✦ LIBER ✦

Cross polarization with long delayed contact in rotating solids

✍ Scribed by Shangwu Ding; Charles A. McDowell

Publisher: Elsevier Science
Year: 1996
Tongue: English
Weight: 338 KB
Volume: 255
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(96)00332-6

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✦ Synopsis

The cross polarization NMR spectra and cross relaxation rates of polycrystalline hexamethylbenzene and adamantane were obtained by employing a long delay before contact for samples spinning at, and off, the magic angle with respect to the static magnetic field. The results are compared with those obtained by using the conventional cross polarization pulse sequence. The results support the memory effect explanation of origin of the SPEDA spectra in contrast with the assumptions that the high resolution SPEDA spectra arising either, from the nearly isotropic motion of a very small fraction, or a pool of highly thermo-activated molecules, or from special spin pairs within the crystallites which are orientated at the magic angle with respect to the static magnetic field.

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