Anisotropic relaxation of nuclear spins dipolar energy of water molecules in two-dimensional nanopores - A single crystal NMR study,Solid State Nuclear Magnetic Resonance

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Anisotropic relaxation of nuclear spins dipolar energy of water molecules in two-dimensional nanopores - A single crystal NMR study
Solid State Nuclear Magnetic Resonance ( IF 1.8 ) Pub Date : 2024-06-19 , DOI: 10.1016/j.ssnmr.2024.101944
Alexander M Panich ₁ , Jan Swenson ₂

Affiliation

Energy transfer from Zeeman to dipolar order discovered by Jeener et al. is usually observed in solids with a strong dipole-dipole interaction of nuclear spins. It is not observed in liquids, where fast molecular motion completely averages this interaction. The intermediate case, when the dipole-dipole interaction of nuclear spins is only partially averaged, has been poorly studied. We report on the first measurement of an angular-dependent proton spin relaxation of a dipolar reservoir in mobile water molecules confined in the interlayer pores of a vermiculite single crystal. In this layered crystal, the intramolecular dipole-dipole interactions of nuclear spins are only partially averaged due to the restricted anisotropic molecular motion in nanopores. We show that this allows the formation of dipolar echo. We measured the spin-lattice relaxation times of the dipolar order at different angles between the normal to the crystal surface and the applied magnetic field and obtained a distinct angular dependence of . The minimum relaxation rate was found around the magic angle of 54.74°.

中文翻译：

二维纳米孔中水分子核自旋偶极能的各向异性弛豫——单晶核磁共振研究

Jeener 等人发现从塞曼到偶极级的能量转移。通常在具有强核自旋偶极-偶极相互作用的固体中观察到。在液体中观察不到这种相互作用，液体中快速的分子运动完全平均了这种相互作用。当核自旋的偶极子-偶极子相互作用仅部分平均时，中间情况的研究很少。我们报告了首次测量限制在蛭石单晶层间孔隙中的流动水分子中偶极储层的角度依赖性质子自旋弛豫。在这种层状晶体中，由于纳米孔中受限的各向异性分子运动，核自旋的分子内偶极-偶极相互作用仅部分平均。我们证明这可以形成偶极回波。我们测量了晶体表面法线与施加磁场之间不同角度下偶极级的自旋晶格弛豫时间，并获得了明显的角度依赖性。在魔角 54.74° 附近发现了最小弛豫率。

更新日期：2024-06-19

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