Figure 39.

Sequences employed to recouple ¹H–¹H dipolar interactions at the first (a,b) and second order of AHT (c,d). (a) Finite-pulse RFDR with xy8 phase cycling, a versatile scheme applied for a variety of conditions for broadband ¹H–¹H mixing, also in fully protonated samples. (b) DREAM mixing for selective recoupling within amide or methyl protons. (c,d) Sequences designed to enhance ¹H spin-diffusion through (c) ¹H spin-lock field (rotating-frame spin-diffusion) or (d) optimized RF irradiation of the X-nucleus (e.g., ¹⁵N), which affects (broadens) the ZQ linewidth of a coupled (bonded) proton. All schemes except AM-MIRROR use only ¹H RF irradiation. The spin operator (either polarization ¹H_z or transverse magnetization ¹H_xy) at the start of the mixing period is indicated.