RUI: Forced Rayleigh scattering on heterogeneous liquid crystals: Directional solidification at forced wavevectors

三一大学的丹尼尔·R·斯皮格尔博士因其在非均相液晶上的强迫瑞利散射(FRS)的研究而受到化学系物理化学计划的资助。在向列相定向凝固过程中，界面调制伴随着杂质扩散驱动的不稳定性，可以用FRS技术来模拟和探测。在这种变换系统的选定波长(频率)上的非均匀微扰将被用来实验地探索这种液晶系统的非线性反应扩散模型和图案的形成。利用FRS泵浦光束干涉条纹对定向凝固液晶的向列相-各向同性界面进行调制。利用绕射的FRS探测光束将跟踪特定傅里叶分量幅度的时间演变。从根本上说，与基本线性不稳定性相关的重要色散关系将在实验上得到映射。非线性动力系统，包括那些产生非平衡图案形成的系统，在研究和化学工业中正变得越来越普遍。对这类系统的分析和建模对于开发控制这类现象的定量方法很重要。三一大学的FRS实验应该提供明确的手段，以改进我们开发此类模型的实验方法，并测试我们对此类模型的理解。此外，参加这项研究计划的本科生将获得无价的最先进的培训。

Dr. Daniel R. Spiegel of Trinity University is funded for his research on forced Rayleigh scattering (FRS) on heterogeneous liquid crystals by the Physical Chemistry Program of the Chemistry Division. The interfacial modulation accompanying an impurity-diffusion-driven instability during nematic-directional solidification can be stimulated and probed by FRS techniques. Non-homogeneous perturbations at selected wavelengths (frequencies) of such transforming systems will be used to experimentally probe the nonlinear reaction-diffusion modeling and pattern formation of such liquid-crystal systems. FRS pump-beam interference fringes will be used to effect modulation of the nematic-isotropic interface of a directionally solidified liquid crystal. The temporal evolution of specific Fourier component amplitudes will be tracked using diffracted FRS probe beams. Fundamentally important dispersion relations relevant to the basic linear instability will be mapped experimentally.Nonlinear dynamical systems, including those that produce non-equilibrium pattern formation, are becoming increasingly upbiquitous in research and in chemcial industry. The analysis and modeling of such systems is important for developing quantitative methods for controlling such phenomena. The FRS experiments at Trinity University should provide definite means for improving our experimental approaches to developing such models, and for testing our understanding of such models. Furthermore, invaluable state-of-the-art training will be afforded the undergraduates participating in this research program.