Rotational Excitation of Diatomic Molecules by Electron Impact

Rotational excitation of homonuclear diatomic molecules can be simply yet accurately calculated from the scattering parameters of elastic electron-molecule scattering in the fixed-nuclei approximation. The total scattering cross sections for $\Delta j\ne 0$ transitions are independent of $s$-wave parameters, and ratios of $\Delta j=\pm 2$ cross sections agree with experimental results in ${\mathrm{H}}_2$ and with rotational close-coupling calculations. Absolute total and differential cross sections can be explained.