For the lowest 50 levels, the following radiative data have been calculated using the Multi-Configuration Dirac–Fock (MCDF) approximation: transition wavelength, transition rates, oscillator strength, line strength, and radiative rates like the electric dipole (E1) and electric quadrupole (E2) transitions of the highly ionized Ne-like Se⁺²⁴ ion (Se XXV) and magnetic dipole (M1) and magnetic quadrupole (M2) transitions. GRASP and FAC were used to calculate the results. For Se XXV, our measured excitation energies, wavelengths, oscillator strengths, and line strengths all correspond well with the existing data, including the NIST data. We have also calculated Einstein coefficients for the spontaneous emission, stimulated emission, transition dipole moment, emission and absorption oscillator strength, and E1 transitions for Se XXV. Lifetimes for the lower levels of Se XXV have also been computed. Our computed atomic and radiative data of Ne-like Se should be useful for the identification and evaluation of spectral lines from various fusion plasmas, solar plasma modeling, and astrophysical investigations.

We present high-precision ab initio calculations of the magnetic-dipole and electric-quadrupole hyperfine-structure constants for the $2p_{1/2}$ and $2p_{3/2}$ states of boron-like $^{35,37}$Cl$^{12+}$ ions. The calculations are carried out within the framework of bound-state quantum electrodynamics (QED) and include a systematic treatment of electron–electron correlation and radiative effects. The one-photon exchange and the one-loop self-energy and vacuum-polarization corrections are evaluated to first order in perturbation theory using established QED methods [Volotka et al., Phys. Rev. A 78, 062507 (2008)]. Higher-order contributions from interelectronic interactions are taken into account nonperturbatively within the Breit approximation by means of large-scale configuration–interaction calculations employing a Dirac–Fock–Sturm orbital basis [Tupitsyn, Opt. Spectrosc. 94, 319 (2003)]. Finite nuclear-size effects, including the Bohr–Weisskopf correction associated with the nuclear magnetization distribution, are incorporated within a single-particle nuclear model [Shabaev, J. Phys. B 27, 5825 (1994)]. A detailed analysis of theoretical uncertainties arising from uncalculated higher-order contributions is performed. The resulting theoretical predictions for the hyperfine splitting in boron-like chlorine ions are in excellent agreement with recent high-resolution spectroscopic measurements [Liu et al., Spectrochim. Acta Part B 235, 107349 (2026)], providing a stringent validation of the treatment of effects of interelectronic interactions and QED in mid-$Z$ highly charged ions.

Atomic parameters are fundamental to technological progress and understanding the Universe’s complexity: from nucleosynthesis in extreme astrophysical environments to medical physics applications, including studies of stellar and atmospheric compositions, radiation shielding materials, and diagnostic imaging optimization [1–5].
Among these parameters, atomic energy levels (AELs) are the most essential. All other quantities—transition probabilities, collisional cross-sections (e.g., electron-impact excitations, recombination, dielectronic recombination), Auger rates, and fluorescence yields—depend on them. Thus, accurate and extensive AEL data are crucial to ensure the reliability of derived quantities.
Our group performs large-scale atomic calculations for key r-process heavy elements [2,6,7] using the Flexible Atomic Code (FAC) [8] and AUTOSTRUCTURE (AS) [9], both based on central potentials. FAC employs a spherically averaged potential for all shells, while AS uses scaling parameters for each subshell. A recently developed sequential model-based optimization procedure enhances these calculations, improving efficiency and accuracy across heavy-element systems [6,7]. This poster compares AEL results from FAC and AS, for a few selected lanthanides, under different optimization techniques and explores runtime and memory performance.
All systematically generated data are compiled into a comprehensive database to serve the broader research community.

[1] B.P. Abbott et al., Astrophysical Journal, 848, L13. 2017.
[2] A.J. Levan et al., Nature, 626, 737. 2024.
[3] Akman et al., Radiation Physics and Chemistry, 107, 75–81. 2015.
[4] Polat, R. et al., Annals of Nuclear Energy, 54, 267–273. 2013.
[5] da Silva, A.R., & Smilesnice, R., Astronomy & Astrophysics, 696, A122. 2025.
[6] A. Flörs et al., Monthly Notices of the Royal Astronomical Society, 524, 3083. 2023.
[7] Ferreira da Silva et al., Physical Review A, 112(1), 012802. 2025.
[8] M.F. Gu, Canadian Journal of Physics, 86, 675. 2008.
[9] N.R. Badnell, Astrophysics Source Code Library, ascl:1612.014. 2016.

Theoretical predictions of hyperfine splitting in heavy atoms and molecules hold significant importance across various fundamental physical applications. They serve as crucial tests for the accuracy of calculated properties necessary for interpreting experiments aimed at detecting violations of spatial parity and time-reversal symmetries in fundamental interactions using atoms and molecules. Hyperfine splittings in the spectra of highly charged ions offer opportunities to test bound-state quantum electrodynamics. Accurate calculations are essential for determining the magnetic moments of short-lived isotopes.

