Electron scattering from acetylene: elastic integral and differential cross sections at low energies

Abstract

Calculations have been carried out for the scattering of slow electrons from acetylene molecules in the gas phase, using the fixed-nuclei (FN) dynamical approximation and computing elastic cross sections only, integral and differential. Ab initio results at the exact static-exchange (ESE) level have been supplemented by a model local potential describing short-range and long-range polarization forces. The target wavefunction was obtained at the SCE level from a multicentre expansion over Gaussian orbitals (GTOs). Both the static and exchange interactions, Vst and Vex, were obtained from a discrete basis by using multicentre orbitals and the separable exchange approximation. The final results are compared with available experiments and a detailed search for the 2.6 eV shape resonance is discussed. The very-low-energy computed cross sections also reveal the presence of a Ramsauer-Townsend (RT) minimum.