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.

Figure 1

The model of $E$ space for the hydrogen atom in nonrelativistic approximation. The horizontal dotted lines represent filled states of the space. The solid lines represent spectroscopic states. The base level represents here the ground level

Figure 2

Condensed $E^{\left(s\right)}$ space of degree $s=2$. The base level represents here the ground level. The dashed lines represent virtual states. The solid lines except for base level also represent virtual states in that space. Note that solid lines correspond to the spectroscopic states in original E space.