Hung Ivan, Wong Alan, Howes Andy P, Anupõld Tiit, Samoson Ago, Smith Mark E, Holland Diane, Brown Steven P, Dupree Ray
Physics Department, University of Warwick, Coventry, UK.
J Magn Reson. 2009 Apr;197(2):229-36. doi: 10.1016/j.jmr.2009.01.005. Epub 2009 Jan 13.
Using a two-dimensional multiple-quantum (MQ) double rotation (DOR) experiment the contributions of the chemical shift and quadrupolar interaction to isotropic resonance shifts can be completely separated. Spectra were acquired using a three-pulse triple-quantum z-filtered pulse sequence and subsequently sheared along both the nu(1) and nu(2) dimensions. The application of this method is demonstrated for both crystalline (RbNO(3)) and amorphous samples (vitreous B(2)O(3)). The existence of the two rubidium isotopes ((85)Rb and (87)Rb) allows comparison of results for two nuclei with different spins (I=3/2 and 5/2), as well as different dipole and quadrupole moments in a single chemical compound. Being only limited by homogeneous line broadening and sample crystallinity, linewidths of approximately 0.1 and 0.2 ppm can be measured for (87)Rb in the quadrupolar and chemical shift dimensions, enabling highly accurate determination of the isotropic chemical shift and the quadrupolar product, P(Q). For vitreous B(2)O(3), the use of MQDOR allows the chemical shift and electric field gradient distributions to be directly determined-information that is difficult to obtain otherwise due to the presence of second-order quadrupolar broadening.
通过二维多量子（MQ）双旋转（DOR）实验，可以完全分离化学位移和四极相互作用对各向同性共振位移的贡献。使用三脉冲三量子z滤波脉冲序列采集光谱，随后沿ν(1)和ν(2)维度进行剪切。该方法在晶体（RbNO(3)）和非晶样品（玻璃态B(2)O(3)）中均得到了验证。两种铷同位素（(85)Rb和(87)Rb）的存在使得可以比较两个具有不同自旋（I = 3/2和5/2）以及在单一化合物中具有不同偶极矩和四极矩的核的结果。仅受均匀线宽展宽和样品结晶度的限制，在四极和化学位移维度上，(87)Rb的线宽可测量至约0.1和0.2 ppm，从而能够高精度地确定各向同性化学位移和四极乘积P(Q)。对于玻璃态B(2)O(3)，使用MQDOR可直接确定化学位移和电场梯度分布——由于存在二阶四极展宽，否则很难获得这些信息。
