Time-Domain Light Scattering Spectroscopy of Condensed Matter

一个全面的实验计划，研究几个 凝聚态动力学中的相关问题， 提出了分辨光谱技术。 “冲动” 受激拉曼、布里渊和瑞利散射 技术，这些技术一起构成了一个全时域 光散射光谱的形式，将进行 飞秒到纳秒的时间尺度来研究 结构相变附近的晶体动力学， 无公度结晶相和粘弹性， “简单”流体。强耦合、高耗散模式 在这些系统中重要的是将通过直接 观察它们随时间变化的运动。 在晶体附近 结构相变，（通常过阻尼）顺序 在无公度相位中的参数和声学模式将是 考察 粘弹性流体中的色散声学行为 将表征液体-玻璃化转变区附近的。 最后，阻尼振动（即惯性）的性质， 简单分子液体中的定向运动 阐明。 时域方法使用互补 常规频域光散射光谱 这些系统，因为它非常适合表征 极低频模式，严重阻尼（包括 过阻尼）模式、色散模式和强 这些类型的耦合模式。 行为上的相似之处 要研究的物质种类将有助于 实验工作和分析以及理论 结果的解释。

A comprehensive experimental program for the study of several related problems in condensed-matter dynamics using novel time- resolved spectroscopy techniques is proposed. "Impulsive" stimulated Raman, Brillouin, and Rayleigh-scattering techniques, which taken together comprise an all-time-domain form of light-scattering spectroscopy, will be carried out on femtosecond through nanosecond time scales to examine the dynamics of crystals near structural phase transitions, incommensurate crystalline phases, and viscoelastic and "simple" fluids. Strongly coupled, highly dissipative modes important in these systems will be characterized through direct observation of their time-dependent motions. In crystals near structural phase transitions, the (often overdamped) order parameter and acoustic modes in incommensurate phases will be examined. Dispersive acoustic behavior in viscoelastic fluids near the liquid-glass transition region will be characterized. Finally, the damped vibrational (i.e. inertial) nature of orientational motion in simple molecular liquids will be elucidated. The time-domain approach used complements conventional frequency-domain light-scattering spectroscopy of these systems since it is well suited for characterization of very low-frequency modes, heavily damped (including overdamped) modes, dispersive modes, and strongly coupled modes of these types. The similarities in behavior of the classes of matter to be studied will facilitate experimental work and analysis as well as theoretical interpretation of results.