External magnetic field ligand

Consideration of the spin-orbit interaction and the effect of an external magnetic field on the electronic ground state of an ion in a CF allows evaluation of the various terms in the spin-Hamiltonian of Equation (31). In addition, the interaction of the nucleus of the paramagnetic ion and ligand nuclei with the d-electron cloud must be considered. In this way the experimentally determined terms of the spin-Hamiltonian may be related to such parameters as the energy differences between levels of the ion in the CF and amount of charge transfer between d-electrons and ligands. 

This interaction, which does not depend on the orientation of the molecule with respect to the external magnetic field, gives valuable information on the local structure, such as for example the bond strength and geometry of hydrogen bonds to the radical or on the covalency of metal ligand bonds. 

The splitting of the 2 7 + 1 snblevels enclosed in a spectroscopic level requires either a ligand field, which may partly break the degeneracy, or an external magnetic field in one direction, which completely breaks the degeneracy. 

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