Ultra-wideline solid-state NMR: developments and applications of the WCPMG experiment

© Springer International Publishing AG, part of Springer Nature 2018. Large anisotropic interactions can lead to solid-state NMR powder patterns that exceed the excitation and detection bandwidths of standard NMR techniques and hardware. By combining the advantages of broadband, frequency-sweptWURST pulses with CPMG signal enhancement achieved through the continuous refocusing of the transverse magnetization, the WCPMG experiment and its derivatives are the most efficient way to acquire these so-called ultra-wideline NMR spectra. This chapter describes the WCPMG pulse sequence and outlines several related developments including broadband cross polarization, dynamic nuclear polarization, and relaxation-based resolution enhancement methods. A number of example applications of the WCPMG experiment to study spin-half, half-integer quadrupolar, and integer spin quadrupolar nuclei in a variety of materials are then summarized.