High-frequency electron paramagnetic resonance spectra were studied which corresponded to magnetic dipole transitions between the doublet-singlet-doublet group of the lowest crystal-field levels of the trigonal single ion, and symmetrical dimer centers. In the case of the dimer center, the absorption spectra in the manifold of the lowest 1024 electron-nuclear states were simulated by successive diagonalization of the electron-nuclear Hamiltonian. The latter included the crystal field, the electronic Zeeman energies, the magnetic and quadrupole hyperfine interactions and dipole–dipole interactions between the paramagnetic ions. The crystal-field parameters of Ho3+ ions in the symmetrical dimer were determined.

Submillimeter EPR Spectroscopy of Lanthanide Compounds - Pair Centers of Ho3+ in CsCdBr3. B.Z.Malkin, A.I.Iskhakova, V.F.Tarasov, G.S.Shakurov, J.Heber, M.Altwein: Journal of Alloys and Compounds, 1998, 275-277, 209-13