Feasibility of Cooling and Trapping Metastable Alkaline-Earth Atoms

Metastability and long-range interactions of Mg, Ca, and Sr in the lowest-energy metastable ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$ state are investigated. The calculated lifetimes are 38 min for ${\mathrm{Mg}}^{*}$, 118 min for ${\mathrm{Ca}}^{*}$, and 17 min for ${\mathrm{Sr}}^{*}$, supporting feasibility of cooling and trapping experiments. The quadrupole-quadrupole long-range interactions of two metastable atoms are evaluated for various molecular symmetries. Hund's case (c) $4_g$ potential possesses a large 100–1000 K potential barrier. Therefore magnetic trap losses can possibly be reduced using cold metastable atoms in a stretched $M=2\mathrm{}$ state. Calculations were performed in the framework of ab initio relativistic configuration interaction method coupled with the random-phase approximation.