Atoms

7 pages, 249 KB

Open AccessArticle

Calculation of Hyperfine Structure in Tm ii

by Andrey I. Bondarev

Atoms 2026, 14(1), 7; https://doi.org/10.3390/atoms14010007 - 21 Jan 2026

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The first measurements of the magnetic dipole hyperfine structure constants A in singly ionized thulium revealed substantial discrepancies with the corresponding theoretical calculations. Subsequent measurements expanded the very limited available dataset and demonstrated that two of the previously reported experimental A values were [...] Read more.

The first measurements of the magnetic dipole hyperfine structure constants A in singly ionized thulium revealed substantial discrepancies with the corresponding theoretical calculations. Subsequent measurements expanded the very limited available dataset and demonstrated that two of the previously reported experimental A values were incorrect, thereby motivating new theoretical calculations. In this work, we employ the configuration interaction method to calculate the A constants for several low-lying levels in Tm ii, with the random-phase-approximation corrections also taken into account. Our results show good agreement with the new experimental data and provide reliable predictions for additional states where measurements are not yet available. Full article

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

13 pages, 583 KB

Open AccessArticle

Search for Possible Stable Structures in the

T_{c c \bar{q} \bar{s}}

System

by Linkai Li, Xiaohuang Hu, Yuheng Xing, Xinxing Wu, Ning Xu, Yuanrun Zhu, Yue Tan and Yuheng Wu

Atoms 2026, 14(1), 6; https://doi.org/10.3390/atoms14010006 - 20 Jan 2026

Cited by 1 | Viewed by 231

Abstract

Inspired by the well-known experimental connections between

X (3872)

,

Z_{c s} (4220)

, and

Y (4620)

, we systematically study the recently reported strange partner of

T_{c c}

, the

1^{+}

[...] Read more.

Inspired by the well-known experimental connections between

X (3872)

,

Z_{c s} (4220)

, and

Y (4620)

, we systematically study the recently reported strange partner of

T_{c c}

, the

1^{+}

c c \bar{q} \bar{s}

system, and its orbital excitation state

1^{-}

c c \bar{q} \bar{s}

. A chiral quark model incorporating SU(3) symmetry is considered to study these two systems. To better investigate their spatial structure, we introduce a precise few-body calculation method, the Gaussian Expansion Method (GEM). In our calculations, we include all possible physical channels, including molecular states and diquark structures, and consider channel coupling effects. To identify the stable structures in the system (bound states and resonance states) we employ a powerful resonance search method, the Real-Scaling Method (RSM). According to our results, in the

1^{+}

c c \bar{q} \bar{s}

system, we obtain two bound states with energies of 3890 MeV and 3940 MeV, as well as two resonance states with energies of 3975 MeV and 4090 MeV. The decay channels of these two resonance states are

D D_{s}^{*}

and

D^{*} D_{s}

, respectively. In the

1^{-}

c c \bar{q} \bar{s}

system, we obtain only one resonance state, with an energy of 4570 MeV, and two main decay channels:

D D_{s 1}^{*}

and

D^{*} D_{s 1}^{'}

. We strongly suggest that experimental groups use our predictions to search for these stable structures. Full article

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

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22 pages, 2932 KB

Open AccessArticle

Theoretical Calculation of Ca^q+ (q = 0, 1, 2) Interacting with a Krypton Atom: Electronic Structure and Vibrational Spectra Association

by Wissem Zrafi, Mohamed Bejaoui, Hela Ladjimi, Jamila Dhiflaoui and Hamid Berriche

Atoms 2026, 14(1), 5; https://doi.org/10.3390/atoms14010005 - 12 Jan 2026

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Abstract

The potential energy curves and spectroscopic constants of the ground and several low-lying excited states of the Ca^q+-Kr (q = 0, 1, 2) van der Waals complexes were investigated using one- and two-electron pseudopotential approaches. This treatment effectively reduces the number [...] Read more.

