The earlier works also do not consider relaxation caused by the f

The earlier works also do not consider relaxation caused by the formation of Xe–131Xe van der Waals complexes that leads to a gas density independent relaxation term [24], [25], [26] and [27]

at the field strengths and gas pressures used in this work. Like the longitudinal relaxation, the spectral features observed in 131Xe NMR are dominated by this isotope’s high nuclear spin and large nuclear quadrupole moment. If 131Xe is placed in an anisotropic environment, for instance when dissolved in a liquid crystal, a triplet is observed in the NMR spectrum that displays resonance line learn more splittings in the kHz regime. The triplet in liquid crystalline phase is caused by interactions of the nuclear quadrupole moment with the electric field gradient (EFG) induced by the anisotropic solvent (see [28] for a review). Even the surfaces of macroscopic containers can cause a 131Xe quadrupolar

splitting that can be detected in the gas phase. This splitting was originally observed in spin-exchange optical pumping experiments at low magnetic fields of a few mG IDH inhibitor drugs (see below) [29], [30], [31], [32], [33], [34] and [35]. However, the effect of surface orientation and temperature on the gas phase 131Xe quadrupolar splitting can also be observed in thermally polarized high-field NMR spectroscopy [36] and [37]. Another unique property of 131Xe is

that a quadrupolar splitting pattern of a few Hz can also be generated in the bulk gas phase, independent of the presence of surfaces [19]. The effect is caused by high magnetic fields, B→0, that generate an electric field gradient (EFG) in atoms located within this field. The EFG is a result of interactions Sorafenib of the external magnetic field B→0 with the magnetization M→ of the xenon electron cloud. The EFG tensor orientation is always aligned with B→0, thus leading to a quadrupolar splitting, reminiscent of the much stronger splittings in liquid crystals. As was shown previously with thermally polarized 131Xe [19], this “high-field’ quadrupolar splitting displays a quadratic dependence upon |B→0|. Theoretical papers following the initial experimental observation agree with the quadratic magnetic field dependence of the splitting, but disagreed about the presence of an additional linear term [38] and [39]. At current, a magnetic field dependent splitting has only been observed with the noble gas isotope 131Xe, due to its unique combination of a large and easily distortable electron cloud, spherical symmetry of the unbound noble gas atoms, ‘high resolution grade’ NMR linewidth in the gas phase, and its large nuclear electric quadrupole moment at a relatively small spin I = 3/2 value.

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