Nonrelativistic energy levels of helium atom

The nonrelativistic energy levels of a helium atom are calculated for S, P, D and F states. The calculations are based on the variational method of "exponential" expansion. The convergence of the calculated energy levels is studied as a function of the number of basis functions N. This allows us to claim that the obtained energy values (including the values for the states with a nonzero angular momentum) are accurate up to 28-35 significant digits. © 2019 Sissa Medialab Srl. All rights reserved.