By making use of an atomic beam instead of an ordinary gas or vapour, it is possible to observe structures of spectral lines very much smaller than the normal Doppler width. The structure of resonance lines can thus be observed as fine absorption lines on the background of the emission line possessing the full Doppler width. This method was used by the present authors for the detection and measurement of the hyperfine structure of the resonance lines of potassium and sodium. The following paper gives an account of the investigation of the structure of the singlet resonance line (2852 A) of magnesium by the same method. The line was found to possess two components at a separation of 0.033 cm
-1
, the component of longer wave-length being very much stronger than the other.
Isotope shift and hyperfine structure of stable platinum isotopes
