Atoms

18 pages, 5982 KiB

Open AccessArticle

Relativistic Atomic Structure Calculations for the Study of Electron Dynamics of Sr⁺ Ion Confined Inside Fullerene

by Biplab Goswami, Mobassir Ahmad, Jobin Jose and Raghavan K. Easwaran

Atoms 2025, 13(4), 36; https://doi.org/10.3390/atoms13040036 - 18 Apr 2025

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This article presents the maiden investigation of the electronic structural properties of the Sr⁺ ion confined inside fullerene. The Dirac equations are solved to calculate the energy levels, probability distributions, etc. for various confinement depths of the Gaussian Annular Square Well (GASW) [...] Read more.

This article presents the maiden investigation of the electronic structural properties of the Sr⁺ ion confined inside fullerene. The Dirac equations are solved to calculate the energy levels, probability distributions, etc. for various confinement depths of the Gaussian Annular Square Well (GASW) potential using the Multi-Configuration Dirac Hartree–Fock (MCDHF) formalism. The wavelengths, transition probabilities, and oscillator strengths are reported for the

5 S_{1 / 2} ⟷ 5 P_{1 / 2}

(

D_{1}

line) and

5 S_{1 / 2} ⟷ 5 P_{3 / 2}

(

D_{2}

line) transitions of the encapsulated ion. We also estimate variations in the line intensity ratio, electron density, Coulomb coupling parameter, etc. A suggested direction for the calculation of electron impact ionization cross-section using the binary-encounter Bethe (BEB) model with the present data is also given. 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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9 pages, 286 KiB

Open AccessOpinion

Challenges in Atomic Spectroscopy of Low-Ionisation-Stage Heavy Elements for Astrophysics

by Milan Ding

Atoms 2025, 13(4), 35; https://doi.org/10.3390/atoms13040035 - 16 Apr 2025

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Abstract

Accurate knowledge of the fine structure of low-ionisation-stage heavy elements is crucial for plasma modelling in stellar astronomy, galactic evolution studies, and nucleosynthesis investigations. The experimental determination of atomic energy levels and transitions in these elements is essential for the meaningful interpretation of [...] Read more.

Accurate knowledge of the fine structure of low-ionisation-stage heavy elements is crucial for plasma modelling in stellar astronomy, galactic evolution studies, and nucleosynthesis investigations. The experimental determination of atomic energy levels and transitions in these elements is essential for the meaningful interpretation of high-resolution astrophysical spectra obtained with modern telescopes, as theoretical calculations of transition wavelengths and strengths often lack sufficient accuracy. This article provides a brief review of the major challenges in empirical atomic structure investigations of the low-ionisation open d- and f-subshell elements, which have the most complex atomic spectra. Full article

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

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10 pages, 4390 KiB

Open AccessArticle

The Laboratory Measurement of the Line Ratios in X-Ray Emission Resulting from the Charge Exchange Between Mg¹¹⁺ and Helium

by Kebao Shu, Caojie Shao, Shuo Zhang, Ruitian Zhang, Cheng Qian, Yingli Xue, Mingwu Zhang, Jinlei Tian, Zhenqiang Wang, Xiaolong Zhu, Liangting Sun, Junxia Ran and Deyang Yu

Atoms 2025, 13(4), 34; https://doi.org/10.3390/atoms13040034 - 14 Apr 2025

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Abstract

The line ratios in X-ray emission resulting from charge exchange between highly charged ions (HCIs) and neutral atoms are not only crucial for accurately modeling astrophysical X-ray emissions but also offer a unique perspective on the charge exchange processes happening during collisions. The [...] Read more.

The line ratios in X-ray emission resulting from charge exchange between highly charged ions (HCIs) and neutral atoms are not only crucial for accurately modeling astrophysical X-ray emissions but also offer a unique perspective on the charge exchange processes happening during collisions. The K X-ray spectra following charge exchange between Mg¹¹⁺ and He are presented for a collision velocity of 1489 km/s (11.5 keV/amu). The spectra were measured by two Silicon Drift Detectors capable of resolving the Mg¹⁰⁺ Kα, Kβ, Kγ, and Kδ+ lines. The line intensity ratios of Kβ, Kγ, and Kδ+ relative to the Kα line, as well as the hardness ratio, were obtained. The experimental results were compared with the theoretical results from a cascade model that utilizes the state cross-sections produced by multichannel Landau–Zener (MCLZ) calculation. It was discovered that the K X-ray spectrum features can be reproduced well by MCLZ theory when the contributions of both single electron capture (SEC) and autoionizing double capture (ADC) processes are included. This finding implies that the ADC feeding mechanism is significant and should be taken into account for the X-ray emission during charge exchange between highly charged ions and multielectron atoms. Full article

(This article belongs to the Special Issue X-Ray Spectroscopy in Astrophysics)

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9 pages, 253 KiB

Open AccessArticle

Revisiting the Influence of Neutron Transfer Coupling on Surface Diffuseness Parameters for Carbon-Induced Fusion Reactions

by Rakesh Dubey

Atoms 2025, 13(4), 33; https://doi.org/10.3390/atoms13040033 - 9 Apr 2025

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Abstract

The influence of neutron transfer coupling on surface diffuseness has been thoroughly investigated in the study of carbon-induced fusion reactions. Through analysis of experimental measurements using advanced coupled-channel computational frameworks, we have examined how neutron exchange processes modify nuclear interaction potentials with a [...] Read more.

The influence of neutron transfer coupling on surface diffuseness has been thoroughly investigated in the study of carbon-induced fusion reactions. Through analysis of experimental measurements using advanced coupled-channel computational frameworks, we have examined how neutron exchange processes modify nuclear interaction potentials with a particular focus on surface diffuseness parameters. The findings reveal that neutron transfer mechanisms substantially contribute to reducing surface diffuseness values, with this effect being particularly pronounced in reactions involving neutron-rich isotopic combinations. This research highlights the critical importance of incorporating neutron transfer pathways when modeling fusion cross-sections, offering valuable perspectives for subsequent investigations of nuclear reaction dynamics. Full article

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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

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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

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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

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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

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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

Viewed by 155

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

Viewed by 182

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

Viewed by 262

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

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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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