Ultrafast bimolecular radical reaction between S1p-terphenyl and carbon tetrachloride: mode-specific acceleration of vibrational dephasing in reactant molecule

✍ Scribed by Koichi Iwata

• Publisher: John Wiley and Sons
• Year: 2008
• Tongue: English
• Weight: 217 KB
• Volume: 39
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/jrs.2104

✦ Synopsis

Abstract

Ultrafast bimolecular radical reaction proceeds between photoexcited p‐terphenyl and carbon tetrachloride. The lifetime of the first excited singlet (S~1~) state of p‐terphenyl in carbon tetrachloride measured with picosecond time‐resolved fluorescence spectroscopy is 5.6 ps, shorter than the typical lifetime in ordinary solvents, 0.95–2.8 ns, by a factor of 170 or more. Time‐resolved infrared spectroscopy reveals the generation of the trichloromethyl (CCl~3~) radical as a reaction intermediate. The decay kinetics of the CCl~3~ radical indicates that the CCl~3~ radical and the p‐terphenyl–Cl radical adduct, both of which are produced simultaneously by a radical reaction between S~1~p‐terphenyl and carbon tetrachloride, recombine to form the product. The picosecond time‐resolved Raman spectrum of the reactant S~1~p‐terphenyl shows that the dephasing process for the four vibrational modes at 1640, 1497, 1180, and 1017 cm^−1^ is selectively accelerated in carbon tetrachloride. The four vibrational modes probably have a large contribution from the motion of a specific atom or atoms where the intermolecular interaction that induces the bimolecular reaction is present. Copyright © 2008 John Wiley & Sons, Ltd.