Atoms

12 pages, 1538 KiB

Open AccessArticle

Properties of a Static Dipolar Impurity in a 2D Dipolar BEC

by Neelam Shukla and Jeremy R. Armstrong

Atoms 2025, 13(3), 24; https://doi.org/10.3390/atoms13030024 - 10 Mar 2025

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We study a system of ultra-cold dipolar Bose gas atoms confined in a two-dimensional (2D) harmonic trap with a dipolar impurity implanted at the center of the trap. Due to recent experimental progress in dipolar condensates, we focused on calculating properties of dipolar impurity systems that might guide experimentalists if they choose to study impurities in dipolar gases. We used the Gross–Pitaevskii formalism solved numerically via the split-step Crank–Nicolson method. We chose parameters of the background gas to be consistent with dysprosium (Dy), one of the strongest magnetic dipoles and of current experimental interest, and used chromium (Cr), erbium (Er), terbium (Tb), and Dy for the impurity. The dipole moments were aligned by an external field along what was chosen to be the z-axis, and we studied 2D confinements that were perpendicular or parallel to the external field. We show density contour plots for the two confinements, 1D cross-sections of the densities, calculated self-energies of the impurities while varying both number of atoms in the condensate and the symmetry of the trap. We also calculated the time evolution of the density of an initially pure system where an impurity is introduced. Our results show that while the self-energy increases in magnitude with increasing number of particles, it is reduced when the trap anisotropy follows the natural anisotropy of the gas, i.e., elongated along the z-axis in the case of parallel confinement. This work builds upon work conducted in Bose gases with zero-range interactions and demonstrates some of the features that could be found when exploring dipolar impurities in 2D Bose gases. Full article

(This article belongs to the Section Cold Atoms, Quantum Gases and Bose-Einstein Condensation)

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10 pages, 816 KiB

Open AccessArticle

Theoretical Investigation on Vortex Electron Impact Excitation of a Mg Atom Confined in a Solid-State Environment

by Sophia Strnat, Aloka K. Sahoo, Lalita Sharma, Jonas Sommerfeldt, Daesung Park, Christian Bick and Andrey Surzhykov

Atoms 2025, 13(3), 23; https://doi.org/10.3390/atoms13030023 - 24 Feb 2025

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Abstract

We present a theoretical investigation of the inelastic scattering of vortex electrons by many-electron atoms embedded in a solid-state environment. Special emphasis is placed on the probability of exciting a target atom and on the relative population of its magnetic substates as described by the set of alignment parameters. These parameters are directly related to the angular distribution of the subsequent radiative decay. To demonstrate the application of the developed theoretical approach, we present calculations for the

3 s^{2} {}^{1}S_{0} \to 3 s 3 p {}^{3}P_{1}

excitation of a Mg atom and its subsequent

3 s 3 p {}^{3}P_{1} \to 3 s^{2} {}^{1}S_{0}

radiative decay. Our results highlight the significance of the orbital angular momentum (OAM) projection as well as the relative position of the vortex electron with respect to the target atom. Full article

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

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10 pages, 659 KiB

Open AccessArticle

Stopping Power of Iron for Protons: Theoretical Calculations from Very Low to High Energies

by Jesica P. Peralta, Alejandra M. P. Mendez, Dario M. Mitnik and Claudia C. Montanari

Atoms 2025, 13(3), 22; https://doi.org/10.3390/atoms13030022 - 20 Feb 2025

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Abstract

The energy loss in iron can serve as valuable knowledge due to its extended use in technological applications and open topics in fundamental physics. The electronic structure of solid Fe is challenging, given that it is the first of the groups of transition metals with some of the d-electrons promoted to the conduction band while others remain bound. The low energy description, the deviation from velocity proportionality at low impact energies, and the contribution of the loosely bound d-electrons to the energy loss are active featured fields when it comes to the stopping in Fe. Very recent TDDFT calculations have been compared with the first stopping measurements in steel, showing surprisingly good agreement. In the present work, we applied a recent model based on the momentum distribution function of the d-electrons to the case of Fe. A comparison with other models is discussed, as well as with experimental data. We also highlight discrepancies among datasets regarding the stopping maximum and the need for new experimental efforts. Full article

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

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Atoms, Volume 13, Issue 3 (March 2025) – 3 articles

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