Radial and angular correlations of two excited electrons. IV. Comparison of configuration-interaction wave functions with the group-theoretical basis functions

Doubly-excited-state basis (DESB) functions of Herrick and Sinano {g} {g}{}lu are compared with the large-scale configuration-interaction (CI) wave functions of Lipsky et al., and with the adiabatic channel functions in hyperspherical coordinates. It is shown that DESB functions will represent those states where the mean value of θ₁₂ is large. Owing to the absence of intershell correlations, and a consequent underestimation of radial correlations, the DESB functions give excessive concentrations near θ₁₂=0 for other, less sharply correlated in angle, states.