The kinetic translational energy released in the unimolecular fragmentation reaction C6H5Br+ --> C6H5+ + Br has been experimentally studied in the microsecond time scale and theoretically analyzed by the maximum entropy formalism. The appropriate functional form relating the actual distribution to its prior distribution (eq 2.3) involves the square root of the kinetic energy (i.e. the momentum associated with the relative translational energy). A value of 0.26 +/- 0.02 is obtained for the entropy deficiency distribution at an internal energy of 0.85 eV above the reaction threshold. From this value, it can be concluded that about 77% of the transition state phase space is effectively sampled.