VUV photon induced fluorescence study of SF5CF3

Abstract

The interaction of SF₅CF₃ with vacuum-UV radiation has been investigated by photon induced fluorescence spectroscopy. Total fluorescence yield and dispersed fluorescence spectra of SF₅CF₃ were recorded in the 200–1000 nm fluorescence window. In all cases, the fluorescence spectra resemble those of CF₃X (X = H, F, Cl, and Br) molecules. At photon energies below 20 eV, the emission is attributed to the excited CF₃ and CF₂ fragments. The threshold for the CF₃ emission is 10.2 ± 0.2 eV, giving an upper limit estimate for the SF₅–CF₃ bond dissociation energy of 3.9 ± 0.3 eV. The excitation functions of the CF₃ and CF₂ emissions were measured in the photon energy range 13.6–27.0 eV. The resonant structures observed in SF₅CF₃ are attributed to electronic transitions from valence to Rydberg orbitals, following similar assignments in CF₃X molecules. The photoabsorption spectrum of SF₅CF₃ shows features at the same energies, indicating a strong contribution from Rydberg excitations.