Atoms

9 pages, 1173 KiB

Open AccessArticle

Cooperative Decay of N Atoms in a Ring Configuration

by Nicola Piovella

Atoms 2025, 13(1), 8; https://doi.org/10.3390/atoms13010008 - 16 Jan 2025

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We provide an analytic expression of the spectrum of the cooperative decay rate of N two-level atoms regularly distributed on a ring in the single-excitation configuration. The results are obtained first for the scalar model and then extended to the vectorial light model, [...] Read more.

We provide an analytic expression of the spectrum of the cooperative decay rate of N two-level atoms regularly distributed on a ring in the single-excitation configuration. The results are obtained first for the scalar model and then extended to the vectorial light model, assuming all the dipoles are aligned. Full article

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

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8 pages, 257 KiB

Open AccessArticle

The Feshbach Resonances Applied to the Calculation of Stark Broadening of Ionized Spectral Lines: An Example of Interdisciplinary Research

by Sylvie Sahal-Bréchot and Haykel Elabidi

Atoms 2025, 13(1), 7; https://doi.org/10.3390/atoms13010007 - 16 Jan 2025

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Abstract

In the present paper, we revisit the determination of Feshbach resonances in the elastic and fine-structure cross-sections of the spectral lines of ionized atoms colliding with electrons. The Gailitis approximation will be recalled and used to calculate the Feshbach resonances. A historical point [...] Read more.

In the present paper, we revisit the determination of Feshbach resonances in the elastic and fine-structure cross-sections of the spectral lines of ionized atoms colliding with electrons. The Gailitis approximation will be recalled and used to calculate the Feshbach resonances. A historical point of view will be used, emphasizing the interest of interdisciplinary research, with a back and forth between physics and astrophysics. First, the theory of Feshbach (arising at end of the 1950s and beginning of the 1960s) resonances will be briefly recalled and applied to the calculation of the cross-sections. In the beginning of the 1970s, the insertion of Feshbach resonances in spectroscopic diagnostics calculations permitted researchers to interpret the intensities of solar coronal lines. Then, in the middle of the 1970s, this gave rise to the idea of including the Feshbach resonances in the calculation of electron impact broadening (the so-called “Stark” broadening) of isolated spectral lines of ionized atoms. Finally, in the recent example of the Stark broadening of the Mo VI

5 d {}^{2}D_{5 / 2} - 5 p {}^{2}{P °}_{3 / 2}

line, the S-matrices will be calculated using the semi-classical perturbation formalism and will be compared to those of the more recent quantum distorted wave formalism. Full article

12 pages, 617 KiB

Open AccessArticle

Exploring the Nuclear Chart via Precision Mass Spectrometry with the TITAN MR-TOF MS

by Annabelle Czihaly, Soenke Beck, Julian Bergmann, Callum L. Brown, Thomas Brunner, Timo Dickel, Jens Dilling, Eleanor Dunling, Jake Flowerdew, Danny Fusco, Leigh Graham, Zach Hockenbery, Chris Izzo, Andrew Jacobs, Brian Kootte, Yang Lan, Stephan Malbrunot-Ettenauer, Fernando Maldonado Millán, Ali Mollaebrahimi, Erich Leistenschneider, Eleni Marina Lykiardopoulou, Ish Mukul, Stefan F. Paul, Wolfgang R. Plaß, Moritz Pascal Reiter, Christoph Scheidenberger, James L. Tracy, Jr. and A. A. Kwiatkowski Show full author list Hide full author list

Atoms 2025, 13(1), 6; https://doi.org/10.3390/atoms13010006 - 9 Jan 2025

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Abstract

Isotopes at the limits of nuclear existence are of great interest for their critical role in nuclear astrophysical reactions and their exotic structure. Experimentally, exotic nuclides are challenging to address due to their low production cross-sections, overwhelming amounts of contamination, and lifetimes of [...] Read more.

