Atoms

14 pages, 1283 KB

Open AccessArticle

A Comparative Study of COMPLET Code Predictions with Experimental Data on Alpha Particle-Induced Reactions on Cobalt Isotope up to 120 MeV

by Cherie Sisay Mekonen and Ayyagari Venkata Mohan Rao

Atoms 2025, 13(12), 96; https://doi.org/10.3390/atoms13120096 (registering DOI) - 4 Dec 2025

Abstract

A comparative study of alpha-induced reactions on cobalt isotope with the predictions by COMPLET code is presented for nine excitation functions, ⁵⁹Co(α,p5n)⁵⁷Ni, ⁵⁹Co (α,p6n)⁵⁶Ni, ⁵⁹Co(α,2pn)⁶⁰Co, ⁵⁹Co(α,3pn)⁵⁹Fe, ⁵⁹Co(α,αn)⁵⁸Co, ⁵⁹ [...] Read more.

A comparative study of alpha-induced reactions on cobalt isotope with the predictions by COMPLET code is presented for nine excitation functions, ⁵⁹Co(α,p5n)⁵⁷Ni, ⁵⁹Co (α,p6n)⁵⁶Ni, ⁵⁹Co(α,2pn)⁶⁰Co, ⁵⁹Co(α,3pn)⁵⁹Fe, ⁵⁹Co(α,αn)⁵⁸Co, ⁵⁹Co(α,α2n)⁵⁷Co, ⁵⁹Co(α,α3n)⁵⁶Co, ⁵⁹Co(α,2αn)⁵⁴Mn, and ⁵⁹Co(α,2α3n)⁵²Mn. The experimental values were taken from the EXFOR data base. Theoretical cross-sections were calculated using initial exciton number n₀ = 4 (4p0h) and level density parameter a (=ACN/10) globally. While several reactions showed excellent agreement with experimental data, others displayed a notable discrepancy. This is because of the limitations of the COMPLET code to take the alpha emission in a pre-equilibrium phase. Full article

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11 pages, 257 KB

Open AccessOpinion

Effective Action Approach to Quantum and Thermal Effects: From One Particle to Bose–Einstein Condensates

by Luca Salasnich

Atoms 2025, 13(12), 95; https://doi.org/10.3390/atoms13120095 (registering DOI) - 1 Dec 2025

Abstract

We present a detailed derivation of the quantum and quantum–thermal effective action for non-relativistic systems, starting from the single-particle case and extending to the Gross–Pitaevskii (GP) field theory for weakly interacting bosons. In the single-particle framework, we introduce the one-particle-irreducible (1PI) effective action [...] Read more.

We present a detailed derivation of the quantum and quantum–thermal effective action for non-relativistic systems, starting from the single-particle case and extending to the Gross–Pitaevskii (GP) field theory for weakly interacting bosons. In the single-particle framework, we introduce the one-particle-irreducible (1PI) effective action formalism, taking explicitly into account the choice of the initial quantum state, its saddle-point plus Gaussian-fluctuation approximation, and its finite-temperature extension via Matsubara summation, yielding a clear physical interpretation in terms of zero-point and thermal contributions to the Helmholtz free energy. The formalism is then applied to the GP action, producing the 1PI effective potential at zero and finite temperature, including beyond-mean-field Lee–Huang–Yang and thermal corrections. We discuss the gapless and gapped Bogoliubov spectra, their relevance to equilibrium and non-equilibrium regimes, and the role of regularization. Applications include the inclusion of an external potential within the local density approximation, the derivation of finite-temperature Josephson equations, and the extension to D-dimensional systems, with particular attention to the zero-dimensional limit. This unified approach provides a transparent connection between microscopic quantum fluctuations and effective macroscopic equations of motion for Bose–Einstein condensates. Full article

14 pages, 6427 KB

Open AccessArticle

Electron Scattering from Superheavy Elements: Copernicium and Oganesson

by Shruti Sarswat, Saumyashree Baral and Jobin Jose

Atoms 2025, 13(11), 94; https://doi.org/10.3390/atoms13110094 - 20 Nov 2025

Abstract

Superheavy elements are an ideal testbed for studying relativistic, exchange, and correlation effects in scattering phenomena. In this work, we investigate electron scattering from copernicium

(Z = 112)

and oganesson

(Z = 118)

atoms. Both the relativistic Dirac and [...] Read more.

