General Aspects on Static Quadrupole Effects of Mesomorphous Systems

General Aspects on Static Quadrupole Effects of Mesomorphous Systems 

Here eq denotes the largest component of the electric field gradient tensor and eQ the quadrupole moment. 0 is the angle between the field gradient and the magnetic field. A second-order perturbation treatment of the quadrupole interaction shows the central line to be shifted. 

For a polycrystalline or powder sample where all directions of the field gradient are equally probable NMR absorption takes place over a wide range. The resulting so-called powder pattern is depicted in Fig. 7.2(a). The frequency separation between adjacent peaks is given by 

The powder pattern of the central component affected by second-order quadrupole effects is shown in Fig. 7.2(b). 

NMR studies of partial orientation of molecules or ions in liquid crystals are being increasingly applied to obtain information on, for example, molecular geometry and electric field gradients. Useful introductions to this field of research are given in articles by Buckingham and McLauchlan [Z94]f by Diehl and co-workers [895 504] and by Luck-hurst [ 96], Here we will follow the treatment of Ref. [327]. 

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