A simple model for heteronuclear spin decoupling in solid-state NMR

We propose a simple model to describe heteronuclear spin decoupling in solid−state NMR under magic−angle sample spinning (MAS). It is based on a coherent description of two heteronuclear dipolar−coupled spins (I and S) and an incoherent description of the interaction of the I−spin with a large number of other I−spins. The abundant and strongly coupled I−spins are irradiated. The selected I−spin is coupled by a spin−diffusion type superoperator to the I−spin bath, and this coupling is described by a single spin−diffusion rate constant. Such a model allows us to simulate efficiently the behavior of a spin system under heteronuclear decoupling in the case of CW irradiation as well as in the case of phase−modulated sequences such as TPP