The broad and featureless spectrum of a solid sample in a static experiment can be improved by spinning it at moderately high frequencies in a MAS experiment. A demonstration of this can be seen in Figure for the three unaged samples of cross-linked NR, SBR, and the 50/50 blend, one-dimensional spectra of which are obtained after Fourier transformation of the respective FIDs following a 90° pulse. Thus, MAS yields high-resolution spectra for phase-specific studies. The cross-link densities in this case can be measured by obtaining build-up curves in a 2D fashion using the BaBa-xy16 pulse sequence. Like the static MQ experiment discussed earlier, this DQ MAS experiment yields the typical IDQ and Iref signals, which can be obtained by taking one-dimensional projections of every two-dimensional resonance peak of interest. The rotorsynchronized pulse sequence facilitates obtaining of points at every rotor period. However, for these studies, signals at every even multiple of the rotor period were measured.