Atoms

11 pages, 6956 KiB

Open AccessArticle

UK APAP R-Matrix Electron-Impact Excitation Cross-Sections for Modelling Laboratory and Astrophysical Plasma

by Giulio Del Zanna, Guiyun Liang, Junjie Mao and Nigel R. Badnell

Atoms 2025, 13(5), 44; https://doi.org/10.3390/atoms13050044 - 14 May 2025

Viewed by 114

Systematic R-matrix calculations of electron-impact excitation for ions of astrophysical interest have been performed since 2007 for many iso-electronic sequences as part of the UK Atomic Process for Astrophysical Plasma (APAP) network. Rate coefficients for Maxwellian electron distributions have been provided and used [...] Read more.

Systematic R-matrix calculations of electron-impact excitation for ions of astrophysical interest have been performed since 2007 for many iso-electronic sequences as part of the UK Atomic Process for Astrophysical Plasma (APAP) network. Rate coefficients for Maxwellian electron distributions have been provided and used extensively in the literature and many databases for astrophysics. Here, we provide averaged collision strengths to be used to model plasma where electrons are non-Maxwellian, which often occurs in laboratory and astrophysical plasma. We also provide many new Maxwellian-averaged collision strengths, which include important corrections to the published values. Recently, we made available the H- and He-like collision strengths. Here, we provide data for ions of the Li-, Be-, B-, C-, N-, O-, Ne-, Na-, and Mg-like sequences. Full article

► Show Figures

Figure 1

14 pages, 1754 KiB

Open AccessArticle

The Single-Active-Electron Approximation with Angular-Momentum-Dependent Potentials: Application to the Helium Atom

by Juan Carlos del Valle and Klaus Bartschat

Atoms 2025, 13(5), 43; https://doi.org/10.3390/atoms13050043 - 14 May 2025

Viewed by 109

Abstract

We discuss an extension of the Single-Active-Electron (SAE) approximation in atoms by allowing the model potential to depend on the angular-momentum quantum number ℓ. We refer to this extension as the ℓ-SAE approximation. The main ideas behind ℓ-SAE are illustrated [...] Read more.

We discuss an extension of the Single-Active-Electron (SAE) approximation in atoms by allowing the model potential to depend on the angular-momentum quantum number ℓ. We refer to this extension as the ℓ-SAE approximation. The main ideas behind ℓ-SAE are illustrated using the helium atom as a benchmark system. We show that introducing ℓ-dependent potentials improves the accuracy of key quantities in atomic structure computed from the Time-Independent Schrödinger Equation (TISE), including energies, oscillator strengths, and static and dynamic polarizabilities, compared to the standard SAE approach. Additionally, we demonstrate that the ℓ-SAE approximation is suitable for quantum simulations of light−atom interactions described by the Time-Dependent Schrödinger Equation (TDSE). As an illustration, we simulate High-order Harmonic Generation (HHG) and the three-sideband (3SB) version of the Reconstruction of Attosecond Beating by Interference of Two-photon Transitions (RABBITT) technique, achieving enhanced accuracy comparable to that obtained in all-electron calculations. One of the main advantages of the ℓ-SAE approach is that existing SAE codes can be easily adapted to handle ℓ-dependent potentials without any additional computational cost. Full article

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

► Show Figures

Figure 1

17 pages, 2106 KiB

Open AccessArticle

Informational Entropy Analysis of Artificial Helium Atoms

by Marcilio N. Guimarães, Rafael N. Cordeiro, Wallas S. Nascimento and Frederico V. Prudente

Atoms 2025, 13(5), 42; https://doi.org/10.3390/atoms13050042 - 12 May 2025

Viewed by 88

Abstract

We use the Shannon informational entropies as a tool to study the artificial helium atom, namely, two electrons confined in a quantum dot. We adopt configurations with spherical and cylindrical symmetries for the physical system of interest. Using the informational quantities, we analyze [...] Read more.

