A process of energy redistribution in the collision of I-2(-)(CO2)(n) (n = 1-50) with a silicon surface was investigated by measuring the surface-parallel translational energy at the collision energy of 50 eV per I-2(-) and at the two different angles of incidence, 26 degrees and 45 degrees, with respect to the surface normal. The distributions of the surface-parallel translational energy for all the fragment anions produced from a given parent cluster anion are found to be almost identical in shape and are expressed in terms of a shifted Maxwell-Boltzmann distribution with an effective temperature and a center-of mass translational energy. It is concluded that (1) an incoming parent cluster anion and its neighboring surface atoms reach quasi-equilibrium before its fragment anions leave the surface and (2) a smaller number of surface atoms participate in the energy redistribution at a larger angle of incidence.