Analytic description of the scattering of electrons by molecules

The scattering of electrons by molecules is considered. The structure of the molecule is described in terms of the vibron model, which is an algebraic approach to the description of rotational and vibrational molecular excitations. The dynamics of electron-molecule collision is discussed in terms of coupled-channel calculations, where we assume an isocentrifugal approximation. In the sudden limit, where the excitation energies of the molecule are neglected, the coupled-channel system decouples into eigenchannels. The scattering amplitudes of the eigenchannels, characterized by 1/r2 potentials, are obtained analytically. The resulting probabilities of excitation of the molecular states and the limiting values of the quasielastic cross sections are evaluated in the U(3) and the O(4) limits. A comparison of the results for the differential cross sections with experimental data and other calculations is made for LiF and KI.