Agradecimentos: S.d'A.S. and M.H.F.B. acknowledge support from CNPq, FINEP (under project CT-Infra) and from Fundação Araucária. M.T.doN.V. and M.A.P.L. acknowledge support from CNPq and FAPESP. S.d'A.S. and M.H.F.B acknowledge computational support from Carlos M. de Carvalho at DFis-UFPR and at LCPAD-UFPR. The authors also acknowledge computational support from CENAPAD-SP. This work was also conducted under a Memorandum of Understanding between the University of Trento and the Flinders University node of the Australian Research Council Centre for Antimatter-Matter Studies Ver menos

Abstract: We present experimental and theoretical cross sections for positron collisions with ethene molecules. The experimental total cross sections (TCSs) were obtained with a linear transmission technique, for energies from 0.1 eV up to 70 eV. The calculations employed the Schwinger multichannel method and were performed in the static plus polarization approximation for energies up to 10 eV. Our calculated elastic cross sections indicate a Ramsauer-Townsend minimum around 2.8 eV and a virtual state, in agreement with previous calculations by da Silva et al. [Phys. Rev. Lett. 77, 1028 (1996)]. We found reasonable agreement between the calculated elastic integral cross section and the measured total cross section below the positronium formation threshold. The present results are also in quite good agreement with available theoretical and experimental data, although for the experiments this is only true for TCSs above about 7 eV Ver menos