A different approach of nuclear magnetic resonance (NMR) relaxation of the rotational motion of BH₄ tetrahedron in light metal borohydrides was introduced. Previous NMR relaxation studies were mainly performed using an approximation which is based on a single exponential transition approach for the spin–lattice relaxation of the spin under quadrupolar interaction. In this new approach, a relaxation rate equation was derived by strictly taking into account both electric quadrupolar and magnetic dipolar contributions to the transitions between Zeeman energy states of quadrupolar ¹¹B nucleus that was coupled to many proton spins. Two exponential relaxation times derived from our theoretical treatment were applied to the analysis of ¹¹B spin–lattice relaxation of LiBH₄ and Ca(BH₄)₂. The activation energies and the correlation times of the reorientational motions of BH₄ were evaluated from the two experimental spin–lattice relaxation times. The results were compared to previous activation energies and correlation times.

中文翻译：

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BH4在金属硼氢化物中的核磁弛豫研究

介绍了一种不同的核磁共振 (NMR) 弛豫方法，用于轻金属硼氢化物中 BH ₄四面体的旋转运动。以前的 NMR 弛豫研究主要使用基于四极相互作用下自旋的自旋-晶格弛豫的单指数跃迁方法的近似值进行。在这种新方法中，通过严格考虑电四极和磁偶极对与许多质子自旋耦合的四极¹¹ B 核的塞曼能态之间的跃迁的贡献，推导出弛豫率方程。从我们的理论处理中得出的两个指数弛豫时间被应用于分析¹¹LiBH ₄和Ca(BH ₄ ) _{2 的}B自旋-晶格弛豫。从两个实验自旋-晶格弛豫时间评估了 BH ₄的重新定向运动的激活能和相关时间。将结果与之前的活化能和相关时间进行比较。