A method is proposed for determination of the number of nuclei contributing to a particular line in a resonance spectrum. The method exploits the maximum signal-to-noise (S/N) ratio of which the system is capable and is based on an examination of the saturation properties of the absorption line. This provides an advantage over methods which measure simply the integrated intensities and which are correct only at low rf power levels, where the S/N ratio is correspondingly low. The procedure is successfully applied to some pure metal spectra.
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4.
From a practical viewpoint the problem of the frequency dependence of Q (defined as ωL/R) arises only in cases where the frequency is varied over a large percentage of its absolute value, e.g., in resonance experiments in ferromagnetic materials. There is not complete agreement in the literature on this question. Reference 5 maintains that at very high frequencies (presumably >2 MHz) in addition to skin effect there are dielectric losses which give rise to a resistance in series with the coil that is proportional to ω3, thus causing Q to decrease at high frequencies. On the other hand, Ref. 1 takes Q ∝ ω1/2. In the absence of experimental data on a particular coil we favor treating Q as independent of frequency.
5.
TermanF. E., Electronic and Radio Engineering (McGraw–Hill, New York, 1955), p. 30 ff.
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