Satellite-Transition MAS NMR of Low-gamma Nuclei at Natural Abundance: Sensitivity, Practical Implementation and Application to 39K (I = 3/2) and 25Mg (I = 5/2)

Satellite-transition magic angle spinning (STMAS) is a recently introduced technique for recording high-resolution NMR spectra of quadrupolar nuclei in solids. We present numerical calculations of STMAS signal intensity as a function of radio frequency field strength (v(1)) and spinning rate (v(R)) and show that the sensitivity advantage of STMAS over the older multiple-quantum technique (MQMAS) is greatest for low v(1) field strengths and high v(R) rates, making STMAS particularly suitable for the study of low-gamma nuclei. The practical implementation of STMAS in NMR of low-y nuclei is discussed and several experimental examples of high-resolution K-39 (I = 3/2) and Mg-25 (I = 5/2) NMR spectra are presented, including Mg-25 spectra of brucite (Mg(OH)(2)), diopside (CaMgSi2O6), and talc (Mg3Si4O10(OH)(2)) recorded at the natural Mg-25 abundance of 10%.