The potential energy curves and spectroscopic constants of the ground and several low-lying excited states of the Ca^q+-Kr (q = 0, 1, 2) van der Waals complexes were investigated using one- and two-electron pseudopotential approaches. This treatment effectively reduces the number of active electrons in Ca^q+-Kr to a single valence electron for q = 1 and two valence electrons for q = 0, allowing the use of large and flexible basis sets for both Ca and Kr atoms. Within this work, potential energy curves (PECs) were calculated at the SCF level for the Ca⁺-Kr system, while both SCF and full configuration interaction (FCI) calculations were performed for the neutral Ca-Kr. Spin–orbit coupling effects were explicitly included in all calculations to accurately describe the fine-structure splitting of the asymptotic atomic states. The short-range core–core interaction for Ca²⁺-Kr was obtained using high-level CCSD(T) calculations. Spectroscopic constants were derived from the computed PECs and compared with available theoretical and experimental results, showing consistent trends. Furthermore, the transition dipole moments (TDM) were evaluated as a function of internuclear distances, including spin–orbit effects, to provide a comprehensive description of the electronic structure and radiative properties of these weakly bound systems. Full article

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

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18 pages, 799 KB

Open AccessArticle

Invariant Approach to the Interaction Between Several Fields and an Atom

by Marco A. García-Márquez, Irán Ramos-Prieto and Héctor M. Moya-Cessa

Atoms 2026, 14(1), 4; https://doi.org/10.3390/atoms14010004 - 8 Jan 2026

Viewed by 397

Abstract

We present a general procedure to describe the dynamics of N degenerate quantized fields interacting resonantly with a two–level atom, all coupled with the same strength, within the rotating–wave approximation. Starting from the analysis of the two and three field cases, we generalize [...] Read more.

We present a general procedure to describe the dynamics of N degenerate quantized fields interacting resonantly with a two–level atom, all coupled with the same strength, within the rotating–wave approximation. Starting from the analysis of the two and three field cases, we generalize the method by identifying dynamical invariants that lead to a factorized form of the time–evolution operator. A unitary transformation reduces the problem to an effective Jaynes–Cummings Hamiltonian, where only one field interacts with the atom and the remaining modes contribute as free fields. Assuming initially coherent fields and an atomic superposition, we compute the atomic inversion and the mean photon number, revealing vacuum Rabi oscillations with a frequency determined by an effective coupling constant that exceeds the individual atom–field coupling, as well as the characteristic collapse–revival behavior. Full article

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16 pages, 1936 KB

Open AccessArticle

L-Shell Photon Excitation Cross Sections for the Chlorine Isonuclear Sequence Cl^{q+ (q=1−4)}: An Experimental Study

by Jean-Paul Mosnier, Eugene T. Kennedy, Denis Cubaynes, Ségolène Guilbaud and Jean-Marc Bizau

Atoms 2026, 14(1), 3; https://doi.org/10.3390/atoms14010003 - 4 Jan 2026

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Abstract

We report experimental measurements of the absolute photoionization cross sections for chlorine ions in different stages of ionization, over photon energy ranges corresponding to the L-shell (2s and 2p subshells) excitations. Single, double and triple photoionization channels were investigated for the ions Cl [...] Read more.

We report experimental measurements of the absolute photoionization cross sections for chlorine ions in different stages of ionization, over photon energy ranges corresponding to the L-shell (2s and 2p subshells) excitations. Single, double and triple photoionization channels were investigated for the ions Cl⁺, Cl²⁺, Cl³⁺ and Cl⁴⁺. The measurements were performed on the PLéIADES beamline at the SOLEIL radiation storage ring facility, using the Multi-Analysis Ion Apparatus (MAIA). Resonance energies and line strengths are provided for the isonuclear sequence and the evolution of the inner shell photoionization behaviour is demonstrated for the chlorine ions as the degree of ionization is increased. While dominated by photoionization from the corresponding ground state ions, the photoion yields may also contain contributions from low-lying metastable states. The results provide useful data on these ions for plasma modelling and can serve as benchmarking experimental data for future atomic theoretical calculations. Full article

