Theoretical study of interesting fine-structure splittings for 2 3P0,1,2 states along helium isoelectronic sequence

Using the multi-configuration Dirac-Fock method including the Breit interactions and QED corrections, we calculate the fine-structure energy levels of the 2 P-3(0,1,2) states along the helium isoelectronic sequence with atomic number up to Z = 36, where LS-coupling is appropriate. Our calculation results agree with the experimental results within about 1%. We elucidate the mechanism of the interesting fine-structure splittings for the 2 P-3(0,1,2) states along the helium isoelectronic sequence, i.e. the competitions between the spin-orbit interactions and the Breit interactions which represent the relativistic retardation effect of electromagnetic interactions.