Hyperfine quenching of the metastable P0,2 states in divalent atoms

Hyperfine quenching rates of the lowest-energy metastable P0 and P2 states of Mg, Ca, Sr, and Yb atoms are computed. The calculations are carried out using ab initio relativistic many-body methods. The computed lifetimes may be useful for designing novel ultraprecise optical clocks and trapping experiments with the P2 fermionic isotopes. The resulting natural widths of the P0 S0 clock transition are 0.44 mHz for 25Mg, 2.2 mHz for 43Ca, 7.6 mHz for 87Sr, 43.5 mHz for 171Yb, and 38.5 mHz for 173Yb. Compared to the bosonic isotopes, the lifetime of the P2 states in fermionic isotopes is noticeably shortened by the hyperfine quenching but still remains long enough for trapping experiments.