CW Transmission Spectrometer for Direct Detection of Nuclear Acoustic Resonance Utilizing Magnetic Field or Frequency Modulation

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Abstract
A continuous wave transmission spectrometer operating in the radio frequency range has been developed for direct detection of nuclear acoustic resonance (NAR) in solids. The inherent flexibility of a spectrometer of this type makes possible studies over a wider range of frequencies and ultrasonic powers than is attainable by the more conventional marginal oscillator acoustic spectrometer. With the transmission spectrometer one can observe both absorption and dispersion of acoustic waves, while with the marginal oscillator one is limited to NAR absorption only. An additional feature is the ease of operation of the transmission spectrometer as compared to the marginal oscillator technique. Both magnetic field and frequency modulation have been used with the transmission spectrometer. Certain advantages of frequency modulation, especially with respect to investigations in bulk conductors, are cited.