We use the Shannon informational entropies as a tool to study the artificial helium atom, namely, two electrons confined in a quantum dot. We adopt configurations with spherical and cylindrical symmetries for the physical system of interest. Using the informational quantities, we analyze the effects of electronic confinement, we validate the entropic uncertainty relation, we identify that the Coulomb interaction potential between the electrons is no longer important for strong confinements, and we indicate/predict the avoided crossing phenomena. Finally, we carried out a density function analysis. When available, the results are compared with those in the literature. Full article

(This article belongs to the Section Atom Based Quantum Technology)

► Show Figures

Figure 1

15 pages, 1508 KiB

Open AccessArticle

Neutron Cross-Section Uncertainty and Reactivity Analysis in MOX and Metal Fuels for Sodium-Cooled Fast Reactor

by Oyeon Kum

Atoms 2025, 13(5), 41; https://doi.org/10.3390/atoms13050041 - 6 May 2025

Viewed by 161

Abstract

This study presents a comprehensive uncertainty and sensitivity analysis of the effective neutron multiplication factor (

k_{eff}

) in a large-scale sodium-cooled fast reactor (SFR) modeled after the European Sodium Fast Reactor. Utilizing the Serpent Monte Carlo code and the ENDF/B-VII.1 cross-section [...] Read more.

This study presents a comprehensive uncertainty and sensitivity analysis of the effective neutron multiplication factor (

k_{eff}

) in a large-scale sodium-cooled fast reactor (SFR) modeled after the European Sodium Fast Reactor. Utilizing the Serpent Monte Carlo code and the ENDF/B-VII.1 cross-section library, this research investigates the impact of cross-section perturbations in key isotopes (²³⁵U, ²³⁸U, and ²³⁹Pu for both mixed oxide (MOX) and metal fuels. Particular focus is placed on the capture, fission, and inelastic scattering reactions, as well as the effects of fuel temperature on reactivity through Doppler broadening. The findings reveal that reactivity in MOX fuel is highly sensitive to the fission cross sections of fissile isotopes (²³⁹Pu and ²³⁸U, while capture and inelastic scattering reactions in fertile isotopes such as ²³⁸U play a significant role in reducing reactivity, enhancing neutron economy. Additionally, this study highlights that metal fuel configurations generally achieve a higher (

k_{eff}

) compared to MOX, attributed to their higher fissile atom density and favorable thermal properties. These results underscore the importance of accurate nuclear data libraries to minimize uncertainties in criticality evaluations, and they provide a foundation for optimizing fuel compositions and refining reactor control strategies. The insights gained from this analysis can contribute to the development of safer and more efficient next-generation SFR designs, ultimately improving operational margins and reactor performance. Full article

► Show Figures

Figure 1

6 pages, 294 KiB

Open AccessCommunication

Triple-Differential Cross-Section Calculations for Positron Impact Ionization of Argon

by Radu I. Campeanu, Zsuzsánna Bálint and Ladislau Nagy

Atoms 2025, 13(5), 40; https://doi.org/10.3390/atoms13050040 - 4 May 2025

Viewed by 161

Abstract

Triple-differential cross-sections for the positron impact ionization of argon were calculated using a distorted-wave Born approximation (DWBA) convoluted to the experimental uncertainties. In almost all of the cases studied, our results agree well with the positions and heights of the experimental peaks. Full article

► Show Figures

Figure 1

20 pages, 1096 KiB

Open AccessArticle

Elastic e-Atom Scattering Using Multi-Configuration Dirac–Fock Partial Wave Analysis

by R. Aiswarya and Jobin Jose

Atoms 2025, 13(5), 39; https://doi.org/10.3390/atoms13050039 - 30 Apr 2025

Viewed by 132

Abstract

A novel scattering formalism, the multi-configuration Dirac–Fock partial wave analysis (MCDF-PWA), is presented in this study. This approach extends the conventional Dirac partial wave analysis by incorporating multiple atomic configurations of the target scatterer. The newly formulated methodology is employed to compute the [...] Read more.

