Prediction of <i>I</i> _g ,6d _3/2 → <i>I</i> _g , 7p _1/2 , <i>I</i> _g , 7s _1/2 → <i>I</i> _g , 7p _1/2 and <i>I</i> _g , 7p _1/2 → <i>I</i> <sub>m

Abstract The 229 Th nucleus has attracted considerable attention due to the existence of its low-energy isomeric state; however, direct laser excitation in ionic systems poses significant challenges for current laser technologies. In the 229 Th 3+ ion, the electronic bridge (EB) process enables the conversion of direct laser excitation into an effective two-photon process ( I g , 6d 3/2 → I g ,7 p 1/2 → I m ,7s 1/2 ), thereby circumventing the requirement for laser radiation at 148 nm. In this work, we employ many-body perturbation theory (MBPT) to calculate the hyperfine structure constants and field shift factors for several low-lying excited states of the 229 Th 3+ ion. By combining these theoretical results with previously reported experimental data, we predict three transition frequencies associated with the EB process in the 229 Th 3+ ion and identify the most suitable transition pathway for EB-assisted nuclear excitation.