Energy calculation of 2s2 1S, 2p2 1D, 3s2 1S, 3p2 1D, 3d2 1G, 4p2 1D, 4d2 1D, 4f2 1I doubly excited states using a new wave function to four terms for 2≤Z≤152≤Z≤15

•Accurate energy for doubly excited states of He-like systems 2≤Z≤152≤Z≤15.•Well-comparable results to theoretical literature values.•Satisfactory agreements with theoretical calculations.

Calculation of the energy levels of atoms and ions with 2≤Z≤152≤Z≤15 are carried out in this paper using a Hyllerass approximation. The method used is one of Screen Constant by Nuclear Charge Unit to calculate the total energy of two-electron atomic systems in ground and different doubly excited states. Employing a new wave function including correlation, we were able to calculate excited states (nl)2 (n≤4n≤4). The Comparison of these results with the ones of other methods shows a good agreement.