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

We have made the first measurements of total cross sections (QT) for 5 to 302 eV positrons (e⁺) and 31 to 302 eV electrons (e^-) scattered by atomic hydrogen. A beam transmission technique is used where the e⁺ or e^- 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 QT by using the factor required to normalize our present relative e^+-{H}₂$ ${Q}T$ measurements to our prior absolute results. The present ${e}⁺$- and ${e}^{{{-}}}$-H ${Q}T$ are found to be merged within about 5% between 31 and 302 eV.