Electronic excitation of benzene by low energy electron impact and the role of higher lying Rydberg states

Abstract

Benzene is undoubtedly one of the most studied target molecules in electron scattering experiments and calculations. However, there is still a huge knowledge gap on the electronic excitation cross sections of this fundamental collision. Here, we report calculated differential and integral cross sections for elastic and electronic excitation, as well as total cross sections, for electron scattering by the benzene molecule, for impact energies in the 10–50 eV range. We have employed the Schwinger multichannel method, in two levels of approximation. By including extra diffuse functions in the second calculation, the role of higher lying Rydberg states in the multichannel coupling scheme was assessed. We found that such states have minor effects on the elastic and total cross sections. In contrast, the electronic excitation cross sections of the lower-lying bands decrease in magnitude when accounting for the higher Rydberg states, and this effect becomes more pronounced at lower impact energies. Our computed elastic cross sections are in quite good agreement with the available experimental data, whereas the comparison for the electronic excitation channels is still satisfactory. We also discuss the need for accurate excitation energies in order to properly compare theoretical and experimental electronic excitation cross sections.

Graphic Abstract