Gradient pulse PGSE experiment

Consequently, the slope of the low q echo attenuation data allows (Z (A))/. to be measured directly. This represents the simplest of all possible signal analysis in the case of the narrow gradient pulse PGSE experiment. In the study of hindered and restricted diffusion, such an analysis provides a useful guide to interdependence of length and time... 

One of the fastest growing areas in NMR over the past decade has been the use of pulsed field gradients , or PFG-NMR, for selective ID and 2D experiments. The basic pulsed gradient spin-echo (PGSE) experiment [174] relies on the use of pulsed linear magnetic field gradients (of amplitude g, duration 8 and separation A) that are applied during a spin-echo experiment [184],... 

Other types of PGSE experiments, including those involving alternating or sinusoidal field gradient pulses 2S), have particular applications which may be useful in polymer systems. 

The PGSE experiment can detect the presence of two or more diffusivities in the species at resonance. The intensity of the spin echo is a function of the duration 8, magnitude G and the time A between the applied magnetic field gradient pulses ... 

The PGSE NMR method relies on the use of two sharp gradient pulses separated by a well-defined time interval and is therefore naturally suited to time-domain analysis of motion. However, it is important to realize that this particular form of two-pulse gradient modulation is not unique. In particular, a number of other time-modulation schemes are possible in which the molecular motion is detected in a different manner. However, as we shall see, whenever modulated gradients are used to encode the spin magnetization for motion rather than position, it is appropriate to refocus any phase shift due to absolute spin position by means of a spin echo. Consequently, we refer to this more general type of experiment as modu-... 

We now consider the simple case of a spin echo in which two rectangular linear gradient pulses are applied as shown in Fig. 1. In this pulsed gradient spin-echo (PGSE) experiment, the time t used in Eq. (41) will refer to the position of the spin-echo formation. In analyzing this experiment, we will assume the weak inhomogeneous field limit and the uniform... 

The pulsed (field) gradient-spin echo (PFGSE or PGSE) experiment is used to measure translational diffusion constants [29] (which must not be confused with spin diffusion). It is based on the two-pulse spin-echo experiment (Fig. 12 Sec.II.E.l), with the addition of two field-gradient periods to create a spatial frame of reference in the x and y dimensions. The first gradient is applied between the two pulses the second, between the 180°... 

Figure 1 (a) Pulse sequence for the PGSE (pulsed-field gradient spin echo) experiment, (b), (c), and (d) Vectorial representation of... 

R 477 H.O. Portner, F.C. Mark and C. Bock, Oxygen Limited Thermal Tolerance in Fish Answers Obtained by Nuclear Magnetic Resonance Techniques , Resp.Physiol.Neurobi., 2004,141,243 R 478 W.S. Price and O. Soederman, Some Reflections on the Effects of Finite Gradient Pulse Lengths in PGSE NMR Experiments in Restricted Systems , Israel J.Chem., 2003,43,25 R 479 M. Prudencio and M. Ubbink, Transient Complexes of Redox Proteins Structural and Dynamic Details from NMR Studies , J.Mol.Re-cognit., 2004,17,524... 

In Figure 15.4 the results from a PGSE experiment performed on a 1% CTAB solution is shown. The experiment was carried out on a 500 MHz spectrometer equipped with a broad-band probe and pulsed-field gradients with a maximum of 0.6 T/m at 10 A... 

Figure 2 The pulsed-gradient spin-echo (PGSE) experiment (A), and its stimuiated echo anaiogue (B). Radiofrequency puise phase cyciing is required to isoiate the stimuiated echo from four other echo peaks that occur as a resuit of three RF puises (at times 2r, 2t2 - 2r, 2t2 - 2r, and 2t2).

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