Extended Hartree–Fock Calculations for Li and Li-like Ions

An extended Hartree–Fock (EHF) calculation is performed for the ${\text{1s}}^2\text{2s}$ ground state of Li and Li‐like ions for $z$ values from 2 through 9. The EHF wavefunction is a two determinant eigenfunction of S² and $S_z$ . The single‐particle orbitals are found by solving the coupled integro‐differential equations by an iterative numerical integration technique. The results should be the best for the approximate wavefunction used, since the single‐particle orbitals do not rely on a choice of basis functions. The total energy, ionization energy, and hyperfine splitting are calculated and the results are compared with similar previous calculations.