Statistical fragmentation of doubly charged anthracene induced by fluorine-beam impact at 3 keV

The fragmentation scheme of the doubly charged anthracene molecule (C14H102+) has been studied via monocharged fluorine impact at 3 keV using the CIDEC method (collision-induced dissociation under energy control). Doubly or singly charged fragments resulting from the loss of neutrals (H, C2H2) or CxHy+ (x = 1-5; y = 1-5) have been measured versus the excitation energy of the parent molecule C14H102+. The branching ratio of the CxHy+ emission process was found to be 16%. For the major neutral evaporation channels via nH or nC(2)H(2) (n = 1, 2) emission, the measured population distributions have been fitted using a Rice-Ramsperger-Kassel (RRK) statistical dissociation and cascade model. The simulated rate-energy dependences of the two primary competing pathways, i.e., the loss of H or C2H2 from C14H102+, present a crossing point at 13 eV. This feature is characteristic of two different fragmentation mechanisms: a direct cleavage for the loss of H for energy above the crossing point and a rearrangement process for the loss of C2H2 bellow the crossing point.