Ytterbium in quantum gases and atomic clocks: van der Waals interactions and blackbody shifts

We evaluated the $C_6$ coefficients of Yb-Yb and Yb-alkali/group II van der Waals interactions with 2\% uncertainty. The only existing results for such quantities are for the Yb-Yb dimer. Our value, $C_6 = 1929(39)$ a.u., is in excellent agreement with the recent experimental determination of 1932(35) a.u. [M. Kitagawa, {\em et al., Phys. Rev. A } {\bf 77}, 012719 (2008)]. We have also developed a new approach for the calculation of the dynamic correction to the blackbody radiation shift. We have calculated this quantity for the Yb $6s^2$ $^1{\rm S}_0 - 6s6p$ $^3{\rm P}^{\circ}_0$ clock transition with 3.5\% uncertainty. This reduces the fractional uncertainty due to the blackbody radiation shift in the Yb optical clock at 300 K to the $10^{-18}$ level. For further details, see http://arxiv.org/abs/1208.1456