A Variational Perturbation Theory Study of Some Two-Electron Atomic Systems, with Particular Emphasis on Relativistic Corrections to the Energy for the States (1s)2 Singlet S And (2p)2 Triplet P. Part I. Theory and Results

摘要

The Hylleraas-Scherr-Knight variation perturbation procedure has been reviewed, and a few extensions and modifications have been suggested. In particular, an upper bound theorem for the energy has been established. The procedure has been applied to the two-electron atomic states (1s)2 singlet S and (2p)2 triplet P through 20th perturbation order. Perturbation coefficients and expectation values for a number of important operators have been computed. Particular emphasis has been laid upon the evaluation of relativistic and radiative energy corrections for the two states. The results are compared - where possible - with the values obtained by conventional variational calculations, and with experimental values. (Author)