A previous interpretation of the kinetic energy release distribution (KERD) observed in the fragmentation of protonated fluorobenzene is confirmed by a maximum entropy analysis. The KERD is bimodal, with an intense and broad component due to the production of the cyclic phenyl ion. Ab initio calculations indicate the existence of several open-chain isomers, with an energy about 1.0-1.2 eV higher than that of the phenyl ring. A weaker component of the KERD corresponds to the formation of one or several of these acyclic structures. Its abundance represents about 6% of the main component (but drops down to 3% for the perdeuterated isomer). More translational energy than the statistical estimate is released during the dissociation process because of the presence of a barrier along the reaction path leading to the generation of the cyclic phenyl ion. About one-half of the energy of the barrier is released as translation, thereby indicating the operation of strong exit-channel interactions between separating fragments.