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Trifluoroiodomethane (CF3I) is one of the most appealing candidates for applications in plasma-based technologies in view of its many interesting advantages when compared to more standard gases such as trifluorobromomethane (CF3Br). Low-energy electrons are prone to decomposing these molecules into reactive species, and knowledge on the collision cross sections is fundamental for modeling transport and reactivity in plasma environments. Despite many studies on electron collisions with the abovementioned molecules, there are conflicting results on the assignment of shape resonances and on the magnitudes of total cross sections. Here, we try to clarify these aspects by performing ab initio electron scattering calculations. We found integral cross sections in fair agreement with the most recent measurements, in contrast to previous reports. For each molecule, we found a σCX*resonance (antibonding between the carbon and the heavy halogen) at 1 eV in CF3Br and at ∼0 eV in CF3I. Furthermore, there are three shape resonances of σCF*character; two are degenerate and account for a broad feature around 6 eV and the other one appears around 9.5 eV. We also discuss the possible role of the degenerate resonance in dissociative electron attachment reactions, as well as the impact of the heavy halogen on the cross sections and on the shape resonances.

We report a combined experimental and theoretical study of the electronic state spectroscopy of acrylic acid (C3H4O2) in the gas phase, by high-resolution vacuum ultraviolet (VUV) photoabsorption measurements in the 4.0–10.8 eV energy range, together with ab initiocalculations (vertical energies and oscillator strengths), which were used in the assignment of the valence transitions. We also discuss the Rydberg transitions for this molecular target, obtained using the experimental ionization energies available in the literature. The experimental spectrum presented in this paper represents the highest resolution data yet reported for acrylic acid and reveals new features not previously reported in the literature. The dominant transitions have been assigned to (π*(4a″) ← π(3a″)) and (π*(4a″) ← π(2a″)), the latter exhibiting excitation of the ν5′(a′) C = O stretching mode with mean energy of 0.155 eV. The measured absolute photoabsorption cross sections have been used to calculate the photolysis lifetime of acrylic acid in the upper stratosphere (20–50 km).

We report the extension of a model, based on geometrical optics, that was developed to explain similarities found in the cross sections of electron collisions with small hydrocarbons. Here we discuss the modifications made in the model and apply it to electron-collisions with molecules containing other atoms besides carbon and hydrogen. We then apply the model to predict the cross sections for the larger molecules C6H6, C8H8, C60and C6F6, and find that, even in this case, the model is useful for a first estimate of the theoretically calculated and experimental elastic cross sections.

We present elastic integral and differential cross sections for electron collisions with CS₂ molecules for energies up to 10 eV. To compute the cross sections we employed the Schwinger multichannel method implemented with pseudopotentials at the static-exchange plus polarization approximation. In particular, our integral cross section shows a sharp increase near zero energy, which is an indication of the existence of an s-wave virtual state, followed by a Ramsauer–Townsend minimum around 0.7 eV. Our results agree well with available experimental and theoretical results.

We present elastic integral and differential cross sections for electron collisions with CS2molecules for energies up to 10 eV. To compute the cross sections we employed the Schwinger multichannel method implemented with pseudopotentials at the static-exchange plus polarization approximation. In particular, our integral cross section shows a sharp increase near zero energy, which is an indication of the existence of an s-wave virtual state, followed by a Ramsauer-Townsend minimum around 0.7 eV. Our results agree well with available experimental and theoretical results.

Abstract We report results from an ab initio calculation of low-energy electron scattering by OCS molecules. We used the Schwinger multichannel method with pseudopotentials at the fixed-nuclei static-exchange approximation to calculate elastic integral, differential and momentum transfer cross sections in the energy range from 5 to 50 eV. We compare our results with available theoretical results and experimental data. Through the symmetry decomposition of our integral cross section and eigenphase sum analysis, we found structures in the cross sections that may be interpreted as shape resonances for ∑, ∏ and Δ symmetries. We compared the results for OCS with our previous results on the e––CS2 collision. In particular, we found a similar behaviour in the shape of the symmetry decomposed cross sections of OCS and of CS2 when, for the latter, we sum over the ‘g’ and ‘u’ contributions.