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The excitation energies of the Be-like ions (4 ≤ Z ≤ 74) doubly excited state 1 s 2 2 p 2 and doubly core-excited state 2 s 2 p 3 are calculated using the multi-configuration Dirac–Hartree–Fock method. The contributions of relativistic effects, Breit interaction, and QED effects to the excitation energies are analyzed and discussed in detail. A reasonable electron correlation model has been constructed using the active set method. The electron correlation and the finite size of the atomic nucleus correction have also been appropriately considered. The calculated results agree with the available theoretical and experimental data. It is found that the contribution of relativistic effects, Breit interaction, and QED effects to the excitation energy becomes significant with increasing Z. The contribution of the relativistic effects reaches about 8.5% at Z=74. The 3 P 0 level of the doubly excited state 1 s 2 2 p 2 is sensitive to the Breit interaction and the QED effects, but these two contributions cancel each other out. For the doubly core-excited state 2 s 2 p 3 , the Breit interaction and the QED effects are almost equally important, and their maximum contribution is about 0.5%. These results are expected to help future experimental and theoretical work. [ABSTRACT FROM AUTHOR]

The dielectronic recombination of Li-like Xe (2s) ions was studied using the flexible atomic code based on the relativistic configuration interaction method. The resonance energies, radiative and autoionization rates, and resonance strengths were calculated systematically for the doubly excited states (2 p n l )( n = 18−32) and (2 p n′ l )( n′ = 9−27) of Be-like Xe ions. For the higher Rydberg resonance states with n ≥ 33 and n′ ≥ 28, the resonance energies and strengths were obtained by extrapolation based on quantum defect theory. The theoretical rate coefficients, covering the center-of-mass energy range 0-505 eV, are in a better agreement with the experimental results measured at the heavy-ion storage ring ESR than the Multi-Configuration Dirac-Fock calculations, especially at the resonance energy range close to the series limits. Graphical abstract: [ABSTRACT FROM AUTHOR]

• A systematic study of spatiotemporal evolution of extreme ultraviolet spectra in laser-produced silver (Ag) plasmas is performed with aid of a spatio-temporally resolved emission spectroscopy and multiconfiguration Hartree-Fock calculations. • Complex spectral structures were accurately revealed based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collision-radiative model, which are dominated from the contributions of 4p and 4d excitations of Ag7+–Ag13+ ions. • Theoretical plasma-state parameters near the target surface at the initial stage of the laser-produced Ag plasma were determined via the steady-state collision-radiation model. Experimental and theoretical analyses are reported for the spatiotemporal evolution of extreme ultraviolet spectra in laser-produced silver (Ag) plasmas. The time-resolved spectra were acquired 1.5 mm from the target surface. The 4p and 4d excitations of Ag7+–Ag13+ ions were calculated with the aid of multiconfiguration Hartree-Fock calculations. The spectral line distributions of transitions in the dominant 4p and 4d excitation configurations and their variations with the degree of ionization were analyzed. Complex spectral structures were accurately revealed based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collision-radiative model. Experimental peak origins were identified by comparing experimental and simulated spectra. These results will provide data for energy-level structures of highly-charged ions of middle- and high-Z elements and their radiative characteristics in plasmas. [ABSTRACT FROM AUTHOR]