Probing Intermolecular Dynamics with Nonlinear Ultrafast THz Spectroscopy

在化学部化学结构、动力学和机理(CSDM-A)计划的支持下，加州理工学院(加州理工学院)的杰弗里·布莱克和斯科特·库欣正在开发复杂的光谱，以研究液体和液体混合物的结构和动力学。例如，决定液态水性质的分子之间的作用力，只能用频率远低于可见光的光直接探测，大约是几太赫兹(THz)。尽管如此，液体中的运动速度非常快，一个重大的技术挑战是开发非常短但量身定做的太赫兹光脉冲。布莱克和库欣博士和他们的学生将推进超快非线性太赫兹光谱仪，以研究在溶解离子存在的情况下氢键液体(如水)中的分子间力。他们的发现可能导致新的太赫兹方法，推动可持续能源、电信和国家安全方面的应用。该项目将提供一个高度跨学科的环境，不仅包括来自加州理工大学的研究生和本科生，还包括来自附近少数族裔/拉美裔服务机构的本科生，从而降低进入量子科学的门槛。直接探测液体和其他分子材料中的分子间力，特别是那些涉及氢键的分子间作用力，需要太赫兹光子，但必要的时间分辨率是亚皮秒。因此，必须产生频率和载波包络相位含量可控的多倍频程脉冲。加州理工学院的这一合作团队将把库欣集团的近红外/可见光脉冲压缩专业知识与加州理工学院制造的新型太赫兹发射器结合起来，将布莱克集团首创的泵浦-探测和太赫兹-太赫兹-拉曼(TTR)方法驱动到10-30飞秒的范围内。主要的科学重点将是研究液态水和混合物中的氢键动力学，特别是在高离子强度和表现出不寻常的混合热力学的醇等组分之间的氢键动力学。量身定制的太赫兹脉冲能力的更广泛的科学应用包括在可持续能源生成和存储以及量子信息科学中对广泛过程的选择性非线性研究。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Structure, Dynamics, and Mechanisms-A (CSDM-A) program in the Division of Chemistry, Geoffrey Blake and Scott Cushing of the California Institute of Technology (Caltech) are developing sophisticated spectroscopies to study the structure and dynamics of liquids and liquid mixtures. The forces between molecules that determine the properties of liquid water, for example, can be directly probed only using light that is much lower frequency than that of visible light, on the order of a few terahertz (THz). Still, the motions in liquids are very fast, and a significant technical challenge is to develop very short, yet tailored, pulses of THz light. Drs. Blake and Cushing and their students will advance ultrafast nonlinear THz spectroscopies to study the intermolecular forces in hydrogen bonding liquids (e.g., water) in the presence of dissolved ions. Their discoveries could lead to new THz methodologies that advance applications in sustainable energy, telecommunications, and national security. The project will provide a highly interdisciplinary environment that includes graduate students and undergraduates, not only from Caltech but from nearby minority/Hispanic serving institutions, lowering the barriers for entry into quantum science.Direct probes of intermolecular forces in liquids and other molecular materials, especially those involving hydrogen bonds, require THz photons, yet the necessary time resolution is sub-picosecond. Thus, multi-octave pulses with controllable frequency and carrier envelope phase content must be generated. This collaborative Caltech team will combine the near-IR/Visible pulse compression expertise in the Cushing group with novel THz emitters fabricated at Caltech to drive pump-probe and THz-THz-Raman (TTR) approaches pioneered in the Blake group into the 10-30 femtosecond regime. The principal scientific focus will be studies of the hydrogen bond dynamics in liquid water and mixtures, especially at high ionic strength and with components such as alcohols that demonstrate unusual thermodynamics of mixing. The broader scientific applications of the tailored THz pulse capabilities include the selective nonlinear studies of a broad range of processes in sustainable energy generation and storage, and in quantum information science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.