Accurate low-energy electron scattering data are needed in many fields of
physics. However, accurate experiments are difficult to design and to carry
out. By 1967 low-energy electron–He cross sections had been measured by
two different techniques, designed to provide accurate data. Unfortunately,
the data differed by amounts well outside the estimated error bars. Despite
the relative simplicity of the He atom, decisive theoretical calculations on
the e–He system could not be done with methods available in 1967. After
a decade of development of theoretical methodology it became possible in 1979
to carry out calculations with absolute estimates of residual error limits.
The results were found to agree closely with the momentum transfer cross
section deduced from electron swarm data and with recent beam data by improved
techniques, but were inconsistent with the original beam data of 1965. More
recently, a similar conflict exists between data measured for electron-impact
vibrational excitation of the hydrogen molecule by electron swarm and beam
techniques. This conflict has persisted despite great progress in beam
scattering techniques and in theoretical methods. A brief review of the
relevant electron scattering theory will be given.
Resonant vibrational-excitation cross sections and rate constants for low-energy electron scattering by molecular oxygen
