Abstract
Coincidences between the sodium D1 and D2 lines and two corresponding 127I2 lines have permitted the determination of the absolute wavelengths of the hyperfine components of the sodium D lines by using a cw tunable dye laser. The laser frequency, locked in turn on the "o" and "n" hyperfine components of the P 114 (14-1) and P 38 (15-2) iodine lines, was measured at BIPM on the Michelson interferometer. The values of the wavelengths of these iodine lines are respectively: 589 756 661.7 fm and 589 158 022.0 fm.