Faculty of Mathematics and Computer Science, University of Warmia and Mazury in Olsztyn, Sloneczna 54, PL-10710 Olsztyn, Poland.
J Chem Phys. 2013 Mar 28;138(12):124506. doi: 10.1063/1.4795006.
The work presents a theory of nuclear ((1)H) spin-lattice relaxation dispersion for solutions of (15)N and (14)N radicals, including electron spin relaxation effects. The theory is a generalization of the approach presented by Kruk et al. [J. Chem. Phys. 137, 044512 (2012)]. The electron spin relaxation is attributed to the anisotropic part of the electron spin-nitrogen spin hyperfine interaction modulated by rotational dynamics of the paramagnetic molecule, and described by means of Redfield relaxation theory. The (1)H relaxation is caused by electron spin-proton spin dipole-dipole interactions which are modulated by relative translational motion of the solvent and solute molecules. The spectral density characterizing the translational dynamics is described by the force-free-hard-sphere model. The electronic relaxation influences the (1)H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against (1)H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-(15)N and 4-oxo-TEMPO-d16-(14)N covering the frequency range of 10 kHz-20 MHz. The studies are carried out as a function of temperature starting at 328 K and going down to 290 K. The theory gives a consistent overall interpretation of the experimental data for both (14)N and (15)N systems and explains the features of (1)H relaxation dispersion resulting from the electron spin relaxation.
本文提出了一种用于（15）N 和（14）N 自由基溶液的核（1）H 自旋晶格弛豫频散的理论，包括电子自旋弛豫效应。该理论是 Kruk 等人提出的方法的推广。[J. Chem. Phys. 137, 044512 (2012)]。电子自旋弛豫归因于电子自旋-氮自旋超精细相互作用的各向异性部分，由顺磁分子的旋转动力学调制，并通过 Redfield 弛豫理论来描述。（1）H 弛豫是由电子自旋-质子自旋偶极-偶极相互作用引起的，这些相互作用受溶剂和溶质分子相对平移运动的调制。描述平移动力学的谱密度由无外力硬球模型描述。电子弛豫通过对分子间偶极相互作用的波动产生影响来影响（1）H 弛豫。所开发的理论通过与 4-氧代-TEMPO-d16-(15)N 和 4-氧代-TEMPO-d16-(14)N 甘油溶液的（1）H 自旋晶格弛豫频散数据进行对比测试，该数据覆盖了 10 kHz-20 MHz 的频率范围。这些研究作为温度的函数进行，从 328 K 开始，一直到 290 K。该理论对（14）N 和（15）N 体系的实验数据进行了一致的整体解释，并解释了电子自旋弛豫导致的（1）H 弛豫频散的特征。
