MEASUREMENT OF COMPLEX RF SUSCEPTIBILITY USING A SERIES Q-METER

In this paper we have for the first time derived closed form expressio ns for the nuclear magnetic susceptibility in terms of the series Q-me ter output voltage. We discuss the corrections involved in determining nuclear polarization from NMR signals by using the deuteron and proto n spin systems as examples. Deuteron signals are shown to exhibit a fa lse asymmetry, while proton signals have substantial shape distortions . Moreover, for the first time the importance of making a phase correc tion is demonstrated. We conclude that the series Q-meter with real pa rt detection is not sufficient to produce an output voltage from which the nuclear susceptibility can be determined. An additional phase-sen sitive detector is proposed for obtaining the imaginary part of the si gnal required for unambiguous extraction of the complex RF susceptibil ity.