Recommendation-CIPM-2009-2

Recommendation 2 of the 98th CIPM (2009)

Updates to the list of standard frequencies

The International Committee for Weights and Measures (CIPM),

considering that

  • a common list of “Recommended values of standard frequencies for applications including the practical realization of the metre and secondary representations of the second” has been established;
  • the CCL-CCTF Frequency Standards Working Group (FSWG) has reviewed several promising candidates for inclusion in the list;

recommends that the following transition frequencies shall be included or updated in the list of recommended standard frequencies:

  • the unperturbed optical transition 5s2 1S0 – 5s 5p 3P0 of the 87Sr neutral atom with a frequency of f = 429 228 004 229 873.7 Hz and a relative standard uncertainty of 1 × 10–15 (this radiation is already endorsed by the CIPM as a secondary representation of the second);
  • the unperturbed optical transition 5s2 1S0 – 5s 5p 3P0 of the 88Sr neutral atom with a frequency of f = 429 228 066 418 012 Hz and a relative standard uncertainty of 1 × 10–14;
  • the unperturbed optical transition 4s 2S1/2 – 3d 2D5/2 of the 40Ca+ ion with a frequency of f = 411 042 129 776 393 Hz and a relative standard uncertainty of 4 × 10–14;
  • the unperturbed optical transition 2S1/2 (F = 0) – 2F7/2 (F = 3, mF = 0) of the 171Yb+ ion with a frequency of f = 642 121 496 772 657 Hz and a relative standard uncertainty of 6 × 10–14;
  • the unperturbed optical transition 6s2 1S0 (F = 1/2) – 6s 6p 3P0 (F = 1/2) of the 171Yb neutral atom with a frequency of f = 518 295 836 590 864 Hz and a relative standard uncertainty of 1.6 × 10–13.

reference The reader should note that the official version of this Resolution is the French text

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