Dielectronic recombination (DR) is widely recognized as a fundamental atomic process in many astrophysical and laboratory plasmas, where it plays a crucial role in determining ionization balance and level populations over a broad temperature range. Reliable DR resonance strengths and plasma rate coefficients for such plasma modeling can be computed using the Jena Atomic Calculator (JAC)—a relativistic code based on the multiconfiguration Dirac–Hartree–Fock (MCDHF) method. In this work, we investigate the DR of Li-like Ar15+ ions in their ground state (2s), focusing on resonances associated with the fine-structure core excitations 2s1/2→2p1/2,3/2. The resulting fine-structure-resolved DR resonance strengths and plasma rate coefficients are in good agreement with recent high-resolution DR measurements of Ar15+ ions performed at the Main Cooler Storage Ring (CSRm) in Lanzhou, China. These results provide a stringent benchmark for JAC calculations and support their applicability in plasma modeling.

The radiation pattern emitted by two atoms, interacting with each other via the vacuum radiation field, has been calculated, including effects of magnetic state degeneracy for atoms with a ground state having G=0 angular momentum and an excited state having H=1 angular momentum. For an initial condition in which both atoms are inverted, the time-integrated radiation pattern is identical to that for non-interacting atoms if the atoms lie on the z-axis, but differs if the atoms lie on the x-axis. The underlying dynamics giving rise to this behavior are examined.

We study the planar repulsive two-center Coulomb system in the presence of a uniform magnetic field perpendicular to the plane, taking the inter-center separation a and the magnetic field strength B as independent control parameters. The free-field system B=0 is Liouville integrable and the motion is unbounded. The magnetic confinement introduces nonlinear coupling that breaks integrability and gives rise to chaotic bounded dynamics. Using Poincaré sections and maximal Lyapunov exponents, we characterize the transition from regular motion at aB=0 to mixed regular–chaotic dynamics for aB≠0. To probe the recoverability of the dynamics, we apply sparse regression techniques to numerical trajectories and assess their ability to capture the equations of motion across mixed dynamical regimes. Our results clarify how magnetic confinement competes with two-center repulsive interactions in governing the emergence of chaos and delineate fundamental limitations of data-driven model discovery in nonintegrable Hamiltonian systems. We further identify an organizing mechanism whereby the repulsive two-center system exhibits locally one-center-like dynamics in the absence of any static confining barrier.

In this work, the He and Ar triplet autoionizing states have been studied using a non-monochromatic electron beam and a high-resolution electrostatic analyzer at low incident electron energies and three ejection angles: 40°, 90°, and 130°. Low-energy electrons have been used because they have a high probability of exciting triplet states regardless of whether they are discrete isolate states or are embedded in the ionization continuum. Additionally, the He ejected electron spectra have been measured at several ejection angles between 20° and 130° and two incident energies, namely 60.5 eV and 101 eV. The anisotropic angular distributions indicate that orbital angular momentum exchange between the ejected and scattered electrons occurred. The energies of the first triplets 3s3p64s(3S) and 3s3p64p(3P) states of argon are found to be (24.985 ± 0.020) eV and (26.52 ± 0.02) eV, respectively.

Inspired by the well-known experimental connections between X(3872), Zcs(4220), and Y(4620), we systematically study the recently reported strange partner of Tcc, the 1+ccq¯s¯ system, and its orbital excitation state 1−ccq¯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+ccq¯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 DDs∗ and D∗Ds, respectively. In the 1−ccq¯s¯ system, we obtain only one resonance state, with an energy of 4570 MeV, and two main decay channels: DDs1∗ and D∗Ds1′. We strongly suggest that experimental groups use our predictions to search for these stable structures.

The potential energy curves and spectroscopic constants of the ground and several low-lying excited states of the Caq+-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 Caq+-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.

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.

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 |1S0⟩→|1P1⟩ transition at 461 nm 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 |1S0⟩→|3P1⟩ intercombination transition at 689 nm, bringing 5 × 105 atoms down to 5μK 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)μK 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.

Auger decay of all levels of the double core-hole states 4d−2 of Xe2+, including collective Auger decay (CAD) pathways, is investigated using the relativistic distorted-wave approximation. Large-scale configuration interaction calculations were performed to obtain level-to-level Auger decay rates. In addition to the typical Auger decay final levels associated with the configurations of 4d−15s25p4, 4d−15s15p5, and 4d−15s05p6, evident contributions are identified from excited channels, leading to configurations such as 4d94f15s25p3, 4d95s25p35d1, 4d95s25p36s1, and 4d95s25p36p1. These contributions arise from strong electron correlation between the valence electronic orbitals and the 4d inner-shell orbital. The CAD rates and branching ratios (BRs) are determined for each double core-hole level with a minimum CAD BR of 1.28% and a maximum of 4.08% among all CAD channels. The configuration-averaged CAD BR is predicted to be 1.93%, which helps explain recent unexplained experimental findings. The inclusion of CAD processes enriches Auger electron spectroscopy, thereby extending potential applications of this important experimental tool in both fundamental and applied research.

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.