Isotope Shifts in the Atomic Spectrum of Calcium

The isotope shift in several spectral lines of 40 Ca and 48 Ca has been measured. A triplet of the arc spectrum shows a specific mass effect a little larger than the normal mass effect and in the opposite direction. In the resonance line and a doublet of the spark spectrum the specific mass shift is very small and in the same direction as the normal shift. Comparison with analogous transitions in magnesium indicates that the specific mass effect shows a similar behaviour in both elements.