The interaction of low-energy electron collisions with molecules may lead to temporary anions via resonant processes. While experimental measurements, e.g. electron transmission spectroscopy or dissociation electron attachment spectroscopy, are efficient to characterize the temporary anions, simulating the electron attachment is still very challenging. Here, we propose a methodology to calculate the resonance energies of the electron attachment using ab initio (TD)-DFT calculations together with two different basis sets: a large basis set with diffuse functions to compute the vertical electron affinity, and a smaller one to calculate the excitation energy of the anion. To demonstrate the capabilities and the reliability of this computational approach, 53 resonance energies from 18 molecules are calculated and compared to experimental data.

Acetonitrile and water are molecules detected not only in space but also in planetary atmospheres. On the Earth, the nitrile compound is emitted from biomass burning and can be found up to the stratosphere. Trapped in water ice cores, they may be exposed to energetic particles, photons and secondary electrons, and contribute to the formation of complex organic molecules. Here, we show that methanol is the main product from the effective reaction of low-energy (<15 eV) electrons with acetonitrile–water films deposited on a substrate maintained at 85 K. In this process, each of the molecules is decomposed by the colliding electrons, producing respectively methyl and hydroxyl radicals, which further recombine to form methanol, as supported by density functional theory (DFT) calculations. In addition, we also report production of a small amount of glycolonitrile, a key precursor of adenine. This information contributes to a better comprehension and description of chemistry of icy grains.

Weakly bound non-valence anions are molecular systems where the excess electron stabilizes in a very diffuse orbital whose size, shape, and binding energy (∼1−100 meV) are governed by the long-range electrostatic potential of the molecule. Its binding energy comes mainly from charge−dipole or charge− multipole interactions or dispersion forces. While highly correlated methods, like coupled cluster methods, are considered to be the state of the art for describing anionic systems, especially when the electron lies in a very diffuse orbital, we consider here the possibility to use DFT-based calculations. In such molecular anions, the outer electron experiences long-range exchange and correlation interactions. We show that DFT can describe longrange bound states provided that a correct asymptotic exchange and correlation potential is used, namely, that from a range-separated hybrid functional. This opens an alternative to the computationally demanding highly correlated method calculations. It is also suggested that the study of weakly bound anions could help in the construction of new DFT potentials to study systems where nonlocal effects are significant.