  A statistical multifragmentation model (SMM) is applied to the experimentally
observed multifragmentation events in an intermediate heavy ion reaction.Using
the temperature and symmetry energy extracted from the isobaric yield ratio
(IYR) method based on the Modified Fisher Model (MFM), SMM is applied to the
reaction $^{64}$Zn + $^{112}$Sn at 40 MeV/nucleon. The experimental isotope
distribution and mass distribution of the primary reconstructed fragments are
compared without afterburner and they are well reproduced. The extracted
temperature $T$ and symmetry energy coefficient $a_{sym}$ from SMM simulated
events, using the IYR method, are also consistent with those from the
experiment. These results strongly suggest that in the multifragmentation
process there is a freezeout volume, in which the thermal and chemical
equilibrium is established before or at the time of the intermediate-mass
fragments emission.
