Elastic and inelastic low-energy electron scattering from pyridine

A comprehensive investigation of elastic and inelastic electron scattering from molecular pyridine is reported using the ab initio R-matrix method with the static exchange plus polarization and close-coupling approximations for incident energies up to 10 eV. The two well-known low-lying 1 B-2(1) and 1 (2)A(2) shape resonances as well as a 2 B-2(1) mixed-character resonance compare well with the theoretical and experimental results. We also detect five core-excited resonances (1 (2)A(1), 1 B-2(2), 3 B-2(1), 2 (2)A(2), and 4 B-2(1)), which lie above the first electronic excitation threshold. The total elastic cross sections and momentum transfer cross sections agree reasonably with previous reference data. Comparisons of the differential elastic cross sections of pyridine with those measured for benzene, pyrazine, and pyrimidine show remarkable agreement at scattering angles above 40 degrees but behave differently for forward scattering below 40 degrees below 6 eV, due to the dominant effect of the permanent dipole moment on the differential cross section in the low energy region with narrow scattering angles. Inelastic electronic excitation cross sections are presented, showing the influence of core-excited resonances below the ionization threshold for the first time.