Four-body classical study of H-H collisions

The Classical Trajectory Monte Carlo (CTMC) method has been applied to the study of atomic hydrogen collisions. The classical dynamics consists here i n a four-body Coulomb problem formulation involving mio protons and two ele ctrons. For each atom a microcanonical ensemble has been used for constitut ing the initial conditions of the trajectories. The asymmetry introduced in the calculations by giving to the projectile atom initial positions with v ariable impact parameter b values in relation with the target one, is waive d by the correct statistical treatment, in accordance with the physical sym metry of the collision. In the studied collision energy region, 5 to 200 ke V, the obtained values compare favorably with existing experimental data an d quantal calculations. For low energies, the integration of trajectories c orresponding to the cases of ionization (direct and transfer ionization of the projectile and of the target), has to be improved in order to comply wi th the well-known problem of the "saddle points".