Black-body radiation shifts in ground and metastable levels of Mg and Ca

The effects of black-body radiation in the 1S0 ground level and the 3Psub(0,1,2) metastable levels of Mg and Ca and the corresponding frequency shifts of intercombination line and fine-structure transitions are evaluated. These transitions are of noticeable interest in metrology, since atomic beam submillimetric and optical frequency standards could be based on them. The a.c. Stark effect of black-body radiation is much more important of the a.c. Zeeman effect, as expected. Although these effects do not seem to be a limit stronger than the second-order Doppler shift for these standards, their contribution should be taken into account, at least for Ca, in evaluating their potential accuracy