ELECTRON-SCATTERING FROM ACETYLENE - ELASTIC INTEGRAL AND DIFFERENTIAL CROSS-SECTIONS AT LOW ENERGIES

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, V-st and V-ex, 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.