A novel scattering formalism, the multi-configuration Dirac–Fock partial wave analysis (MCDF-PWA), is presented in this study. This approach extends the conventional Dirac partial wave analysis by incorporating multiple atomic configurations of the target scatterer. The newly formulated methodology is employed to compute the cross-sections in elastic e-atom scattering. The analysis is performed for a few atomic targets like Mg, Ca, and Ba. Full article

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

► Show Figures

Figure 1

13 pages, 1058 KiB

Open AccessArticle

A Novel Approach to Calculate the Range of High-Energy Charged Particles Within a Medium

by Ioannis Psychogios, Stylianos Vasileios Kontomaris, Anna Malamou and Andreas Stylianou

Atoms 2025, 13(5), 38; https://doi.org/10.3390/atoms13050038 - 27 Apr 2025

Viewed by 162

Abstract

The determination of energy loss of charged particles as they pass through a medium and consequently the calculation of their range within the medium are of tremendous importance in various areas of physics from both theoretical and practical perspectives. Previous works have derived [...] Read more.

The determination of energy loss of charged particles as they pass through a medium and consequently the calculation of their range within the medium are of tremendous importance in various areas of physics from both theoretical and practical perspectives. Previous works have derived approximate equations regarding the range of ions within a medium, focusing on providing simple solutions for practitioners in the radiotherapy field that do not require significant computational cost, unlike traditional Monte Carlo methods. These solutions focus on radiotherapy and are limited to specific ions’ initial speeds, which should be up to 0.65c (where c is the speed of light in vacuum). In this paper, solutions for significantly larger initial velocities are explored. A new analytical equation for determining the range of charged particles within a medium for initial velocities between 0.6c and 0.9c is presented. This equation provides excellent results when compared to the accurate numerical solution. Beyond its theoretical and mathematical interest, this solution is also reliable for radiotherapy applications. It provides excellent results for protons with initial energies between 200 MeV and 350 MeV and has the major advantage of being expressed in terms of elementary functions, making its use more straightforward compared to other approaches. Full article

► Show Figures

Figure 1

15 pages, 570 KiB

Open AccessArticle

Electron and Positron Collision with Plasma Wall Coating Elements

by Balajee R, Yurekha S.P., Snigdha Sharma and Dhanoj Gupta

Atoms 2025, 13(5), 37; https://doi.org/10.3390/atoms13050037 - 26 Apr 2025

Viewed by 222

Abstract

The investigation of integral elastic cross-section (ICS), momentum transfer cross-section (MTCS), viscosity cross-section (VCS), absorption cross-section (ABSCS), and total cross-section (TCS) of atoms by electron (

e^{-}

) and positron (

e^{+}

) impact is very crucial and essential for understanding [...] Read more.

The investigation of integral elastic cross-section (ICS), momentum transfer cross-section (MTCS), viscosity cross-section (VCS), absorption cross-section (ABSCS), and total cross-section (TCS) of atoms by electron (

e^{-}

) and positron (

e^{+}

) impact is very crucial and essential for understanding fundamental atomic processes and their applications in various fields such as plasma physics, molecular physics, and astrophysics. This study investigates and analyses the ICS, MTCS, VCS, ABSCS, and TCS of the atoms, Li, Be, B, Ti, and W, over a wide energy range. By employing the computational Optical Potential Method (OPM) and quantum scattering integrated in a computational package, ELSEPA (Elastic scattering of electrons and positrons by atoms, positive ions and molecules), the cross-sections of atoms by electron and positron impact are calculated. The present results shows good agreement with all the experimental and theoretical data available in the literature. The obtained cross-sections may facilitate the development of accurate models for plasma simulations and fusion research. Full article

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

► Show Figures

Figure 1

Journal Menu

Journal Browser

Atoms, Volume 13, Issue 5 (May 2025) – 8 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI