Measurement of the Hyperfine Quenching Rate of the Clock Transition in   $^{171}$Yb
  We report the first experimental determination of the hyperfine quenching rate of the $6s^2\ ^1\!S_0\ (F=1/2) - 6s6p\ ^3\!P_0\ (F=1/2)$ transition in $^{171}$Yb with nuclear spin $I=1/2$. This rate determines the natural linewidth and the Rabi frequency of the clock transition of a Yb optical frequency standard. Our technique involves spectrally resolved fluorescence decay measurements of the lowest lying $^3\!P_{0,1}$ levels of neutral Yb atoms embedded in a solid Ne matrix. The solid Ne provides a simple way to trap a large number of atoms as well as an efficient mechanism for populating $^3\!P_0$. The decay rates in solid Ne are modified by medium effects including the index-of-refraction dependence. We find the $^3\!P_0$ hyperfine quenching rate to be $(4.42\pm0.35)\times10^{-2}\ \mathrm{s}^{-1}$ for free $^{171}$Yb, which agrees with recent ab initio calculations. 
C.-Y. Xu, J. Singh, J. C. Zappala, K. G. Bailey, M. R. Dietrich, J. P.   Greene, W. Jiang, N. D. Lemke, Z.-T. Lu, P. Mueller...
physics.atom-ph