Accurate algebraic densities and intracules for heliumlike ions

Accurate electron number densities and interelectronic distance (intracule) densities are given in simple algebraic form for the ground states of H-, He, Li+, Be2+, B3+, and Ne8+. The densities are obtained from systematic sequences of increasingly accurate Hylleraas-type wave functions. The most accurate densities are obtained from 204-term wave functions that lead to variational energies no more than 16 nano-Hartrees above the exact ones. The algebraic densities permit the evaluation of systematic sequences of many expectation values. Some moments of the densities are evaluated in this manner. 22 refs., 1 fig., 6 tabs