Effect of the {sup 129}I impurity on the radiation frequency of a stabilised He - Ne/{sup 127}I{sub 2} laser

The radiation frequency of a He - Ne/{sup 127}I{sub 2} laser stabilised to the hyperfine structure component of molecular iodine exhibits shifts caused by the presence of impurities in the iodine cell. The specific effect of the {sup 129}I impurity on the radiation frequency of a stabilised laser is considered. It is shown that even for a 0.25 % concentration of {sup 129}I, the frequency shift in a He - Ne/{sup 127}I{sub 2} laser caused by this isotope plays a decisive role. To exclude the possible effect of other iodine isotopes on the accuracy of reproducibility of the frequency of metrological lasers, it is expedient to carry out the laser fluorescence test of the cells to check for the presence of heteroisotopic molecular iodine impurity. (control of laser radiation parameters)