Measurements of total cross sections for positrons and electrons colliding with atomic hydrogen

We have made the first measurements of total cross sections (${\mathrm{Q}}_{\mathit{T}}$) for 5 to 302 eV positrons (${\mathit{e}}^{+}$) and 31 to 302 eV electrons (${\mathit{e}}^{\mathrm{-}}$) scattered by atomic hydrogen. A beam transmission technique is used where the ${\mathit{e}}^{+}$ or ${\mathit{e}}^{\mathrm{-}}$ beam passes through a low temperature scattering cell containing a mixture of hydrogen atoms and molecules generated in an adjacent radio-frequency discharge region. We obtain absolute ${\mathrm{Q}}_{\mathit{T}}$ by using the factor required to normalize our present relative ${\mathit{e}}^{+\mathrm{-}}$ ${\mathrm{H}}_2$ ${\mathrm{Q}}_{\mathit{T}}$ measurements to our prior absolute results. The present ${\mathit{e}}^{+}$- and ${\mathit{e}}^{\mathrm{-}}$-H ${\mathrm{Q}}_{\mathit{T}}$ are found to be merged within about 5% between 31 and 302 eV.