Electron collisions with atoms in excited states

Abstract

Cross sections for electron excitation of helium metastable levels to higher levels have been measured. When the metastable atoms are generated by a hollow cathode discharge, the measurements are limited to incident electron energies below 16 eV. An alternate target source utilizes the charge‐exchange reactions between He+ ions and alkali atoms which yield predominately He atoms in the metastable levels. With this target source cross section measurements have been made with electron energies up to 300 eV. Recently laser‐cooled atom traps have been used to measure electron scattering cross sections and electron‐impact ionization cross sections. This technique may be well suited for studying electron collisions with excited atoms.