UPPER AND LOWER BOUNDS FOR GROUND-STATE ENERGIES IN THE HELIUM ISOELECTRONIC SEQUENCE

The formula of Rayleigh [1] and Ritz [2] is used for determining upper bounds for E0's, E1's and E2's of nine members of the helium isoelectronic sequence. A rough estimation for the lower bounds of E0's is carried out using Temple's relation [3]. The calculations show that a 50-dimensional expansion space can be adjusted to obtain results in good agreement with those of other authors and to confine the exact E0's in gaps of the order of 10-5. © 1979.