Atoms

12 pages, 1305 KiB

Open AccessArticle

Monte Carlo FLUKA Simulation of Gamma Backscattering for Rebar Detection in Reinforced Concrete with Basaltic Aggregates

by Alexandre Osni Gral Iori and Emerson Mario Boldo

Atoms 2025, 13(7), 67; https://doi.org/10.3390/atoms13070067 - 9 Jul 2025

Viewed by 62

Abstract

Compton backscattering is a versatile non-destructive technique for material characterization and structural evaluation in reinforced concrete. This methodology enables a single-sided inspection of large structures—which is particularly useful where only one side of the material is accessible for examination—is relatively inexpensive, and can [...] Read more.

Compton backscattering is a versatile non-destructive technique for material characterization and structural evaluation in reinforced concrete. This methodology enables a single-sided inspection of large structures—which is particularly useful where only one side of the material is accessible for examination—is relatively inexpensive, and can be made portable for field applications. This study aims to assess the influence of basaltic coarse aggregates on the accurate localization and dimensioning of rebar in reinforced concrete using the gamma-ray Compton backscattering technique at two distinct incident photon energies—59.5 keV and 1170 keV. The analysis was performed through Monte Carlo simulations using the FLUKA code, providing insights into the feasibility and limitations of this non-destructive method for structural evaluation. Both photon energies successfully detected the rebar embedded at a 3 cm depth in mortar, achieving a good spatial resolution and contrast, despite the presence of a significant amount of iron oxide within the aggregate. Among the evaluated sources, ⁶⁰Co yielded the highest contrast and count values, demonstrating its potential for rebar detection at greater depths within concrete structures. The single-sided Compton scattering technique proved to be effective for the investigated application and presents a promising alternative for the non-destructive assessment of real-world reinforced concrete structures. Full article

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

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24 pages, 1450 KiB

Open AccessArticle

Introducing Machine Learning in Teaching Quantum Mechanics

by M. K. Pawelkiewicz, Filippo Gatti, Didier Clouteau, Viatcheslav Kokoouline and Mehdi Adrien Ayouz

Atoms 2025, 13(7), 66; https://doi.org/10.3390/atoms13070066 - 8 Jul 2025

Viewed by 86

Abstract

In this article, we describe an approach to teaching introductory quantum mechanics and machine learning techniques. This approach combines several key concepts from both fields. Specifically, it demonstrates solving the Schrödinger equation using the discrete-variable representation (DVR) technique, as well as the architecture [...] Read more.

In this article, we describe an approach to teaching introductory quantum mechanics and machine learning techniques. This approach combines several key concepts from both fields. Specifically, it demonstrates solving the Schrödinger equation using the discrete-variable representation (DVR) technique, as well as the architecture and training of neural network models. To illustrate this approach, a Python-based Jupyter notebook is developed. This notebook can be used for self-learning or for learning with an instructor. Furthermore, it can serve as a toolbox for demonstrating individual concepts in quantum mechanics and machine learning and for conducting small research projects in these areas. Full article

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

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10 pages, 14429 KiB

Open AccessArticle

Polarization Reconstruction Based on Monte Carlo Simulations for a Compton Polarimeter

by Tobias Over-Winter, Wilko Middents, Günter Weber and Thomas Stöhlker

Atoms 2025, 13(7), 65; https://doi.org/10.3390/atoms13070065 - 4 Jul 2025

Viewed by 122

Abstract

State-of-the-art 2D sensitive semiconductor detectors developed within the SPARC collaboration can be utilized as dedicated Compton polarimeters in the hard X-ray regime. We report on the technique of Compton polarimetry utilizing such a detector and present a method to determine the linear polarization [...] Read more.

State-of-the-art 2D sensitive semiconductor detectors developed within the SPARC collaboration can be utilized as dedicated Compton polarimeters in the hard X-ray regime. We report on the technique of Compton polarimetry utilizing such a detector and present a method to determine the linear polarization of an analyzed hard X-ray beam by means of Monte-Carlo-simulated data sets. 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, 398 KiB

Open AccessArticle

Electron Impact Ionization and Partial Ionization Cross Sections of Plasma-Relevant SiCl_x (x = 1–3) Molecules

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

Atoms 2025, 13(7), 64; https://doi.org/10.3390/atoms13070064 - 3 Jul 2025

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Abstract

The electron-impact ionization and partial ionization cross sections are reported for few silicon-chlorine molecules using semi-empirical methods. The partial ionization cross sections are determined using a modified version of the binary-encounter-Bethe model. In this approach, the binary-encounter-Bethe model is modified through a two-step [...] Read more.

