Transform technique, pulse Fourier

The isotope has a nuclear spin quantum number I and so is potentially useful in nmr experiments (receptivity to nmr detection 17 X 10 that of the proton). The resonance was first observed in 1951 but the low natural abundance i>i S(0.75%) and the quadrupolar broadening of many of the signals has so far restricted the amount of chemically significant work appearing on this rcsonance, However, more results are expected now that pulsed fourier-transform techniques have become generally available. 

NMR has been used comparatively little for quantitative analysis although peak areas are directly proportional to concentration. The principal drawbacks are the expensive instrumentation and a lack of sensitivity. The latter can be improved with the aid of computers to accumulate signals from multiple scans or by using a pulsed (Fourier transform) technique. Relative precision lies in the range 3-8%. 

The most economical and efficient method of sensitivity enhancement in 13C NMR of organic molecules is the pulse Fourier transform technique (PFT) in combination with decoupling methods such as proton broad band decoupling and polarization transfer. These methods will be described in the following sections. 

The foregoing has been a brief introductory discussion of NMR which has concentrated on some basic principles that are very useful in understanding the technique. The actual practice of NMR today is much more advanced. The incorporation of Fourier transform techniques has revolutionized NMR spectroscopy. All types of pulse sequences and two-dimensional (2D) techniques have been developed to provide even greater structural detail than has been discussed above. A discussion of such techniques belongs in a more specialized text, but it must be remembered that while these techniques are faster, more sensitive, and much more sophisticated, they are still largely based on the principles presented here, as is the interpretation of the results. 

Another exciting possibility for high sensitivity molecular surface mass spectrometry is the use of laser-excited ion desorption in a pulsed ion cyclotron resonance experiment using Fourier transform techniques. In an ideal situation, this scheme could include all those attributes which are desirable for solid-surface molecular characterization ... 

In the present work, we monitor the laser-driven dynamics designed by the present formulation by numerically solving the time-dependent Schrodinger (5.2). It is solved by the split operator method [52] with the fast Fourier transform technique [53]. In order to prevent artificial reflections of the wavepacket at the edges, a negative imaginary absorption potential is placed at the ends of the grid [54]. The envelope of the pulses employed is taken as... 

Fourier transform techniques are used throughout the whole spectroscopic region, particularly in the infrared and visible. As we pass from the microwave region to the far-infrared, Fourier transform methods are still used, but based now on interferometry rather than pulsed methods. Perhaps this region of the spectrum will, in... 

There are two basic methods to determine the resonance condition and to record a NMR spectrum, viz. a) the continuous wave technique (CWNMR) and b) the pulsed NMR or pulsed Fourier Transform technique (FTNMR). 

A Fourier transform is the mathematical technique used to compute the spectrum from the free induction decay, and this technique of using pulses and collecting transients is called Fourier transform spectroscopy. A Fourier transform spectrometer requires sophisticated electronics capable of generating precise pulses and accurately receiving the complicated transients. A good 13C NMR instrument usually has the capability to do H NMR spectra as well. When used with proton spectroscopy, the Fourier transform technique produces good spectra with very small amounts (less than a milligram) of sample. 

Further improvements in superconducting materials50 permitted the development in 1970 of a 300-MHz spectrometer that is equipped with a low-loss Dewar vessel, an improved sweep-system that allows both field sweeps and frequency sweeps up to a maximum width of 20 kHz, and accessories for a variety of nuclei and pulse-Fourier-transform techniques. 

Basically two nuclear magnetic resonance (NMR) techniques can be used to determine the partition coefficient. The first is based on the Fourier transform NMR pulsed-gradient spin echo (FT-PGSE) self-diffusion techiuque, the other by the NMR paramagnetic relaxation technique. In both techniques the fraction of solute in the micelle, a, is determined and can thus be calculated through Equation 6.10. 

The natural abundance 13C NMR spectra of five protopine alkaloids were measured at 22.628 MHz by application of the pulse Fourier transform technique (688). Several techniques were employed to make spectral assignments. It was possible to make self-consistent assignments for all the resonances of these alkaloids. Evidence was presented for transannular interaction between the amino group and the carbonyl group at C-14. 

Using a Fourier transform technique, an improvement on a previous determination " which used a selective audiofrequency pulse technique, has enabled the hydrogen nuclear relaxation times of all the protons in vindoline (1) to be... 

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