Hyperfine structure and Zeeman-effect of the resonance lines of lithium

Hyperfine structures have now been found and investigated in the resonance lines of all alkali metals except lithium. The low atomic weight of this element causes a relatively great Doppler width of the lines and very narrow hyperfine structures so that even with a cooled hollow-cathode tube the width of the lines is many times greater than the hyperfine structure. The structure of the resonance line 6708 A revealed by this light-source is due to the multiplet splitting and isotope shift (Schüler and Wurm 1927); it consists of two strong lines and one weak line, as shown in figure 1.