Isotope Shift in theCe58ii Spectrum

The spectrum of Ce ii from enriched samples of ${\mathrm{Ce}}^{136}$ and ${\mathrm{Ce}}^{138}$ has been studied and compared with the same spectrum from natural Ce. Only a negligible isotope shift, certainly less than 6 percent of that between the isotopes with 82 and 84 neutrons, has been found between the isotopes with 78, 80, and 82 neutrons.