Superheavy elements are an ideal testbed for studying relativistic, exchange, and correlation effects in scattering phenomena. In this work, we investigate electron scattering from copernicium

(Z = 112)

and oganesson

(Z = 118)

atoms. Both the relativistic Dirac and non-relativistic partial wave methods are employed to analyze the scattering dynamics, with the interaction between the projectile and target atom modeled within the framework of the optical potential approach. Our results demonstrate that relativistic, exchange, and correlation effects play a significant role in modifying the scattering cross-sections and scattering length, highlighting the influence of these interactions on the scattering processes from superheavy atomic systems. The work also attempts to identify common features of the scattering cross-section by comparing those of lighter elements in the same group. Full article

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

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13 pages, 914 KB

Open AccessArticle

Antiprotonic Atoms as Gateways to HCI

by Lidia Lappo, Jakub Zieliński, Fredrik P. Gustafsson, Malgorzata Grosbart, Georgy Kornakov and Michael Doser

Atoms 2025, 13(11), 93; https://doi.org/10.3390/atoms13110093 - 19 Nov 2025

Abstract

The present study investigates the production of highly charged ions (HCIs) through the novel application of antiprotonic atoms and explores their potential for studying atomic and nuclear structures. Utilizing the Geant4 simulation toolkit, comprehensive simulations were conducted for all known isotopes with atomic [...] Read more.

The present study investigates the production of highly charged ions (HCIs) through the novel application of antiprotonic atoms and explores their potential for studying atomic and nuclear structures. Utilizing the Geant4 simulation toolkit, comprehensive simulations were conducted for all known isotopes with atomic numbers below 100. These simulations recorded key parameters of the resulting nuclear fragments, including mass, momentum, charge, and yield. The results obtained from this study offer valuable insights into the mechanisms of HCI production and provide a foundation for planning and analyzing future experimental investigations. This work demonstrates the feasibility of using antiprotonic atoms to advance nuclear and atomic physics research. Full article

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

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18 pages, 1413 KB

Open AccessArticle

Hybrid Basis and Multi-Center Grid Method for Strong-Field Processes

by Kyle A. Hamer, Heman Gharibnejad, Luca Argenti and Nicolas Douguet

Atoms 2025, 13(11), 92; https://doi.org/10.3390/atoms13110092 - 17 Nov 2025

Abstract

We present a time-dependent framework that combines a hybrid basis, consisting of Gaussian-type orbitals (GTOs) and finite-element discrete-variable representation (FEDVR) functions, with a multicenter grid to simulate strong-field and attosecond dynamics in atoms and molecules. The method incorporates the construction of the orthonormal [...] Read more.

We present a time-dependent framework that combines a hybrid basis, consisting of Gaussian-type orbitals (GTOs) and finite-element discrete-variable representation (FEDVR) functions, with a multicenter grid to simulate strong-field and attosecond dynamics in atoms and molecules. The method incorporates the construction of the orthonormal hybrid basis, the evaluation of electronic integrals, a unitary time-propagation scheme, and the extraction of optical and photoelectron observables. Its accuracy and robustness are benchmarked on one-electron systems such as atomic hydrogen and the dihydrogen cation (

H_{2}^{+}

) through comparisons with essentially-exact reference results for bound-state energies, high-harmonic generation spectra, photoionization cross sections, and photoelectron momentum distributions. This work establishes the groundwork for its integration with quantum-chemistry methods, which is already operational but will be detailed in future work, thereby enabling ab initio simulations of correlated polyatomic systems in intense ultrafast laser fields. 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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20 pages, 2241 KB

Open AccessArticle

Computational and Spectroscopic Investigation of Diaminomethane Formation: The Simplest Geminal Diamine of Astrochemical Interest

by Pravi Mishra, Parmanand Pandey, Rachana Singh, Manisha Yadav, Shivani, Aftab Ahamad, Alka Misra, Amritanshu Shukla and Poonam Tandon

Atoms 2025, 13(11), 91; https://doi.org/10.3390/atoms13110091 - 12 Nov 2025

Abstract

A high-level ab initio characterization and formation of diaminomethane (DAM), the simplest geminal diamine, is presented to support its spectroscopic detection and astrochemical relevance in the interstellar medium. The C_2v DAM conformer is identified as the global minimum, while C₁ [...] Read more.

