Infrared laser induced multiphoton dissociation of decafluorocyclopentane in a concerted pathway: time-resolved evidence of difluorocarbene formation

Abstract

The infrared multiphoton dissociation (IRMPD) of decafluorocyclopentane (DFCP) generates tetrafluoroethylene and difluorocarbene as the primary products. The :CF₂ dimerizes to form C₂F₄; the kinetics of the reaction is followed by monitoring the disappearance of :CF₂ absorption at 249 nm in real time after the CO₂ laser pulse, with a rate constant k₂ = 4.35 × 10⁷ M^-1s^-1. The vibrational temperature associated with the nascent :CF₂ is found to be 1100 K. The MPD yield of DFCP shows a strong fluence dependence, with a threshold of approx. 0.5 J/cm² for the 10 R(40) CO₂ laser line. The MPD spectra reveal two peaks, one 22 cm^-1 red-shifted from the 989 cm^-1 strong IR absorption band. Addition of SF₆ decreases the MPD yield.