Bräuniger Thomas, Hempel Günter, Madhu P K
Department of Physics, University of Halle, Friedemann-Bach-Platz 6, 06108 Halle, Germany.
J Magn Reson. 2006 Jul;181(1):68-78. doi: 10.1016/j.jmr.2006.03.016. Epub 2006 Apr 17.
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) 403-410] is explored in more detail for static spectra. It is shown that by sweeping the modulation frequencies linearly over the pulse pairs (SW1/tau-FAM), the shape of the frequency distribution is improved in comparison to the original pulse scheme (SWtau-FAM). For static spectra of 27Al (I=5/2), better signal-enhancement performance is found for the SW1/tau-FAM sequence, as demonstrated both by experiments and numerical simulations.
在具有半整数自旋(I)的四极核的固态核磁共振中，快速幅度调制（FAM）脉冲序列已被用于通过将自旋布居从卫星跃迁转移来增强中心跃迁信号的强度。在本文中，针对静态谱，更详细地探讨了最近引入的具有扫频调制频率的SW - FAM脉冲序列的信号增强性能[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) 403 - 410]。结果表明，与原始脉冲方案（SWtau - FAM）相比，通过在脉冲对（SW1/tau - FAM）上线性扫频调制频率，频率分布的形状得到了改善。对于(^{27}Al)（(I = 5/2)）的静态谱，实验和数值模拟均表明SW1/tau - FAM序列具有更好的信号增强性能。
