The splitting isotope shift (SIS) in heliumlike carbon: A comparison of theory and experiment

A comparison with theory for the splitting isotope shift (SIS) provides a clear test of experimental accuracy [1]. It is defined as the difference in fine-structure splittings between different isotopes of the same atom after averaging over hyperfine structure. The theoretical SIS is determined by the relativistic finite nuclear mass and recoil contributions to the energy. Uncertainties due to higher-order quantum electrodynamic corrections are strongly suppressed since, to lowest order, they are independent of both nuclear mass and the fine structure quantum number J.. A comparison between theory and experiment will be presented for the 1s2p ³P_J SIS of heliumlike carbon-13 relative to carbon-12. The calculated 2 ³S₁ - 2 ³P₀ transition frequency is 1,316,056(20) GHz. For the J = 0 → 1 and J = 0 → 2 transitions, the theoretical SIS is -2.08(2) MHz and 28.36(2) MHz respectively, in good agreement with the corresponding experimental values -5(3) MHz and 30.2(3.1) MHz.

[1] L.-M. Wang et al. Phys. Rev. A 95, 032504 (2017).