Spin-lattice and spin-spin relaxation of 29Si via paramagnetic centers in the MAS NMR of zeolites

Abstract

The ²⁹Si nuclear spin-lattice (T₁) and spin-spin relaxation (T₂) decays have been measured using the magic angle spinning (MAS) technique in zeolite-Y with varying amounts of Fe³⁺. Analysis of T₁ data shows that the ²⁹Si nuclei are dipolar-coupled to paramagnetic centres and the observed non-exponential decay of the 29Si spin magnetisation can be satisfactorily explained by a suitable theory. The ²⁹Si transverse magnetisation, on the other hand, is both homogeneously and in homogeneously broadened by the presence of Fe³⁺ centers.