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

Calculations have been carried out for the scattering of slow electron s from acetylene molecules in the gas phase, using the fixed-nuclei (F N) dynamical approximation and computing elastic cross sections only, integral and differential. Ab initio results at the exact static-excha nge (ESE) level have been supplemented by a model local potential desc ribing short-range and long-range polarization forces. The target wave function was obtained at the SCE level from a multicentre expansion ov er Gaussian orbitals (GTOs). Both the static and exchange interactions , V-st and V-ex, were obtained from a discrete basis by using multicen tre orbitals and the separable exchange approximation. The final resul ts are compared with available experiments and a detailed search for t he 2.6 eV shape resonance is discussed. The very-low-energy computed c ross sections also reveal the presence of a Ramsauer-Townsend (RT) min imum.