2004/08/31 by P. Indelicato, Paul Indelicato, Eva Lindroth +2 · 1 citation
Physics and Astronomy · #Advanced Chemical Physics Studies #Atomic and Molecular Physics #Cold Atom Physics and Bose-Einstein Condensates #physics.atom-ph
paper · pdf · doi:10.1103/physrevlett.94.013002
published as Physical Review Letters 94 (2005) 013002 · AUgust 9th, 2004 Second version Nov. 18th, 2004
arxiv created 2004/11/18 · openalex publication_date 2005/01/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We solve a long standing problem with relativistic calculations done with the widely used multiconfiguration Dirac-Fock method. We show, using relativistic many-body perturbation theory (RMBPT), how, even for relatively high-Z, relaxation or correlation causes the nonrelativistic limit of states of different total angular momentum but identical orbital angular momentum to have different energies. We show that only large scale calculations that include all single excitations, even those obeying Brillouin's theorem, have the correct limit. We reproduce very accurately recent high-precision measurements in F-like Ar, and turn then to a precise test of QED. We obtain the correct nonrelativistic limit not only for fine structure but also for level energies and show that RMBPT calculations are not immune to this problem.