Commission 1. Radio measurement methods and standards


  • H. M. Altschuler


K. Evenson (USA) delivered the paper, ‘Stabilized laser-frequency measurements: Methane-stabilized HeNe 3.39 μm and CO2-stabilized 9.3 and 10.2 μm.’

The most notable results reported were the measurements by the National Bureau of Standards (NBS), Boulder, Colorado of both the frequency and wave-length of the HeNe laser stabilized on the 3.39-µm saturated absorption in methane. By this means the velocity of light has been deduced with an estimated accuracy of about 3 parts in 109. This result is at least 100 times more accurate than previous determinations of the velocity of light and is in reasonable agreement with the previously adopted value published by Froome and Essen [1969]. The new value for the velocity of light determined by NBS with to the fundamental standards of time (cesium) and length (krypton) is:

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