We review long-range effects in electron collisions with polar molecules, starting with elastic scattering. We then go to rotationally and vibrationally inelastic processes and dissociative electron attachment. The last two are strongly affected by vibrational Feshbach resonances which have been observed and described theoretically in many systems from simple diatomic molecules to more complex polyatomics, biologically relevant molecules, and van der Waals clusters. We then review environmental effects which include electron interaction with molecules adsorbed on surfaces and molecules in cluster environments. We concentrate on physics rather than on listing results of ab initio calculations. With increasing complexity of targets and processes model approaches become more relevant. We demonstrate their success in the theoretical description of electron attachment to polyatomic molecules and to molecules in complex environments.

Cross sections for elastic and inelastic electron collisions with $\mathrm{C}{\mathrm{H}}_{3}X$ $(X=\mathrm{Cl},\mathrm{Br},\mathrm{I})$ molecules are calculated. For the lowest partial wave, the resonance $R$-matrix theory, and for the higher partial waves, the theory of scattering by dipolar plus polarization potential, are used. It is shown that the rotationally elastic scattering amplitude for a polar molecule in the fixed-nuclei approximation is logarithmically divergent for the forward direction, and a closure formula is derived to speed up the convergence at small angles. In treating the nuclear motion, only $\mathrm{C}\text{−}X$ stretch vibrations are taken into account. The dipole moment as a function of the $\mathrm{C}\text{−}X$ distance is modeled by a function incorporating the experimental value of the molecular dipole moments at the equilibrium distance and the derivatives of the dipole moments extracted from the experimental data on infrared intensities. This is supplemented by ab initio calculations of the dipole moment function for $\mathrm{C}{\mathrm{H}}_3\mathrm{Br}$ using the multiconfigurational valence bond method. The results for scattering cross sections show pronounced features caused by vibrational Feshbach resonances and threshold cusps. The features are most noticeable at the $v=6$, 7, and 8 thresholds in $\mathrm{C}{\mathrm{H}}_3\mathrm{Cl}$, at the $v=3$ and 4 thresholds in $\mathrm{C}{\mathrm{H}}_3\mathrm{Br}$, and at the $v=1$ threshold in $\mathrm{C}{\mathrm{H}}_3\mathrm{I}$.

Quantum mechanical and semiclassical formulae for the spatial distribution of the electrons photodetached from negative ions in a static electric field are derived. Sample calculations for the negative hydrogen ion are presented for photon energies both above and below the zero-field photodetachment threshold. Realistic experimental conditions for observation of photodetached electrons are discussed.

We calculate elastic scattering of positronium (Ps) by the Xe atom using the recently developed pseudopotential method (Fabrikant and Gribakin 2014 Phys. Rev. A 90 052717) and review general features of Ps scattering from heavier rare-gas atoms: Ar, Kr and Xe. The total scattering cross section is dominated by two contributions: elastic scattering and Ps ionization (break-up). To calculate the Ps ionization cross sections we use the binary-encounter method for Ps collisions with an atomic target. Our results for the ionization cross section agree well with previous calculations carried out in the impulse approximation. Our total Ps–Xe cross section, when plotted as a function of the projectile velocity, exhibits similarity with the electron-Xe cross section for the collision velocities higher than 0.8 a.u., and agrees very well with the measurements at Ps velocities above 0.5 a.u.

We study $e^{+}-\mathrm{H}(n$) and $\mathrm{Ps}\left(n\right)-p$ collisions near the three-body breakup threshold and thresholds for the charge-transfer processes. We show that classical trajectory Monte Carlo (CTMC) simulations for the three-body breakup agree reasonably well in this energy region with quantum-mechanical convergent close-coupling (CCC) calculations even if the initial hydrogen atom or positronium atom is in the ground state. The threshold behavior of the three-body breakup cross section in $e^{+}$-H($1s$) and $\mathrm{Ps}\left(1s\right)-p$ collisions agrees with the Wannier law with Klar's exponent and obeys the classical scaling laws, although some deviation from the Klar-Wannier behavior is observed in the CCC results. Below the threshold the agreement between CTMC and CCC disappears. In particular the CTMC method fails completely for the processes of H formation in $\mathrm{Ps}\left(1s\right)-p$ collisions and Ps formation in $e^{+}$-H collisions well below the three-body breakup threshold. For higher initial states the CTMC results below the threshold improve substantially, in accordance with the correspondence principle. This is explained by comparing the quantum-mechanical threshold laws with the classical laws.