arXiv subjects

Jacek Rzadkiewicz

Publications and source records attributed to Jacek Rzadkiewicz.

6 recordsLinked to original sources

arXiv2025

Nuclear Excitation by Near-Resonant Electron Transition in $^{229}$Th$^{39+}$ Ions

Theoretical considerations are made for the nuclear excitation from the ground state to the 8 eV $^{229m}$Th isomer via near-resonant electron transitions in Sb-like ($q=39+$) thorium ions. The energy of the first excited atomic state ($J=7/2$) in the $^{229}$Th$^{39+}$ ion is estimated to be 8.308$\pm$0.069 eV, which is very close to the new reference value for the $^{229m}$Th nuclear isomer energy, 8.356 eV [Zhang et al., Nature 633, 63 (2024)]. Therefore, the $^{229}$Th$^{39+}$ ion provides a unique opportunity to study the nuclear excitation by electron transition process under well-defined atomic conditions in the regime of extremely low nuclear excitation energy. Our results indicate that the upper theoretical limit for the $^{229m}$Th isomer excitation rate reaches an enormous value of $1.27\times10^{16}$ s$^{-1}$ at resonance ($Δ=0$ meV), but drops many orders of magnitude for the value of electronic transition energy within its uncertainty interval. Additionally, it was shown that using an electron beam ion trap, the production of the $^{229}$Th isomer can reach rates ranging from a few to approximately $7\times10^{19}$ $^{-1}$.

physics.atom-ph↗

arXiv2025

De-excitation of $K$-shell hollow atoms with $12 \le Z \le 20$: transition rates and branching ratios

Investigating $K$-shell hollow atom spectra enhances our understanding of femtosecond phenomena in atomic physics, chemistry, and biology. Synchrotron measurements of two-electron one-photon (TEOP) transitions in low-$Z$ atoms have revealed discrepancies between experimental results and theoretical predictions of TEOP relative intensities. These discrepancies appear to originate from an incomplete description of an atom's response to the strong perturbation caused by $K$-shell double photoionization (DPI). The multiconfiguration Dirac-Hartree-Fock relativistic configuration interaction method has been applied for studying the TEOP spectra of Mg, Al, Si, S, Ar, and Ca atoms. The results show that branching ratios can be accurately reproduced by accounting for the effects of core and valence electron correlations, as well as the outer-shell ionization and excitation processes following $K$-shell DPI.

physics.atom-ph↗

arXiv2024

Energies of $I^{8+}$ through $I^{12+}$ low-lying levels

High-accuracy Multi-Configuration Dirac-Hartree-Fock with Configuration Interaction calculations of level energies and transition rates have been carried out for iodine $I^{8+}$ through $I^{12+}$ ions related to the [Kr]4d$^n$ ($n$ = 5-9) configurations. For $I^{10+}$ through $I^{12+}$ ions the present data fill up the lack of such data in the literature.

physics.atom-ph↗

arXiv2024

Multiconfiguration Dirac-Hartree-Fock and configuration-interaction study of $4d-3p$ x-ray transitions in Cu- and Ni-like tungsten ions

The $4d \to 3p$ x-ray transitions in Cu- and Ni-like tungsten ions have been studied theoretically. The multiconfiguration Dirac-Hartree-Fock (MCDHF) method and the large-scale relativistic configuration-interaction (CI) method have been employed in order to take into account electron correlation effects on the wavelengths and transition rates. It was found that the wavelengths and transition rates obtained from the MCDHF-CI method depend strongly on the size and the type of the active space used in the calculations. It has been found that extending the active space of orbitals without careful control of the configuration state function base does not always lead to good quality MCDHF-CI results for highly ionized tungsten ions.

physics.atom-ph↗

arXiv2023

Ionization energies of W$^{2+}$ through W$^{71+}$

High-accuracy Multi-Configuration Dirac-Hartree-Fock calculations of ionization energies with Configuration Interaction have been carried out for tungsten ions (W$^{2+}$ to W$^{71+}$) by means of the GRASP code. A comparison with other available experimental and theoretical data, including those calculated by FAC code based on the Dirac-Hartree-Fock-Slater method and with the NIST database has been presented. This work provides a new set of recommended ionization energy values for tungsten ions using state-of-the-art theoretical calculations with uncertainties ranging from 0.07 eV to 0.4 eV, which seems to be a significant improvement over the previous reference uncertainties.

physics.atom-ph↗

arXiv2020

Theoretical level energies, radiative lifetimes and transitions in W IX

The atomic states of the W IX (W8+) tungsten ion lying below the W9+ ionisation threshold have been studied theoretically, employing the multiconfiguration Dirac-Hartree-Fock method with configuration interaction. The level electronic structures and their energies are presented. The electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) radiative transitions have been computed in order to calculate the radiative lifetimes of given states. Transition wavelengths, energies, and decay rates are also presented for selected high-intensity E1 transitions. The configuration interaction method was applied to estimate electron correlation effects. The aim of the present research was to fill a lack of atomic data for low-charged tungsten ions, which may be useful in low-temperature plasma diagnostics and may form the base for collisional-radiative modelling of spectra for low-charged tungsten ions.

physics.atom-ph↗