We report Zeeman infra-red spectroscopy of electronic-nuclear levels 5I8 →5I7 transitions Ho3+ in the C4v(F−) centre CaF2 with magnetic field along ⟨111⟩ direction crystal. Transitions to lowest 5I7 state, an isolated electronic doublet, and next group states, a pseudo-quadruplet consisting doublet two nearby singlets, exhibit strongly non-linear splittings intensity variations. Simulated spect...
