Excitation functions for the formation of metastable He and Ar by electron impact

Abstract
The authors report the measurement of the electron impact excitation functions from threshold to 200 eV, for the formation of metastable helium and argon, using the time of flight technique. Both excitation functions have a broad maximum approximately 10 eV above threshold. Near threshold the results are in excellent agreement with earlier measurements, but they are in serious disagreement with the results of Kuprianov, the only previous measurements available over a large energy range. Recent plane and distorted wave Born approximation calculations for argon give a poor representation of the data.