Energy levels for S , P , and D states in He through precision variational calculations

Nonrelativistic variational calculations with the relativistic correction to order α² have been carried out to obtain the energy levels for the n ¹,3S, n ¹,3P, and n¹,3D series in He up to n=8. The calculated term values have converged generally to within an uncertainty of {~}10^-4 cm^-1, a value matching the accuracy of recent high-precision wavelength measurements. The results are combined with theoretical Lamb shifts and systematically compared with currently available high-precision experimental data. The consistency between theory and experiment is good, although for some low-lying (n=3--6) S and P states there exist small discrepancies, presumably caused by the estimated Lamb shifts. The calculated term values for high-lying excited states have better accuracies than existing experimental data. Addition of the theoretical term values to the corresponding experimental excitation energies suggests a value of 198 310.7725(5) cm^-1 for the ground-state ionization energy on the energy scale fixed by the 2¹P value of 171 135.0000 cm^-1.