Hyperfine quenching of the metastable ³P_0,2 states in divalent atoms

Hyperfine quenching rates of the lowest-energy metastable ³P₀ and ³P₂ 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 ³P₂ fermionic isotopes. The resulting natural widths of the ³P₀-¹S₀ 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 ³P₂ states in fermionic isotopes is noticeably shortened by the hyperfine quenching but still remains long enough for trapping experiments.