Schnell I, Lupulescu A, Hafner S, Demco D E, Spiess H W
Max-Planck-Institut für Polymerforschung, Mainz, D-55021, Germany.
J Magn Reson. 1998 Jul;133(1):61-9. doi: 10.1006/jmre.1998.1432.
Two techniques for resolution and sensitivity enhancement are introduced in multiple-quantum (MQ) MAS spectroscopy of rigid solids. The first makes use of ultrafast MAS with spinning frequencies of up to 35 kHz, while the second combines MAS at moderately fast spinning frequencies of about 13 kHz with multiple-pulse (MP) dipolar decoupling. For the latter approach, a semiwindowless WHH-4 sequence is applied during the MQ evolution period (MQ dimension) and/or detection period (single-quantum dimension). In the MQ dimension, the MP sequence has to be supplemented by two bracketing pulses in order to preserve the order and the intensities of the evolving MQ coherences. Double-quantum 1H NMR spectra of l-alanine recorded using both decoupling techniques are shown and compared to each other. Triple-quantum 1H NMR spectra under ultrafast MAS conditions are also presented.
在刚性固体的多量子（MQ）MAS光谱中引入了两种提高分辨率和灵敏度的技术。第一种技术利用高达35 kHz的自旋频率的超快MAS，而第二种技术则将约13 kHz的适度快速自旋频率的MAS与多脉冲（MP）偶极去耦相结合。对于后一种方法，在MQ演化期（MQ维度）和/或检测期（单量子维度）应用半无窗WHH-4序列。在MQ维度中，MP序列必须由两个括号脉冲补充，以保持演化的MQ相干性的顺序和强度。展示了使用两种去耦技术记录的L-丙氨酸的双量子1H NMR光谱，并进行了相互比较。还给出了超快MAS条件下的三量子1H NMR光谱。
