Elastic and pure rotational excitation of the hydrogen molecule by intermediate-energy electrons

The eikonal amplitude for a fixed molecular orientation is used in the framework of the adiabatic approximation to calculate pure elastic excitation (0→0 and 1→1), pure rotational excitation (0→2 and 1→3), and average elastic cross sections of the hydrogen molecule in its ground electronic and vibrational states using electrons as incident projectiles. Both differential and integral cross sections are reported at electron energies 20-200 eV. For elastic processes, the effects of target polarization and electron exchange are considered, while for inelastic processes only the effect of the target polarization is taken into account. Results obtained are compared with those of other theoretical and experimental workers. It is found that pure elastic and pure rotational excitation cross sections are comparable at intermediate and large scattering angles, and that they depend on the initial rotational state $J$ of the molecule in such a way that the average elastic cross sections remain independent of $J$.