121st General Meeting of the KCS

Type Symposium
Area Recent Trends in Time- and Spatial-resolved Spectromicroscope
Room No. Room 402
Time THU 16:30-:
Code PHYS1-3
Subject Ultrafast chemical reactions investigated by time-resolved stimulated Raman spectroscopy
Authors YOONSOO PANG*, Myungsam Jen, Sebok Lee
Department of Chemistry, Gwangju Institute of Science and Technology, Korea
Abstract Ultrafast chemical reactions in the excited states are directly observed by femtosecond stimulated Raman spectroscopy with both high temporal (<50 fs) and spectral (<10 cm-1) resolutions. Intramolecular proton transfer reaction of alizarin (1,2-dihydroxyanthraquinone) occurs in 70-80 fs upon the photoexcitation, where the population decays and the spectral changes (peak shifts and bandwidth changes) of the major C=C and C=O stretching vibrations of reactant (locally-excited) and product (proton-transferred) molecules of the proton transfer reaction. We propose that the intramolecular proton transfer of alizarin may occur via a transition state of a newly formed six-membered ring composed of carbonyl and adjacent hydroxyl groups. In addition to solute vibrational features, the changes in the solvent vibrational mode the S=O stretching of DMSO have been extensively studied to probe changes in the solvation via hydrogen bonding. Another proton transfer reaction of curcumin in DMSO was also investigated, where the ground state bleaching for the solute vibrational modes and the S=O stretching bands of DMSO both represent a fast chemical reaction (~3 ps) and subsequent solvent relaxations (15-20 ps). From these results, we showed that femtosecond stimulated Raman spectroscopy can be successfully applied to probe both ultrafast chemical reactions of reactants in the excited states and the following solvation between the products and solvent molecules.
E-mail ypang@gist.ac.kr