J-compensated homonuclear cross polarization in NMR spectroscopy
作者:
A. Mohebbi,
A.J. Shaka,
期刊:
Molecular Physics
(Taylor Available online 1993)
卷期:
Volume 78,
issue 1
页码: 29-39
ISSN:0026-8976
年代: 1993
DOI:10.1080/00268979300100041
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
We show how to modify homonuclear cross polarization or mixing sequences to compensate for a range of spin coupling constants. The basis of the method is an analogy between complete polarization transfer, represented as a 180° pulse in a zero-quantum frame, and normal spin inversion pulses. The analogy lets us adapt existing compensation schemes for radiofrequency field inhomogeneity to the problem ofJcompensation in homonuclear cross polarization. We find that, inAXspin systems, complete polarization transfer can be made to occur for a broad range ofJvalues, providing the chemical shift difference between the spins is known. A contour plot of cross polarization efficiency as a function of pulse flip angle and precession angle under the chemical shift difference shows the degree of compensation for different combinations of these parameters. In arbitraryAMXspin systems, the formal analogy breaks down, but someJcompensation can still be achieved. These results can play an important role in maximizing cross peak intensity for 2D and 3D nuclear magnetic resonance applications.
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