The behavior of electron paramagnetic resonance spectra due to 15N and 14N nitroxide free radicals undergoing spin exchange in liquids at frequencies $$\omega_{\text{ex}}$$ωex that are high, of the same order of magnitude as the nitrogen hyperfine coupling constant $$A_{0}$$A0, is investigated. The well-known features are reconfirmed: (1) at low values of $$\omega_{\text{ex}}$$ωex where the lines broaden, shift toward the center of the spectrum, and change shape due to the introduction of a resonance of the form of a dispersion component; (2) at values of $$\omega_{\text{ex}}$$ωex comparable to $$A_{0}$$A0, where the lines merge into one; and (3) at values much larger than $$A_{0}$$A0, where the merged line narrows. It is found that each line of a spectrum may be decomposed into an admixture of a single absorption and a single dispersion component of Lorentzian shape. These two- or three-line absorption–dispersion admixtures, for 15N and 14N, respectively, retain their individual identities even after the spectrum has merged and has begun to narrow. For both isotopes, the average broadening and integrated intensities are equal to the predictions of perturbation theory although, in the case of 14N, the outer lines broaden faster than the central line and intensity moves from the outer lines to the central line. In fact, the outer line intensity becomes zero and then negative at higher values of $$\omega_{\text{ex}}$$ωex which is compensated by the central line becoming more intense than the overall integrated intensity. For both isotopes, the dispersion components and the line shifts depart from the perturbation predictions. The results are presented in terms of measurable quantities normalized to $$A_{0}$$A0 so that they may be applied to any two- or three-line spectrum.

中文翻译：

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由于液体中氮氧自由基之间的自旋交换导致 EPR 线位移和线形变化 10. 氮超精细相互作用阶数的自旋交换频率：一个假设

由于 15N 和 14N 氮氧自由基在液体中以高频率 $$\omega_{\text{ex}}$$ωex 进行自旋交换而产生的电子顺磁共振谱的行为，与氮超精细的数量级相同耦合常数 $$A_{0}$$A0 进行了研究。再次确认了众所周知的特征：（1）在 $$\omega_{\text{ex}}$$ωex 的低值处，由于引入了色散分量形式的共振；(2) 在 $$\omega_{\text{ex}}$$ωex 与 $$A_{0}$$A0 相当的值处，其中线合并为一个；(3) 值远大于 $$A_{0}$$A0，合并线变窄。发现光谱的每条谱线都可以分解为单个吸收和单个洛伦兹形色散分量的混合物。这些两线或三线吸收色散混合物，分别为 15N 和 14N，即使在光谱合并并开始变窄后仍保留其各自的特性。对于两种同位素，平均展宽和积分强度与微扰理论的预测相同，尽管在 14N 的情况下，外线的展宽速度比中心线快，并且强度从外线移动到中心线。事实上，外线强度变为零，然后在 $$\omega_{\text{ex}}$$ωex 的较高值处为负，这由中心线变得比整体积分强度更强烈来补偿。对于两种同位素，色散分量和线位移偏离了扰动预测。结果以标准化为 $$A_{0}$$A0 的可测量量表示，因此它们可以应用于任何两线或三线谱。