The electron-impact ionization and partial ionization cross sections are reported for few silicon-chlorine molecules using semi-empirical methods. The partial ionization cross sections are determined using a modified version of the binary-encounter-Bethe model. In this approach, the binary-encounter-Bethe model is modified through a two-step process, namely, transforming the binding energies of the occupied orbitals and introducing a scaling factor. The scaling can be done using either the mass spectrometry data or experimental values of cross sections. It correctly adjusts the scaling term of the BEB model so that the order of magnitude of resulting partial ionization cross sections is the same as that of experimental values. Further, the use of the experimental value of ionization and appearance energy values ensures that the cross sections have a correct threshold. This further mitigates the dependence of cross sections on energy at low values. The role of the scaling factor and the behavior of branching ratios is also examined at different energies. The species whose partial ionization cross sections are reported are highly relevant in plasma processing. However, the proposed model can be extended to any multi-centerd molecular structures comprising a large number of atoms or electrons, except in cases where resonance effects or additional ionization channels become significant. The mass spectrometry data is of utmost importance in computing partial ionization cross sections in order to obtain reliable results. Full article

(This article belongs to the Special Issue Electron-Impact Ionization: Fragmentation and Cross-Section)

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18 pages, 433 KiB

Open AccessArticle

Controlling the Ionization Dynamics of Argon Induced by Intense Laser Fields: From the Infrared Regime to the Two-Color Configuration

by Soumia Chqondi, Souhaila Chaddou, Ahmad Laghdas and Abdelkader Makhoute

Atoms 2025, 13(7), 63; https://doi.org/10.3390/atoms13070063 - 1 Jul 2025

Viewed by 197

Abstract

The current study presents the results of a methodical investigation into the ionization of rare gas atoms, specifically focusing on argon. In this study, two configurations are examined: ionization via a near-infrared (NIR) laser field alone, and ionization caused by extreme ultraviolet (XUV) [...] Read more.

The current study presents the results of a methodical investigation into the ionization of rare gas atoms, specifically focusing on argon. In this study, two configurations are examined: ionization via a near-infrared (NIR) laser field alone, and ionization caused by extreme ultraviolet (XUV) radiation in the presence of a strong, synchronized NIR pulse. The theoretical investigation is conducted using an ab initio method to solve the time-dependent Schrödinger equation within the single active electron (SAE) approximation. The simulation results show a sequence of above-threshold ionization (ATI) peaks that shift to lower energies with increasing laser intensity. This behavior reflects the onset of the Stark effect, which modifies atomic energy levels and increases the number of photons required for ionization. An examination of the two-color photoionization spectrum, which includes sideband structures and harmonic peaks, shows how the ionization probability is redistributed between the direct path (single XUV photon absorption) and sideband pathways (XUV ± n × IR) as the intensity of the infrared field increases. Quantum interference between continuum states is further revealed by the photoelectron angular distribution, clearly indicating the control of ionization dynamics by the IR field. Full article

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19 pages, 764 KiB

Open AccessArticle

Subradiance Generation in a Chain of Two-Level Atoms with a Single Excitation

by Nicola Piovella

Atoms 2025, 13(7), 62; https://doi.org/10.3390/atoms13070062 - 1 Jul 2025

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Abstract

Studies of subradiance in a chain N two-level atoms in the single excitation regime focused mainly on the complex spectrum of the effective Hamiltonian, identifying subradiant eigenvalues. This can be achieved by finding the eigenvalues N of the Hamiltonian or by evaluating the [...] Read more.

Studies of subradiance in a chain N two-level atoms in the single excitation regime focused mainly on the complex spectrum of the effective Hamiltonian, identifying subradiant eigenvalues. This can be achieved by finding the eigenvalues N of the Hamiltonian or by evaluating the expectation value of the Hamiltonian on a generalized Dicke state, depending on a continuous variable k. This has the advantage that the sum above N can be calculated exactly, such that N becomes a simple parameter of the system and no longer the size of the Hilbert space. However, the question remains how subradiance emerges from atoms initially excited or driven by a laser. Here we study the dynamics of the system, solving the coupled-dipole equations for N atoms and evaluating the probability to be in a generalized Dicke state at a given time. Once the subradiant regions have been identified, it is simple to see if subradiance is being generated. We discuss different initial excitation conditions that lead to subradiance and the case of atoms excited by switching on and off a weak laser. This may be relevant for future experiments aimed at detecting subradiance in ordered systems. Full article

