Prisco Nathan A, Pinon Arthur C, Emsley Lyndon, Chmelka Bradley F
Department of Chemical Engineering, University of California Santa Barbara, USA.
Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland.
Phys Chem Chem Phys. 2021 Jan 21;23(2):1006-1020. doi: 10.1039/d0cp03195j.
By analogy to heat and mass transfer film theory, a general approach is introduced for determining hyperpolarization transfer rates between dilute electron spins and a surrounding nuclear ensemble. These analyses provide new quantitative relationships for understanding, predicting, and optimizing the effectiveness of hyperpolarization protocols, such as Dynamic Nuclear Polarization (DNP) under magic-angle spinning conditions. An empirical DNP polarization-transfer coefficient is measured as a function of the bulk matrix 1H spin density and indicates the presence of two distinct kinetic regimes associated with different rate-limiting polarization transfer phenomena. Dimensional property relationships are derived and used to evaluate the competitive rates of spin polarization generation, propagation, and dissipation that govern hyperpolarization transfer between large coupled spin ensembles. The quantitative analyses agree closely with experimental measurements for the accumulation, propagation, and dissipation of hyperpolarization in solids and provide evidence for kinetically-limited transfer associated with a spin-diffusion barrier. The results and classical approach yield general design criteria for analyzing and optimizing polarization transfer processes involving complex interfaces and composite media for applications in materials science, physical chemistry and nuclear spintronics.
通过类比热质传递膜理论，引入了一种用于确定稀电子自旋与周围核系综之间超极化转移速率的通用方法。这些分析为理解、预测和优化超极化协议（如魔角旋转条件下的动态核极化（DNP））的有效性提供了新的定量关系。测量了作为本体基质1H自旋密度函数的经验性DNP极化转移系数，并表明存在与不同速率限制极化转移现象相关的两种不同动力学机制。推导了尺寸性质关系，并用于评估控制大耦合自旋系综之间超极化转移的自旋极化产生、传播和耗散的竞争速率。定量分析与固体中超极化的积累、传播和耗散的实验测量结果密切吻合，并为与自旋扩散势垒相关的动力学限制转移提供了证据。结果和经典方法产生了用于分析和优化涉及复杂界面和复合介质的极化转移过程的通用设计标准，以应用于材料科学、物理化学和核自旋电子学。
