We investigated the magnetooptical properties of 0.9 eV luminescence in AlN. The zero-phonon lines at 0.943 eV in AlN are attributed to a transition within ad2configuration because of a characteristic threefold ground-state splitting in magnetic fields. We determine agvalue of1.96±0.07and a zero-field splitting of120±30 &mgr;eVfor the3A2(F)ground state. On the basis of the temperature dependence in a magnetic field, we attribute the 0.943 eV zero-phonon line in AlN to the1E(D)–3A2(F)transition of isolatedV3+.The different fine structures of the excited state in AlN and GaN are explained in a Tanabe–Sugano diagram. ©1997 American Institute of Physics.