Anion production cross sections in collisions between Cn+, Cn carbon clusters (n ≤ 5) and helium atoms have been measured in high-velocity collisions (v = 2.25 and 2.6 au). This paper focuses on two of the three processes responsible for the Cn− production, namely double electron capture (DEC) onto Cn+ cations and single electron capture onto neutral (SECN) Cn. They were experimentally distinguished from a gaseous thickness dependence study. Dissociative and non-dissociative cross sections were measured and, in the case of DEC, all dissociative branching ratios measured; for these small systems, the C2− fragment was found magical. Data concerning electron capture in neutral–neutral collisions are extremely rare, especially at high velocity. Introduction of this measured process in the independent atom and electron (IAE) model allowed us to revisit and satisfactorily reproduce the so-far unexplained size evolution of single electron capture (SEC) cross sections in 2.6 au Cn+–He (n ≤ 10) collisions (Chabot et al 2006 J. Phys. B: At. Mol. Opt. Phys. 39 2593–603). IAE calculations for DEC cross sections and their comparison with experiment suggest a loss of electron in anionic Cn− species after the collision, competing with fragmentation and depending on the size.

Comparison between measured vibrational infrared spectra and corresponding computed ones has been used as a powerful approach to assign the ground state geometry of isolated atomic clusters. Nevertheless, the coexistence of more than one stable isomers often makes the geometrical assignment practically more challenging especially for large-size and doped species. In this study, we report the vibrational infrared spectra of most stable SinMn2+ clusters (n=5–9) using density functional theory calculations. An attempt has been made to theoretically construct infrared spectra of the investigated clusters in case of more than one stable isomers coexisting. The finding results would serve as fringerprints for further structural identification of interested clusters.