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21 pages, 964 KiB

Open AccessArticle

Curvature Effects on the Regimes of the Lateral van der Waals Force

by Alexandre P. Costa, Lucas Queiroz and Danilo T. Alves

Atoms 2025, 13(7), 61; https://doi.org/10.3390/atoms13070061 - 25 Jun 2025

Viewed by 220

Abstract

Recently, it has been shown that, under the action of the lateral van der Waals (vdW) force due to a perfectly conducting corrugated plane, a neutral anisotropic polarizable particle in vacuum can be attracted not only to the nearest corrugation peak but also [...] Read more.

Recently, it has been shown that, under the action of the lateral van der Waals (vdW) force due to a perfectly conducting corrugated plane, a neutral anisotropic polarizable particle in vacuum can be attracted not only to the nearest corrugation peak but also to a valley or an intermediate point between a peak and a valley, with such behaviors called peak, valley, and intermediate regimes, respectively. In the present paper, we discuss how the curvature of the corrugated surface affects the occurrence of the mentioned regimes. For this, we calculate the vdW interaction between a polarizable particle and a grounded conducting corrugated cylinder. We consider the corrugations along the azimuthal (

ϕ

-direction) angle or along the cylinder axis (z-direction). We show that when the corrugation occurs in the z-direction, the curvature has a small effect on the occurrence of the valley regime. On the other hand, it inhibits the intermediate regimes up to a certain particle–surface distance above which it amplifies the occurrence of this regime. When the corrugation occurs in the

ϕ

-direction, we show that the curvature inhibits both the valley and intermediate regimes. Full article

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18 pages, 332 KiB

Open AccessArticle

Hydrogenic Matrix Elements with Different Effective Charges: Non-Relativistic and Relativistic Cases

by Héctor O. Di Rocco and Julio C. Aguiar

Atoms 2025, 13(7), 60; https://doi.org/10.3390/atoms13070060 - 20 Jun 2025

Viewed by 178

Abstract

This work explores the evaluation of hydrogenic matrix elements for non-relativistic and relativistic cases under the Screened Hydrogenic Model (SHM). It focuses on scenarios where the initial and final states have different effective charges

Z_{1} \neq Z_{2}

, deriving closed-form solutions [...] Read more.

This work explores the evaluation of hydrogenic matrix elements for non-relativistic and relativistic cases under the Screened Hydrogenic Model (SHM). It focuses on scenarios where the initial and final states have different effective charges

Z_{1} \neq Z_{2}

, deriving closed-form solutions for particular cases

n_{1} = n_{2}

and

Z_{1} = Z_{2}

. In addition, analytical expressions for radial matrix elements

⟨ n^{'} l^{'} | r^{β} | n l ⟩

and their relativistic counterparts are presented. These are applicable for discrete–discrete transitions and allow simplifications for specific configurations using Laplace transforms. The study discusses generalizations of SHM for calculating cross-sections in hot and dense plasmas, employing the Plane Wave Born Approximation (PWBA). It also addresses the transition from LS to jj coupling for matrix elements, providing rules for such transformations. Full article

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

9 pages, 533 KiB

Open AccessArticle

Comparison of Different Rydberg Atom-Based Microwave Electrometry Techniques

by Eliel Leandro Alves Junior, Manuel Alejandro Lefrán Torres, Jorge Douglas Massayuki Kondo and Luis Gustavo Marcassa

Atoms 2025, 13(7), 59; https://doi.org/10.3390/atoms13070059 - 20 Jun 2025

Viewed by 224

Abstract

In this study, we have compared different Rydberg atom-based microwave electrometry techniques under the same experimental conditions and using the same Rydberg states (

68 S_{1 / 2}

,

68 P_{3 / 2}

, and

67 P_{3 / 2}

). [...] Read more.

In this study, we have compared different Rydberg atom-based microwave electrometry techniques under the same experimental conditions and using the same Rydberg states (

68 S_{1 / 2}

,

68 P_{3 / 2}

, and

67 P_{3 / 2}

). The comparison was carried out for the following techniques: (i) auxiliary microwave field, (ii) microwave amplitude modulation, and (iii) polarization spectroscopy. Our results indicate that all three techniques have a similar minimum measurable microwave electric field. A slightly better result can be obtained by performing polarization spectroscopy using a Laguerre–Gauss coupling laser beam. Full article

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

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