Indirect NMR detection in solids with multiple cross-polarization periods

The use of indirect detection for signal enhancement in solids is much less common than in liquids, but has attracted renewed interest recently. In th is work we describe an indirect detection scheme that offers a large signal enhancement for rare spins in solids. The method uses multiple periods of cross polarization, each followed by an evolution period. The latter is inc reased stepwise in a pseudo 2D experiment, in which the signal of the rare spin is detected as modulation of the abundant spin. As an illustration of this method, the natural abundance deuterium NMR spectrum of a static powde r sample of 1,2,4,5-tetramethylbenzene is presented. (C) 2001 Academic Pres s.