Isotope Shift in Magnesium

Abstract

The previous investigations concerning the isotope shift of magnesium have been repeated and extended by means of an improved atomic beam source and a Perot-Fabry interferometer. The values of Meissner have been checked to within experimental error in most cases. In addition, several new lines have been resolved, and their isotope shifts determined. The $3{}_{}{}^1{}_{}{}^{}P-m{}_{}{}^1{}_{}{}^{}D$ series has been resolved from $m=3\mathrm{}$ out as far as the member $m=11\mathrm{}$. In this series the values of $\Delta \nu (={\nu }_{26}-{\nu }_{24})$ seem to converge to a value of about 0.068 ${\mathrm{cm}}^{-1\mathrm{}}$ rather than the value 0.056 ${\mathrm{cm}}^{-1\mathrm{}}$ obtained by Meissner. The isotopic shifts of the members $m=5\mathrm{}$ and $m=6\mathrm{}$ of the series $3{}_{}{}^1{}_{}{}^{}P-m{}_{}{}^1{}_{}{}^{}S$ have been measured. The results obtained are discussed in connection with the theoretical work of Vinti, who assumed the splitting to be solely a mass effect. The experimental and theoretical values of $\Delta \nu$ agree in sign, but the former are usually larger by a factor of about two. The $3{}_{}{}^2{}_{}{}^{}D-4\mathrm{}{}_{}{}^2{}_{}{}^{}F$ doublet of Mg II at 4481A has been measured very carefully and the separation of the two components found to be 1.000±0.002 ${\mathrm{cm}}^{-1\mathrm{}}$.