Coherent electron emission from simple molecules by impact of energetic charged particles

We review the theoretical and experimental progress in the field of coherent electron emission from simple molecules by the impact of energetic charged particles. We describe in detail the different theoretical approaches to tackle the single ionization of diatomic molecules by the impact of ions and electrons. Furthermore, we compare with experimental measurements, where available. The case of photon impact is also considered, in order to obtain a deeper understanding of the physics involved. An attempt is made to emphasize the phenomenology behind these molecular processes and to discuss the advantages and drawbacks of the different theoretical approaches. Additionally, we highlight the differences and similarities between the particular projectiles which initiate the process, namely ions, electrons or photons.