Two-Dimensional Multiple-Quantum MAS NMR of Quadrupolar Nuclei: A Comparison of Methods. Brown, S. P. & Wimperis, S. Journal of Magnetic Resonance, 128(1):42–61, September, 1997. Publisher: Academic Press Inc.![Two-Dimensional Multiple-Quantum MAS NMR of Quadrupolar Nuclei: A Comparison of Methods [link]](https://bibbase.org/img/filetypes/link.svg "link")
Paper doi abstract bibtex Multiple-quantum magic-angle-spinning (MQMAS) NMR experiments have recently been used to remove second-order broadening from the central transition of half-integer quadrupolar nuclei. In this paper, the various methods that have been proposed for obtaining pure absorption-mode lineshapes in MQMAS experiments are described and compared. The methods can be classified according to whether the data are amplitude- or phase-modulated as a function of the evolution period, t1. Both classes of experiment are usually performed in such a way that the inhomogeneous quadrupolar broadening is spread out along a ridge which, for spins I = 3/2 and 5/2, respectively, has a slope of -7/9 or 19/12 with respect to the F2 axis. This paper shows, however, that there are disadvantages associated with recording the data in this fashion and demonstrates, in particular, that a shearing transformation of the final two-dimensional spectrum can lead to distorted line-shapes. Novel amplitude- and phase-modulated "split-t1" MQMAS experiments are introduced which fully refocus the second-order broadening during the evolution period, t1, thereby avoiding the need for a shearing transformation. The considerable practical advantages of these split-t1 experiments are discussed, particularly with regard to ease of implementation and processing. In general, the sensitivities achievable using the split-t1 MQMAS experiments are predicted to be similar to those obtainable with other methods and, in the special case of the spin I = 3/2 phase-modulated experiments, are even shown to be slightly superior. © 1997 Academic Press.
@article{Brown1997,
title = {Two-{Dimensional} {Multiple}-{Quantum} {MAS} {NMR} of {Quadrupolar} {Nuclei}: {A} {Comparison} of {Methods}},
volume = {128},
issn = {10907807},
url = {https://linkinghub.elsevier.com/retrieve/pii/S1090780797912179},
doi = {10.1006/jmre.1997.1217},
abstract = {Multiple-quantum magic-angle-spinning (MQMAS) NMR experiments have recently been used to remove second-order broadening from the central transition of half-integer quadrupolar nuclei. In this paper, the various methods that have been proposed for obtaining pure absorption-mode lineshapes in MQMAS experiments are described and compared. The methods can be classified according to whether the data are amplitude- or phase-modulated as a function of the evolution period, t1. Both classes of experiment are usually performed in such a way that the inhomogeneous quadrupolar broadening is spread out along a ridge which, for spins I = 3/2 and 5/2, respectively, has a slope of -7/9 or 19/12 with respect to the F2 axis. This paper shows, however, that there are disadvantages associated with recording the data in this fashion and demonstrates, in particular, that a shearing transformation of the final two-dimensional spectrum can lead to distorted line-shapes. Novel amplitude- and phase-modulated "split-t1" MQMAS experiments are introduced which fully refocus the second-order broadening during the evolution period, t1, thereby avoiding the need for a shearing transformation. The considerable practical advantages of these split-t1 experiments are discussed, particularly with regard to ease of implementation and processing. In general, the sensitivities achievable using the split-t1 MQMAS experiments are predicted to be similar to those obtainable with other methods and, in the special case of the spin I = 3/2 phase-modulated experiments, are even shown to be slightly superior. © 1997 Academic Press.},
number = {1},
urldate = {2021-05-28},
journal = {Journal of Magnetic Resonance},
author = {Brown, Steven P. and Wimperis, Stephen},
month = sep,
year = {1997},
note = {Publisher: Academic Press Inc.},
keywords = {notion},
pages = {42--61},
}
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Both classes of experiment are usually performed in such a way that the inhomogeneous quadrupolar broadening is spread out along a ridge which, for spins I = 3/2 and 5/2, respectively, has a slope of -7/9 or 19/12 with respect to the F2 axis. This paper shows, however, that there are disadvantages associated with recording the data in this fashion and demonstrates, in particular, that a shearing transformation of the final two-dimensional spectrum can lead to distorted line-shapes. Novel amplitude- and phase-modulated \"split-t1\" MQMAS experiments are introduced which fully refocus the second-order broadening during the evolution period, t1, thereby avoiding the need for a shearing transformation. The considerable practical advantages of these split-t1 experiments are discussed, particularly with regard to ease of implementation and processing. 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