He, Liming Cao, Wei 2006 With many-body perturbation theory, ¹D–³D term intervals of helium 1<i>snd</i> (<i>n</i> = 12 ∼ 20) configurations are calculated. Based on two different models, Rayleigh-Schrodinger perturbation expansion terms consisting of bound states only, and those of continua are evaluated, respectively. As for bound states, zeroth-order wave functions are strictly generated from self-iteration solutions of the Hartree equation and residues of infinite expansion series are dealt with by the integral processing method, while a simplified hydrogen potential is adopted to get the continua. Using Rayleigh–Schrodinger expansions, we evaluate exchange energy up to third-order terms. It is found that level splittings are mainly attributed to summations over bound states. The fine-structure level splittings yielded here are found to agree quite well with experimental results. application/pdf https://folia.unifr.ch/global/documents/300328 https://folia.unifr.ch/documents/300328/files/cao_mbc.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1139/p07-002 info:eu-repo/semantics/openAccess License undefined Canadian Journal of Physics. - 2006, vol. 84, no. 12, p. 1097-1106 info:eu-repo/classification/udc/53 Many-body calculation of helium ¹D–³D term intervals for 1<i>snd</i> (<i>n</i> = 12 ∼ 20) high Rydberg states http://purl.org/coar/resource_type/c_6501