Kinetic energy release distributions in the dissociation of energy-selected fluoroethene and 1,1-difluoroethene ions

The unimolecular dissociation of energy-selected fluoroethene and 1,1-diflu oroetheneions has been investigated by the threshold photoelectron photoion coincidence (TPEPICO) technique. The breakdown diagrams of the 1,1-difluor oethene and fluoroethene have been recorded in the range 13-22 eV. From the time-of-flight spectra, complete distributions of the kinetic energy relea sed (KERD) in the dissociation of these energy-selected ions have been deri ved. For the HF loss reaction channel, the KERD peaks at about 200 meV for low excitation energies but becomes thermal at higher excitation energies. For the F loss channel, the KERD peaks at zero kinetic energy for low excit ation energy but at about 200 meV for high excitation energy. The analysis of the KERD provides evidence that consecutive fragmentation takes place fo r 1,1-difluoroethene at energies above 19 eV.