Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

A Spin-1/2 Optical Lattice Clock



Nathan D. Lemke, Andrew D. Ludlow, Zeb Barber, Tara M. Fortier, Scott A. Diddams, Yanyi Jiang, Steven R. Jefferts, Thomas P. Heavner, Thomas E. Parker, Christopher W. Oates


We experimentally investigate an optical clock based on 171Yb (I = 1/2) atoms confined in an optical lattice. We have evaluated all known frequency shifts to the clock transition, including the density-dependent collision shift, with an uncertainty of 0.19 Hz, or 3.6× 10−16 fractionally, limited principally by uncertainty in the blackbody radiation Stark shift. We have measured the absolute clock transition frequency relative to the NIST-F1 Cs fountain clock and find the frequency to be 518 295 836 590 865.7(0.9) Hz.
Physical Review Letters


lasers, other standards, spectroscopy


Lemke, N. , Ludlow, A. , Barber, Z. , Fortier, T. , Diddams, S. , Jiang, Y. , Jefferts, S. , Heavner, T. , Parker, T. and Oates, C. (2009), A Spin-1/2 Optical Lattice Clock, Physical Review Letters, [online], (Accessed May 25, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created August 7, 2009, Updated February 19, 2017