Lifetime measurement of the 3P2 metastable state of strontium atoms.

We have measured the lifetime of the 5s5p 3P2 metastable state of strontium atoms by magneto-optically trapping the decayed atoms to the ground state, which allowed sensitive detection of the rare decay events. We found that the blackbody radiation-induced decay was the dominant decay channel for the state at T=300 K. The lifetime was determined to be 520(+310)(-140) s in the limit of zero temperature, arguably the longest lifetime ever determined in a laboratory environment.