Introduction: Photoionization of atoms and highly charged ions plays crucial role in diverse areas such as astrophysics, planetary science, and laboratory plasma research. These investigations are essential not only for understanding plasma equilibrium properties but also for obtaining accurate and reliable opacity data in strongly coupled plasmas.

Methods: To perform present calculations, analytical plasma screening (APS) potential and more general exponential cosine screened Coulomb (MGECSC) potential has been incorporated in the relativistic configuration interaction (RCI) technique and relativistic distorted wave (RDW) method employed in the Flexible Atomic Code (FAC).

Results and Discussion: We investigated the influence of plasma screening on the total photoionization (PI) cross sections of the ground and excited states of Li-like Si XII embedded in plasma. The excitation energies of the target ion Si XIII and the transition probabilities for the 1s^{2 1}S₀ → 1s3p ^3,1P₁ transitions of Si XIII have been examined under various plasma conditions. In addition, the effect of plasma screening on the continuum wavefunctions corresponding to the 1s, 2s, and 2p orbitals of Si XIII have been analyzed. The impact of plasma screening on the PI cross sections for the 1s²2s ²S_1/2 and 1s²2p ²P_1/2,3/2 states of Li-like Si XII has also been studied.

Conclusions: It is observed that transition energies for these K-shell transitions are red shifted and the ionization threshold, the energy of 1s electron removal, reduces for higher plasma density. We believe that the present results will be advantageous for the diagnostics and modelling of astrophysical plasmas.

The study and description of atomic spectra requires the systematic
consideration of quantum electrodynamic (QED) corrections.
In one-electron systems, the leading QED corrections for a bound electron correspond
to the self-energy (SE) and vacuum polarization (VP) diagrams.
To date, methods for calculating them are well developed
for spherically symmetric systems—atoms and ions [1–4].
Molecules, on the other hand, do not possess such symmetry and
only approximate methods for estimation of the corresponding corrections are available [5-6].

In this work, we propose a method that allows for a rigorous
calculation of the SE diagram contribution to the
bound-state energy of two-center systems.
The auxiliary–symmetric dual kinetic balance method (A-DKB) [7] is used to solve
the Dirac equation with a two-center potential;
a number of well-known techniques [1] are generalized to the case of axially symmetric systems.

The SE diagram contribution to the ground-state energy of the one-electron uranium diatomic quasimolecule U_2^183+ is calculated. The results obtained
are in reasonable agreement with the results of Refs. [8-9],
where the same contributions were
calculated within the partial expansion of the two-center potential.

[1] V. A. Yerokhin and V. M. Shabaev, Phys. Rev. A 60, 800 (1999).
[2] V. A. Yerokhin et al., Phys. Rev. A 111, 012802 (2025).
[3] O. V. Andreev et al., Phys. Rev. A 85, 022510 (2012).
[4] D. A. Glazov et al., Phys. Rev. Lett. 123, 173001 (2015).
[5] V. M. Shabaev et al., Phys. Rev. A 88, 012513 (2013).
[6] A. A. Kotov et al., Atoms 9(3), 44 (2021).
[7] E. B. Rozenbaum et al., Phys. Rev. A 89, 012514 (2014).
[8] A. N. Artemyev and A. Surzhykov, Phys. Rev. Lett. 114, 243004 (2015).
[9] A. N. Artemyev et al., Phys. Rev. A 106, 012813 (2022).
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We present a high-precision study of the ionization potential (IP) and electron affinity (EA) of superheavy element 119 (E119). Accurate IP and EA values for E119 are important for providing benchmarks for future experimental research investigating periodic-law trends beyond oganesson.

Electronic correlation was treated within the relativistic single-reference coupled-cluster theory with single, double, and iterative triple excitations, SR-CCSD(T). Contributions up to triple and perturbative quadruple cluster amplitudes in the SR-CCSDT(Q) method were included to account for electron correlation beyond the SR-CCSD(T) model. For this purpose, a compact atomic natural orbital (ANO)-like set was constructed. The corrections arising from the Gaunt electron–electron interaction and quantum-electrodynamic (QED) effects were evaluated. Extensive tests of the basis set and correlation convergences were performed and a detailed uncertainty analysis was carried out.

Two different schemes for constructing Dirac–Hartree–Fock orbitals were used to calculate the IP and EA of E119. Inclusion of high-order amplitudes significantly reduces the discrepancy between calculations employing different schemes. Enlarging the basis set leads to an increase in the IP, whereas the EA is less sensitive to the addition of new functions. The calculated Gaunt and QED corrections are small but non-negligible within estimated uncertainties. The dominant sources of uncertainty are the ghi-functions and high-order excitations.

