Long term measurement of the ${}^{87}$Sr clock frequency at the limit of primary Cs clocks

R. Schwarz, S. Dörscher, A. Al-Masoudi +7

We report on a series of 42 measurements of the transition frequency of the 429~THz (5s${}^2$)~${}^1$S${}_0$--(5s5p)~${}^3$P${}_0$ line in ${}^{87}$Sr taken over three years from 2017 to 2019.…