The trifluoromethyl radical, CF3•, is studied for the first time by means of threshold photoelectron spectroscopy (TPES). The radical is produced in the gas phase using the flash-pyrolysis technique from hexafluoroethane as a precursor. CF3+ total ion yield and mass-selected TPES of the radical are recorded using a spectrometer based upon velocity map imaging and Wiley-McLaren time-of-flight coupled to the synchrotron radiation. The high resolution of the instrument and of the photons allows the observation of rich vibrational progressions in the TPES of CF3•. By using Franck-Condon factors computed by Bowman and coworkers, we have been able to simulate the TPES. The initial vibrational temperature of the radical beam has been evaluated at 350 ± 70 K. The structures have been identified as transitions between (n1,n2) and (n1+,n2+) vibrational levels of CF3 and CF3+ with small excitation of the breathing mode, ν1+, and large excitation (n2+ = 10–26) of the umbrella mode, ν2+, in the cation. From the energy separation between the two resolved peaks of each band, a value of 994 ± 16 cm−1 has been derived for the ν1+ breathing frequency of CF3+. For the high-lying n2+ levels, the apparent ν2+ umbrella spacing, 820 ± 14 cm−1, is fairly constant. Taking into account the ν2+ anharmonicity calculated by Bowman and coworkers, we have deduced ν2+ = 809 ± 14 cm−1, and semi-empirical estimations of the adiabatic ionization energy IEad.(CF3•) are proposed in good agreement with most of previous works. A value of the vertical ionization potential, IEvert.(CF3•) = 11.02 eV, has been derived from the observation of a photoelectron spectrum recorded at a fixed photon energy of 12 eV.
Comprehensive vacuum ultraviolet photoionization study of the CF3• trifluoromethyl radical using synchrotron radiation
Present address: Institut Parisien de Chimie Moléculaire, UMR 7201–CSOB, Université Pierre et Marie Curie, 4, Place Jussieu BP 45, 75252 Paris Cedex 05, France.
Héloïse Dossmann (Soldi-Lose), Gustavo A. Garcia, Laurent Nahon, Barbara K. C. de Miranda, Christian Alcaraz; Comprehensive vacuum ultraviolet photoionization study of the CF3• trifluoromethyl radical using synchrotron radiation. J. Chem. Phys. 28 May 2012; 136 (20): 204304. https://doi.org/10.1063/1.4719529
Download citation file: