  Multiplicity distributions of intermediate mass fragments (IMF) seen in
intermediate energy heavy ion collisions have been of great interest in the
last ten years. The distributions of single intermediate sized element are
close to Poissonian and have been subjected to widely different physical
interpretations. We calculate the multiplicity distributions in a thermodynamic
model whose physical basis is equal population in phase space which implies
equilibrium statistics. We found distributions of single element are to a good
approximation Poissonian, and such result is attributed to the small emission
probability of a given IMF among all the possible channels. We also found
significant deviation from Poisson distribution for a range of IMFs, and
suggest strong correlations as an explanation. Systematics of the multiplicity
distributions are explored in both one component and two component models. In
one component model, sudden changes for the multiplicity distributions are
found at the phase transition region. In two component model, the multiplicity
distributions have more subtleties. Results from the current model are compared
with available data, and good agreements are found. New signals for the
multi-particle correlations are also suggested.
