On the Nuclear Magnetic Resonance in Metals and Alloys
HARVARD UNIV CAMBRIDGE MA CRUFT LAB
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A Pound-Knight-Watkins type of RF spectrometer Rev. Sci. Instr. 21219, 1950 was used in measuring the shift of nuclear resonance and the line width in alpha- and beta-Sn, Th, Pb, and several alloys. A permanent magnet with a field of about 6000 gauss in a 1.25-in. gap and with 4-in.-diam pole faces was also used. A few measurements were made with an electromagnet at fields between 2000 and 5500 gauss. The samples were made from powdered metals suspended in mineral oil. Gray Sn showed no shift relative to the resonance in insulating compounds, but white Sn had an anisotropic shift of 0.79 along the tetragonal axis and 0.74 perpendicular to it. A theory is given for the anisotropy and asymmetry of the observed line. Thallium had an anomalously broad resonance line with a shift of 1.54. The shift in Th alloys varied continuously with composition in each phase and had discontinuities when phase transitions occurred. The intensity of the Cu resonance in pure Cu was increased by annealing and decreased by cold work. The intensity in alloys such as alpha- brass and Cu-Ag decreased rapidly with increasing Zn or Ag content. These effects are explained in terms of quadrupole interaction.
- Atomic and Molecular Physics and Spectroscopy