Toward the Coherent Control of Large Amplitude Molecular Dynamics

在这个由化学系化学结构、动力学和机制计划资助的项目中，加州理工学院的杰弗里·布莱克教授将进行一项研究计划，寻求使用亚皮秒太赫兹(THz)脉冲来相干控制孤立分子和氢键团簇中的大振幅分子动力学。具体地说，通过在铌酸锂晶体中产生倾斜的脉冲前沿和/或气体介质中的等离子体丝化，将产生强烈的(高达mV/cm)太赫兹电场，以便将目标系统中最软的分子内和分子间模式泵浦到高激发程度。由此产生的态分布和内部动力学将用啁啾脉冲傅里叶变换微波光谱来探测，并具有完全本征态分辨率。第一个目标是小的益生菌分子，它们也是对生物聚合物的结构和活动至关重要的氢键相互作用的分子模型，以及氢键簇，它阐明了支配大气中水相气溶胶形成的基本相互作用。泵浦-探测光谱和时间分辨动力学将提供使用下一代微波到太赫兹望远镜(如阿塔卡马大毫米阵列)进行观测所需的转换工具，用于探索液体和生物聚合物的复杂势能面，以及开发用于大幅度运动的相干控制策略，即使是在最简单的氢键组件构建块中也是如此。这项研究使用了新的光源和探测技术，使人们能够以前所未有的分辨率观察氢键分子之间微弱但非常重要的相互作用。了解这些相互作用在许多领域都很重要；这项工作的重点是在空间和水团中监测到的小益生菌分子之间的相互作用，这些相互作用对于了解大气中气溶胶粒子的形成和去向很重要。该项目将在研究生和本科生的协助下进行，其中包括妇女和代表人数不足的少数群体成员。除了这些活动，布莱克教授领导的小组还积极参与加州理工学院K-12教育/推广计划，并正在为当地课堂上的实践科学课程开发新的光谱学教学模块。这里提供的支持还将使开发低成本的实验室仪器和实验成为可能，用于以探究为基础的本科教学，突出分子动力学和光谱学之间的紧密联系。

In this project, funded by the Chemical Structure, Dynamics and Mechanisms Program of the Chemistry Division, Prof. Geoffrey Blake of the California Institute of Technology will conduct a research program that seeks to coherently control the large amplitude molecular dynamics in isolated molecules and hydrogen bonded clusters using sub-picosecond Terahertz (THz) pulses. Specifically, intense (up to MV/cm) THz electric fields will be generated by tilted pulse front generation in lithium niobate crystals and/or plasma filamentation in gaseous media in order to pump the softest intramolecular and intermolecular modes in target systems to high degrees of excitation. The resulting state distributions and internal dynamics will be probed, with complete eigenstate resolution, by chirped pulse-Fourier Transform MicroWave spectroscopy. The first targets are small prebiotic molecules that also serve as molecular models of hydrogen bonding interactions pivotal to the structure and activities of biopolymers, along with hydrogen bonded clusters that illuminate the fundamental interactions that govern the formation of aqueous aerosols in the atmosphere. The pump-probe spectra and time-resolved dynamics will provide the transformational tools that are needed for observations with the next generation of microwave to THz telescopes such as the Atacama Large Millimeter Array, in the exploration of the complex potential energy surfaces of liquids and bioplymers, and in the development of coherent control strategies for the large amplitude motion that operate in even the simplest building blocks of hydrogen bonded assemblies. This research uses new light source and detection technology that allows the weak but very important interactions between hydrogen bonded molecules to be observed with unprecedented resolution. Understanding these interactions is important in many fields; this work focuses on interactions in small prebiotic molecules that are monitored in space and water clusters that are important to understanding the formation and fate of aerosol particles in the atmosphere. This project will be conducted with the assistance of graduate and undergraduate students, including women and members of underrepresented minorities. In addition to these activities, the group headed by Prof. Blake is strongly involved in the Caltech K-12 educational/outreach programs, and is developing new teaching modules in spectroscopy for hands-on science curricula in local classrooms. The support provided here will also make it possible to develop low-cost laboratory instruments and experiments for inquiry-based undergraduate instruction that highlights the strong ties between molecular dynamics and spectroscopy.