Hu J Z, Zhou J, Yang B, Li L, Qiu J, Ye C, Solum M S, Wind R A, Pugmire R J, Grant D M
Laboratory of Magnetic Resonance, and Atomic and Molecular Physics, Wuhan Institute of Physics, Chinese Academy of Sciences, People's Republic of China.
Solid State Nucl Magn Reson. 1997 Apr;8(2):129-37. doi: 10.1016/s0926-2040(96)01263-5.
A 15N dynamic nuclear polarization (DNP) experiment is reported in which a 15N DNP enhancement factor of approximately 2.6 x 10(2) is obtained on free radical doped samples of 99% 15N labeled benzamide. The free radicals BDPA (1:1 complex of alpha, gamma-bisdiphenylene-beta-phenylallyl with benzene) and DPPH (2,2-Di(4-tert-octylphenyl)-1-picrylhydrazyl) are used as dopants and the spin relaxation effects of adding these dopants are studied by means of changes in proton and nitrogen T1 values of the samples. The combination in solids of a very low natural abundance, 0.37%, a small gyromagnetic ratio, and a long spin-lattice relaxation time for 15N nuclei create severe sensitivity problems that, in large part, are ameliorated by the signal enhancement observed in the 15N DNP experiment on samples containing free electrons.
报道了一项15N动态核极化（DNP）实验，在99% 15N标记苯甲酰胺的自由基掺杂样品上获得了约2.6×10²的15N DNP增强因子。自由基BDPA（α,γ-双亚苯基-β-苯基烯丙基与苯的1:1配合物）和DPPH（2,2-二（4-叔辛基苯基）-1-苦基肼）用作掺杂剂，并通过样品质子和氮T1值的变化研究添加这些掺杂剂的自旋弛豫效应。15N核极低的天然丰度（0.37%）、小的旋磁比和长的自旋晶格弛豫时间在固体中的组合产生了严重的灵敏度问题，在很大程度上，含自由电子样品的15N DNP实验中观察到的信号增强缓解了这些问题。
