Electron Spin Resonance Caused by Iron Proteins

ELECTRON SPIN RESONANCE CAUSED BY IRON PROTEINS 2.L Introduction 

In an ESR spectrometer, the sample is placed inside a microwave cavity designed to resonate at a frequency of either about 10 GHz (X band) 

It is found ions in crystals and complexes that the interaction between the magnetic field and the paramagnetic spin is generally anisotropic. To allow for anisotropy a tensor, g, is introduced so that the interaction or spin Hamiltonian takes the form 

The angular variation of the spectrum is described by the familiar relation 

Powder spectra, on the other hand, may be analyzed using computer simulation techniques to yield the principal g values, but structural relationships can only be inferred on the basis of the other evidence. The line widths of the observed spectra are related to relaxation effects which will be discussed later. 

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