Isotope shifts due to the 1s²2s ²S_1/2 → 1s²2p ²P_1/2,3/2 transitions of Li-like Th⁸⁷⁺ ions

The transition energies of the 1s²2s ²S_1/2 → 1s²2p ²P_1/2,3/2 transitions in Li-like Th⁸⁷⁺ ions were calculated by combining the multi-configuration Dirac–Hartree–Fock (MCDHF) method with the model-quantum electrodynamics (model-QED) approach. The effects of electron correlation, Breit interaction, and QED effects were analyzed in detail. The isotope shifts, including the mass shifts and field shifts, due to the 2s ²S_1/2 → 2p ²P_1/2,3/2 transitions were then calculated using two different methods, namely, the MCDHF method and the finite-field method. The results show that these two methods are in excellent agreement.