Quantum calculations are carried out for the scattering of electrons from sulphur dioxide molecules in the energy range from about 1.0 eV up to 30 eV. Integral and differential cross sections are obtained for the elastic process and for the excitation processes of the target asymmetric rotor into various final rotational levels. Comparison with experimental data, both of the momentum transfer cross sections and the angular distributions, indicates rather good agreement between measured and computed values over the whole range of the examined energies, while the integral elastic cross sections (rotationally summed) show disagreement at low energy with the experimental estimates. Born corrections to the calculations are also shown to provide the correct behaviour of the forward scattering angular distributions and a reliable guide to experimental extrapolation procedures.

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The scattering of electrons from the H2O molecule in its ground electronic state is analyzed by carrying out quantum calculations of the coupled equations in the body-fixed (BF) frame and using exact static-exchange interaction forces (ESE) within a single-center expansion (SCE) formulation. The effect of correlation-polarization forces is included via a density functional approach and the necessary corrections to the nonconvergent behavior of the angular distributions from fixed nuclei calculations involving polar molecules are carried out. Elastic and rotationally inelastic differential and momentum transfer cross sections are compared with experiments and the effects on the inelastic processes of the long-range dipolar potential are examined in some detail. The electron efficiency in exciting molecular rotations over a broad range of energies is also obtained and discussed.

Ab initio quantum scattering calculations are carried out for the O 3 molecule, in its ground electronic state, from which low-energy electrons are scattered in the gas phase. The results of the computations are compared with the existing experimental angular distributions for elastic ͑rotationally summed͒ scattering processes and for rotationally inelastic cross sections. The agreement of the present calculations with the available experiments is found to be remarkably good and the corresponding efficiency of rotationally inelastic processes is also discussed and analyzed in terms of the role played by the small permanent dipole moment of this target molecule.

Abstract.A new form of a local, model polarisationcorrelation potential obtained via Density Functional Theory (DFT) is proposed for the treatment of positron scattering from Hz and N2 molecules at energies below the threshold of positronium formation. The derivation of the potential is briefly discussed and its relative importance for the elastic channels of the scattering process is analysed in detail.Final elastic cross sections, rotationally summed, are compared with experiments and with existing theoretical results. They are found to agree reasonably well with measurements and suggest the present model as a useful, and simple, method for treating short-range correlation forces in positron scattering calculations for molecular systems.

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