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

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13 pages, 1356 KB

Open AccessArticle

Fractatomic Physics: Atomic Stability and Rydberg States in Fractal Spaces

by Nhat A. Nghiem and Trung V. Phan

Atoms 2026, 14(1), 2; https://doi.org/10.3390/atoms14010002 - 31 Dec 2025

Viewed by 857

Abstract

We explore the physical quantum properties of atoms in fractal spaces, both as a theoretical generalization of normal integer-dimensional Euclidean spaces and as an experimentally realizable setting. We identify the threshold of fractality at which Ehrenfest atomic instability emerges, where the Schrödinger equation [...] Read more.

We explore the physical quantum properties of atoms in fractal spaces, both as a theoretical generalization of normal integer-dimensional Euclidean spaces and as an experimentally realizable setting. We identify the threshold of fractality at which Ehrenfest atomic instability emerges, where the Schrödinger equation describing the wavefunction of a single electron orbiting around an atom becomes scale-free, and discuss the potential of observing this phenomena in laboratory settings. We then study the Rydberg states of stable atoms using the Wentzel–Kramers–Brillouin approximation, along with a proposed extension for the Langer modification, in general fractal dimensionalities. We show that fractal space atoms near instability explode in size even at low-number excited state, making them highly suitable to induce strong entanglements and foster long-range many-body interactions. We argue that atomic physics in fractal spaces—“fractatomic physics”—is a rich research avenue deserving of further theoretical and experimental investigations. Full article

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15 pages, 10342 KB

Open AccessEditor’s ChoiceArticle

Single Sr Atoms in Optical Tweezer Arrays for Quantum Simulation

by Veronica Giardini, Luca Guariento, Andrea Fantini, Shawn Storm, Massimo Inguscio, Jacopo Catani, Giacomo Cappellini, Vladislav Gavryusev and Leonardo Fallani

Atoms 2026, 14(1), 1; https://doi.org/10.3390/atoms14010001 - 19 Dec 2025

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Abstract

We report on the realization of a platform for trapping and manipulating individual ⁸⁸Sr atoms in optical tweezers. A first cooling stage based on a blue shielded magneto-optical trap (MOT) operating on the [...] Read more.

We report on the realization of a platform for trapping and manipulating individual ⁸⁸Sr atoms in optical tweezers. A first cooling stage based on a blue shielded magneto-optical trap (MOT) operating on the

|^{1} S_{0} ⟩ \to |^{1} P_{1} ⟩

transition at

461 n m

enables us to trap approximately 4 × 10⁶ atoms at a temperature of 6.8 mK. Further cooling is achieved in a narrow-line red MOT using the

|^{1} S_{0} ⟩ \to |^{3} P_{1} ⟩

intercombination transition at 689 nm, bringing 5 × 10⁵ atoms down to

5 μ K

and reaching a density of 4 × 10¹⁰ cm³. Atoms are then loaded into 813 nm tweezer arrays generated by crossed acousto-optic deflectors and tightly focused onto the atoms with a high-numerical-aperture objective. Through light-assisted collision processes we achieve the collisional blockade, which leads to single-atom occupancy with a probability of about 50%. The trapped atoms are detected via fluorescence imaging with a fidelity of

99.986 (6) %

, while maintaining a survival probability of

97 (2) %

. The release-and-recapture measurement provides a temperature of

12.92 (5) μ K

for the atoms in the tweezers, and the ultra-high-vacuum environment ensures a vacuum lifetime higher than 7 min. These results demonstrate a robust alkaline-earth tweezer platform that combines efficient loading, cooling, and high-fidelity detection, providing the essential building blocks for scalable quantum simulation and quantum information processing with Sr atoms. Full article

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

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Atoms, Volume 14, Issue 1 (January 2026) – 7 articles

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