Isotopes at the limits of nuclear existence are of great interest for their critical role in nuclear astrophysical reactions and their exotic structure. Experimentally, exotic nuclides are challenging to address due to their low production cross-sections, overwhelming amounts of contamination, and lifetimes of typically less than a second. To this end, a Multiple-Reflection Time-of-Flight mass spectrometer at the TITAN-TRIUMF facility was built to determine atomic masses. This device is the preferred tool to work with exotic nuclides due to its ability to resolve the species of interest from contamination and short measurement cycle times, enabling mass measurements of isotopes with millisecond half-lives. With a relative precision of the order 10⁻⁷, we demonstrate why the TITAN MR-TOF MS is the tool of choice for precision mass surveys for nuclear structure and astrophysics. The capabilities of the device are showcased in this work, including new mass measurements of short-lived tin isotopes (^104–107Sn) approaching the proton dripline as well as ⁸⁹Zr, ⁹⁰Y, and ⁹¹Y. The last three illustrate how the broadband surveys of MR-TOF MS reach beyond the species of immediate interest. Full article

(This article belongs to the Special Issue Advances in Ion Trapping of Radioactive Ions)

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11 pages, 1889 KiB

Open AccessArticle

Chemical Lasers Based on Polyatomic Reaction Dynamics: Research of Vibrational Excitation in a Reactive

by José Daniel Sierra Murillo

Atoms 2025, 13(1), 5; https://doi.org/10.3390/atoms13010005 - 9 Jan 2025

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Abstract

The research presented by the author investigates a polyatomic reaction occurring in the gas phase. This study employs the Quasi-Classical Trajectory (QCT) approach using the Wu–Schatz–Lendvay–Fang–Harding (WSLFH) potential energy surface (PES), recognized as one of the most reliable PES models for this type [...] Read more.

The research presented by the author investigates a polyatomic reaction occurring in the gas phase. This study employs the Quasi-Classical Trajectory (QCT) approach using the Wu–Schatz–Lendvay–Fang–Harding (WSLFH) potential energy surface (PES), recognized as one of the most reliable PES models for this type of analysis. The substantial sample size enables the derivation of detailed results that corroborate previous findings while also identifying potential objectives for future experimental work. The Gaussian Binning (GB) technique is utilized to more effectively highlight the variation in the total angular momentum (J′) of the excited product molecule, HOD*. A key aim of the study is to explore the reaction dynamics due to their importance in excitation and emission processes, which may contribute to the development of a chemical laser based on this reaction. Increasing the vibrational level, v, of one reactant, D₂, significantly enhances the excitation of HOD* and shifts the P(J′) distributions towards higher J′ values, while also broadening the distribution. Although the current research focuses on a few initial conditions, the author plans to extend the study to encompass a wider range of initial conditions within the reaction chamber of this type of chemical laser. Full article

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13 pages, 1408 KiB

Open AccessArticle

Cooper Pairs in 2D Trapped Atoms Interacting Through Finite-Range Potentials

by Erick Manuel Pineda-Ríos and Rosario Paredes

Atoms 2025, 13(1), 4; https://doi.org/10.3390/atoms13010004 - 7 Jan 2025

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Abstract

This work deals with the key constituent behind the existence of superfluid states in ultracold fermionic gases confined in a harmonic trap in 2D, namely, the formation of Cooper pairs in the presence of a Fermi sea in inhomogeneous confinement. For a set [...] Read more.

This work deals with the key constituent behind the existence of superfluid states in ultracold fermionic gases confined in a harmonic trap in 2D, namely, the formation of Cooper pairs in the presence of a Fermi sea in inhomogeneous confinement. For a set of finite-range models representing particle–particle interaction, we first ascertain the simultaneity of the emergence of bound states and the divergence of the s-wave scattering length in 2D as a function of the interaction potential parameters in free space. Then, through the analysis of two particles interacting in 2D harmonic confinement, we evaluate the energy shift with respect to the discrete harmonic oscillator levels for both repulsive and attractive cases. All of these results are the basis for determining the energy gaps of Cooper pairs arising from two particles interacting in the presence of a Fermi sea consisting of particles immersed in a 2D harmonic trap. Full article

(This article belongs to the Special Issue Quantum Technologies with Cold Atoms)

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11 pages, 1434 KiB

Open AccessArticle

Emergence of Quantum Vortices in the Ionization of Helium by Proton Impact, and How to Measure Them

by Tamara A. Guarda, Francisco Navarrete and Raúl O. Barrachina

Atoms 2025, 13(1), 3; https://doi.org/10.3390/atoms13010003 - 6 Jan 2025

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Abstract

This study investigates how the presence of quantum vortices affects the ionization cross-section of helium atoms by 75 keV proton impact, with special attention to the region near the electron capture to the continuum (ECC) cusp. It has been found that these vortices [...] Read more.

