Experimental Methods

Abstract

In this chapter, we briefly discuss a few basic experimental methods that have become standard in the arsenal of the NMR spectroscopist. First, we focus on the need to determine the signs of frequencies in the rotating frame and point out how this is achieved in practice with the suppression of the attendant errors. The effects of pulse errors are then mentioned, starting with rf inhomogeneity problems in line-narrowing and cross-polarization studies on solids. The composite pulse approach to surmounting the problem of pulse imperfections is dealt with in the context of specific applications, including coherence transfer experiments, broadband spin inversion in liquids and solids, broadband excitation of quadrupolar spin-1 nuclei in solids, and heteronuclear broadband decoupling in liquids. Finally, “retrograde” compensation schemes are mentioned in the context of depth resolution by accentuating B₁ inhomogeneity in surface coil imaging applications.