ABSTRACT
In 1960 the platinum-iridium meter bar was abrogated as the international standard of length, and the meter was redefined as equal to 1 650 763.73 wavelengths in vacuum of the radiation corresponding to the transition between the 2p 10 and 5d 5 levels of the krypton-86 atom. 1 Since then the wavelength of this orange-red line has been the primary standard of wavelength, and is equal to 605.780 211 nm in vacuum, or 605.612 525 nm in air.
