On accurate computations of slowly convergent atomic properties in few-electron ions and electron-electron correlations

We discuss an approach to accurate numerical computations of slowly convergent properties in two-electron atoms/ions which include the negatively charged Ps − ( e − e + e − ) and H − ions, He atom and positively charged, helium-like ions from Li + to Ni 26+ . All these ions are considered in their ground 1 1 S-state(s). The slowly convergent properties selected in this study include the electron-nulceus ( r 2k eN ) and electron-electron ( r 2k ee ) expectation values for k = 2, 3, 4 and 5.