This study investigates how the presence of quantum vortices affects the ionization cross-section of helium atoms by 75 keV proton impact, with special attention to the region near the electron capture to the continuum (ECC) cusp. It has been found that these vortices cause a significant reduction in the intensity of the

{| T |}^{2}

distribution in the low-energy region of the ECC cusp, leading to a considerable distortion that facilitates its experimental determination. Furthermore, the analysis shows that one of the vortices coincides with the Thomas angle (a parameter coming from the classical ion-electron Thomas mechanism). Full article

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11 pages, 260 KiB

Open AccessArticle

Nuclear Hyperfine Mixing Effect in Highly Charged ²⁰⁵Pb Ions

by Wu Wang, Yong Li and Xu Wang

Atoms 2025, 13(1), 2; https://doi.org/10.3390/atoms13010002 - 3 Jan 2025

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Abstract

In highly charged ions, significant nuclear hyperfine mixing (NHM) effects can arise when the electromagnetic field generated by the electrons interacts strongly with the nucleus, leading to mixing of nuclear states. While previous studies have primarily attributed the NHM effect to unpaired valence [...] Read more.

In highly charged ions, significant nuclear hyperfine mixing (NHM) effects can arise when the electromagnetic field generated by the electrons interacts strongly with the nucleus, leading to mixing of nuclear states. While previous studies have primarily attributed the NHM effect to unpaired valence electrons, we present a reformulation of the theoretical framework using dressed hyperfine states and investigate the NHM effect in ²⁰⁵Pb⁷⁶⁺, ²⁰⁵Pb⁷⁵⁺, ²⁰⁵Pb⁷⁴⁺, and ²⁰⁵Pb⁷³⁺ ions. Our numerical results show that significant NHM effects occurred in all of the studied ions, even in the absence of unpaired valence electrons in ²⁰⁵Pb⁷⁶⁺ and ²⁰⁵Pb⁷⁴⁺. We found that the lifetime of the isomeric state was reduced by 2–4 orders of magnitude compared with the bare ²⁰⁵Pb nucleus, depending on the charge state of the ion. These results indicate that it is the active valence electrons rather than unpaired electrons which play a key role in the NHM effect, thereby deepening our understanding of this phenomenon. Full article

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

17 pages, 481 KiB

Open AccessArticle

Angular Distributions and Polarization of Fluorescence in an XUV Pump–XUV Probe Scheme

by Cristian Iorga and Viorica Stancalie

Atoms 2025, 13(1), 1; https://doi.org/10.3390/atoms13010001 - 24 Dec 2024

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Abstract

This work provides theoretical calculations of fluorescence angular distribution and polarization within an XUV pump–XUV probe scheme designed for determining ultra-short lifetimes of highly charged heavy ions. The initial pumping leads to a non-zero alignment in the excited levels. After the probing stage, [...] Read more.

This work provides theoretical calculations of fluorescence angular distribution and polarization within an XUV pump–XUV probe scheme designed for determining ultra-short lifetimes of highly charged heavy ions. The initial pumping leads to a non-zero alignment in the excited levels. After the probing stage, the anisotropies in angular distribution and polarization of subsequent fluorescence are significantly enhanced due to the existence of a previous alignment. Furthermore, two-photon sequential excitation from a ground state with zero angular momentum to a level with angular momentum one by two aligned linearly polarized photon beams is strictly prohibited by the selection rules and may be used as a diagnostic tool to determine beam misalignment. The present approach is based on the density matrix and statistical tensor framework. We provide the analytical form for the alignment parameters caused by successive photoexcitation either with linearly polarized photon beams, or with unpolarized photons. The analytical results can generally be used to compute angular distribution asymmetry parameters and linear polarization of subsequent fluorescence for a large array of atomic systems used in pump–probe experiments. Full article

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Atoms, Volume 13, Issue 1 (January 2025) – 8 articles

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