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|Title:||Applications of Nuclear Quadrupole Double Resonance Spectroscopy|
|Author(s):||Butler, Leslie Gordon|
|Department / Program:||Chemistry|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Nuclear quadrupole double resonance (NQR) spectroscopy can yield direct information about the nature of chemical bonding at a particular quadrupolar nucleus (S (GREATERTHEQ) 1) in a molecular crystal. However, due to experimental difficulties related to the low transition frequencies generally associated with the light nuclei (D, ('10)B, ('11)B, ('14)N, and ('17)O) and, in the case of ('17)O, the low natural abundance, the contribution of NQR spectroscopy to our understanding of chemical bonding has been small. Only recently have nuclear quadrupole double resonance techniques been developed to facilitate observation of NQR spectra of the light elements.
A new instrument was constructed which employs the established technique of nuclear quadrupole double resonance by adiabatic demagnetization in the laboratory frame (ADLF). By this technique, NQR spectra in zero applied magnetic field can be obtained from 500 mg or less of polycrystalline material. Several instrumental functions are under computer control, resulting in nearly total automatic operation. In addition, variable temperature operation in the range of 20-300 K is also feasible.
NQR spectroscopy provides information about the electric field gradient about a quadrupolar nuclei. Since the elements of the electric field gradient tensor are determined by the electric charge distribution in the molecule, details of chemical bonding can be obtained. In this work, D and ('17)O NQR spectra were obtained on a wide variety of inter- and intramolecular hydrogen bonds. The experimentally obtained electric field gradient parameters were interpreted by a theoretical analysis of the formaldehyde-water hydrogen bonding interaction. Large changes in the electric field gradient parameters were observed at the deuterium and oxygen sites.
The first complete NQR spectrum for an S = 3 spin system, ('10)B, has been obtained from a study of boric acid. Techniques developed in this work have been applied to the study of the ('10)B and ('11)B NQR of decaborane(14) and ortho-carborane.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
|Date Available in IDEALS:||2014-12-13|