A Theoretical Study on the Electronic Excitation of the Pyridine Molecule by Electron Impact

In this work, we present a theoretical investigation of electron collisions by the pyridine molecule. Elastic cross sections and electronic inelastic cross sections involving the transitions from the ground state to the 1³ A ₁, 1³ B ₂, 2³ A ₁, 1³ B ₁, 1³ A ₂, 1¹ B ₂, 1¹ B ₁, and 1¹ A ₂ excited states of pyridine are reported in the energy range from 0 to 50 eV. The scattering amplitudes were obtained using the Schwinger multichannel method, and the effects of multichannel coupling were accounted for by means of the minimal orbital basis for single-configuration interactions strategy. This strategy gives rise to an up to 301-states level of channel coupling calculation and enables us to evaluate the influence of flux stealing due to competition of energetically accessible channels upon the magnitude of the cross sections. Our computed elastic cross sections are in very good agreement with existing experimental data and provide positions for the three π* resonances, which are consistent with previous assignments. The present results involving the transitions from the ground state to the lowest-lying excited states of the pyridine are shown to be very sensitive to the influence of opening thresholds. Compared with the only theoretical result reported in the literature so far, our excitation cross sections present a higher magnitude. Despite this fact, for almost all transitions considered, the agreement in terms of general trends is reasonable and quite encouraging.