Low Energy Electron-Molecule Scattering Experiments and the Theory of Rotational Excitation

The various experimental techniques used to obtain differential, total, and momentum-transfer electron-molecule scattering cross sections at low electron energies are reviewed, and observations are compared with theory, especially with theoretical calculations of rotational excitation cross sections for slow electrons incident on homonuclear diatomic molecules. A detailed discussion of the theory of rotational excitation by slow electrons is given, with particular attention to the merits and deficiencies of recent attempts to improve on the lowest-order Born approximation predictions, via the so-called rotational close coupling and adiabatic-nuclei approximations.