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Titolo:
PROTON 2-DIMENSIONAL EXCHANGE NUCLEAR-MAGNETIC-RESONANCE STUDY OF A P-XYLENE-D(6) ZEOLITE INCLUSION COMPOUND
Autore:
KUBO A; DUBEY AK; MCDOWELL CA;
Indirizzi:
KYOTO UNIV,FAC SCI,DEPT CHEM KYOTO 606 JAPAN UNIV BRITISH COLUMBIA,DEPT CHEM VANCOUVER V6T 1Z1 BC CANADA
Titolo Testata:
Molecular physics
fascicolo: 5, volume: 81, anno: 1994,
pagine: 1125 - 1142
SICI:
0026-8976(1994)81:5<1125:P2ENSO>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
SOLID-STATE NMR; HOMONUCLEAR 2-SPIN SYSTEMS; MULTIPLE-QUANTUM NMR; TWO-DIMENSIONAL NMR; MAGIC-ANGLE; ROTATING SOLIDS; LIQUID-CRYSTALS; SPIN DIFFUSION; CHEMICAL-SHIFT; MOLECULAR REORIENTATIONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
81
Recensione:
Indirizzi per estratti:
Citazione:
A. Kubo et al., "PROTON 2-DIMENSIONAL EXCHANGE NUCLEAR-MAGNETIC-RESONANCE STUDY OF A P-XYLENE-D(6) ZEOLITE INCLUSION COMPOUND", Molecular physics, 81(5), 1994, pp. 1125-1142

Abstract

Proton two-dimensional (2D) exchange nuclear magnetic resonance (NMR)experiments and dipolar spin-lattice relaxation rate, T1D, measurements were performed using magic-angle spinning (MAS) on a zeolite Na-ZSM-5/p-xylene alpha - alpha'-d6 inclusion compound. The value of T1D wasfound to be 3-2 ms, which is much longer than the T1D values reportedfor rigid solids when the sample is spun perpendicular to the static magnetic field. This long T1D can be interpreted as arising from the weak intermolecular H-1-H-1 dipolar interactions, because of the significant separation of the molecules in the cavities of the host. A satisfactory theoretical treatment which describes the 2D spectra, was developed. At short mixing times the 2D spinning-sideband intensities observed depended on the flip-angles of the second and third pulses. We show that the off-diagonal 2D spinning sidebands could be suppressed by the appropriate choice of the flip-angles of the second and the third pulses, since in the present sample the included molecules are close to being isolated two-spin systems. When the mixing time was increased,the 2D spinning-sideband intensities became less dependent on the pulse flip-angles. This experimental feature was interpreted to occur because of the decay of the dipolar order. This was confirmed by computercalculations and simulations of the 2D spinning-sideband intensities.

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Documento generato il 19/09/20 alle ore 09:08:23