Fourier synthesized excitation of nuclear magnetic resonance with application to homonuclear decoupling and solvent line suppression

Abstract

A method is described for exciting a nuclear magnetic resonance spectrum with a radio frequency source having any desired frequency spectrum. The frequency spectrum of the source is first specified and then Fourier synthesized to define a function which is used to modulate a radio frequency carrier. The NMR spectrum is obtained by Fourier transforming the response of the spin system to this excitation. The technique is applied to the problem of suppressing a strong solvent line while simultaneously observing all other resonance lines in a spectrum and to homonuclear decoupling while observing a complete spectrum.

Beg, borrow, or steal. finding ideas for new NMR experiments

“…The search for such "designer pulses" usually has to proceed by indirect methods such as gradient descent or simulated annealing or is forced to "make do" with the Fourier synthesis approximation (34). Neural networks offer an interesting alternative strategy.…”

HCCCH Experiment for Through-Bond Correlation of Thymine Resonances in13C-Labeled DNA Oligonucleotides

“…The corresponding shaped pulse must therefore perform satisfactorily both as a phase reversal and z-inversion pulse. This is achieved using a G3 Gaussian cascade waveform (19) for amplitude modulation of the 180°pulses with a cosinusoidal modulation (20,21) m ϭ 49 ppm superimposed on the shaping envelope. The cosinusoidal modulation splits the excitation spectrum of the shaped pulse into two sidebands at c Ϯ m with the excitation maxima at 110 and 12 ppm, respectively, in order to manipulate the C5 and Cme spins at their two distinct frequencies 98 ppm apart.…”

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“…19). At first, a single slice perpendicular to the *-axis is selected by applying a magnetic-field gradient along the x-axis and selectively saturating all volume elements outside this slice by means of tailored excitation (Tomlinson & Hill, 1973). A wide spectrum of frequencies is applied for saturation while the frequency of the selected slice is purposely suppressed to avoid saturation within this slice.…”