Dynamics, Control and Energy Transfer at Terahertz Frequencies.

化学反应和生物反应是由超快的化学事件与慢得多的时间尺度上的动力学的耦合所支配的。这些超快化学事件通常发生在太赫兹频率上，有一系列间接的实验和理论证据表明，在这些频率上的振动运动的耦合控制了化学和生物中一系列反应的动力学。在这项提议中，在最近的技术发展的推动下，我将开发一台太赫兹多维光谱仪，它将能够在超快时间尺度上直接测量这些模式之间的耦合。这将使我能够测量太赫兹频率模式之间的能量转移和其中涉及的时间尺度。一旦证明这一点，这将是一种新的、强大的分析技术，具有许多可能的应用。初始测量将在两种非常不同的材料类型上进行，第一种是高能材料，第二种是在光照射下显示出戏剧性结构变化的材料(光诱导相变或PIPT)。在这两种材料中，都有强有力的间接实验和理论证据表明，THz频率振动之间的耦合控制着这些材料中的反应路径。这些材料的太赫兹多维光谱测量将提供第一个直接的实验证据，证明这些太赫兹振动之间的耦合直接控制着反应的路径和动力学。一旦这一点被证明，在这两组不同的材料中，这一新的分析技术可以应用于许多化学或生物问题，提供了对超快时间尺度上的反应动力学的理解--本质上使我们能够观察化学的发生。对反应动力学的这种基本理解也将为未来具有量身定制的物理和化学特性的材料的合理设计奠定基础。在使用太赫兹多维光谱测量太赫兹模式之间的耦合之后，专门设计的强太赫兹脉冲将被用于直接与这种振动运动相互作用，基本上控制和控制化学动力学。这种控制，再加上对反应动力学和相关时间尺度的了解，直接由太赫兹多维光谱提供，导致了一种可以控制反应的方法-具有巨大的潜在应用。该研究金将集中于太赫兹驱动的动力学的三个可能的应用，即(A)控制酶反应，(B)控制固态相变(药物相关多晶型的浓度)和(C)控制催化反应。

Chemical and biological reactions are governed by the coupling of ultrafast chemical events to dynamics on much slower timescales. These ultrafast chemical events often occur at THz frequencies and there is a range of indirect experimental and theoretical evidence to suggest that the coupling of vibrational motion at these frequencies governs the dynamics of a range of reactions across chemistry and biology. In this proposal, enabled by recent technological developments, I will develop a THz multidimensional spectrometer that will be able to measure directly the coupling between these modes on an ultrafast timescale. This will enable me to measure energy transfer between THz frequency modes and the timescales involved therein. Once demonstrated this will be a new, powerful analytical technique with many possible applications. Initial measurements will be performed on two very different material types, the first being energetic materials, and the second, materials that show a dramatic structural change upon illumination by light (a photo-induced phase transition or PIPT). In both materials there is strong indirect experimental and theoretical evidence that the coupling between THz frequency vibrations governs the reaction pathways in these materials. THz multidimensional spectroscopic measurements of these materials will provide the first direct experimental evidence that the coupling between these THz vibrations directly governs the pathway, and dynamics, of a reaction. Once this has been demonstrated, in these two diverse sets of materials, this new analytical technique can be applied to many chemical or biological questions, providing an understanding of reaction dynamics on ultrafast timescales - essentially enabling us to watch chemistry happen. This underlying understanding of reactions dynamics will also underpin the future rational design of materials with tailored physical and chemical properties. Following on from measuring the coupling between THz modes using THz multidimensional spectroscopy, specifically designed intense THz pulses will then be used to interact directly with this vibrational motion, essentially controlling and steering the chemical dynamics. This control, coupled with the understanding of reaction dynamics and the associated timescales provided directly by THz multidimensional spectroscopy, leads to a method where reactions can be steered and controlled - with huge potential applications. This fellowship will concentrate on three possible applications for THz-driven dynamics, namely (a) the control of enzymatic reactions, (b) the control of solid state phase transformations (concentrating of pharmaceutically relevant polymorphs) and (c) the control of catalytic reactions.