A high-level ab initio characterization and formation of diaminomethane (DAM), the simplest geminal diamine, is presented to support its spectroscopic detection and astrochemical relevance in the interstellar medium. The C_2v DAM conformer is identified as the global minimum, while C₁ DAM and C₂ DAM represent higher-energy local minima. The proposed reaction pathways are exothermic and proceed without activation barriers. Simulated infrared spectrum reproduces accurate key spectral signatures with several vibrational modes exhibiting strong IR intensities (>80 km mol⁻¹), particularly in the 800–3000 cm⁻¹ range and band shapes. Dipole moments and accurate rovibrational spectroscopic parameters, including rotational constants, anharmonic vibrational frequencies, quartic and sextic distortion constants, and nuclear quadrupole coupling constants are reported to assist with high-resolution spectroscopic identification. This study provides significant theoretical benchmarks for its formation and offers guidance for future laboratory spectroscopy and molecular searches in interstellar environments. Full article

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14 pages, 6876 KB

Open AccessArticle

Improving Quantitative Analysis of Lithium in Brines Using Laser-Induced Breakdown Spectroscopy with τ–Algorithm (τLIBS)

by Juan Molina M., Carlos Aragón, José A. Aguilera, César Costa-Vera and Diego M. Díaz Pace

Atoms 2025, 13(11), 90; https://doi.org/10.3390/atoms13110090 - 12 Nov 2025

Abstract

In this work, a quantitative analysis of Li in natural brines was carried out by laser-induced breakdown spectroscopy (LIBS) assisted by the τ–algorithm for detailed analysis of the experimental line shapes (τLIBS). Brine samples were collected from different salars located in the Puna [...] Read more.

In this work, a quantitative analysis of Li in natural brines was carried out by laser-induced breakdown spectroscopy (LIBS) assisted by the τ–algorithm for detailed analysis of the experimental line shapes (τLIBS). 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. The emission intensities of Li I, H_α, and Mg I–II lines were measured and spatially integrated along the line of sight with temporal resolution by using a high-spectral-resolution spectrometer equipped with an intensified charge-coupled device (iCCD) detector. The plasma was characterized through the determination of the electron density and the temperature. The τ–algorithm calculated the optical thicknesses of the Li I lines to generate synthetic intensity profiles that were subsequently fitted to the experimental spectra. By applying the developed τLIBS approach, valuable spectroscopic insight was recovered about the physical processes occurring in the plasma, such as self-absorption. The analytical process involved an univariate external calibration process using the resonant Li I line at 6707.7 Å measured from a series of Li standard samples. Self-absorption effects were evaluated and subsequently compensated. The final LIBS results, with an enhanced accuracy of 15%, were validated by crosschecking them against those obtained with the standard AAS method. Full article

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Graphical abstract

16 pages, 1425 KB

Open AccessArticle

Combining Physics and Machine Learning: Hybrid Models for Predicting Interatomic Potentials

by Kaoutar El Haloui, Nicolas Thome and Nicolas Sisourat

Atoms 2025, 13(11), 89; https://doi.org/10.3390/atoms13110089 - 10 Nov 2025

Abstract

Constructing accurate Potential Energy Surfaces (PES) is a central task in molecular modeling, as it determines the forces governing nuclear motion and enables reliable quantum dynamics simulations. While ab initio methods can provide accurate PES, they are computationally prohibitive for extensive applications. Alternatively, [...] Read more.

Constructing accurate Potential Energy Surfaces (PES) is a central task in molecular modeling, as it determines the forces governing nuclear motion and enables reliable quantum dynamics simulations. While ab initio methods can provide accurate PES, they are computationally prohibitive for extensive applications. Alternatively, analytical physics-based models such as the Morse potential offer efficient solutions but are limited by their rigidity and poor generalization to excited states. In recent years, neural networks have emerged as powerful tools for determining PES, due to their universal function approximation capabilities, but they require large training datasets. In this work, we investigate hybrid-residual modeling approaches that combine physics-based potentials with neural network corrections, aiming to leverage both physical priors and data adaptability. Specifically, we compare three hybrid models—APHYNITY, Sequential Phy-ML, and PhysiNet—in their ability to reconstruct the potential energy curve of the ground and first excited states of the hydrogen molecule. Each model integrates a simplified physical representation with a neural component that learns the discrepancies from accurate reference data. Our findings reveal that hybrid models significantly outperform both standalone neural networks and pure physics-based models, especially in low-data regimes. Notably, APHYNITY and Sequential Phy-ML exhibit better generalization and maintain accurate estimation of physical parameters, underscoring the benefits of explicit physics incorporation. Full article

