Effect of RF Inhomogeneity upon Quantitative Solid-State NMR Measurements

The Effect of RF Inhomogeneity on Heteronuclear Dipolar Recoupling in Solid State NMR: Practical Performance of SFAM and REDOR

“…Effects of rf inhomogeneity on important solid state NMR experiments have been previously published (11,12,20). However, in this study, quantitative estimates of spatially resolved rf inhomogeneity effects for distance measurements and a general strategy to characterize these effects are presented.…”

Cross polarization, radio frequency field homogeneity, and circuit balancing in high field solid state NMR probes

“…In this instance RF field inhomogeneity effects on magnetization transfer via CP become even more important, and are a serious impediment to maximizing sensitivity. Some of the methods that have been used to ensure homogeneous B 1 fields include restricting the sample to the central region of the detection coil [5], winding the sample coil with a variable pitch or width of wire [6][7][8] and utilizing a single sample coil that is resonant at all the frequencies of interest. Probes used in our laboratory at 1 H NMR frequencies of 300 MHz have employed these features and provide for reasonably efficient CP transfers, even at high MAS rates (>20 kHz) on samples with small effective heteronuclear dipolar couplings such as adamantane.…”

Sampling Methods for Quantification of Solid-state Phases in Powder Samples with Solid-state NMR Spectroscopy

“…This was due to the non-uniform CP efficiency and signal collection from each sample location in an NMR coil. 15,16 If only a spherical space at the center of the rotor is used, sample inhomogeneity might not be a significant problem for quantification. However, the experimental time becomes too long to take a spectrum with a reasonable S/N.…”