Multiple quantum filtering and spin exchange in solid state nuclear magnetic resonance

Multiple quantum NMR of coupled spin-$\text{1/2}$ nuclei in a solid has been exploited as a filter to separate different magnetization components in a spatially heterogeneous system. After filtering, the spins labeled according to coherence orders were used to follow the track of spin exchange between different domains. In order to avoid time-consuming two-dimensional experiments, this exchange was detected in a one-dimensional experiment via selective detection of multiple quantum coherences. The technique was demonstrated for samples of solid adamantane in contact with its saturated solution in benzene-$d_6$ and for a high-density polyoxymethylene.