In many cases, the largest uncertainty in the theoretically predicted value of the hyperfine splitting arises from the nuclear component of the problem, namely from the finite nuclear magnetization distribution known as the Bohr–Weisskopf (BW) effect in atoms. This distribution is not well known in most cases. We developed a model-independent approach to address the BW effect in atoms and molecules.

This method is applied to the radium monofluoride molecule, demonstrating the possibility of separating the contribution of the BW effect to the hyperfine constant of a heavy atom or molecule into a purely electronic-structure part and a universal parameter dependent on the nucleus. This factorization allows for the extraction of the nuclear magnetization distribution from experimental data on the hyperfine structure in an atom or molecule, which can then be used to predict the BW effect in any other compound of the atom under consideration. This method has been experimentally verified. We also theoretically study the hyperfine structure of Po and Ag atoms. By employing the factorization method, we achieve substantially improved values for the nuclear magnetic dipole moments of different isotopes of these atoms.

This proposed formalism enables the deduction of nuclear magnetic dipole moments from hyperfine data for both atoms and molecules at a new level of precision.

Highly charged ions provide an outstanding platform for investigating bound-state quantum electrodynamics (BS-QED) [1-3]. One notable example is the study of the Lamb shift in lithium-like uranium [4-5]. Additionally, experiments have recently achieved exceptional levels of accuracy [6-11]. Combined with theoretical calculation, these achievements have made it possible to obtain the most accurate determination of the electron mass to date [12,13]. Continued development of theoretical and experimental methods opens up new possibilities for independent extraction of nuclear parameters, determination of the fine-structure constant and studies of physics beyond the Standard Model [14-16]. This progress also paves the way for the study of QED effects beyond the Furry picture in the strong coupling regime [16-19].

In this work, we investigate correlation effects within the Breit approximation using both the Coulomb and several screening potentials. We analyze the convergence of perturbation series for energies depending on the choice of the zeroth-order potential. The calculations are performed for helium- and lithium-like ions in both the ground and excited states. We employ the dual kinetic balance method [20] with a finite B-spline basis and the recursive formulation of perturbation theory [21], which allows perturbative terms of arbitrary order to be generated without explicit diagrammatic treatment. The results obtained will allow us to determine the limits of the applicability of perturbation theory to various states and to assess the effectiveness of using certain shielding potentials. This will ensure the correct application of the recursive perturbation theory apparatus, not only for calculating energies but also for determining the g factor and HFS.

Inelastic processes in atomic collisions are far from being fully understood, in spite of the several efforts made from experimental and theoretical researchers along the last decades. In particular, the description of charge exchange processes still represents a challenging scenario when highly charged projectiles are considered, even when their probability outcomes are of great interest in fusion devices nowadays[1]. In this context, this problem has been tackled in recent years from different theoretical perspectives, which include both quantum and classical numerical methods [2, 3].
In this talk we present a projectile charge dependence study of state-selective charge exchange cross-sections following the collision of fully stripped ions with atomic hydrogen in its ground and first excited states. The projectile impact energy range spans from 1 keV/u to 500 keV/u. Calculations are carried out by means of classical trajectory models, which are based on microcanonical and hydrogenic initializations for the target electron. For H(1s), our results are contrasted to the data reported within the AOCC, TC-AOCC and WP-CCC quantum mechanical methods, where available, while, for H*(n=2), we compare our results to those provided by the AOCC model.
Results here shown analyse a broad range of projectile charges and impact energies, allowing for a critical insight on the similarities and differences of the cross-sections predicted by the different models across different collisional regimes.
[1] P. Beiersdorfer. J. Phys. B: At. Mol. Opt. Phys. 48, 144017 (2015).
[2] A. M. Kotian, C. T. Plowman, I. B. Abdurakhmanov, I. Bray and A. S. Kadyrov. J. Phys. B: At. Mol. Opt. Phys. 55 115201 (2022).

[3] N. D. Cariatore, N. Bachi, E. Acebal and S. Otranto. Plasma Physics and Controlled Fusion 67, 55003 (2025).

Work at IFISUR was supported by Grant No. PGI 24/F084 (UNS), Argentina. This research was conducted under the Coordinated Research Project, code F43026, of the IAEA, Austria.

