Electron-pair densities of singly charged atoms

For the singly charged 53 cations from Li+ to Cs+ and 43 anions from H− to I− in their ground states, spherically averaged electron-pair intracule (relative-motion) density h(u), extracule (center-of-mass-motion) density d(R), and their moments 〈un〉 and 〈Rn〉 are examined, where u and R are the interelectronic distance and the center-of-mass radius of a pair of electrons, respectively. The intracule and extracule densities of all the 96 ions are found to be monotonically decreasing functions, as for neutral atoms. Approximate relations d(R)≅8h(2R) and 〈un〉/〈Rn〉≅2n are confirmed to be valid for the charged atoms as well.