Relativistic configuration interaction calculations for some two- and three-electron systems with screened hydrogenic spin orbitals

An approach is proposed for the generation of virtual spin orbitals required to construct a configuration state function basis set for relativistic configuration interaction calculations. Screened hydrogenic spin orbitals, corresponding to noninteger nuclear numbers determined separately for each orbital employing the so-called condensed-space concept are proposed and used here. To test the method calculations are performed of ionization and transition energies of two- and three-electron systems such as He, He-like Ne and He-like U, Li, Li-like Ne and Li-like U, including Breit interaction and quantum electrodynamic corrections.