Theoretical study of the thermalization of the positronium interacting with atoms

We simulate the thermalization process of a high energetic positronium gas trapped in a silica pore. The gas dynamics is reproduced by using a kinetic approach. Our approach includes the two-body scattering interaction and the exchange of energy between the atoms and the internal surface of the pore cavity. We discuss the formation of a quasi-equilibrium state induced by the fast internal thermalization of the gas and the evolution of the gas temperature. We estimate the time necessary to achieve the total thermalization of the gas. The reliability of our model is verified by comparing the numerical results with some experimental data.