EPR investigation of atoms in chemical traps Original Research Article

By performing high-resolution EPR and ENDOR experiments on nitrogen atoms encapsulated in C60, the capability of the quartet spin system to sense small local fields at the site of the atom is demonstrated. Such symmetry lowering can either be induced by chemical modification of the cage or by a phase transition in polycrystalline C60. Additional line splittings in the EPR spectrum indicate the presence of a non-vanishing zero-field-splitting. Freezing of cage rotation can be observed via the magnetic dipole interaction with 13C nuclei of the carbon shell resulting in broadening of ENDOR transitions. Fluctuating magnetic fields originating from additional paramagnetic species in solution can also be detected by their influence on the spin relaxation times.