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首页> 外文期刊>The Journal of Chemical Physics >Inertial effects in the orientational relaxation of rodlike moleculesin a uniaxial potential
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Inertial effects in the orientational relaxation of rodlike moleculesin a uniaxial potential

机译：杆状分子在单轴势中取向弛豫的惯性效应

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摘要

The inertial rotational Brownian motion and dielectric relaxation of an assembly of noninteractingrodlike polar molecules in a uniaxial potential are studied. The infinite hierarchy ofdifferential-recurrence relations for the equilibrium correlation functions is generated by averagingthe governing inertial Langevin equation over its realizations in phase space. The solution of thishierarchy for the one-sided Fourier transforms of the relevant correlation functions is obtained usingmatrix continued fractions yielding the longitudinal dipole correlation function, the correlation time,and the complex polarizability, which are calculated for typical values of the model parameters.Pronounced inertial 'effects appear in these characteristics in the high-frequency region for lowdamping. The exact longitudinal correlation time is compared with the predictions of the Kramerstheory of the escape rate of a Brownian particle from a potential well as extended by Mel'nikov andMeshkov [J. Chem. Phys. 85, 1018 (1986)]. In the low temperature limit, the universal Mel'nikovand Meshkov formula for the inverse of the escape rate provides a good estimate of the longitudinalcorrelation time for all values of the dissipation including the very low damping, very high damping,and Kramers turnover regimes. Moreover, the low-frequency part of the spectra of the longitudinalcorrelation function may be approximated by a single Lorentzian with a halfwidth determined bythis universal escape rate formula.
机译：研究了单轴势中非相互作用杆状极性分子组装体的惯性旋转布朗运动和介电弛豫。平衡相关函数的微分递归关系的无限层次是通过将控制惯性Langevin方程在相空间中的实现平均得到的。使用矩阵连续分数获得纵向相关性函数的单阶傅里叶变换的层次结构，得到纵向偶极子相关函数，相关时间和复极化率，并针对模型参数的典型值进行计算。这些特性会在高频区域产生低阻尼效应。精确的纵向相关时间与布朗粒子从势阱中逃逸率的克莱默斯理论的预测结果进行了比较，并通过梅尔尼科夫和梅什科夫的方法进行了扩展[J．化学物理85，1018（1986）]。在低温极限下，逃逸率倒数的通用Mel'nikovand Meshkov公式可以很好地估计所有耗散值的纵向相关时间，包括非常低的阻尼，非常高的阻尼和Kramers转换方式。而且，纵向相关函数的频谱的低频部分可以由具有由该通用逸出率公式确定的半角宽度的单个洛伦兹近似。

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