Multiple - quantum magic - angle spinning NMR: a new technique for probing quadrupolar nuclei in solids

Journal of the Brazilian Chemical Society

Medek, Ales¹  Frydman, Lucio¹  University of Illinois at Chicago, Chicago¹ 

关键词: solid state NMR;    quadrupolar nuclei;    resolution enhancement;    2D NMR spectroscopy;   

DOI  :  10.1590/S0103-50531999000400003

学科分类：化学（综合）

来源: SciELO

【 摘 要 】

A majority of all magnetically active nuclides in the Periodic Table possess half - integer spin numbers higher than 1 (I = 3/2, 5/2, 7/2 and 9/2; Fig. 1)2. This implies that unlike their more common spin -1/2 counterparts such as 1H and 13C, which interact exclusively with either external or internal magnetic fields, such higher half - integer nuclei will possess quadrupole moments and thus also interact with the electric field gradients (EFG) originated from asymmetries in the charge distribution of the surrounding lattice3. Depending on the degree of distortion in this local charge distribution the resulting quadrupole couplings can be large, sometimes even comparable or exceeding the Zeeman coupling between the nuclear magnetic moment and the external magnetic field B0. However in a majority of cases (including all the ones that we will consider here) quadrupolar couplings can be treated as perturbations to the main Zeeman interaction due to the relatively small size of their coupling constants e2Q/h with respect to the Larmor frequency uL. The resulting quadrupole couplings are then, to first order, orientation - dependent and proportional to the square of the z component of the angular momentum m, where -I < m < I. In the

【 授权许可】

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