Total cross sections for electron scattering by NH3 molecules in the energy range 300-5000 eV

Total cross sections for electron scattering by NH3 molecules in the energy range 300-5000 eV have been measured with experimental errors of about 3%. The method was based on a transmission-beam technique and a detailed error-source analysis is included. Present results have been compared with available experimental and theoretical data. The dependence on electron energy of the total cross sections obtained shows an asymptotic behaviour, in agreement with the Born-Bethe approximation. In addition, an analytical formula is provided to extrapolate total cross sections to higher energies.