S-matrix calculations of energy levels of the lithium isoelectronic sequence

Abstract

A QED approach to the calculation of the spectra of the lithium isoelectronic sequence is implemented. A modified Furry representation based on the Kohn-Sham potential is used to evaluate all one-and two-photon diagrams with the exception of the two-loop Lamb shift. Three-photon diagrams are estimated with Hamiltonian methods. After incorporating recent calculations of the two-loop Lamb shift and recoil corrections a comprehensive tabulation of the 2s, 2p 1/2 and 2p 3/2 energy levels as well as the 2s − 2p 1/2 and 2s − 2p 3/2 transition energies for Z = 10 − 100 is presented.

Identification and Plasma Diagnostics Study of Extreme Ultraviolet Transitions in Highly Charged Yttrium

“…Although recent results are sensitive to higher order QED terms, further developments are expected, especially in the moderately high-Z region where experiments can provide accurate data due to the wavelength range available to grazing incidence EUV spectrometers. Our current relative uncertainty of 57 × 10 −6 for the wavelength of the (2s + )-(2p − ) transition shows good agreement with previous high precision calculations [70][71][72]; however, the (2s + )-(2p + ) theoretical results [70,72] are slightly outside our relative uncertainty of 82 × 10 −6 as shown in Figure 6. Upon close examination, a small feature of unidentified origin was found in the low wavelength wings of both Li-like lines.…”

Correlation, Breit, and QED effects in spectra of Mg-like ions

“…Sometimes, one-electron QED corrections (Lamb shifts) are also included using effective, or model potentials [26][27][28][29][30].…”

QEDMOD: Fortran program for calculating the model Lamb-shift operator

“…[29]. Only one extended nuclear model is supported, since it should be consistent with the model used for the computation of the matrix elements of the exact self-energy operator (6).…”

“…The best theoretical accuracy for highly charged ions is presently obtained in rigorous QED calculations which account for all effects systematically order by order by applying perturbation theory in parameter 1/Z , where Z is the nuclear charge number. Such calculations have been performed during the past decades for the lowest-lying levels of simplest systems: hydrogenlike ions [1,2], heliumlike ions [3], lithiumlike ions [4][5][6], and boronlike ions [7,8]. These calculations were technically highly demanding and required large computer resources as well as coordinated efforts of many people.…”