(This article belongs to the Special Issue Artificial Intelligence for Quantum Sciences)

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15 pages, 1029 KB

Open AccessArticle

Single Ionization with Dressed Projectiles: An Improved Theory for Both Long- and Short-Range Interactions

by Nicolás J. Esponda, Michele A. Quinto, Roberto D. Rivarola and Juan M. Monti

Atoms 2025, 13(11), 88; https://doi.org/10.3390/atoms13110088 - 9 Nov 2025

Abstract

In this work, we present a theoretical model to investigate electron emission in collisions between dressed ions with He atoms and H₂ molecules. The projectile potential is described as the sum of a long- and short-range terms. The last term includes a [...] Read more.

In this work, we present a theoretical model to investigate electron emission in collisions between dressed ions with He atoms and H₂ molecules. The projectile potential is described as the sum of a long- and short-range terms. The last term includes a screening function that has its maximum at short distances. The present model is based on the Continuum Distorted Wave Eikonal Initial State (CDW-EIS) theory, but the Eikonal approximation is only made within the long-range transition amplitude. This now leads to physically correct predictions, whenever dressed projectiles are involved, in the binary-encounter peak. Indeed, double-differential cross-sections spectra is calculated and compared with existing experimental data, finding that this model is capable of reproducing some well-known phenomena depending on the projectile charge state. Namely, the dependence of the binary-encounter peak magnitude with the projectile charge state. Full article

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

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38 pages, 792 KB

Open AccessArticle

First and Second Law of Thermodynamics Constraints in the Lifshitz Theory of Dispersion Forces

by Fabrizio Pinto

Atoms 2025, 13(11), 87; https://doi.org/10.3390/atoms13110087 - 5 Nov 2025

Abstract

The presence of dominant interatomic dispersion forces on the nanoscale holds the promise for breakthrough applications in key areas of quantum sensing, such as accelerometry, as well as nano-manipulation and energy storage. In order to do work, nano-machines enabled by dispersion forces must [...] Read more.

The presence of dominant interatomic dispersion forces on the nanoscale holds the promise for breakthrough applications in key areas of quantum sensing, such as accelerometry, as well as nano-manipulation and energy storage. In order to do work, nano-machines enabled by dispersion forces must exchange energy with the surrounding environment. Such processes can be described in terms of thermodynamical engine cycles involving individual atoms or material boundaries, separated by possibly empty gaps and interacting via time-dependent dispersion forces. The fundamental strategy indispensable to achieve dispersion force time-modulation, demonstrated experimentally by independent groups on different scales, is based on the illumination of interacting, semiconducting elements by appropriate radiation beams. Here we analyze the operation of ideal nano-engines in the quasi-static regime by means of the Lifshitz theory of dispersion forces involving semiconducting boundary or atom irradiation. Firstly, we verify that the First Law of Thermodynamics is satisfied so that the total energy of the system is rigorously conserved. Secondly, we show that, within this first approximate treatment, the Second Law of Thermodynamics may be violated for extremely small interboundary gap widths. We identify important limitations to be addressed to determine whether this is a reliable conclusion. The technological and historic backdrops are presented, and important topics for future research are identified. Full article

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8 pages, 467 KB

Open AccessArticle

The Arrow of Time in Quantum Theory

by Jean-Patrick Connerade

Atoms 2025, 13(11), 86; https://doi.org/10.3390/atoms13110086 - 26 Oct 2025

Abstract

In Classical Mechanics, time is reversible, i.e., it implies no particular choice: only the observer knows in which direction it flows. The present article re-examines whether this remains true in Quantum Mechanics. In the context of Atomic Physics, it is concluded that the [...] Read more.

In Classical Mechanics, time is reversible, i.e., it implies no particular choice: only the observer knows in which direction it flows. The present article re-examines whether this remains true in Quantum Mechanics. In the context of Atomic Physics, it is concluded that the existence of an arrow of time depends on the manner in which the radiation field is introduced, which must be non-perturbative. Full article

12 pages, 1196 KB

Open AccessArticle

The Opacity Project: R-Matrix Calculations for Opacities of High-Energy-Density Astrophysical and Laboratory Plasmas

by Anil K. Pradhan and Sultana N. Nahar

Atoms 2025, 13(10), 85; https://doi.org/10.3390/atoms13100085 - 20 Oct 2025

Cited by 1

Abstract

Accurate determination of opacity is critical for understanding radiation transport in both astrophysical and laboratory plasmas. We employ atomic data from R-Matrix calculations to investigate radiative properties in high-energy-density (HED) plasma sources, focusing on opacity variations under extreme plasma conditions. Specifically, we analyze [...] Read more.

