Complete Hyperfine Structure of a Molecular Iodine Line

The complete hyperfine structure of the $P(117)$ line of the 21-1 band of the $B\ensuremath{\leftarrow}X$ transition of $^{127}\mathrm{I}_{2}$ is observed at 568.2 nm. A resolution in excess of ${10}^{8}$ is obtained by a sensitive technique of saturation spectroscopy using a krypton-ion laser. The spectrum can be fitted by a model which includes both a nuclear electric quadrupole and a magnetic hyperfine interaction.