Half-integer Quadrupole Nuclear System Quadrupole Tensor Relative Orientation Of Measurement

The aim of this thesis is to investigate the application of multi-quantummagic-angle spinning (MQMAS) technique to the measurement of the relativeorientation of a pair of electric field gradient (EFG) tensors of two half-integerquadrupolar nuclei spins.This information of relative orientation of two EFG tensors, normally described bythree Euler angles, may be extracted from the cross peaks of a spin exchange/diffusion spectrum by numerically simulating the experimental spectrum. The spinexchange/diffusion between two quadrupolar spins can be facilitated either by directdipolar interaction or by their common coupling partners (protons in many cases). Thetheoretical analysis, simulation programs and experimental verification related to thispurpose have been completed. The major conclusions are: (1) The strengths of thethree RF pulses have much less pronounced effect than spinning speed as long as theRF field is not too weak (～tens of kilohertz), suggesting that the principal factor thataffects the lineshape of the cross peaks (hence the precision of relative orientation ofthe EFG tensors) is the sample spinning speed; (2) When the spinning speed is verylow, overlap of sidebands and the cross peaks may occur that complicates thelineshape and simulation; (3) The spin exchange/diffusion can be enhanced byintroducing recoupling pulses during the mixing period.