Figure 45.

Schematic RF irradiation schemes employed to record ¹H–¹H (a–c) or ¹³C–¹³C proximities (d) with ¹H detection. The asymmetric schemes (a) and (b) employ a heteronuclear (X) chemical shift evolution period before and after ¹H recoupling, respectively. Panel (c) shows an extended version with two heteronuclear (X) indirect dimensions, optionally augmented to a 4D experiment with a supplementary indirect ¹H evolution of the spin of origin. The RF diagram (d) is used to record heteronuclear distances via second-order recoupling.