Protonated molecular clusters: promoting molecular complexity

Molecules identified in Space display a diversity greater than ever, yet the mechanisms responsible for this complexity remain largely unknown. The extreme conditions faced by these molecules under astrophysical conditions raise several questions about their persistence and evolution. In this work, we explore the role of gas-phase protonated molecular dimers, which act both as protectors of existing molecules and as promotors in the emergence of new species. Experiments were conducted using the DIAM irradiation device on four protonated dimers of astrophysical interest, namely the pyridine, methanol, glycine pure dimers and the diglycine-glycine mixed dimer. Analysis of the observed relaxation channels following an energy deposition mimicking cosmic radiation reveals three main mechanisms of evaporation, covalent bond breaking, and unimolecular reaction. Focusing on the latter, our experiments combined with quantum chemical calculations of the relevant pathways shed new light onto the role of the protonation site on the reactants.