Calculation of the 4S4P0 spectrum of lithiumlike ions by the Hylleraas method

The energies of the five lowest 4S and 4P0 states for three‐electron ions for 3⩽Z⩽10 have been calculated by the Hylleraas method. The largest basis set used contained 97 terms with odd as well as even powers of rij. The change of scale r′ = Zr was applied to the Hamiltonian so that the same basis sets could be used for all the three‐electron ions leading to great savings in computing time.