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The optical calcium frequency standards of PTB and NIST



U Sterr, C Degenhardt, H Stoehr, Ch. Lisdat, H Schnatz, J Helmcke, F Riehle, G Wilpers, Christopher W. Oates, Leo W. Hollberg


We describe the current status of the optical calcium frequency standard with laser-cooled neutral atoms realized in two different laboratories for the purpose of developing a possible future optical atomic clock. Frequency measurements performed at PTB and NIST make the frequency of the clock transition of 40}Ca one of the best known optical frequencies (relative uncertainty 1.2 x 10u-14}) and agree in both laboratories to well within their respective uncertainties. Prospects for orders of magnitude improvement in the standard look feasible.
Comptes Rendus Mathematique


atomic clock, laser spectroscopy, optical frequency standard


Sterr, U. , Degenhardt, C. , Stoehr, H. , Lisdat, C. , Schnatz, H. , Helmcke, J. , Riehle, F. , Wilpers, G. , Oates, C. and Hollberg, L. (2004), The optical calcium frequency standards of PTB and NIST, Comptes Rendus Mathematique, [online], (Accessed May 29, 2024)


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Created November 4, 2004, Updated October 12, 2021