The hyperfine structure of the Zeeman components of the resonance lines of sodium

Abstract

The existence of a nuclear spin, which is responsible for the hyperfine structure of spectral lines, also causes the components of the Zeeman pattern to have a hyperfine structure of a similar width of splitting. In order to find the value I of the nuclear spin from the normal hyperfine structure, accurate measurements of intensity ratios or interval ratios are in general necessary. The magnetic hyperfine structure however yields the value of I in a more direct and certain way. In a sufficiently strong field, each Zeeman component consists of 2I+1 hyperfine structure lines of fairly uniform spacings and intensities. It it is possible to resolve this structure, the value of the nuclear spin can be established with absolute certainty from the number of lines. It the magnetic field is decreased, the relative position of this hyperfine structure lines changes, as a result of the change in the relative coupling between the field and the angular moments J and I of the electrons and of the nucleus. Quantum mechanics gives a complete quantitative description of this change of the pattern in intermediate fields.