The signal 1C shifts more pronouncedly in field, from 1083 cm -1 at 0 T to 1091 cm -1 at 14 T, (Fig. ), and therefore differs markedly from the Raman bands at lower energy. According to the computations, excitations to the M = ± 3 2 components of the excited quartet state are expected in this region. The corresponding ground quartet M = - 2 → excited quartet M = -3 2 transition is spin conserving and can thus couple to the electric field of the incident radiation. We thus conclude that the signal 1C is a purely electronic transition. The blue shift of this band indicates a smaller magnetic moment of the excited M = -3/2 state, which is in line with the predicted magnetic moments of these states in the ab initio calculations. The band can be simulated satisfactorily without assuming any additional coupling to phonons (Fig. ). The observation of the three signals 1A-1C not only corroborates our extended model of two strongly coupled quartet states, eq. 3, it also allows extracting the essential parameters for this model from experiment, see Table . In particular, the energetic splitting of the initial quartet states is ∆ = 500 cm -1 and the strength of the spin-orbit coupling is γ = 322 cm -1 , in good agreement with the theoretically predicted values.