Optical Frequency Standards Based on Neutral Atoms and Molecules

  • Fritz Riehle
  • Jürgen Helmcke
Part of the Topics in Applied Physics book series (TAP, volume 79)


The current status and prospects of optical frequency standards based on neutral atomic and molecular absorbers are reviewed. Special attention is given to an optical frequency standard based on cold Ca atoms which are interrogated with a pulsed excitation scheme leading to resolved line structures with a quality factor Q τ; 1012. The optical frequency was measured by comparison with PTB’s primary clock to be νCa = 455 986 240 494.13 kHz with a total relative uncertainty of 2.5 × 10−13. After a recent recommendation of the International Committee of Weights and Measures (CIPM), this frequency standard now represents one of the most accurate realizations of the length unit.


Laser Frequency Neutral Atom Atomic Beam Frequency Standard Laser Cool 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • Fritz Riehle
    • 1
  • Jürgen Helmcke
    • 1
  1. 1.Physikalisch-Technische Bundesanstalt (PTB)BraunschweigGermany

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