Individual Efficiency Curves for the Excitation of 23S and 21S States of Helium by Electron Impact

Abstract

Measurement of kinetic energy of electrons released in ionization of argon by helium atoms in metastable 2¹S and 2³S states was applied for the determination of separated efficiency curves for the two states. No quenching in electric field or deflection in an inhomogeneous magnetic field was necessary. The ratio of the cross sections for the 2¹S and 2³S states, excited by electron impact, was found larger than that determined in experiments in which secondary electron emission was used for detecting metastable atoms. This seems to indicate that the Penning ionization cross section for argon by helium atoms in the 2¹S state is larger than that by the atoms in the 2³S state.