Pylaeva Svetlana, Ivanov Konstantin L, Baldus Marc, Sebastiani Daniel, Elgabarty Hossam
Chemistry Department, MLU Halle-Wittenberg , 06120 Halle (Saale), Germany.
International Tomography Center SB RAS , Novosibirsk 630090, Russia.
J Phys Chem Lett. 2017 May 18;8(10):2137-2142. doi: 10.1021/acs.jpclett.7b00561. Epub 2017 Apr 28.
Dynamic nuclear polarization (DNP), a technique that significantly enhances NMR signals, is experiencing a renaissance owing to enormous methodological developments. In the heart of DNP is a polarization transfer mechanism that endows nuclei with much larger electronic spin polarization. Polarization transfer via the Overhauser effect (OE) is traditionally known to be operative only in liquids and conducting solids. Very recently, surprisingly strong OE-DNP in insulating solids has been reported, with a DNP efficiency that increases with the magnetic field strength. Here we offer an explanation for these perplexing observations using a combination of molecular dynamics and spin dynamics simulations. Our approach elucidates the underlying molecular stochastic motion, provides cross-relaxation rates, explains the observed sign of the NMR enhancement, and estimates the role of nuclear spin diffusion. The presented theoretical description opens the door for rational design of novel polarizing agents for OE-DNP in insulating solids.
动态核极化（DNP）是一种能显著增强核磁共振（NMR）信号的技术，由于方法学上的巨大发展，它正在经历复兴。DNP的核心是一种极化转移机制，该机制赋予原子核大得多的电子自旋极化。传统上已知通过奥弗豪泽效应（OE）进行的极化转移仅在液体和导电固体中起作用。最近，令人惊讶的是，已报道在绝缘固体中存在很强的OE-DNP，其DNP效率随磁场强度增加。在这里，我们结合分子动力学和自旋动力学模拟对这些令人困惑的观察结果给出解释。我们的方法阐明了潜在的分子随机运动，提供了交叉弛豫率，解释了观察到的NMR增强的符号，并估计了核自旋扩散的作用。所提出的理论描述为合理设计用于绝缘固体中OE-DNP的新型极化剂打开了大门。
