We have studied the stability of C₅₉ anions as a function of time, from their formation on femtosecond timescales to their stabilization on second timescales and beyond, using a combination of theory and experiments. The C₅₉ fragments were produced in collisions between C₆₀ fullerene anions and neutral helium gas at a velocity of 90 km/s (corresponding to a collision energy of 166 eV in the center-of-mass frame). The fragments were then stored in a cryogenic ion-beam storage ring at the DESIREE facility where they were followed for up to one minute. Classical molecular dynamics simulations were used to determine the reaction cross section and the excitation energy distributions of the products formed in these collisions. We found that about 15 percent of the C₅₉ ions initially stored in the ring are intact after about 100 ms, and that this population then remains intact indefinitely. This means that C₆₀ fullerenes exposed to energetic atoms and ions, such as stellar winds and shock waves, will produce stable, highly reactive products, like C₅₉, that are fed into interstellar chemical reaction networks.

We have performed molecular dynamics simulations on the formation of mixed molecular clusters of buckminster- fullerene and coronene, (C₂₄H₁₂)_n(C₆₀)_N−n. We report on our findings on the structures and their relative stabilities for cluster sizes N = 5 and 13 and for all possible combinations of the two species within these sizes, including the pure clusters of each type. Generally, we see that the two species mix rather poorly and that compactly bound clusters are favoured over spatially extended ones. For a given ratio of coronene and fullerene, clusters with one or two coronene stacks tend to be more stable than those with a larger number of stacks. In the case of small clusters, the coronene and fullerene molecules tend to separate into two different cluster parts. For larger clusters, this is often but not always the case.

We have performed classical molecular dynamics simulations of 3 keV Ar + (C₂₄H₁₂)_n(C₆₀)_m colli- sions where (n,m) = (3,2), (1,4), (9,4) and (2,11). The simulated mass spectra of covalently bound reaction products reproduce the main features of the corresponding experimental results reported by Domaracka et al., PCCP, 2018, 20, 15052. The present results support their conclusion that molecular growth is mainly driven by knockout where individual atoms are promptly removed in Rutherford type scattering processes. The so formed highly reactive fragments may then bind with neighboring molecules in the clusters producing a rich variety of growth products extending up to sizes containing several hundreds of atoms, and here we show examples of such structures. In addition, knocked out atoms may be absorbed such that e.g. hydrogenated coronene and fullerene molecules are formed.