魔角的准确快速确定

慢旋转条件下,四极相互作用产生的FID分解为一系列旋转回波。当旋转轴向与外磁场方向夹角趋近于魔角时,观测到的回波数增加。由此,可在MAS-NMR实验中准确、迅速地确定魔角。本文分析了自旋为1的核的FID解析式,理论上解释了这一现象。以氘代HMB为例的实验证明确定魔角的准确度可达到±0.05°的数量级。 关键词：

ACCURATE AND QUICK SETTING OF MAGIC ANGLE

The FID arising from the quadrupole interaction is broken into a rotational echo train under the slow rotation condition, and the number of these echoes increases when adjusting the angle between the rotational axis and the applied magnetic field towards the Magic Angle. Thus, a accurate and quick setting of the Magic Angle in MAS-NMR experiments can he easily obtained by this phenomenon. It is theoretically explained by analysing the FID of a spin-1 system. The setting accuracy within 0.05°with a per-deuterated HMB sample is experimentally demonstrated.