Electron-impact core excitation of SF6. II. Generalized oscillator strengths in the S 2p region

Cross sections for the valence shell excitations of nitrous oxide studied by fast electron impact

The generalized oscillator strengths, differential cross sections, as well as the integral cross sections for electron impact excitation of the B (1)Delta, C (1)Pi, and D (1)Sigma(+) states of N(2)O have been determined at an incident electron energy of 2500 eV. A generalized oscillator strength analysis reveals that the B (1)Delta<--X (1)Sigma(+) transition is dominated by the quadrupolar component. From the comparison to the previous experimental results, it is found that the first Born approximation is not satisfied for the C (1)Pi excitation while it is valid for the D (1)Sigma(+) excitation at an incident electron energy of 200 eV. The BE-scaled integral cross section for the B (1)Delta excitation from its threshold to 5000 eV was calculated based on its generalized oscillator strength, and the present integral cross sections for the excitation of the C (1)Pi and D (1)Sigma(+) states are in good agreement with the calculations using the BEf-scaling approach.

Shape resonances in molecular clusters: the 2t2gshape resonances in S 2p-excited sulfur hexafluoride clusters

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.