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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Molecular Dipole Chains: Excitations and Dissipation
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Molecular Dipole Chains: Excitations and Dissipation

机译：分子偶极链：兴奋和消散

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摘要

As a model for orientational excitation of molecular arrays, we examine the excitation behavior and energy flow patterns in a model system. The model is simply a chain of classical point dipoles with fixed mass center, rotating in a plane containing the intermolecular axis, and interacting by the classical dipole potential. At low energies, the dispersion relation is quite different from that for a phonon system, showing a flat frequency maximum at κ = 0. Correlation function analysis shows a significant transition from the low-energy regime in which the local dipole motion is predominantly oscillatory (with periodic correlation functions and Fourier components that maximize at a well-defined oscillation frequency), to a high-energy situation in which a Rayleigh peak occurs in the κ = 0 Fourier component, and finite frequency response occurs only for higher wave vector. Physically, this transition occurs for thermal energy roughly equal to the typical magnitude of the local dipolar interaction. Thus for energies above this transition, the kinetic energies are high enough that the local motion is predominantly rotatory rather than oscillatory. These changes are also seen in the frequency moments and Kirkwood g-factors. The simulations show that initial energy deposited in one rotating dipole passes down the chain almost like a solitary wave, reflecting off of the free chain end and then traversing the chain again.
机译：作为分子阵列定向激发的模型，我们研究了模型系统中的激发行为和能流模式。该模型只是具有固定质心的经典点偶极子链，在包含分子间轴的平面中旋转，并通过经典偶极子势相互作用。在低能量下，色散关系与声子系统的色散关系有很大不同，在κ= 0处显示出平坦的最大频率。相关函数分析显示，与低能量状态相比有明显的转变，在低能量状态下，局部偶极子运动主要是振荡的（具有周期性相关函数和在明确定义的振荡频率处最大化的傅立叶分量），到高能态，在其中瑞利峰出现在κ= 0傅立叶分量中，而有限频率响应仅出现在较高的波矢上。从物理上讲，这种转变是在热能大致等于局部偶极相互作用的典型幅度时发生的。因此，对于高于此跃迁的能量，动能足够高，以至于局部运动主要是旋转的而不是振荡的。在频率矩和柯克伍德g因子中也可以看到这些变化。仿真表明，沉积在一个旋转偶极子中的初始能量几乎像一个孤波一样沿链向下传播，从自由链末端反射回来，然后再次穿过链。

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