HIGH‐RESOLUTION SATURATION SPECTRA OF THE IODINE ISOTOPE I2129 IN THE 633‐nm WAVELENGTH REGION

Using a He3–Ne20 laser as a light source and techniques of saturation spectroscopy, the relative positions of 38 separate lines have been resolved in a free spectral range of 650 MHz in the 633‐nm wavelength region. The absolute reproducibility of the positions of these lines has also been investigated with the view of use of them as wavelength standards and is found to be of the order of 1 part in 109 or better.