Relativistic many-body perturbation theory applied ton=2 triplet states of heliumlike ions

Abstract

Relativistic many-body perturbation theory calculations of the energies of the 2 Po, 2 P2, and 2 Sq states of heliumlike ions with nuclear charges Z in the range 10 -36 are presented. These calculations include Coulomb correlation corrections through third order, correlation corrections of first order in the Breit interaction and zeroth, first, and second order in the Coulomb interaction, together with second-order Breit-Breit corrections and first-order corrections for retardation of the Breit interaction. At Z = 10, the calculated energies of the 2 Po, 2 P2, and 2 Sz states di8'er by 2.9, 0.02, and 0.3 cm, respectively, from benchmark calculations based on variational wave functions. For higher Z, the difference between the present calculations and the benchmark calculations increases smoothly. Radiative and mass-polarization corrections are added to the many-body calculations and comparisons are made with measured 2 Po-2 Sq and 2 P2-2 Sq intervals.

QED calculation of then=1andn=2energy levels in He-like ions

“…A similar deviation was reported previously in the literature [18,19,20], where it was attributed to corrections of order α 2 (αZ) 4 to the electron-electron interaction that were not accounted for by Drake's unified method but can be (to a certain extent) included by methods based on the no-pair QED Hamiltonian [77]. Irregularities of the Z-dependence of the plotted difference, which can be observed for S states in the medium-and high-Z region, is explained by more recent values for the rms nuclear radii employed in the present calculation.…”

“…It is to be noted that the results by Johnson and Sapirstein [18] and by Chen et al [19] obtained In Table VIII, we list transition energies for which experimental results are available. Comparison is made with the MBPT calculation by Johnson and Sapirstein [18], with the CI calculations by…”

Precision studies of fundamental atomic structure with heaviest few-electron ions

“…Theoretical investigations of He-like ions in the high-Z domain have experienced considerable progress during the last decade where a new generation of relativistic many-body theory (RMBT), multiconfiguration Dirac-Fock (MCDF) and the configuration interaction (CI) methods have established improved benchmarks for the non-QED part of the electron-electron interaction [16][17][18][19]. This was followed by calculations of the ground-state two-electron QED contributions: the so called two-electron Lamb shift, including all corrections of order α 2 [20,21].…”

Near-coincident K-line and K-edge energies as ionization diagnostics for some high atomic number plasmas

“…As is discussed in what follows, Ir's ionization shift measured in the PFRP is consistent with results from two of these codes. 13,14 Our interest in measuring the ionization shift has a third motivation. Nuclear isomers are metastable nuclei that could be induced, by irradiation with x-rays, to give up their energy at densities and with rates conceivably much higher than possible with chemical reactions.…”