Accurate determination of opacity is critical for understanding radiation transport in both astrophysical and laboratory plasmas. We employ atomic data from R-Matrix calculations to investigate radiative properties in high-energy-density (HED) plasma sources, focusing on opacity variations under extreme plasma conditions. Specifically, we analyze environments such as the base of the convective zone (BCZ) of the Sun (

2 \times 10^{6}

K,

N_{e} = 10^{23}

/cc), and radiative opacity data collected using the inertial confinement fusion (ICF) devices at the Sandia Z facility (

2.11 \times 10^{6}

K,

N_{e} = 3.16 \times 10^{22}

/cc) and the Lawrence Livermore National Laboratory National Ignition Facility. We calculate Rosseland Mean Opacities (RMO) within a range of temperatures and densities and analyze how they vary under different plasma conditions. A significant factor influencing opacity in these environments is line and resonance broadening due to plasma effects. Both radiative and collisional broadening modify line shapes, impacting the absorption and emission profiles that determine the RMO. In this study, we specifically focus on electron collisional and Stark ion microfield broadening effects, which play a dominant role in HED plasmas. We assume a Lorentzian profile factor to model combined broadening and investigate its impact on spectral line shapes, resonance behavior, and overall opacity values. Our results are relevant to astrophysical models, particularly in the context of the solar opacity problem, and provide insights into discrepancies between theoretical calculations and experimental measurements. In addition, we investigate the equation-of-state (EOS) and its impact on opacities. In particular, we examine the “chemical picture” Mihalas–Hummer–Däppen EOS with respect to level populations of excited levels included in the extensive R-matrix calculations. This study should contribute to improving opacity models of HED sources such as stellar interiors and laboratory plasma experiments. Full article

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

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14 pages, 865 KB

Open AccessArticle

Single Electron Capture by Dressed Projectiles Within the Distorted Wave Formalism

by Michele Arcangelo Quinto, Juan Manuel Monti and Roberto Daniel Rivarola

Atoms 2025, 13(10), 84; https://doi.org/10.3390/atoms13100084 - 3 Oct 2025

Abstract

Single electron capture in collisions involving neutral hydrogen atoms impacted by highly charged dressed projectiles is theoretically investigated using the distorted wave formalism. A series of continuum distorted wave approximations is employed to investigate the electron capture from neutral hydrogen atom impact by [...] Read more.

Single electron capture in collisions involving neutral hydrogen atoms impacted by highly charged dressed projectiles is theoretically investigated using the distorted wave formalism. A series of continuum distorted wave approximations is employed to investigate the electron capture from neutral hydrogen atom impact by boron and carbon projectiles. The projectile potential is described using a two-parameter analytical Green–Sellin–Zachor (GSZ) model potential. The theoretical prediction of total cross sections are compared against other theories and experiments. We looked at a very broad range of collision energies, from 10 keV/u up to 10 MeV/u. In addition, the state-selective cross sections for boron ions are presented. Full article

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

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28 pages, 3057 KB

Open AccessEditor’s ChoiceArticle

Proton Interactions with Biological Targets: Inelastic Cross Sections, Stopping Power, and Range Calculations

by Camila Strubbia Mangiarelli, Verónica B. Tessaro, Michaël Beuve and Mariel E. Galassi

Atoms 2025, 13(10), 83; https://doi.org/10.3390/atoms13100083 - 24 Sep 2025

Abstract

Proton therapy enables precise dose delivery to tumors while sparing healthy tissues, offering significant advantages over conventional radiotherapy. Accurate prediction of biological doses requires detailed knowledge of radiation interactions with biological targets, especially DNA, a key site of radiation-induced damage. While most biophysical [...] Read more.

