We report the first experimental study of ions interacting with clusters of polycyclic aromatic hydrocarbon (PAH) molecules. Collisions between 11.25 keV 3He+ or 360 keV 129Xe20+ and weakly bound clusters of one of the smallest PAH molecules, anthracene, show that C14H10 clusters have much higher tendencies to fragment in ion collisions than other weakly bound clusters. The ionization is dominated by peripheral collisions in which the clusters, very surprisingly, are more strongly heated by Xe20+ collisions than by He+ collisions. The appearance size is k=15 for [C ₁₄H₁₀](k)2+.

International audienceThe interaction of multiply charged ions (He(2+), O(3+), and Xe(20+)) with gas-phase pericondensed polycyclic aromatic hydrocarbon (PAH) molecules of coronene (C(24)H(12)) and pyrene (C(16)H(10)) is studied for low-velocity collisions (v <= 0.6 a.u.). The mass spectrometric analysis shows that singly and up to quadruply charged intact molecules are important reaction products. The relative experimental yields are compared with the results of a simple classical over-the-barrier model. For higher molecular charge states, the experimental yields decrease much more strongly than the model predictions due to the instabilities of the multiply charged PAH molecules. Even-odd oscillations with the number of carbon atoms, n, in the intensity distributions of the C(n)H(x)(+) fragments indicate a linear chain structure of the fragments similar to those observed for ion-C(60) collisions. The latter oscillations are known to be due to dissociation energy differences between even-and odd-n C(n)-chain molecules. For PAH molecules, the average numbers of H atoms attached to the C(n)H(x) chains are larger for even-n reflecting acetylenic bond systems