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The wavelengths and transition rates of W40+-W42+ ions within the range of 40–140 Å, have been calculated using the Flexible Atomic Code of the Dirac-Fock-Slater method with a central potential. We investigated the charge state distribution of W38+-W45+ ions at different temperatures by constructing an appropriate rate equation and demonstrate the importance of the dielectronic recombination process. Additionally, we simulated the emission spectra of W40+-W42+ ions in a Tokamak plasma environment using collisional-radiative modeling. Our findings demonstrate strong agreement with experimental results and other related theoretical investigations. Finally, we propose certain pairs of transition lines as diagnostic tools for plasma temperature and density, leveraging the correlation between line intensity ratio and electron temperature and density. [ABSTRACT FROM AUTHOR]

The mass- and field-shift parameters of the two 2s 2S1/2 → 2p 2P1/2,3/2 transitions in the Li-like Ca ions are calculated by using multi-configuration Dirac–Hartree–Fock (MCDHF) and the relativistic configuration interaction (RCI) methods with the inclusion of the transverse photon (Breit) interaction, vacuum polarization and self-energy corrections. In addition, the mass shift and field shift of these two transitions are calculated, where the field shift is calculated by using the evaluated value δ〈 r2〉 obtained by [Atomic Data and Nuclear Data Tables 99 69 (2013)]. It is found that the mass shift of Li-like Ca ions is greater than the field shift. [ABSTRACT FROM AUTHOR]

K‐shell dielectronic, trielectronic, and quadruelectronic recombination and polarization of X‐ray emission have been studied for the highly charged Si9+ ions in the initial ground state 2P1/2 and the metastable state 2P3/2 using the Flexible Atomic Code. It is found that the resonant recombination cross section from the long‐lived metastable state is comparable in magnitude with that of the ground state, so it is important for plasma diagnostics. For Si9+(2P1/2), trielectronic recombination contributions of nearly 25% to the total resonant recombination strength are predicted, which is less than previous calculations. We compare the degree of linear polarization for the eleven dominant resonant recombination satellite lines from the initial parent Si9+(2P1/2) and Si9+(2P3/2) ions. For the same X‐ray lines, large variations of polarization are found between 2P1/2 and 2P3/2, which can be employed to diagnose formation mechanisms of intermediate resonance states and corresponding X‐ray lines. [ABSTRACT FROM AUTHOR]

The properties and spectrum of the highly charged tungsten ions draw more and more attention, due to its potential application in the next generation fusion reactor. The transition wavelength and rate of the magnetic-dipole transition between the levels of the ground configuration of W53+ ion in the range of 10 − 20 nm were calculated by Dirac–Fock–Slater (DFS) method with a local central potential and Multi-Configuration Dirac-Hartree-Fock (MCDHF) method, respectively. The results are consistent with the previous EBIT experimental data and other theoretical data. A collisional-radiative model was constructed, and the spectrum of magnetic-dipole transition of W53+ ion observed on EBIT (Y. Ralchenko et al., Phys. Rev. A. 83 , 032517, 2011) was reproduced theoretically. Another two new transitions near the wavelength of 16.683 nm and 18.018 nm are also assigned to the M1 transition of W53+ ion. • The EBIT spectrum of W53+ ion was reproduced and analyzed by CRM with accurate atomic data. • The new M1 transition between the ground configuration of W53+ ions were assigned to the experimental spectrum. • The MCDHF transition wavelength was used instead of DFS results to get better agreement with the experiments. [ABSTRACT FROM AUTHOR]

The energy levels of 1s2, 1s2s, and 2s2p configurations for He-like ions (4 ≤ Z ≤ 54) are calculated using the multi-configuration Dirac–Hartree–Fock​ methods. The transition energies, transition rates, and oscillator strengths of 2s2p → 1s2 and 2s2p → 1s2s are also calculated. A parallel calculation based on the Dirac–Fock–Slater method with a local central potential is performed using the Flexible Atomic Code to cross-check the accuracy of the data. The Breit interaction and quantum electrodynamics effects, including self-energy and vacuum polarization, are included as perturbations in these calculations. The average relative standard deviation of the energy levels from the available NIST data is about 0.2% for both methods. The transition energies and rates are in reasonable agreement with other available theoretical and experimental data, and the consistency between the transition energies calculated by the two methods reaches 99.9%. These results are expected to help future investigations on double K-shell vacancy decays of He-like ions. [ABSTRACT FROM AUTHOR]