EPR line shifts and line shape changes due to spin exchange of nitroxide free radicals in liquids 2. Extension to high spin exchange frequencies and inhomogeneously broadened spectra
EPR line shifts and line shape changes due to spin exchange of nitroxide free radicals in liquids 2. Extension to high spin exchange frequencies and inhomogeneously broadened spectra
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DOI：
10.1021/jp014518g
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发表时间：
2002-05-16
影响因子：
2.9
通讯作者：
Peric, M
中科院分区：
文献类型：
--
作者：
Bales, BL;Peric, M
本系列第一部分的工作 (J. Phys. Chenz. B. 1997, 101, 8707) 在实验和理论上进行了扩展，包括不均匀展宽的硝基氧光谱和高自旋交换频率。硝基氧自旋探针 16-羟基硬脂酸甲酯在没有自旋交换的情况下因未解析的超精细结构而严重不均匀地展宽，在自旋探针经历从慢速交换到高交换的自旋交换的条件下进行了研究，导致三个 N-14 超细线塌陷成一条线。在整个自旋交换频率范围内，理论上预测的光谱基本上可以通过洛伦兹形状的三个吸收线和两个“色散”线的总和来完美地描述。外部线的色散分量具有相反的符号，内部线的色散分量为零。外部吸收线的强度和线宽与中心线不同。理论上，添加不均匀加宽谱线的未解析超精细结构对吸收线的线宽或强度、色散线的强度或线位移没有影响。理论与实验对比表明，线宽、强度、线形吻合良好，而线位移则不一致；实验线相互移动的速度比理论预测的要快。
The work in part I of this series (J. Phys. Chenz. B. 1997, 101, 8707) is extended experimentally and theoretically to include inhomogeneously broadened nitroxide spectra and high spin exchange frequencies. The nitroxide spin probe 16-doxylstearic acid methyl ester, which is severely inhomogeneously broadened by unresolved hyperfine structure in the absence of spin exchange, is studied under conditions in which the spin probe undergoes spin exchange varying from slow exchange to high exchange leading to collapse of the three N-14 hyperfine lines into a single line. Over the entire spin exchange frequency range, theoretically predicted spectra are described essentially perfectly by the sum of three absorption and two "dispersion" lines of Lorentzian shape. The dispersion components are of opposite signs for the outer lines and zero for the inner. The intensities and the line widths of the outer absorption lines are different from the center line. Theoretically, adding unresolved hyperfine structure which inhomogeneously broadens the lines, has no effect on the line widths or intensities of the absorption lines, the intensity of the dispersion lines, or the line shifts. Comparing theory with experiment shows that the line widths, intensities, and line shapes are in excellent accord, whereas the line shifts are not; experimental lines move toward one another faster than predicted by theory.