Improved absolute frequency measurement of the 1S0–3P0 transition of 171Yb at KRISS

We measured the absolute frequency of the
¹
S
0
–
³
P
0
transition of
¹⁷¹
Yb atom relative to the SI second with an uncertainty reduced by a factor of 14 compared with our previous measurement. The determined frequency was 518 295 836 590 863.38(57) Hz. The experimental setup is being improved for the independent uncertainty evaluation by measuring the frequency shift coefficients of our own system.