An ESR Study of Anisotropic Rotational Reorientation and Slow Tumbling in Liquid and Frozen Media
An ESR Study of Anisotropic Rotational Reorientation and Slow Tumbling in Liquid and Frozen Media
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液体和冷冻介质中各向异性旋转重定向和慢翻滚的 ESR 研究
DOI：
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发表时间：
1972
期刊：
影响因子：
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通讯作者：
J. Freed
中科院分区：
文献类型：
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作者：
S. Goldman;G. V. Bruno;C. Polnaszek;J. Freed
本文详细研究了过氧化胺二磺酸(PADS)自由基溶于85%甘油溶液、冰水和D2O中的ESR线型。在冰冻介质中获得了转动相关时间τR的光谱特征，范围为1×10−11秒到~10−6秒，而在甘油中的转动相关时间范围为1×10−10秒到>；10−6秒。冰冻水中非常快速的旋转运动被认为意味着垫子在笼子里旋转。在冰和85%甘油中的活化能分别为14.7±0.1千卡/摩尔和11.3±0.1千卡/摩尔。冰的值与冰中其他速率过程得到的值非常相似。用运动窄区中常见的自旋弛豫理论分析了τR≲10−9秒的线形。这些结果与轴对称旋转扩散模型很好地符合，该模型的对称轴在N、O和S原子的平面上，并平行于一条穿过两个S原子的直线。
A careful study is described of the ESR lineshapes for the peroxylamine disulfonate (PADS) radical dissolved in 85% glycerol solution and in frozen water and D2O. In the frozen media, spectra characteristic of rotational correlation times τR ranging from 1.0 × 10−11sec to > 10−6sec are obtained, while the range in glycerol is from 1 × 10−10sec to >10−6sec. The very rapid rotational motion in frozen water is taken to imply that PADS is rotating in a clathrate cage. The activation energies in ice and 85% glycerol are 14.7 ± 0.1 and 11.3 ± 0.1 kcal/mole, respectively, (from motional‐narrowing data). The value for ice is very similar to that obtained for other rate processes in ice. The lineshapes for τR ≲ 10−9sec are analyzed in terms of the familiar spin‐relaxation theories valid in the motionally narrowed region. These results are well fitted by the model of axially symmetric rotational diffusion with the symmetry axis in the plane of the N, O, and S atoms and parallel to a line passing through the two S a...