Total cross sections for electron ${(e}^{-})$ and positron ${(e}^{+})$ scattering from ${\mathrm{C}}_3{\mathrm{H}}_8$ and ${\mathrm{C}}_3{\mathrm{F}}_8$ have been measured from 0.8 to 600 eV and 0.7 to 600 eV, respectively. We have also investigated differential elastic cross sections by electron impact from 2.0 to 200 eV, and compared them with the present theoretical results. For $e^{-}$ scattering from ${\mathrm{C}}_3{\mathrm{H}}_8,$ the cross sections are found to be larger by a factor of 2 than those of $e^{+}$ scattering below 20–30 eV. They show a large peak at 8 eV due to a shape resonance and a shoulderlike structure in the region of 20–40 eV. For $e^{-}$ scattering from ${\mathrm{C}}_3{\mathrm{F}}_8,$ the cross sections are again larger by at least a factor of 2 than those of $e^{+}$ scattering below 50 eV, and they have two peaks at 4 and 8 eV, followed by a broad peak in the region of 20–40 eV. Some small structures overlie the broad hump. Both $e^{-}$ and $e^{+}$ impact cross sections for ${\mathrm{C}}_3{\mathrm{H}}_8$ and ${\mathrm{C}}_3{\mathrm{F}}_8$ quickly approach each other beyond 200 eV. From the differential cross section study, we have been able to provide more detailed information on shape resonances, and also we have carried out some analysis of resonances in vibrational excitation results. In general, the total and integrated elastic cross sections are in good qualitative and quantitative agreement.

• Received 1 June 1998

DOI:https://doi.org/10.1103/PhysRevA.59.2006