Brinkmann Andreas, Kentgens Arno P M, Anupõld Tiit, Samoson Ago
Physical Chemistry/Solid State NMR, Institute for Molecules and Materials, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands.
J Chem Phys. 2008 Nov 7;129(17):174507. doi: 10.1063/1.3005395.
In this contribution, we extend the theory of symmetry-based pulse sequences of types CN(n) (nu) and RN(n) (nu) in magic-angle-spinning nuclear resonance spectroscopy [M. H. Levitt, in Encyclopedia of Nuclear Magnetic Resonance, edited by D. M. Grant and R. K. Harris (Wiley, Chichester, 2002), Vol. 9]. to the case of rotating the sample simultaneously around two different angles with respect to the external magnetic field (double-rotation). We consider the case of spin-1/2 nuclei in general and the case of half-integer quadrupolar nuclei that are subjected to weak radio frequency pulses operating selectively on the central-transition polarizations. The transformation properties of the homonuclear dipolar interactions and J-couplings under central-transition-selective spin rotations are presented. We show that the pulse sequence R2(2) (1)R2(2) (-1) originally developed for homonuclear dipolar recoupling of half-integer quadrupolar nuclei under magic-angle-spinning conditions [M. Eden, D. Zhou, and J. Yu, Chem. Phys. Lett. 431, 397 (2006)] may be used for the same purpose in the case of double rotation, if the radio frequency pulses are synchronized with the outer rotation of the sample. We apply this sequence, sandwiched by central-transition selective 90 degrees pulses, to excite double-quantum coherences in homonuclear spin systems consisting of (23)Na and (27)Al nuclei.
在本论文中，我们将魔角旋转核磁共振波谱学中类型为CN(n)(ν)和RN(n)(ν)的基于对称性的脉冲序列理论[M. H. 莱维特，载于《核磁共振百科全书》，由D. M. 格兰特和R. K. 哈里斯编辑（威利出版社，奇切斯特，2002年），第9卷]扩展到样品同时绕相对于外磁场的两个不同角度旋转（双旋转）的情况。我们一般考虑自旋1/2核的情况以及半整数四极核的情况，这些半整数四极核受到对中心跃迁极化进行选择性操作的弱射频脉冲作用。给出了中心跃迁选择性自旋旋转下同核偶极相互作用和J耦合的变换性质。我们表明，最初为在魔角旋转条件下半整数四极核的同核偶极再耦合而开发的脉冲序列R2(2)(1)R2(2)( -1)[M. 伊登、D. 周和J. 于，《化学物理快报》431, 397 (2006)]，在双旋转情况下如果射频脉冲与样品的外旋转同步，则可用于相同目的。我们将此序列夹在中心跃迁选择性90度脉冲之间，用于激发由(23)Na和(27)Al核组成的同核自旋系统中的双量子相干。