Proton therapy enables precise dose delivery to tumors while sparing healthy tissues, offering significant advantages over conventional radiotherapy. Accurate prediction of biological doses requires detailed knowledge of radiation interactions with biological targets, especially DNA, a key site of radiation-induced damage. While most biophysical models (LEM, mMKM, NanOx) rely on water as a surrogate, this simplification neglects the complexity of real biomolecules. In this work, we calculate the stopping power and range of protons in liquid water, dry DNA, and hydrated DNA using semi-empirical cross sections for ionization, electronic excitation, electron capture, and electron loss by protons and neutral hydrogen in the 10 keV–100 MeV energy range. Additionally, ionization cross sections for uracil are computed to explore potential differences between DNA and RNA damage. Our results show excellent agreement with experimental and ab initio data, highlighting significant deviations in stopping power and range between water and DNA. Notably, the stopping power of DNA exceeds that of water at most energies, reducing proton ranges in dry and hydrated DNA by up to 20% and 26%, respectively. These findings provide improved input for Monte Carlo simulations and biophysical models, enhancing RBE predictions and dose accuracy in hadrontherapy. Full article

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

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12 pages, 541 KB

Open AccessEditor’s ChoiceArticle

Integral Cross Sections and Transport Properties for Electron–Radon Scattering over a Wide Energy Range (0–1000 eV) and a Reduced Electric Field Range (0.01–1000 Td)

by Gregory J. Boyle, Dale L. Muccignat, Joshua R. Machacek and Robert P. McEachran

Atoms 2025, 13(10), 82; https://doi.org/10.3390/atoms13100082 - 23 Sep 2025

Abstract

We report calculations for electron–radon scattering using a complex relativistic optical potential method. The energy range of this study is 0–1000 eV, with results for the elastic (total, momentum-transfer and viscosity-transfer) cross section, summed discrete electronic-state integral excitation cross sections and electron-impact ionization [...] Read more.

We report calculations for electron–radon scattering using a complex relativistic optical potential method. The energy range of this study is 0–1000 eV, with results for the elastic (total, momentum-transfer and viscosity-transfer) cross section, summed discrete electronic-state integral excitation cross sections and electron-impact ionization cross sections presented. Here, we obtain our cross sections from a single theoretical relativistic calculation. Since radon is a heavy element, a relativistic treatment is very desirable. The electron transport coefficients are subsequently calculated for reduced electric fields ranging from 0.01 to 1000 Td, using a multi-term solution of Boltzmann’s equation. Full article

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11 pages, 351 KB

Open AccessEditor’s ChoiceArticle

Short–Range Hard–Sphere Potential and Coulomb Interaction: Deser–Trueman Formula for Rydberg States of Exotic Atomic Systems

by Gregory S. Adkins and Ulrich D. Jentschura

Atoms 2025, 13(9), 81; https://doi.org/10.3390/atoms13090081 - 11 Sep 2025

Cited by 1

Abstract

In exotic atomic systems with hadronic constituent particles, it is notoriously difficult to estimate the strong-interaction correction to energy levels. It is well known that, due to the strength of the nuclear interaction, the problem cannot be solved using Wigner–Brillouin perturbation theory alone. [...] Read more.

In exotic atomic systems with hadronic constituent particles, it is notoriously difficult to estimate the strong-interaction correction to energy levels. It is well known that, due to the strength of the nuclear interaction, the problem cannot be solved using Wigner–Brillouin perturbation theory alone. Recently, high-angular-momentum Rydberg states of exotic atomic systems with hadronic constituents have been identified as promising candidates in the search for new physics in the low-energy sector of the Standard Model. We thus derive a generalized Deser–Trueman formula for the induced energy shift for a general hydrogenic bound state with principal quantum number n and orbital angular momentum quantum number ℓ, and we find that the energy shift is given by the formula

δ E = 2 α_{n, ℓ} β_{ℓ} {(a_{h} / a_{0})}^{2 ℓ + 1} E_{h} / n^{3}

, where

α_{n, 0} = 1

,

α_{n, ℓ} = \prod_{s = 1}^{ℓ} (s^{- 2} - n^{- 2})

,

β_{ℓ} = (2 ℓ + 1) / {[(2 ℓ + 1)!!]}^{2}

,

E_{h}

is the Hartree energy,

a_{h}

is the hadronic radius and

a_{0}

is the generalized Bohr radius. The square of the double factorial,

{[(2 ℓ + 1)!!]}^{2}

, in the denominator implies a drastic suppression of the effect for higher angular momenta. Full article

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

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13 pages, 3730 KB

Open AccessArticle

IKEBANA: Data-Driven Neural-Network Predictor of Electron-Impact K-Shell Ionization Cross Sections

by Darío M. Mitnik, Claudia C. Montanari, Silvina Segui, Silvina P. Limandri, Judith A. Guzmán, Alejo C. Carreras and Jorge C. Trincavelli

Atoms 2025, 13(9), 80; https://doi.org/10.3390/atoms13090080 - 11 Sep 2025

Abstract

A fully connected neural network was trained to model the K-shell ionization cross sections based on two input features: the atomic number and the incoming electron overvoltage. The training utilized a recent, updated compilation of experimental data covering elements from H to U, [...] Read more.

