Efficiency of heteronuclear dipolar decoupling schemes in solid-state NMR: investigation of effective transverse relaxation times.

We here compare the T(2)(') values of various heteronuclear dipolar decoupling schemes commonly used in solid-state nuclear magnetic resonance experiments. Swept-frequency two-pulse phase modulation scheme is shown to give longer T(2)(') values for the majority of the magic-angle-spinning frequencies and radiofrequency amplitudes considered here. The longer T(2)(') values obtained are shown to yield spectra with higher resolution in experiments, such as INADEQUATE, which incorporate spin-echo blocks. Such blocks normally constitute the indirect dimension of a multidimensional experiment during which heteronuclear dipolar decoupling is applied, thereby making the relevance of T(2)(') manifest clearly. Experimental results are shown on samples of glycine, alanine, and Aβ(42).