Cavity Enhanced Ultrafast Transient Absorption Spectroscopy

在这个由化学系化学测量和成像计划资助的项目中，石溪大学的Thomas K.Allison教授和他的研究小组将开发超快激光技术，以研究分子在极稀薄的气相样品中的运动和反应。基本方法包括所谓的光学谐振腔，这将极大地提高基于激光的测量的灵敏度。这项新技术将被应用于理解分子受光激发时如何运动的基本光化学，以及它们如何处理这种激发能量。这个项目涉及使用频率梳激光和高精度光学谐振器进行飞秒时间分辨光谱的新技术的开发和实施。与传统方法相比，灵敏度有了很大的提高，扩展了全光超快光谱的能力，如宽带瞬时吸收光谱和二维光学光谱，用于稀释分子束中产生的气相样品。这使得能够研究孤立分子和小分子簇的超快动力学，包括在真空中冷超音速膨胀产生的设计分子系统。最初的研究将集中在具有可见发色团的孤立气相系统以及微溶剂化系统(例如，包含感兴趣的分子和几个溶剂分子的簇)中的超快内部转化。将研究氢键小团簇振动动力学的技术扩展到中红外光谱，将有助于阐明氢键液体中的协同效应。

In this project funded by the Chemical Measurement and Imaging Program of the Chemistry Division, Professor Thomas K. Allison and his research group at Stony Brook University will develop ultrafast laser techniques for studying the motions and reactions of molecules in very dilute gas phase samples. The basic approach involves what is called an optical resonant cavity, which will greatly increase the sensitivity of the laser based measurements. This new technique will be applied to understanding the basic photochemistry of how molecules move when they are excited by light, and how they dispose of this excitation energy.This project concerns the development and implementation of new techniques for performing femtosecond time-resolved spectroscopy using frequency comb lasers and high-finesse optical resonators. A large sensitivity improvement over traditional methods extends the capabilities of all-optical ultrafast spectroscopies, such as broad-band transient absorption spectroscopy and 2D optical spectroscopy to dilute gas phase samples produced in molecular beams. This enables the study of ultrafast dynamics of isolated molecules and small clusters of molecules, including designer molecular systems produced in cold supersonic expansions in vacuum. Initial studies will focus on ultrafast internal conversion in isolated gas phase systems with visible chromophores and also micro-solvated systems (e.g. a cluster containing the molecule of interest and a few solvent molecules). Extension of the techniques to the mid-IR to study the vibrational dynamics of small hydrogen bonded clusters will elucidate cooperative effects in hydrogen-bonded liquids.