The effect of spin-orbit coupling on the usual band theory of electrons in a lattice is considered. Particular attention is given to the bands in impurity semiconductors with diamond-type structure. $g$-values are calculated for electron states typical of various possible cases and it is found that different values are obtained according as to whether the Fermi level is near or distant from a band degeneracy. The spin-lattice relaxation time is calculated so that the effect of spin-orbit coupling on the wave functions is included, and times in fair agreement with those observed in silicon and alkali metals are obtained.

• Received 26 May 1954

DOI:https://doi.org/10.1103/PhysRev.96.266