Electronic excitation of the ³B₂ state of thiophene molecule by low-energy electron collisions

The Schwinger multichannel method is employed to study elastic and electronically inelastic collisions of low-energy electrons by the thiophene molecule. It is well known that the elastic integral cross section for electron-thiophene scattering presents three shape resonances, some of which located around the opening region of the first excited state. The main purpose of this work is to evaluate the influence of polarization effects on the positions of the resonances appearing in the elastic channel and its potential impact on the description of the electronic excitation process involving the transition from ground state to the ³ B ₂ excited state of thiophene. Our cross section results indicate that target polarization may affect the electronic excitation process in the region of the threshold of the ³ B ₂ excited state, but its impact seems to be related to the effect of polarization on the resonances in the elastic channel. More specifically, there are cases (A ₂ and B ₁ symmetries) where the overlap of the shape resonance with the threshold changes significantly with the inclusion of polarization resulting in a considerable modification in the magnitude of the electronically inelastic cross section, while in other case (B ₂ symmetry) a similar overlap is not accompanied by sensible changes in the magnitude of the excitation cross section. Our excitation functions at scattering angles of 90° and 135° are compared with the calculations and measurements of Loupas et al (2018 J. Phys. Chem. A 122 1146) and show in general a qualitative agreement. (paper)