The catalytic formation of ammonia synthesis through dimers N-2 and H-2 has already been studied through Monte-Carlo simulation via a model based on a Langmuir-Hinshelwood (thermal) mechanism. The results of this study are well, known. Here, we have studied this reaction on the basis of a non-thermal model. which involves the precursor motion of a H-2 molecule. The most interesting feature of this model is that it yields a steady reactive window, which is separated by continuous and discontinuous irreversible phase transitions.