14N Quadrupole Resonance line broadening due to the earth magnetic field, occuring only in the case of an axially symmetric electric field gradient tensor

Abstract : As demonstrated before, the application of a weak static B0 magnetic field (less than 10 G) may produce definite effects on the 14N Quadrupole Resonance line when the electric field gradient tensor at the nitrogen nucleus level is of axial symmetry. Here, we address more precisely the problem of the relative orientation of the two magnetic fields (the static field and the radio-frequency field of the pure NQR experiment). For a field of 6 G, the evolution of the signal intensity, as a function of this relative orientation, is in very good agreement with the theoretical predictions. There is in particular an intensity loss by a factor of three when going from the parallel configuration to the perpendicular configuration. By contrast, when dealing with a very weak magnetic field (as the earth field, around 0.5 G), this effect drops to ca. 1.5 in the case Hexamethylenetetramine (HMT).This is explained by the fact that the Zeeman shift (due to the very weak magnetic field) becomes comparable to the natural line-width. The latter can therefore be determined by accounting for this competition. Still in the case of HMT, the estimated natural line-width is half the observed line-width. The extra broadening is thus attributed to earth magnetic field. The latter constitutes therefore the main cause of the difference between the natural transverse relaxation time (T2) and the transverse relaxation time derived from the observed line-width View the MathML source(T2⁎).
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Soumis le : mardi 15 novembre 2016 - 16:42:28
Dernière modification le : mardi 21 août 2018 - 09:46:03

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Sarra Aissani, Laouès Guendouz, Pierre-Louis Marande, Daniel Canet. 14N Quadrupole Resonance line broadening due to the earth magnetic field, occuring only in the case of an axially symmetric electric field gradient tensor. Solid State Nuclear Magnetic Resonance, Elsevier, 2015, 68-69, pp.57 - 60. 〈10.1016/j.ssnmr.2015.04.001〉. 〈hal-01397326〉

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