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Two-Dimension Method for High Resolution Solids NMR Spectroscopy of Homonuclear Broadened Spins

IP.com Disclosure Number: IPCOM000041354D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 68K

Publishing Venue

IBM

Related People

Murphy, PD: AUTHOR

Abstract

A two-dimensional Fourier transform (FT) method can be used for obtaining high-resolution solids NMR spectra of abundant spins, such as 1-H, 19-F or 31-P, and quadrupole spins, such as 27-Al, 23-Na or 14-N. Previous and present methods for obtaining solids NMR spectra of these spins employ a multiple-pulse sequence with data sampling at specific points in the pulse train. An illustration of the present technique is shown in Fig. 1. The well known MREV-8-pulse sequence 1 is used for illustrative purposes. In the present method, the decay is digitized point-by-point in the windows following each 8-pulse period. A train 2 of RF pulses is also shown. Following each 8-pulse period, one point of the decay 3 is digitized, and so on. The first 8 points are labeled. A Fourier transform of this decay yields the NMR spectrum.

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Two-Dimension Method for High Resolution Solids NMR Spectroscopy of Homonuclear Broadened Spins

A two-dimensional Fourier transform (FT) method can be used for obtaining high-resolution solids NMR spectra of abundant spins, such as 1-H, 19-F or 31-P, and quadrupole spins, such as 27-Al, 23-Na or 14-N. Previous and present methods for obtaining solids NMR spectra of these spins employ a multiple-pulse sequence with data sampling at specific points in the pulse train. An illustration of the present technique is shown in Fig. 1. The well known MREV-8-pulse sequence 1 is used for illustrative purposes. In the present method, the decay is digitized point-by-point in the windows following each 8-pulse period. A train 2 of RF pulses is also shown. Following each 8-pulse period, one point of the decay 3 is digitized, and so on. The first 8 points are labeled. A Fourier transform of this decay yields the NMR spectrum. The present method requires critical attention to instrumental factors, the most difficult of which include: 1) High powered RF operation to ensure small pulse widths, typically 1 microsecond, and the shortest cycle

time, Tc of Fig. 1, consistent with the experiment 2) a low Q probe/duplexer system capable of rapid RF dampening/fast recovery, typically 1 microsecond 3) a synchronous integrated/hold network for precise data sampling at the specified periods. Because of the instrumental requirements, NMR spectroscopy of such spins as described above is not widely practiced and, in general, the resulting high resolution spectra are actually of low resolution by most standards. The original idea which is the basis of this method is to perform the same experiment in two dimensions. This procedure virtually eliminates the critical instrument problems described above and may possibly improve resolution. The procedure for performing the two-dimensional experiment is described diagrammatically in Fig. 2. The top of the figure shows the iterative pulse sequence 4. It should be noted that any of the well-known homonuclear decoupling sequences can be used and, again for illustrative purposes, the MREV-8 was chosen. The procedure involves successively gene...