Magnitude of the Splitting of the Lowest Level in Chromium Alum

This note contains the results of a recalculation of the lowest energy levels of the chromium ion in chromium potassium alum. After diagonalization of the Hamiltonian of the electric field, the spin-orbit coupling is introduced and the spin Hamiltonian of the lowest level calculated by a formal method. The numerical value differs from those published previously. The result is a different value for the parameter a (radial average of the cylindrical field).