Electron attachment to interstellar grains

We have performed quantum mechanical calculations of cross-sections and rate coefficients for electron attachment to small, neutral, and positively charged grains. In addition to the polarization potential and – for charged grains – the Coulomb potential, we considered the influence of the interaction between the charge of the electron and a possible permanent electric dipole on the grain. We found large discrepancies between the predictions of classical and quantal models of electron scattering on neutral grains at low energies (temperatures) in the absence of a permanent dipole moment, but much closer agreement when a dipole moment was present. The presence of the long-range Coulomb potential also leads to better agreement between classical and quantal models.