Measurements of the triple-differential cross section for low-energy electron-impact ionization of helium

The triple-differential cross section for ionization of helium by low-energy electron impact is investigated over the energy and angular variables. Measurements have been made for primary electron energies near 100 eV, ejected electron energies of 5, 10, and 20 eV, and scattering angles 15^∘{}, 20^∘{}, and 30^∘{}. The forward lobe of the triple-differential cross section is found to be approximately cylindrically symmetric.