固体中半整数四极核的自旋扩散

SPIN DIFFUSION OF HALF-INTEGER QUADRUPOLAR SPINS IN SOLIDS

首先介绍固态中自旋扩散的一般理论,包括半经典描述和建立在投影算子理论上的密度矩阵描述。接着以丰核环境中相互偶合的自旋-1/2系统以及自旋-3/2系统为典型列举了自旋扩散速率的计算。最近藉助多量子魔角旋转(MQMAS)方法实现半整数四极核的多量子谱自旋扩散实验,可以测量固体粉末中半整数四极核体系四极张量相对方向,结合作者最近的计算机模拟和实验测量结果对这一新兴方向作了重点介绍,尤其指出了射频脉冲强度、宽度及样品旋转速度对交叉峰线型的影响。

This review first summarizes the general theory of spin diffusion in solids, including semi-classical description and the more exact approach, i. e., density matrix method based on projection operator formalism. The calculation of spin diffusion rate is demonstrated with two typical cases: a spin-1/2 pair and the central transition of a spin3/2 pair. The analysis of spectral spin diffusion of half-integer quadrupolar spins is emphasized, highlighting the influence of pulse strength, width as well as sample spinning speed.