Our final values for IP and EA are 4.7839(56) and 0.6750(71) eV, respectively. These results tighten previous estimates and provide a reliable theoretical reference for future experiments.

Quantum electrodynamics (QED) is a powerful tool for describing the electronic structure of atomic and molecular systems. After its final formulation in the late 1940s, it was primarily applied to light systems. However, since the mid-1980s, when the experimental possibility to study heavy few-electron ions appeared, highly charged ions have become an object of intense research. Calculations of the Lamb shift in H-like and 2p_{1/2}-2s transition in Li-like uranium are now regarded as benchmarks for stringent tests of bound-state QED. Meanwhile, the QED treatment of Be-like ions can also be challenging. The conventional QED perturbation theory for single levels, which has demonstrated high accuracy for H-like and Li-like ions, may yield unreliable results for Be-like ions due to strong mixing between closely spaced energy levels of identical symmetry.

In this report, a brief overview of the application of the QED perturbation theory for quasidegenerate levels to the study of the electronic structure of Be-like ions is given. The method merges all relevant first- and second-order QED contributions as well as third- and higher-order electron–electron correlation contributions evaluated in the Breit approximation. Recently obtained theoretical predictions [1,2] are compared with the results of high-precision measurements and previous relativistic calculations.

[1] A. V. Malyshev et al., PRA 110, 062824 (2024).
[2] A. V. Malyshev et al., PRA 112, 062811 (2025).

Introduction:

The finite basis set approach is widely accepted as the standard for many atomic and molecular calculations. It has been successfully used in quantum electrodynamic calculations involving electron self-energy loops. However, it has not yet been applied to vacuum polarization loops for a long time. In [Salman and Saue (PRA, 2023)], the Gaussian finite basis set method was used to calculate the main partial contribution |κ| = 1 of the many-potential vacuum polarization charge density. In our work, [Ivanov et al., PRA, 2024], we repeated this technique and extended the calculations up to |κ| = 5. This allowed us to find energy shift corrections that can be compared to existing results [Persson et al., PRA 1993].

Methods:

The presented calculations were obtained using the finite basis set approach. In this method, the solution to the differential equation — the Dirac equation in our case — is presented as a linear combination of basis functions. The coefficients in this combination were found via the variational principle. The obtained solution can accurately present the Green's function in the vacuum polarization loop.

Results and Discussion:

We present our recent progress in vacuum polarization calculations in hydrogen-like ions using finite basis sets. Our calculations used larger basis sets than those used in [Ivanov et al., PRA, 2024]. This allowed us to find the energy correction with higher precision, proving the convergence of the method.

Conclusions:

Our results demonstrate the potential of applying the finite basis set method to vacuum polarization calculations. Our numerical results approach those reachable by standard methods. Promising applications include calculating the vacuum polarization correction to Zeeman and hyperfine splittings (see, for example, [Beier, Physics Reports, 2000]).

Electron–molecule scattering plays a central role in electron-driven processes across semiconductor technology, astrophysical environments, and radiation-damage physics, where reliable cross sections are required over a wide energy range. In this work, I will present a relativistic framework for electron scattering from molecular targets that can be applied consistently from low to high incident energies and is sensitive to the basic features of molecular structure. The approach is based on the Dirac partial-wave formalism combined with a spherical complex optical-model potential, with molecular potentials built using a group-additivity scheme. By solving the coupled radial Dirac equations, we obtain phase shifts that are used to generate differential, elastic, inelastic, momentum-transfer, and total cross sections. The framework naturally incorporates geometry-dependent effects through the construction of the molecular potential, providing a consistent route to high-quality scattering data for modeling electron-induced phenomena in diverse physical and technological fields.

Introduction. Research on the g-factor of highly charged ions has attracted considerable attention in recent years. For instance, high-precision measurements of the g-factor have enabled the most accurate determination of the electron mass and provided rigor verification of relativistic effects in the presence of a magnetic field.

Helium-like ions represent the simplest multi-electron systems, making them convenient objects for studying relativistic effects while accounting for interelectronic interactions. Calculations of correlation corrections to the energy for various electronic configurations of helium-like ions were presented in works of A. N. Artemyev, A. V. Malyshev and Y. S. Kozhedub. In the present work, we focus on the correlation corrections to the g-factor values.

Methods. The calculations were carried out using perturbation methods. The Breit approximation was employed to account for correlation effects. Quasi-degenerate perturbation theory was applied to correctly evaluate the g-factor and its corrections for the 1s2p states.

Results. In the present work, interelectronic-interaction corrections to the g-factor of the excited states for a wide range of nuclei charges (Z = 2 - 100) of helium-like ions are considered.

