Precision calculation of blackbody radiation shifts for optical   frequency metrology
  We show that three group IIIB divalent ions, B+, Al+, and In+, have anomalously small blackbody radiation (BBR) shifts of the ns^2 1S0 - nsnp 3P0 clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions, considers all relevant states in the same systematic way, and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al+ clock to 4 \times 10^{-19} at T=300K. We also reduce the uncertainties due to this effect at room temperature to 10^{-18} level for B+ and In+ to facilitate further development of these systems for metrology and quantum sensing. These uncertainties approach recent estimates of the feasible precision of currently proposed optical atomic clocks. 
M. S. Safronova, M. G. Kozlov, and Charles W. Clark
physics.atom-ph physics.optics quant-ph