Atom-molecule complexes anisotropic interactions

An important EPR parameter, hyperfine coupling constant. A, is required to describe the hyperfine interaction. The A values can be obtained directly from EPR spectra when equally spaced spectral lines are exhibited because of the hyperfine interactions (Fig. 3). In many cases, a matrix, known as A-tensor, is required to describe the A values for a more complex anisotropic system. Because of the hyperfine interaction, EPR is very sensitive to the local surroundings. From a chemical standpoint, this property provides a wealth of information such as the identity and number of atoms that makes up a molecule or complex and their distances from the unpaired electron. This information can often be translated, in favorable cases, into the molecular structure of the sample. 

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