ABSTRACT
For many organic molecules the g-factor of the excited triplet state is almost isotropic and close to that of the free electron. However a large splitting of the first-order (∆MS = ±l) EPR spectrum is common. This doublet, due to dipolar interactions between the unpaired electron spins, is strongly anisotropic leading to very broad EPR transitions in nonoriented samples. The splitting is present even in the absence of an applied external magnetic field.
