Composite pulses for efficient excitation of half-integer quadrupolar nuclei in NMR of static and spinning solid samples
Composite pulses of the type (tau(p))(x)(2 tau(p))(-x)(3 tau(p))(x) allow one to excite the central transition of nuclei with half-integer spin with enhanced efficiency compared to a simple (tau(sp)(p))(x) pulse. The method has been tested on solid samples containing sodium-23 (I = 3/2), aluminium-27 (I = 5/2) and scandium-45 (I = 7/2) under both static and magic-angle spinning conditions. Numerical simulations for I = 3/2 indicate that the enhancement is due to a more efficient conversion of Zeeman population differences associated with the satellite transitions to the central transition. (C) 2012 Elsevier B. V. All rights reserved.
Keywords: Hyperbolic Secant Pulses ; Quantum Cross-Polarization ; Double Frequency Sweeps ; Sensitivity Enhancement ; Central-Transition ; Mqmas Nmr ; Population Transfers ; Amplitude-Modulation ; Magnetic-Resonance ; Signal Enhancement
Record created on 2012-04-05, modified on 2016-08-09