Substantial Nuclear Hyperfine Mixing Effect in Boronlike Pb205 Ions

Nuclear hyperfine mixing (NHM) is a distinctive effect through which nuclear properties and dynamics can be efficiently controlled. Traditionally, the scientific consensus has predominantly associated NHM with its pronounced impact on ²²⁹Th, owing to the existence of its low-lying isomeric state. However, in the present study, by developing a general theory for NHM, we predict a surprisingly substantial NHM effect in boronlike ²⁰⁵Pb ions (specifically, ²⁰⁵Pb⁷⁷⁺), featuring a nuclear transition energy of 2.329 keV. The radiative lifetime of the ²⁰⁵Pb isomer is reduced by 4 orders of magnitude, from 15 min to 32 ms. This remarkable and unexpected NHM effect stems from a heretofore unexplored process: an opening of a magnetic dipole channel that is otherwise forbidden without NHM. ²⁰⁵Pb ions now emerge as an attractive alternative candidate for experimental validation and investigation of the NHM effect.