Precision calculation of blackbody radiation shifts for metrology at the 18th decimal place

We developed a theoretical method within the framework of relativistic many-body theory to accurately treat correlation corrections in atoms with few valence electrons, and applied it to calculate polarizabilities and the blackbody radiation (BBR) shifts of atomic frequency standards. We have performed the calculations of the BBR shifts in B⁺, Al⁺, and In⁺ that allowed to reduce the ultimate uncertainties due to this effect at room temperature to 10^-18 level for B⁺ and In⁺ and to 4×10^-19 for Al⁺. These uncertainties approach recent estimates of the feasible precision of currently proposed optical atomic clocks.