Theory of NMR in the molecular ring Fe10

The proton nuclear spin-lattice relaxation rate in the molecular ring Fe10 is calculated by linear response theory, starting from the unperturbed eige nvalues and eigenvectors, and introducing dipolar superhyperfine interactio ns as a perturbation. A strong enhancement of the rate at critical values o f the applied magnetic field, recently observed by solid-state NMR at low t emperatures, is explained in terms of level crossing between states with \D eltaS\ = 1 and \DeltaM\ = 1. (C) 2001 Elsevier Science B.V. All rights rese rved.