Abstract: The vacuum ultraviolet photoionization and photodissociation of pentafluoroethane have been studied by using synchrotron radiation. The ionization potential of pentafluoroethane is determined to be (12.25±0.10) eV. Photoionization efficiency (PIE) curves for CF₂CF₃⁺、CHFCF₃⁺、CF₂CF₂⁺、CF₃⁺、CHF₂⁺、CHF⁺ and CF⁺ have been measured. The appearance potentials (AP) of these ions are obtained from their PIE curves, and they are (13.93±0.10) eV, (15.25±0.10) eV, (15.12±0.10) eV, (13.30±0.05) eV, (13.05±0.08) eV, (19.17±0.10) eV and (19.56±0.15) eV, respectively. In addition, the energetics of the dissociative photoionizations have been examined by ab initio Gaussian-3 calculations. The computational results are useful in establishing the dissociation channels near the ionization thresholds. According to the experimental results and the energies calculated by Gaussian-3 theory, the main possible pathways of the photodissociation have been analyzed. And the dissociation energies of the molecule and its cation have been derived from experiment and calculation.

Key words: Pentafluoroethane, Photoionization, Appearance potential, Dissociation energy