Wavenumber Reproducibility of the Radiation 2p10?5d5 of Krypton 86

Abstract

The vacuum wavenumber of the radiation 2PlO-5d5 (6056 A) of krypton 86 emitted by a hot cathode Engelhard-type discharge lamp has been established for the temperature range 58-70 oK and current density range 0-1' 0 A/cm'. Wavenumbers relative to the value for the unperturbed state of the radiation have been measured with a reliability of 1 part in 109 using a photoelectric recording and electromechanical scanning FabryPerot interferometer. However, this reproducibility is not possible for different lamps without a more exact specification for the form and operation of the lamp and for the interferometric system used. With the present international specification for the lamp, the reproducibility of this new primary standard of length is better than 1 part in 108.