Solid-State NMR Halle: Journal Publications 2006T. Bräuniger, G. Hempel, P. K. Madhu.
Fast amplitude-modulated pulse trains with frequency sweep (SW-FAM) in static NMR of half-integer spin quadrupolar nuclei.
J. Magn. Reson. 181, 68-78 (2006).
AbstractIn solid-state NMR of quadrupolar nuclei with half-integer spin I, fast amplitude-modulated (FAM) pulse trains have been utilised to enhance the intensity of the central-transition signal, by transferring spin population from the satellite transitions. In this paper, the signal-enhancement performance of the recently introduced SW-FAM pulse train with swept modulation frequency [Chem. Phys. Lett. 383 (2004) 403-410] is explored in more detail for static spectra. It is shown that by sweeping the modulation frequencies linearly over the pulse pairs (SW(1/tau)-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SW(tau)-FAM). For static spectra of 27Al (I=5/2), better signal-enhancement performance is found for the SW(1/tau)-FAM sequence, as demonstrated both by experiments and numerical simulations.