Conclusion. The obtained results will provide additional opportunities for testing quantum electrodynamics methods and determining fundamental constants and nuclear parameters such as the magnetic moment and charge distribution.

The cosmic origin of elements heavier than iron remains one of the open questions in astrophysics. These elements are produced through neutron-capture processes in diverse astrophysical sites, but, to disentangle their contributions and galactic evolution, we rely on accurate stellar abundances. Deriving these abundances requires reliable non-LTE models of stellar spectra. However, for many heavy elements, non-LTE modelling is still missing due to the scarcity of accurate atomic data. This challenge highlights the interconnected nature of atomic physics and astrophysical interpretation: without reliable atomic data, we cannot fully exploit the wealth of stellar observations.

I have worked at this intersection, aiming to improve atomic data and construct more accurate non-LTE models for heavy elements. I will present results from different stages of this work: from theoretical calculations of atomic structure and transition probabilities to non-LTE modelling of copper and silver. I will show how improved atomic data, such as hydrogen collision rates and photoionisation cross-sections, impact non-LTE abundance determinations of these elements and how refined abundance trends in turn sharpen our understanding of nucleosynthetic origins and galactic chemical evolution.

Introduction: The study of spectral properties and electron impact excitation in plasma environments has gained significant attention due to its wide range of applications, such as astrophysical bodies, inertial confinement fusion experiments, high-density spectroscopy applications, and X-ray free-electron laser experiments.

Methods: We employed the relativistic configuration interaction (RCI) technique and the relativistic distorted wave (RDW) method implemented in the Flexible Atomic Code (FAC). To account for plasma effects, both the temperature-dependent ion-sphere potential and the quantum plasma potential are incorporated.

Results and Discussion: The plasma screening effect on spectral properties and electron impact excitation cross-sections of Be-like Ni XXV ion embedded in plasma environment has been calculated. Plasma screening effects on transition energies and decay rates corresponding to the resonance and inter-combination transitions 2snp ^3,1P₁→ 2s^{2 1}S₀ (n = 2,3) of Be-like Ni XXV ion are investigated. Further, we also study the effect of plasma density on excitation cross sections of Be-like Ni XXV ion embedded in dense plasma. The accuracy of our present results has been validated by comparing the calculated energies with the energies available on the NIST database and other available theoretical data, which shows good agreement with the reported values.

Conclusions: We observed blue shifts in the transition energies for transitions with Δn = 0 and red shifts for those with Δn ≠ 0. The electron impact excitation cross-sections decrease with increasing incident electron energy and with increasing plasma density.

The bound-electron g factor of highly charged ions provides a sensitive probe of relativistic, correlation, and quantum electrodynamic (QED) effects [1, 2]. Recent progress in both experiment and theory has highlighted the need for accurate predictions for few-electron systems, including lithiumlike ions, where interelectronic interaction plays a dominant role. In this work, we present a unified theoretical investigation of the g factor for the ground state and the lowest excited 2p_1/2 and 2p_3/2 states of lithiumlike ions over a broad range of nuclear charge numbers.

Interelectronic interaction is treated within bound-state QED. The first-order correction is calculated rigorously to all orders in αZ, while the two-photon-exchange term is evaluated using the Breit approximation supplemented with negative-energy contributions. Higher-order terms are obtained via the recursive formulation of perturbation theory. One-loop QED corrections, self-energy and vacuum polarization, are computed employing finite-basis B-spline techniques, and leading nuclear-recoil effects are included using effective operators. All calculations are performed within the extended Furry picture using several screening potentials to estimate the uncalculated higher-order many-electron contributions.

For the ground and excited states, we obtain significantly improved values of the interelectronic-interaction contribution, with uncertainties reduced by up to an order of magnitude compared with earlier theoretical predictions [3, 4]. For the excited 2p_j states, we additionally calculate the quadratic and cubic Zeeman contributions, which become essential for the interpretation of high-precision spectroscopy [5].

Our calculations provide the most accurate theoretical predictions for the g factor of lithiumlike ions to date. The achieved precision meets the requirements of ongoing and planned high-precision measurements and strengthens the capabilities of bound-state QED tests in strong fields.

1. D. A. Glazov et al., Atoms 11, 119 (2023)
2. S. Sturm et al., Annalen Der Physik 525, 620 (2013)
3. D. V. Zinenko et al., Phys. Rev. A 107, 032815 (2023)
4. D. V. Zinenko et al., arXiv:2505.09567 (2025)
5. D. von Lindenfels et al., Phys. Rev. A 87, 023412 (2013)