carlo calculations for 1 keV positron impact ionization of argon are presented. A combination of energy-weighted triple differential cross-sections is shown to provide good to excellent agreement compared with experimental data, depending on the ejected electron azimuthal angular acceptance range used to define in-plane scattering. For ejected electron energies less than 100 eV, information about the influence of pre- (the impact parameter) and post-(the direction of scattering) collision kinematics on the triple differential level is obtained. An overall picture of these kinematic properties is also presented for single differential cross-sections as a function of ejected electron energy and ejection angle. Full article

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

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64 pages, 2080 KiB

Open AccessReview

Triaxial Shapes in Even–Even Nuclei: A Theoretical Overview

by Dennis Bonatsos, Andriana Martinou, Spyridon K. Peroulis, Dimitrios Petrellis, Polytimos Vasileiou, Theodoros J. Mertzimekis and Nikolay Minkov

Atoms 2025, 13(6), 47; https://doi.org/10.3390/atoms13060047 - 31 May 2025

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Abstract

Triaxial shapes in even–even nuclei have been considered since the early days of the nuclear collective model. Although many theoretical approaches have been used over the years for their description, no effort appears to have been made for grouping them together and identifying [...] Read more.

Triaxial shapes in even–even nuclei have been considered since the early days of the nuclear collective model. Although many theoretical approaches have been used over the years for their description, no effort appears to have been made for grouping them together and identifying regions on the nuclear chart where the appearance of triaxiality might be favored. In addition, over the last few years, discussion has started on the appearance of small triaxiality in nuclei considered so far as purely axial rotors. In the present work, we collect the predictions made by various theoretical approaches and show that pronounced triaxiality appears to be favored within specific stripes on the nuclear chart, with low triaxiality being present in the regions between these stripes, in agreement with parameter-free predictions made by the proxy-SU(3) approximation to the shell model, based on the Pauli principle and the short-range nature of the nucleon–nucleon interaction. The robustness of triaxiality within these stripes is supported by global calculations made in the framework of the Finite-Range Droplet Model (FRDM), which is based on completely different assumptions and possesses parameters fitted in order to reproduce fundamental nuclear properties. Full article

(This article belongs to the Section Nuclear Theory and Experiments)

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12 pages, 9743 KiB

Open AccessArticle

by Peter Van Reeth and John W. Humberston

Atoms 2025, 13(6), 46; https://doi.org/10.3390/atoms13060046 - 28 May 2025

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Abstract

Scattering differential cross-sections (DCSs) are important tools, both experimentally and theoretically, in the investigation of scattering processes in lepton–atom collisions. In the present work, the elastic scattering differential cross-sections (EDCSs) for e⁺-H and e⁺-He below the first excitation threshold [...] Read more.

Scattering differential cross-sections (DCSs) are important tools, both experimentally and theoretically, in the investigation of scattering processes in lepton–atom collisions. In the present work, the elastic scattering differential cross-sections (EDCSs) for e⁺-H and e⁺-He below the first excitation threshold of the target were evaluated using the Kohn variational method and found to be very similar. In both cases, the EDCS below the positronium formation threshold, i.e., for pure elastic scattering, had minimum valley features in which significant minima close to 90 degrees were found at ≈2.8 eV for H and ≈2 eV for He. These minima were shown to be linked to the zero in the s-wave phase shift, which gives rise to the Ramsauer minimum in the elastic integrated cross-sections. They were not vortices, but the overall EDCS structure was found to be related to the structures and vortices found in the Ps formation differential cross-sections just above the Ps formation threshold. The valley-type structure in the EDCS went smoothly through the Ps formation threshold, where it linked up with a similar valley structure in both the EDCS above the threshold and the Ps formation DCS. A comparison with the EDCS for e⁻-H and e⁻-He scattering over the same energy range revealed similarities with the positron EDCS, however, with less pronounced structures that had different angular and momentum dependences. Full article

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

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