Pulsed fourier transform NMR

From the Heisenberg uncertainty principle as stated in Equation (1.16) estimate, in cm and Hz, the wavenumber and frequency spread of pulsed radiation with a pulse length of 30 fs, typical of a very short pulse from a visible laser, and of 6 ps, typical of pulsed radiofrequency radiation used in a pulsed Fourier transform NMR experiment. 

Fourier transform spectroscopy in the radio frequency region has been applied most importantly in pulsed Fourier transform NMR spectroscopy, which is not a subject which... 

OES Optical emission spectrometry PFT-NMR Pulse Fourier-transform NMR... 

Instrumentation. The NMR Process. Chemical Shift. Spin-spin Coupling. Carbon-13 NMR. Pulsed Fourier transform NMR (FT-NMR). Qualitative Analysis - The Identification of Structural Features. Quantitative Analysis. Applications of NMR Spectrometry. 

The NMR spectrum of calcitriol, recorded on a Varian XL-100/Nicolet TT-100 pulsed Fourier Transform NMR spectrometer, with internal deuterium lock, is shown in Figure 2 (2). The spectrum was recorded using a solution of 0.84 mg of sample dissolved in 50 microliters of CD OD (100%D) containing 1% v/v tetramethylsilane in a 1.7 mm capillary tube. The spectral assignments are given in Table I. 

The introduction of additional techniques such as Pulsed Fourier Transform NMR spectroscopy (PFT-NMR) has considerably increased the sensitivity of the method, allowing many magnetic nuclei which may be in low abundance, including 13C, to be studied. The additional data available from these methods allow information on polymer structure, conformation and relaxation behaviour to be obtained (1.18.20). 

Pulsed Fourier Transform NMR, 361 Pulsed NMR, 365 Pure shear flow, 533 Pyrolysis, 765... 

With the popularity of the pulse Fourier transform nmr spectrometers, recent CIDNP experiments were largely performed in a FT spectrometer. The technique has been reviewed by Kaptein (80), who has emphasized the important facts initially pointed out by Ernst et al. (55) in connection with using a FT spectrometer for CIDNP experiments. For homonuclear multiplet effects a small flip angle of less than 20° should be used to exhibit the multiplet features. As a 90° pulse turns the magnetization vector from the z axis to the xy plane, it would eliminate the homonuclear multiplet effects but not the net effects. The... 

The development of pulsed Fourier-transform NMR spectrometers has greatly increased the sensitivity of NMR measurements, allowing spectra to be obtained for and other nuclei at natural abundances and low sample concentrations. In this experiment this enhanced capability is utilized in a low-density gas-phase measurement of the equilibrium constant Kp for H-D exchange in the reaction... 

The temperature dependence of the NMR absorption in coals and pitches has been obtained by using a pulsed Fourier transform NMR spectrometer with a high-tempera-ture probe. With increasing temperature the value of the line width at half height of a brown coal decreases... 

Early studies were made by continuous wave 119Sn NMR, and later by intemuclear 1H 119Sn double resonance (INDOR), in which a tin satellite line in the proton NMR spectrum is monitored as the region of the tin resonance frequency is simultaneously swept.41 42 Since the introduction of pulsed Fourier transform NMR, direct observation of the 119Sn resonance has become the standard technique for measurements,37> 39 some-... 

Figure 15. Block diagram of pulsed Fourier transform NMR spectrometer (from [120]).

In one-dimensional pulsed Fourier transform NMR the signal is recorded as a function of one time variable and then Fourier transformed to give a spectrum which is a function of one frequency variable. In two-dimensional NMR the signal is recorded as a function of two time variables, q and q, and the resulting data Fourier transformed twice to yield a spectrum which is a function of two frequency variables. The general scheme for two-dimensional spectroscopy is... 

In one-dimensional pulse-Fourier transform NMR the free induction signal is... 

In modern instruments, the magnetic field is kept constant, and the radiofrequency is varied in pulse Fourier transform NMR (FT-NMR). In FT-NMR, all of the nuclear spins are excited instantaneously using a mixture of radiofrequencies. The spectrum is obtained by analysing the emission of radiofrequency energy (as the spins return to equilibrium) as a function of time. 

The NMR experiments were performed at 60 MHz using the Bruker WP 60 pulsed Fourier transform NMR spectrometer. 

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