ABSTRACT
The gas-to-solid shift of benzene is reported in the C 1s-core level regime, where the C 1s â π*-transition is investigated between 284.0 eV and 286.5 eV. Simultaneous experiments on the gas phase and condensed species are used to determine the gas-to-solid shift within an accuracy of ±5 meV. Specifically, it is observed that the vibrationally resolved C 1s â π*-transition in solid benzene is red-shifted by 55 ± 5 meV relative to the transition of the isolated molecule. Contrary to previously reported experimental data and estimates this gas-to-solid shift is somewhat smaller than the gas-to-cluster shift. It is significantly smaller than that determined in previous work on gaseous and condensed benzene. These results are discussed in terms of structural properties of molecular clusters and solid benzene by involving ab initio calculations as well as processes leading to spectral shifts of core-excited variable size matter. Finally, changes in the shape of the C 1s â π*-band upon the formation of solid benzene and benzene clusters are discussed.
ABSTRACT
Sulfur hexafluoride clusters are investigated in the S 2p excitation regime. For the first time special emphasis is put on high-energy resolution spectroscopy of shape resonances in free clusters. We have investigated the 2t(2g)-shape resonance occurring above the S 2p threshold as one typical example to study size effects that are related to shape resonances. A small redshift of this resonance of 30 +/- 5 meV occurs in clusters relative to the free molecule and changes in line shape are observed. A double-barrier optical potential model is applied for the analysis of intra- and intermolecular effects occurring in SF6 clusters, which is suitable for rationalizing the experimentally observed spectral changes. The experimental and theoretical results are briefly discussed in comparison to previous work on core-excited van der Waals clusters containing diatomic molecules.
