Photoexcitation, Photoionization, and Photofragmentantion of CF₃CF₂CF₂C(O)Cl Using Synchrotron Radiation between 13 and 720 eV

Abstract

The main inner shell ionization edges of gaseous CF₃CF₂CF₂C­(O)­Cl, including Cl 2p, C 1s, O 1s, and F 1s, have been measured in Total Ion Yield (TIY) mode by using tunable synchrotron radiation, and several resonance transitions have been assigned with the help of quantum chemical calculations. Interestingly, resonance transitions observed in the C 1s region can be assigned to different carbon atoms in the molecule according to the degree of fluorine substitution. Ionic photofragmentation processes have been studied by time-of-flight mass spectrometry in the Photoelectron-Photoion-Coincidence (PEPICO) and Photoelectron-Photoion-Photoion-Coincidence (PEPIPICO) modes. These techniques revealed a “memory-lost” effect especially around the C 1s region, since the fragmentation events are independent of the energy range considered. Moreover, different fragmentation mechanisms were inferred from these spectra in the valence (13.0–21.0 eV) as well as in the inner (180.0–750.0 eV) electronic energy regions. The vibrational spectral features of CF₃CF₂CF₂C­(O)Cl have been interpreted in terms of a conformational equilibrium between two conformations (<i>gauche</i> and <i>anti</i> of the CC single bond with respect to the CCl one) at room temperature, as determined from quantum chemical calculations and the detailed analysis of the infrared spectrum