ABSTRACT
This chapter introduces concepts of homonuclear multidimensional nuclear magnetic resonance (NMR). Two schemes have been derived that permit quadrature detection in indirectly detected dimensions in multidimensional NMR. The first is often called "States", which requires that two experiments be performed at each increment of t1 in order to generate the imaginary part of the data for phasing. An alternative scheme for obtaining quadrature detection in multidimensional NMR is called time-proportional phase incrementation (TPPI). For TPPI quadrature detection of a single-quantum coherence, a p/2 rad shift is applied to the phase of the pulse preceding (or immediately following) the t1 evolution period. Using the operator approach, the chapter shows that coupling evolution of an operator is unaffected by homonuclear nonselective p pulses while the sense of chemical shift evolution is reversed. In recent years, advances in NMR hardware have made it possible to select particular orders of coherence without phase cycling via the application of pulsed-field gradients (PFGs).
