Absolute Total Electron Scattering Cross Sections inH2andD2for Low Electron Energies

Abstract

The Ramsauer technique has been used to measure the total electron scattering cross sections in ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ as a function of electron energy from 0.25 to 15 eV with an estimated probable error of ±3%. Within the experimental error, the cross sections in ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ are identical. The cross section first increases smoothly with increasing electron energy from 9.2 ${\mathrm{\AA }}^2$ at 0.25 eV to a maximum of 15.7 ${\mathrm{\AA }}^2$ at about 2.8 eV and then decreases smoothly to 7 ${\mathrm{\AA }}^2$ at 15 eV. A modified effective-range formula has been used to fit the data for energies less than 1 eV, yielding a zero-energy scattering cross section of 5.53 ${\mathrm{\AA }}^2$. A gas-cathode interaction which may affect the determination of the absolute energy scale in some experiments by as much as 0.35 eV is discussed.