Accurate one-electron momentum-space properties for the lithium isoelectronic sequence

Spin-dependent momentum-space distributions are introduced within the density-matrix formalism and the impulse approximation. The m s components of the spherically averaged momentum densities and isotropic Compton profiles are calculated for the lithium atom and members of its isoelectronic series by using full configuration-interaction wavefunctions that include over 96% of the correlation energy and represent the final stage of a convergent sequence, both in the charge and spin densities in position space. The effects of electron correlation on momentum-space properties of the lithium atom are assessed by comparisons to those obtained from an unrestricted Hartree-Fock wavefunction. Results for the ions B 2+ , N 4+ and F 6+ do not support the observation that the sum of information entropies in momentum and position spaces enhances with the quality of the wavefunction. The conjecture that J HF (0)>J corr ( phi ) is in complete agreement with the results of this study.