Interferometric measurements of isotope shifts in the visible region of a number of lines of singly and doubly ionized mercury have been made from sources containing enriched isotopes Hg198, Hg200, and Hg202. In particular those lines having large isotope shifts were carefully studied. The results indicate a constant value, within experimental limit, of the ratio of the shift of Hg198–Hg200 to that of Hg200–Hg202.
R. W. SHORTHILL and G. R. FOWLES, "Interferometric Measurements of Isotope Shifts in Mercury II and Mercury III with Enriched Isotopes," J. Opt. Soc. Am. 48, 459-459 (1958)