Study of microscopic structure via NMR diffusive scattering

Abstract

Scattering experiments can be carried out by gradient nuclear magnetic resonance(NMR) methods. Magnetic field gradient pulses are utilized to create linear phase ramps of the spin magnetization across the sample along arbitrary directions. The linear phase ramps are defined as dynamic spin magnetization gratings. The measurement of the grating after it undergoes dynamic processes characterized by the local struc­ture leads to the measurement of the average phase changes over the whole sample, ..., a quantity denoted as intermediate scattering function. NMR scattering are measured in spatial and temporal window to sub-microns to tens of micros and milliseconds to a few seconds. In a time scale when spin displacements are larger than the spatial scale of local structure, NMR experiments directly measure the elastic incoherent structure function (EISF) ... powder. The direct control of scattering vector q in NMR scattering enables easy per­formance of multiple scattering experiments. The double scattering experiments, as examples of multiple scattering, lead to the measurement of structure factors ... powder. The latter correlates local struc­tural characteristics along directions that are normal to each other. Anisotropic information in a glassy sample can be determined without the presumptive models which are required in one dimensional or traditional scattering techniques. This thesis work includes detailed derivation of the theory of NMR double scattering, an experiment that can only be performed by NMR. The eccentricity information can be extracted by the differences of scattering curves from double scattering along one axis and along two orthogonal axes. The experiments are carried out for abnormally long yeast cells. The experimental results show good agreement with calculations where the yeast cell shape was approximated as prolate ellipsoids.