Nuclear spin dynamics and thermodynamics of pulsed NMR in solids

Citation

Burum, Douglas Peter (1979) Nuclear spin dynamics and thermodynamics of pulsed NMR in solids. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/MF8E-RD37. https://resolver.caltech.edu/CaltechETD:etd-04302007-153624

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The investigations presented in this thesis deal with two basic topics of solid state NMR: coherent averaging of nuclear spin interactions by rf irradiation, and the application of thermodynamics in strongly time dependent interaction frames. In each case new theoretical insights are presented, and these lead to the development of new experiments. After a general introduction, an extension of coherent averaging theory called the principle of pulse cycle decoupling is presented. This principle greatly facilitates the design and analysis of compound experiments, i.e. techniques which are combinations of several smaller experiments. A number of multiple pulse experiments are analyzed using pulse cycle decoupling and several new techniques are introduced, including 24-pulse and 52-pulse cycles which have a greater ability to resolve anisotropic chemical shifts in solids than any experiment previously developed. The 52-pulse cycle is used to measure proton chemical shift spectra for polycrystalline ice, C6H12, C5H10 and polyethylene. This new technique is also used to study proton chemical shifts in single crystals of gypsum, [...]. The second topic considered in this thesis is the application of thermodynamics to NMR experiments in which the amplitude of the applied rf irradiation is varied in a strongly non-adiabatic fashion. Sources of artificial spin heating are analyzed and methods of eliminating these effects are demonstrated. A calculation is presented of the spin-lattice relaxation time during one basic type of multiple pulse irradiation. Techniques based on this calculation are introduced which measure relaxation times in the laboratory frame, [...], and the rotating frame, [...]. A method for determining the first moment of an NTIR spectrum is also developed. These new techniques are demonstrated using a variety of materials, including CaF2 and C6F6. A simple yet highly flexible pulse sequence generator which is capable of producing all the pulse sequences described in this thesis as well as many more complicated experiments is described in the Appendix.

Thesis Files