The three-body dynamics of the ionization of the atomic hydrogen by 30-keV antiproton impact has been investigated by calculation of fully differential cross sections (FDCSs) using the classical-trajectory Monte Carlo (CTMC) method. The results of the calculations are compared with the predictions of quantum mechanical descriptions: The semiclassical time-dependent close-coupling theory; the fully quantal, time-independent close-coupling theory; and the continuum-distorted-wave-eikonal-initial-state model. In the analysis particular emphasis was put on the role of the nucleus-nucleus ($NN$) interaction played in the ionization process. For low-energy electron ejection the CTMC method predicts a large $NN$ interaction effect on FDCSs, in agreement with the quantum mechanical descriptions. By examining individual particle trajectories it was found that the relative motion between the electron and the nuclei is coupled very weakly with that between the nuclei, consequently the two motions can be treated independently. A simple procedure is presented by which the $NN$ interaction effect can be included in the calculations carried out without it.

• Received 9 May 2014
• Revised 9 July 2014

DOI:https://doi.org/10.1103/PhysRevA.90.022702