Electronic Zeeman interaction high-spin systems

The ESR signal is highly dependent on the nature of the local environment about the absorbing electron that is, the position of the ESR signal and the overall ESR spectral pattern depend on the environment conditions in the vicinity of the electron. The most important types of interactions in the spin system that affect the position and pattern of the ESR spectrum are the electron Zeeman, nuclear hyperfine, and ligand superhyperfine interactions (Wertz and Bolton, 1972). 

Spins are magnetic moments that are associated with angular momentum they interact with external magnetic fields (Zeeman interaction) and with each other (couplings). In most cases, the Zeeman interaction of the electron spin is the largest interaction in the spin system (high-field limit). The electron Zeeman (EZ) interaction can generally be described by the Hamiltonian below. 

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