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CCL-2012-Recommendation-1

Recommandation 1 du 15e CCL (2012)

Updates to the list of standard frequencies

The Consultative Committee for Length,

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 candidates for inclusion into the list
  • the CCTF has recommended these frequencies in its meeting in September 2012

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

 

  • the unperturbed optical transition 3s2 1S0 – 3s3p 3P0 of the 27Al+ ion with a frequency of
    f27Al+ = 1 121 015 393 207 857.3 Hz
    and an estimated relative standard uncertainty of 1.9 × 10−15.

    This radiation is recommended to be endorsed by the CIPM as a secondary representation of the second.

 

  • the unperturbed optical transition 5d106s 2S1/2 – 5d 9 6s2 2D5/2 of the 199Hg+ ion with a frequency of
    f199Hg+ = 1 064 721 609 899 145.3 Hz
    and an estimated relative standard uncertainty of 1.9 × 10−15.

    This radiation is recommended to be endorsed by the CIPM as a secondary representation of the second.

    This radiation is already endorsed by the CIPM as a secondary representation of the second.

 

  • the unperturbed optical transition 6s2 1S0 – 6s6p 3P0 of the 199Hg neutral atom with a frequency of
    f199Hg = 1 128 575 290 808 162 Hz
    and an estimated relative standard uncertainty of 1.7 × 10−14.

 

  • the unperturbed optical transition 6s 2S1/2 – 4f 136s2 2F7/2 of the 171Yb+ ion with a frequency of
    f171Yb+ (octupole) = 642 121 496 772 645.6 Hz
    and an estimated relative standard uncertainty of 1.3 × 10−15.

    This radiation is recommended to be endorsed by the CIPM as a secondary representation of the second.

 

  • the unperturbed optical transition 6s 2S1/2 (F = 0, mF = 0) – 5d 2D3/2 (F = 2, mF = 0) of the 171Yb+ ion with a frequency of
    f171Yb+ (quadrupole) = 688 358 979 309 307.1 Hz
    and an estimated relative standard uncertainty of 3 × 10−15.

    This radiation is already endorsed by the CIPM as a secondary representation of the second.

 

  • the unperturbed optical transition 5s 2S1/2 – 4d 2D5/2 of the 88Sr+ ion with a frequency of
    f88Sr+ = 444 779 044 095 485.3 Hz
    and an estimated relative standard uncertainty of 4.0 × 10−15.

    This radiation is already endorsed by the CIPM as a secondary representation of the second.

 

  • the unperturbed optical transition 4s 2S1/2 – 3d 2D5/2 of the 40Ca+ ion with a frequency of f40Ca+ = 411 042 129 776 395 Hz
    and an estimated relative standard uncertainty of 1.5 × 10−14.

 

  • the unperturbed optical transition 1S – 2S of the 1H neutral atom with a frequency of
    f1H = 1 233 030 706 593 518 Hz
    and an estimated relative standard uncertainty of 1.2 × 10−14.

    Note: This frequency corresponds to half of the energy difference between the 1S and 2S states.

 

  • the unperturbed optical transition 5s2 1S0 – 5s5p 3P0 of the 87Sr neutral atom with a frequency of
    f87Sr = 429 228 004 229 873.4 Hz
    and an estimated 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 6s2 1S0 – 6s6p 3P0 of the 171Yb neutral atom with a frequency of
    f171Yb = 518 295 836 590 865.0 Hz
    and an estimated relative standard uncertainty of 2.7 × 10−15.

    This radiation is recommended to be endorsed by the CIPM as a secondary representation of the second.

 

  • the unperturbed ground-state hyperfine transition of 87Rb with a frequency of
    f87Rb = 6 834 682 610.904 312 Hz
    and an estimated relative standard uncertainty of 1.3 × 10−15.

    This radiation is already endorsed by the CIPM as a secondary representation of the second.

Note: The value of the standard uncertainty is assumed to correspond to a confidence level of 68 %. However, given the very limited number of available data there is a possibility that in hindsight this might not prove to be exact.

and asks the CIPM for approval