ar X iv : n uc l - th / 9 90 30 63 v 2 2 0 Ju l 1 99 9 Chemical and Thermal Freeze - Out Parameters

The present knowledge about hadrons produced in relativistic heavy ion collisions is compatible with chemical freeze-out happening when the energy density divided by the particle density reaches the value of 1 GeV. This observation is used to determine the energy dependence of the chemical freeze-out parameters Tch and μ ch B for beam energies varying between 1 and 200 A·GeV. The consequences of this energy dependence are studied for various particle ratios. Predictions for particle ratios at beam energy 40 A·GeV are presented. The conditions for thermal freeze-out are also determined. These correspond either to an energy density of 45 MeV/fm or to a particle density of 0.05/fm .