Static magnetic gradient

The experimental set-up uses the fact that the gradient field outside the center of the magnet decreases linearly. Thus placing the probe-head in an exactly chosen position outside the center of the magnet, the sample is exposed to a large static magnetic gradient in the order of 10 T/m. The transverse relaxation time T2 needs to be determined independently (in a uniform field experiment), as it cannot be otherwise separated from the diffusion echo decay process. 

Most of the methods are based upon the application of both a static magnetic field gradient and a mechanical wave in order to measure the consequence of the latter on a given NMR parameter. Indeed, the mechanically-induced... 

When a nucleus with spin I is placed in a static magnetic field, the energy splits into 21 + 1 equally spaced levels, and a 2J-fold degenerate resonance line can be observed in an NMR experiment (16). Nuclei with spin I > 1/2 possess an electric quadrupole moment Q which may interact with the gradient of the electric crystal field at the site of the nucleus. This field gradient is a traceless tensor (17). 

Spatial discrimination of the NMR signal is achieved by superimposing a linear magnetic field gradient, G, on the static magnetic field, B0. Then the... 

In Eq. (6.8) the first term is the phase shift due to the static magnetic field and the second term is the phase shift due to the magnetic gradient pulse applied along the z-direction. The next step is applying a 180° rf pulse, which inverts the sign of the precession and the phase as depicted in Fig. 6.1. At time N -F A a second identical pulse gradient is applied which cancels out the induced phase shifts,... 

Fig, 7,2.14 fPuL l Stimulated echo filler for measurement of diffusion in the presence of static background gradients. Note that this filler ends with longitudinal magnetization. 

If evolves under a field gradient applied along the z-direction parallel to the static magnetic field, the evolution of spin coherences under the Zeeman interaction leads to changes described by the transformation... 

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