Position and line shape of the 2t2g-shape resonance in S 2p-excited sulfur hexafluoride clusters

The energy position and line shape of the 2t2g-shape resonance in X-ray absorption spectra near the S 2p edges is investigated for free molecular SF6 and molecular units that are bound in clusters. We apply the double-barrier optical potential model in order to derive relationships between the position and line shape of the shape resonance where both intramolecular S-F and intermolecular SF6-SF6 separations in clusters is considered. The model calculations indicate that these intra- and inter-molecular separations are sensitive parameters. The comparison of the experimental and theoretical results shows that slight changes in molecular and intermolecular geometry affect the energy position and the line shape of the 2t2g-shape resonance in clusters. Processes affecting the line shape are discussed. It is found that the zero-point intramolecular motion leads to a noticeable broadening of the adiabatic 2t2g-shape resonance in free molecules and that the zero-point intermolecular motion also broadens the shape resonance in clustered molecules