Electron momentum distributions and atomic〈rn〉expectation values

The $〈r^n〉$ expectation values have been extracted from the known electron momentum distributions for hydrogen, helium, argon, and krypton atoms with the use of a semiclassical approach. These values compare fairly well with their Hartree-Fock counterparts. This procedure provides a link between the distribution of electrons in the momentum space and that in the coordinate space.