 Zeeman spacing of a single f electron

For a free ion with one $f$ electron in its weak-field ground multiplet, $L=3,S=1/2,J=5/2$ and $g_J=6/7$. The six magnetic substates have adjacent spacing $g_J{\mu }_{B}B$ and full spread $5g_J{\mu }_{B}B$. A crystal field can change the applicable effective low-energy description.