We report the results of a complex Kohn variational calculation of the low-energy electron scattering from ethylene, ${\mathrm{C}}_2$${\mathrm{H}}_4$. Our calculations are the first to confirm the existence of the Ramsauer-Townsend effect in a molecule which possesses a permanent quadrupole moment and suggest that such minima may be found in electron-scattering cross sections for many nonpolar molecules. The calculations also reveal a low-energy shape resonance in ${}_{}{}^2{}_{}{}^{}$${\mathit{B}}_{2\mathit{g}}$ symmetry at 1.83 eV, in excellent agreement with both beam and swarm measurements.

• Received 19 February 1991

DOI:https://doi.org/10.1103/PhysRevLett.66.2728