Sensitivity enhancement of solid-state NMR spectra of half-integer spin quadrupolar nuclei: Double- or single-frequency sweeps? Insights from the hyperbolic secant experiment

Improved sensitivity enhancements of the central NMR transition of non-integer spin quadrupolar nuclei in MAS powder samples are realized when only a single satellite transition spinning side band is irradiated using a conventional double-frequency sweep experiment compared to irradiation of the entire spinning side band manifold. For example, for Rb-87 in RbClO4, enhancement factors of 2.2 versus 1.9 are observed when only one satellite transition spinning side band is targeted versus the entire spinning side band manifold. Similarly, for Al-27 in Al(acac)(3), the corresponding enhancement was 3.4 compared to 2.6. (c) 2007 Elsevier B.V. All rights reserved.