Theory of Nuclear Magnetic Resonance 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 eigenvalues and eigenvectors, and introducing dipolar superhyperfine interactions as a perturbation. A strong enhancement of the rate at critical values of the applied magnetic field, recently observed by solid-state NMR at low temperatures, is explained in terms of level crossing between states with \DeltaS\ = 1 and \DeltaM\ = 1.