Energies and Auger widths of the $LL$ resonances in He-like ions from boron to argon are evaluated by means of a complex scaled configuration-interaction approach within the framework of the Dirac-Coulomb-Breit Hamiltonian. The nuclear recoil and QED corrections are also taken into account. The obtained results are compared with other calculations based on the complex scaling method as well as with the related results evaluated using the stabilization and basis balancing methods.
Energy levels, normal and specific mass shift parameters as well as electronic densities at the nucleus are reported for numerous states along the beryllium, boron, carbon, and nitrogen isoelectronic sequences. Combined with nuclear data, these elect
ronic parameters can be used to determine values of level and transition isotope shifts. The calculation of the electronic parameters is done using first-order perturbation theory with relativistic configuration interaction wave functions that account for valence, core-valence and core-core correlation effects as zero-order functions. Results are compared with experimental and other theoretical values, when available.
We applied a relativistic configuration-interaction (CI) framework to the stabilization method as an approach for obtaining the autoionization resonance structure of heliumlike ions. In this method, the ion is confined within an impenetrable spherica
l cavity, the size of which determines the radial space available for electron wavefunctions and electron-electron interactions. By varying the size of the cavity, one can obtain the autoionization resonance position and width. The applicability of this method is tested on the resonances of He atom while comparing with benchmark data available in the literature. The present method is further applied to the determination of the resonance structure of heliumlike uranium ion, where a relativistic framework is mandatory. In the strong-confinement region, the present method can be useful to simulate the properties of an atom or ion under extreme pressure. An exemplary application of the present method to determine the structure of ions embedded in a dense plasma environment is briefly discussed.
We present a theoretical investigation of dielectronic recombination (DR) of Ar-like ions that sheds new light on the behavior of the rate coefficient at low-temperatures where these ions form in photoionized plasmas. We provide results for the total
and partial Maxwellian-averaged DR rate coefficients from the initial ground level of K II -- Zn XIII ions. It is expected that these new results will advance the accuracy of the ionization balance for Ar-like M-shell ions and pave the way towards a detailed modeling of astrophysically relevant X-ray absorption features. We utilize the AUTOSTRUCTURE computer code to obtain the accurate core-excitation thresholds in target ions and carry out multiconfiguration Breit-Pauli (MCBP) calculations of the DR cross section in the independent-processes, isolated-resonance, distorted-wave (IPIRDW) approximation. Our results mediate the complete absence of direct DR calculations for certain Ar-like ions and question the reliability of the existing empirical rate formulas, often inferred from renormalized data within this isoelectronic sequence.
Calculations of various corrections to the g factor of Li-like ions are presented, which result in a significant improvement of the theoretical accuracy in the region Z = 6-92. The configuration-interaction Dirac-Fock method is employed for the evalu
ation of the interelectronic-interaction correction of order 1/Z^2 and higher. This correction is combined with the 1/Z interelectronic-interaction term derived within a rigorous QED approach. The one-electron QED corrections of first in alpha are calculated to all orders in the parameter alpha Z. The screening of QED corrections is taken into account to the leading orders in alpha Z and 1/Z.
Electronic stopping cross sections (SCS) of nickel, silicon and nickel-silicon alloys for protons and helium (He) ions are studied in the regime of medium and low energy ion scattering, i.e., for ion energies in the range from 500 eV to 200 keV. For
protons, at velocities below the Bohr velocity the deduced SCS is proportional to the ion velocity for all investigated materials. In contrast, for He ions non-linear velocity scaling is observed in all investigated materials. Static calculations using density functional theory (DFT) available from literature accurately predict the SCS of Ni and Ni-Si alloy in the regime with observed velocity proportionality. At higher energies, the energy dependence of the deduced SCS of Ni for protons and He ions agrees with the prediction by recent time dependent DFT calculations. The measured SCS of the Ni-Si alloy was compared to the SCS obtained from Braggs rule based on SCS for Ni and Si deduced in this study, yielding good agreement for protons, but systematic deviations for He projectiles, by almost 20%. Overall, the obtained data indicate the importance of non adiabatic processes such as charge exchange for proper modelling of electronic stopping of in particular medium energy ions heavier than protons in solids.
V. A. Zaytsev
,I. A. Maltsev
,I. I. Tupitsyn
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(2019)
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"Complex scaled relativistic configuration-interaction study of the $LL$ resonances in helium-like ions: from Boron to Argon"
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Vladimir A. Zaytsev
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