Intraradical Interactions

The intraradical interactions provide the mechanism for coherent spin-state mixing and the interradical interactions act contrary to this process. 

The spin state of a given radical is commonly and simply described by a spin vector operator 

Where i, j, and k are unit vectors along the x, y, and z directions. The expectation value of this operator is the electron spin magnetization vector, which describes the bulk electron spin state for a given radical. 

MAGNETIC FIELD EFFECTS ON RADICAL PAIRS IN HOMOGENEOUS SOLUTION 

Unlike a free electron, an electron in a molecule also experiences a complex interaction between spin and orbital angular momentum, spin-orbit coupling. These interactions are described in terms of a tensor, EPR spectroscopy is 

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RP reactions have been found to be well described by the application of a spin Hamiltonian, " a common approach used in the field of magnetic resonance, which reduces the full Hamiltonian to one that contains only spin-dependent terms. The interactions capable of influencing spin-state mixing processes in RPs are concisely introduced in the expression for the spin Hamiltonian of a RP, which can be written as a sum of interradical, intraradical, and external interactions. 

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