Calculation of helium 1D—3D term intervals for 1snd(n=4—11) states

With many-body perturbation theory (MBPT), 1D—3D term intervals of helium　1snd(n=4—11) configurations have been calculated. Based on two different models, Rayleigh-Schrdinger perturbation expansion terms only consisting of bound states and those of continua are calculated respectively. For bound states, the zeroth-order wave functions are strictly generated from self-iteration solutions of Hartree equation and residues of infinite perturbation series are dealt with by integral processing method. For continuum parts, a simplified hydrogen potential model is adopted. According to Rayleigh-Schrdinger expansion, the perturbation corrections to Rydberg states have been evaluated up to the third-order terms. From the calculation, the energy splittings are mainly attributed to bound parts. Singlet-triplet level splittings yielded here are found to agree quite well with two sets of experimental results.