Total cross section measurements for electron scattering from molecular hydrogen at very low energies

Absolute cross sections were determined from transmission measurements made with an electron time-of-flight spectrometer in the energy range of 0.02-2 eV. The total cross section for molecular hydrogen was found to increase monotonically with energy; no resonance-like structures were observed. The isotopes H 2 , D 2 and HD have identical cross sections within the accuracy of the measurements (+or-2.5%). Helium cross section measurements were also made in order to check the spectrometer.