EPR investigation of atoms in chemical traps

By performing high-resolution EPR and ENDOR experiments on nitrogen atoms e ncapsulated in C-60, the capability of the quartet spin system to sense sma ll local fields at the site of the atom is demonstrated. Such symmetry lowe ring can either be induced by chemical modification of the cage or by a pha se transition in polycrystalline C-60. Additional line splittings in the EP R spectrum indicate the presence of a non-vanishing zero-field-splitting Fr eezing of cage rotation can be observed via the magnetic dipole interaction with C-13 nuclei of the carbon shell resulting in broadening of ENDOR tran sitions. Fluctuating magnetic fields originating from additional paramagnet ic species in solution can also be detected by their influence on the spin relaxation times. (C) 2000 Elsevier Science Ltd. All rights reserved.