| Abstract: | 中文摘要
在液體中，分子因能很快的做等方向性運動，使得彼此之間的作用如化學位移異方向性(anisotropy)，偶極－偶極(dipole-dipole)作用，四極子(quadrupole)作用各個平均值為零，因此，在液態分子快速運動下，NMR所測得光譜是由許多尖峰(sharp)組成，其譜線之寬度小於1Hz。但是同樣的實驗條件在固態，有許多必需克服（如譜線之寬度好幾KHz），否則提供很少訊息。因為在固態時，上述之作用仍然存在。本文介紹三種技術可以使固體NMR的光譜圖得到類似液體NMR光譜圖；高能量之去耦(HPD)；跨越極化(CP)和魔角旋轉(MAR)。
Abstract
As is well known to the chemist, the NMR spectrum of a liquid consists of numerous sharp lines typically with less than 1 Hz linewidth, due to the rapid isotropic molecular motion, all possible anisotropic interactions-chemical shift anisotropy, dipole-dipole interaction, quadrupole interaction etc. are averaged to zero. However, analogous experiments on solids have enjoyed a more limited prosperity (i.e., several kilohertz linewith). The reason is all these anisotropic interactions are retained and may be used to monitor the symmetry properties and the electronic state of the solid. Three techniques may be used to obtain high resolution NMR in solids-High Power proton Decoupling (HPD); Cross Polarization (CP) from the proton to the dilute spins; and Magic Angle Rotation (MAR) can produce "liquidlike" NMR spectra of a solid material. |
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