A fully connected neural network was trained to model the K-shell ionization cross sections based on two input features: the atomic number and the incoming electron overvoltage. The training utilized a recent, updated compilation of experimental data covering elements from H to U, and incident electron energies ranging from the threshold to relativistic values. The neural network demonstrated excellent predictive performance, compared with the experimental data, when available, and with full theoretical predictions. The developed model is provided in the ikebana code, which is openly available and requires only the user-selected atomic number and electron energy range as inputs. Full article

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

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12 pages, 2083 KB

Open AccessArticle

Theoretical Study of Spectroscopic Properties of Fe(III)(acac)₃ Under All-Electron Scalar Relativistic Effects

by Luiz C. de Miranda and Nelson H. Morgon

Atoms 2025, 13(9), 79; https://doi.org/10.3390/atoms13090079 - 11 Sep 2025

Abstract

Molecular geometry, infrared (IR) vibrational frequencies, and ultraviolet–visible (UV-Vis) electronic absorption spectra of the trivalent iron tris(acetylacetonate) complex, Fe(III)(acac)₃, were computed using hybrid meta-generalized gradient approximation (meta-GGA) density functional theory (DFT). Calculations employed the Jorge double-

ζ

valence plus polarization basis [...] Read more.

Molecular geometry, infrared (IR) vibrational frequencies, and ultraviolet–visible (UV-Vis) electronic absorption spectra of the trivalent iron tris(acetylacetonate) complex, Fe(III)(acac)₃, were computed using hybrid meta-generalized gradient approximation (meta-GGA) density functional theory (DFT). Calculations employed the Jorge double-

ζ

valence plus polarization basis sets (standard DZP and relativistic DZP + DKH). Solvent effects were modeled using the SMD continuum solvation framework with acetonitrile as the dielectric medium. This charge-neutral complex exhibits predominantly ionic metal–ligand bonding character, which simplifies the computational treatment. Despite extensive DFT applications to coordination compounds, systematic benchmarks for this bidentate ligand system remain limited. The computed harmonic frequencies (

ν

) and electronic excitation energies (

λ_{\max}

) demonstrate excellent agreement with available experimental measurements. These results enable comparative analysis of IR and UV-Vis spectral features, both with and without all-electron scalar relativistic effects with the second-order Douglas–Kroll–Hess approach. Full article

(This article belongs to the Section Quantum Chemistry, Computational Chemistry and Molecular Physics)

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16 pages, 1203 KB

Open AccessArticle

Assessment of Absorbed Dose from a Positron Beam in Biological Tissue and Its Potential for Radiotherapy

by Andrezza O. Arêas and Maikel Y. Ballester

Atoms 2025, 13(9), 78; https://doi.org/10.3390/atoms13090078 - 10 Sep 2025

Abstract

Fast-charged particles have been used in diagnosis and treatment since the 19th century. Positrons are widely used in medical imaging through positron emission tomography, but their therapeutic potential remains underexplored due to technology limitations associated with the lack of research on their effectiveness [...] Read more.

Fast-charged particles have been used in diagnosis and treatment since the 19th century. Positrons are widely used in medical imaging through positron emission tomography, but their therapeutic potential remains underexplored due to technology limitations associated with the lack of research on their effectiveness against cancer. One way to understand their behavior is by calculating absorbed dose distributions in tissue, which can be safely and realistically done using computational simulations such as the Monte Carlo Method. This study investigates the interaction of a positron beam with brain tissue and a tumor through simulations using the TOPAS software. Depth dose profiles and absolute absorbed dose values were obtained in the range of 6–24 MeV. Validation was performed using data from the water phantom with electron beams. The results showed that, at certain depths in brain tissue, the absorbed dose by positrons was higher than that of electrons under the same conditions, ranging from 57% to 463% more. These findings suggest that positrons may offer advantages over conventional electron therapy and contribute to the development of novel therapeutic approaches. Full article

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