JMR; SW-FAM for static NMR of quadrupolar nuclei; Madhu

Journal of Magnetic Resonance
Vol: 181, Issue: 1, July, 2006
pp. 68-78

Title: Fast amplitude-modulated pulse trains with frequency sweep (SW-FAM) in static NMR of half-integer spin quadrupolar nuclei
Authors: Bräuniger, Thomasa; Hempel, Güntera; Madhu, P.K.b
Affiliations: a. Department of Physics, University of Halle, Friedemann-Bach-Platz 6, 06108 Halle, Germany
b. Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005, India
Keywords: Static 27Al NMR; Half-integer spin; Quadrupolar nuclei; SW-FAM
Abstract (English):

In 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 [T. Bräuniger, K. Ramaswamy, P.K. Madhu, Enhancement of the central-transition signal in static and magic-angle-spinning NMR of quadrupolar nuclei by frequency-swept fast amplitude-modulated pulses, Chem. Phys. Lett. 383 (2004) 403â??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/Ï?)-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SW(Ï?)-FAM). For static spectra of 27Al (I=5/2), better signal-enhancement performance is found for the SW(1/Ï?)-FAM sequence, as demonstrated both by experiments and numerical simulations.