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Resolution 5 of the 18th CGPM (1987)
Version française
Study of perturbing effects in the realization of the second

    The 18th Conférence Générale des Poids et Mesures

    recalls that

  • the definition of the second as it results from the decisions of the 13th Conférence Générale des Poids et Mesures implies that the caesium atom used as reference is at rest and unperturbed,
  • this implies in particular that, in its practical realization, measurements must be corrected for the velocity of the caesium atoms with respect to the clock reference frame, for magnetic and electric interactions, spin exchange and other possible perturbations,
  • and, in order to implement the necessary corrections,


  • that theoretical studies of all perturbing effects be developed
  • that experiments in order to identify these effects, to verify their theoretical interpretation and to evaluate the uncertainty of the corresponding corrections be actively pursued.

Comptes Rendus de la 18e CGPM (1987), 1988, p.99
Metrologia, 1988, 25(2), 113-119

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

Other Resolutions of the 18th CGPM (1987)
Resolution 1
Resolution 2
Resolution 3
Resolution 4
Resolution 5
Resolution 6
Resolution 7
Resolution 8
Resolution 9