Critical analysis of the methods of interpretation in the hyperfine structure of free atoms and ions: case of the model space (5d+6s)3 of the lanthanum atom

In this work the method of quantitative determination of two-body contributions to the fine and the hyperfine structure, resulting from the excitations from electronic closed shells to open shells and from open shells to empty shells, is described. On the basis of experimental data, both our own and that available in the literature, the configuration (5d+6s)(3) in the lanthanum atom is analysed. Our investigations indicate that the operator H-hfs = (3)Sigma T-K=1(e)(kappa k)K . T-n((K)) describes the partition of the observed hyperfine splittings into the contributions of ranks K = 1, 2 and 3 within the experimental accuracy, while the operator T-e((kappa k)1) . T-n((1)) = mu(0)mu(B)/2 pi (N)Sigma(i=1)[(l(i)) over cap < r(-3)>(01) - root 10((s(i)) over cap<(C-i(2))over cap>((1))< r(-3)>(12) + (s(i)) over cap < r(-3)>(10)] . T-n((1)) does not fully account for the partition of the interactions of rank K = 1 into contributions kappa k = 01, 12 and 10.