Partial-wave analysis of low-energy electron scattering by quadrupole molecules

The effective-range theory (ERT) for slow electron scattering by quadrupole molecules is developed. A low-energy expansion for the K matrix in the adiabatic approximation is obtained with an accuracy to the order k 3 ln k. Modified formulae taking into account the polarisation potential are also derived. Closed expressions for eigenphase sums in the limit of small energies are presented. The threshold behaviour of the excitation cross sections is investigated. The ERT results for scattering from N 2 and CO 2 and H 2 molecules are compared with the data obtained by close-coupling calculations.