Protonium formation in collisions of antiprotons with hydrogen molecular ions

Protonium formation in molecular collisions, , is theoretically investigated. Within the framework of the adiabatic approximation, the four-body problem can be treated as three-body collisions on a single adiabatic (Born–Oppenheimer) potential energy surface (PES), in the same manner as chemical reaction problems. The adiabatic potential energies of the system are calculated for various configurations. A classical trajectory Monte Carlo calculation is carried out for the collisions on the adiabatic PES. It is found that the dissociative dynamics plays a critical role in protonium formation, and consequently the molecular target is much more effective in protonium formation than the atomic-hydrogen target.