New PFG NMR Spectrometer with a Rotatable Quadrupole Coil for the Measurement of an Anisotropic Self-Diffusion Coefficient Tensor
✍ Scribed by Osamu Oishi; Seiichi Miyajima
- Publisher
- Elsevier Science
- Year
- 1996
- Tongue
- English
- Weight
- 252 KB
- Volume
- 123
- Category
- Article
- ISSN
- 1064-1858
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✦ Synopsis
A new pulsed-field-gradient spin-echo NMR spectrometer is remagic angle from the external field, and then the 1 H NMR ported which is specially designed for the measurement of slow linewidth was drastically narrowed because of the strongly aniand anisotropic self-diffusion by providing an intense and homogesotropic nature of the dipole interaction. For nematic liquid neous field gradient of 12 T m 01 by a quadrupole coil and a highcrystals where the rotational viscosity is low, a revised version quality current stabilizer, and also providing a mechanism by of the MAO method, i.e., fast switching of the external field which both the sample cell and the quadrupole coil are rotated (5), was applied. Very recently dipole-decoupled rare-spin from the axis of the external field. Diffusion anisotropy is mea-( 13 C) NMR was conducted in the nematic phase (6). Use of sured by a combination of coil rotation and magic-angle orientamultiple-quantum coherence to intensify the effect of the field tion of the sample. The theoretical basis for the method of measurgradient (FG) was also made (7, 8) to overcome short T 2 .
ing diffusion anisotropy, instrumentation details, and several sets
As to the anisotropy measurement, it has been shown that of test data are given. The experimental results are reported for the rotation pattern of the diffusion coefficient of a smectic Ad the first derivative of the magnetic field component B z (z is liquid crystal of 4-octyloxy-N-(4-cyanobenzylidene)aniline. The taken parallel to the main external field) with respect to any component parallel to the layer normal is shown to be 2.1 times axis (x) in the zx plane, ÌB z /Ìx, can be made constant, larger than the component within the layer. ᭧ 1996 Academic Press, Inc. and the component parallel to it can be made zero by using a quadrupole coil (4). The high intensity generated by the quadrupole coil can also be an alternative to the use of 64