Electronic wave functions for helium-like atoms

In the case of certain atomic processes including K-shell electrons, the use of single-electron wave functions is not adequate and the atomic system should be described by the correlated wave functions. For this purpose, the Rayleigh-Ritz variational method has been most widely employed to calculate the wave functions for the ground states of the helium isoelectronic sequence. Since the first successful application of this method for He by Hylleraas, many calculations have been performed for two-electron atoms with correlation effect and good agreement with experimental results has been achieved for energy eigenvalues and other quantities. However, most calculations are concerned with He and Li+, and there have been reported only a few results for ground states of helium-like ions with large atomic number. In the present work, the Hylleraas-type 3-parameter wave functions have been calculated numerically for atomic numbers from Z=2 to 82. The numerical values of the parameters obtained are expressed as a simple function of the atomic number Z. These results are very useful for many fields of applications because of their simple form. (author)