LSU Historical Dissertations and Theses

1994

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chemistry

Leslie G. Butler

Abstract

Solution-state nuclear magnetic resonance (NMR) of $\sp1$H and $\sp{13}$C nuclei in molecular species is very common as is solid-state NMR of $\sp{13}$C in a wide variety of substances. Yet many nuclei remain little studied by conventional NMR techniques, for example $\sp2$H, $\sp{11}$B, $\sp{14}$N, $\sp{79}$Br, $\sp{81}$Br, and $\sp{93}$Nb. One method for their study is nuclear quadrupole resonance (NQR). Briefly, the reason that quadrupolar nuclei are difficult to study with conventional NMR techniques is the exceedingly large line widths these nuclei exhibit in high magnetic fields. The first part of my dissertation deals with NQR spectroscopic techniques developed to obtain structural information on solids using three different line narrowing techniques: (1) The results of field swept $\sp{93}$Nb NMR experiments of $\rm BaNb\sb{X}S\sb3$ (x = 0.8,1) are presented with the Oxford 16/18 Tesla superconducting magnet at 4.2 K. (2) The development of a broadband NQR spectrometer having very wide spectral range from 200 to 300 MHz with automatic frequency selection and a novel automatically-tuned probe and the results of $\sp{79}$Br and $\sp{81}$Br NQR of some brominated aromatic compounds are discussed. (3) The development of a field cycling NQR spectrometer based on a conventional NMR, a high speed linear stepping motor, and an Oxford gas flow cryostat is described with some $\sp2$H and $\sp{14}$N NQR spectra. The second part of my dissertation describes novel $\sp{11}$B and $\sp{14}$N NQR imaging techniques that use field cycling as a line narrowing technique and therefore, is a combination of both NQR spectroscopy and NMR imaging. A demonstration of two-dimensional $\sp1$H imaging using an unmodified solution-state NMR spectrometer is also presented.

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