Cavity Enhanced Ultrafast Transient Absorption Spectroscopy

在这个由化学系化学测量和成像项目资助的项目中，托马斯K.艾利森和他在斯托尼布鲁克大学的研究小组将开发超快激光技术，用于研究非常稀的气相样品中分子的运动和反应。 基本方法涉及所谓的光学谐振腔，这将大大增加基于激光的测量的灵敏度。 本项目的目的是利用频率梳状激光器和高精细光学谐振器，开发和实现飞秒时间分辨光谱学的新技术。本项目的目的是研究分子在光的激发下如何运动，以及如何处理激发能量。与传统方法相比，灵敏度的大幅提高扩展了全光学超快光谱的能力，例如宽带瞬态吸收光谱和2D光谱，以稀释分子束中产生的气相样品。这使得研究孤立分子和小分子团簇的超快动力学成为可能，包括在真空中冷超音速膨胀中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和微溶剂化系统（例如，包含感兴趣的分子和一些溶剂分子的簇）中的超快内转换。扩展到中红外技术来研究小氢键团簇的振动动力学将阐明氢键液体中的合作效应。

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.