Recommendation-CIPM-2006-1

Recommendation 1 of the 95th CIPM (2006)

Concerning secondary representations of the second

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” shall be established,
  • the CCL/CCTF Joint Working Group (JWG) on the Mise en Pratique of the Definition of the Metre and the Secondary Representations of the Second in its meeting at the International Bureau of Weights and Measures (BIPM) in September 2005 discussed possible candidates to be included in this list for secondary representations of the second,
  • the CCL/CCTF JWG reviewed and updated the values for the Hg ion, Sr ion, Yb ion, and the Sr neutral atom transition frequencies in its session in September 2006,
  • the CCTF in its Recommendation CCTF 1 (2004) already recommended the unperturbed ground-state hyperfine quantum transition frequency of 87Rb as a secondary representation of the second;

recommends that the following transition frequencies shall be used as secondary representations of the second and be included into the new list of “Recommended values of standard frequencies for applications including the practical realization of the metre and secondary representations of the second”

  • the unperturbed ground-state hyperfine quantum transition of 87Rb with a frequency of f87Rb = 6 834 682 610 904 324 Hz and an estimated relative standard uncertainty of 3 × 10–15,
  • the unperturbed optical 5s 2S1/2 – 4d 2D5/2 transition of the 88Sr+ ion with a frequency of f88Sr+ = 444 779 044 095 484 Hz and a relative uncertainty of 7 × 10–15,
  • the unperturbed optical 5d10 6s 2S1/2 (F = 0) – 5d9 6s2 2D5/2 (F= 2) transition of the 199Hg+ ion with a frequency of f199Hg+ = 1 064 721 609 899 145 Hz and a relative standard uncertainty of 3 × 10–15,
  • the unperturbed optical 6s 2S1/2 (F = 0) – 5d 2D3/2 (F = 2) transition of the 171Yb+ ion with a frequency of f171Yb+ = 688 358 979 309 308 Hz and a relative standard uncertainty of 9 × 10–15,
  • the unperturbed optical transition 5s2 1S0 – 5s 5p 3P0 of the 87Sr neutral atom with a frequency of f87Sr = 429 228 004 229 877 Hz and a relative standard uncertainty of 1.5 × 10–14.

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

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