VUV photon induced fluorescence study of SF5CF3

The interaction of SF$_5$CF$_3$ with vacuum-UV radiation has been investigated by photon induced fluorescence spectroscopy. Total fluorescence yield and dispersed fluorescence spectra of SF$_5$CF$_3$ were recorded in the 200-1000 nm fluorescence window. In all cases, the fluorescence spectra resemble those of CF$_3$X (X=H, F, Cl, and Br) molecules. At photon energies below 20 eV, the emission is attributed to the excited CF$_3$ and CF$_2$ fragments. The threshold for the CF$_3$ emission is 10.2 ± 0.2 eV, giving an upper-limit estimate for the SF$_5$-CF$_3$ 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 SF$_5$CF$_3$ are attributed to electronic transitions from valence to Rydberg orbitals, following similar assignments in CF$_3$X molecules. The photoabsorption spectrum of SF$_5$CF$_3$ shows features at the same energies, indicating a strong contribution from Rydberg excitations