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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Ultrafast Dynamics of Polar Monosubstituted Benzene Liquids Studied by the Femtosecond Optical Kerr Effect
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Ultrafast Dynamics of Polar Monosubstituted Benzene Liquids Studied by the Femtosecond Optical Kerr Effect

机译：飞秒光学克尔效应研究极性单取代苯液体的超快动力学

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摘要

The femtosecond and picosecond dynamics of liquid aniline, nitrobenzene, and benzonitrile have been recorded through measurements of the optically heterodyne detected optical Kerr effect. A major part of the subpicosecond dynamics is assigned to librational motion. This assignment is supported by studies of para-substituted benzonitrile derivatives with differing moments of inertia. The librational frequencies of the three liquids are only weakly dependent on temperature but shift to lower frequency on dilution in inert solvents. The picosecond relaxation dynamics are well described by a biexponential function. The slowest relaxation time behaves, at least qualitatively, as predicted by hydrodynamic models of orientational diffusion. However, quantitative analysis suggests that some of the assumptions concerning the molecular shape or hydrodynamic boundary condition are inadequate to completely describe diffusive orientational motion in these liquids. Measurements of the slowest relaxation time as a function of dilution in nonpolar solvent showed that static orientational pair correlation is negligible in these liquids. The faster of the two picosecond exponential relaxation times could not be ascribed to orientational diffusion, and is instead proposed to arise from structural relaxation occurring on the picosecond time scale in these liquids.
机译：通过测量光学外差检测到的光学克尔效应已记录了液体苯胺，硝基苯和苄腈的飞秒和皮秒动力学。亚皮秒动力学的主要部分分配给自由运动。这种分配得到了具有不同惯性矩的对位取代苯甲腈衍生物的研究的支持。三种液体的释放频率仅微弱地依赖于温度，但是在惰性溶剂中稀释后，其释放频率会降低。皮秒松弛动力学可以通过双指数函数很好地描述。最慢的弛豫时间至少定性地表现，如定向扩散的流体动力学模型所预测的。但是，定量分析表明，有关分子形状或流体动力学边界条件的某些假设不足以完全描述这些液体中的扩散取向运动。测量最慢弛豫时间与在非极性溶剂中稀释的关系，结果表明在这些液体中静态取向对的相关性可以忽略不计。两个皮秒的指数弛豫时间中的较快不能归因于定向扩散，而是被认为是由这些液体中在皮秒时间尺度上发生的结构弛豫引起的。

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