In this work, the 5P_3/2 → 6P_3/2 electric-dipole-forbidden transition in atomic rubidium at room temperature is studied in the presence of a magnetic field in the weak and strong field regimes. The experiment is performed in a rubidium cell with two external cavity diode lasers (ECDLs) in a counterpropagating configuration. A 780 nm laser at the D2 electric-dipole transition prepares atoms in the 5P_3/2 state, and a 911 nm laser produces the 5P_3/2 → 6P_3/2 electric-quadrupole transition. Both beams are linearly polarized in the direction of the magnetic field. Detection of atoms in the 6P_3/2 state is monitored by the 420 nm fluorescence decay (6P_3/2 → 5S_1/2) via current-modulated phase detection. The experimental geometry determines the electric-dipole (ΔM_F = 0) and electric-quadrupole (ΔM_F = ±1) hyperfine selection rules. Breit–Rabi diagrams of all involved states and their differences using these selection rules are presented. This allows for the identification of the resonant frequencies of the spectral lines as functions of the magnetic field in both the weak and the strong limits. Theoretical predictions agreed with the experimental data. Future work includes the calculation of line intensities via transition probabilities and a population equations model.

Above-threshold ionization (ATI) of the sodium atom is investigated in a Debye plasma environment using linearly polarized femtosecond laser pulses of intensity I= 1×10¹³ W/cm². ATI is studied in two-color laser fields by combining fundamental and harmonic frequencies ω–2ω (800–400 nm) and ω–3ω (800–266.67 nm). In the dipole approximation, photoelectron energy spectra (PES) are calculated by solving TDSE in a single active electron approximation with a Hamiltonian. The PES spectra are analyzed for different Debye lengths using the infinite surface flux method. A shift in the PES spectra is observed with the variation in Debye length, and a corresponding shift in the photoelectron momentum occurs as the Debye length changes.

On August 17, 2017, the LIGO/Virgo collaboration detected, for the first time, a gravitational wave signal (GW170817) associated with a neutron star merger. This event marked a milestone in multi-messenger astronomy. The merger ejected a significant amount of hot and radioactive matter into space, where nuclear reactions synthesized elements that were heavier than iron, including lanthanides (Z = 57–71). The radioactive decay of these elements powered a transient electromagnetic phenomenon known as a kilonova.

In the early stages, the kilonova spectrum is dominated by numerous allowed transitions from heavy elements. However, in the later nebular phase, the temperature and density of the ejecta decrease significantly, limiting the ionization stage to at most doubly charged species. Under these conditions, only low-energy levels, such as metastable states, are populated, resulting in forbidden emission lines such as magnetic dipole (M1) and electric quadrupole (E2) transitions. Observations of kilonova AT2017gfo and, more recently, of a similar transient event recorded in March 2023 by the James Webb Space Telescope have revealed infrared spectral features in the late-time spectra that are potentially linked to forbidden transitions of lanthanides and other heavy elements.

To facilitate the analysis of such spectra, new calculations of transition probabilities for M1 and E2 lines between low-lying levels in singly and doubly ionized lanthanide atoms were carried out. The fully relativistic Multi-Configurational Dirac–Hartree–Fock (MCDHF) method, implemented in the GRASP code, was employed to model the atomic structure and compute radiative parameters. Results were compared to those obtained using the pseudo-relativistic Hartree–Fock (HFR) approach to ensure reliability. This work provides a consistent set of atomic data, highlighting the most intense forbidden lines of lanthanides, which are likely to be observed in the infrared spectra of kilonovae during their nebular phase.

Wastewater often contains toxic heavy metals (HMs) that can harm aquatic ecosystems if insufficiently treated. One promising approach is adsorption using metal-oxide engineered nanomaterials (ENMs). ENMs are dosed into water to adsorb target HMs, after which ENM–HM complexes are removed by standard separation. A key limitation is that not all ENM–HM combinations achieve high removal efficiencies, underscoring the need for tools that guide the selective choice and design of ENMs for specific HMs. We aimed to identify the mechanistic atomic factors that affect the ability of a given metal-oxide ENM to remove a specific HM, using atomic- and elemental-level descriptors. We assembled a dataset from a previously published study, which contains the removal rates of 11 HMs by 3 different ENMs (α-Fe₂O₃, CuO, and ZnO), yielding 33 ENM–HM combinations [1]. We used the atomic properties for HMs and descriptors of ENMs (calculated using“Elemental Descriptor Calculator”). We combined these descriptors with a gradient-boosted artificial intelligence classifier (XGBoost) trained on an operational label where the positive class denotes complete HM removal (>99% removal). The model achieved an Area Under the Curve metric of 1 on six held-out records, indicating promising but preliminary predictive performance. Importantly, the trained model highlighted the atomic radius of HM and the sum of ionization potentials of constituent elements in the ENM formula as the most important properties for the HM adsorption by ENMs. Mechanistically, the prominence of the HM radius and the ENM’s summed ionization potentials indicates that adsorption is jointly controlled by size-dependent hydration and steric access to inner-sphere sites. Overall, these findings uncover important mechanistic insights about ENM-HM interaction at the atomic level, allowing for better selectivity and ENM design, in line with the IOCAT objectives.

1. Bouafia et al., Sci Rep 13, 5637 (2023). https://doi.org/10.1038/s41598-023-32938-1