Division of the 2p-shell in oxygen-type atoms

To obtain more accurate results in many fields of atomic physics, the equivalent electron shell can be devided into two groups. The first one is made up of those electrons, which take place in the investigated process, while others perform the function of the background. The suggested metOod can be formulated as a ''partially widened'' method for calculating atomic structures and to find necessary values one should use its complete variant. However, much easier is to use the model of non-orthogonal radial orbitals, with two shells having similar nl. The suggested technique is realized for isoelectron succession from nitrogen to neon in the 1s22s22p4 configuration using generalized hydrogen-like analytical radial orbitals. In this case the p shell splits into groups of one and three electrons. The analysis of results shows, that the use of the split shell approximation improves calculation results. Great energy differences for ''compressed'' and ''diffused'' orbitals obtained by Sasaki are due to bad radial orbitals. The increase of the number of varied parameters brings about the energy values similarity. The most radial orbitals in the case of 2p shell division change significantly