Further Results Concerning Half-Integral Hylleraas Expansions

Previous calculations concerning the ground state of two-electron atoms, involving Ritz-Hylleraas expansions with half-integral powers, are continued through expansions involving 31 parameters. As far as can be judged from a comparison of the energies with those obtained with other expansions, the results continue to be favorable. Thus, already with 18 parameters, the computed energies for He and O vii differ from the best published values by 2 and 0.3 parts per million, respectively. Even better results are obtained for He with expansions involving both half-integral and negative powers. A few initial results of calculations for the excited state $2{}_{}{}^1{}_{}{}^{}S$ are also presented.