Cavity Enhanced Ultrafast Transient Absorption Spectroscopy

Suny At Stony Brook, Stony Brook NY

Investigators

Abstract

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.