The hydrogen-hydrogen collision system is studied employing a four-body quasi-classical trajectory Monte Carlo model of Kirschbaum and Wilets (QCTMC-KW, C. L. Kirschbaun and L. Wilet, Phys. Rev. A: At., Mol., Opt. Phys., 1980, 21, 834). We present the total ionization cross-section of the target and projectile as a result of pure ionization and electron transfer processes. Calculations were performed in the intermediate energy regime, which is crucial to fusion research. Our results were compared with previous theoretical and experimental results. We found that the quasi-classical approach accurately describes the cross sections of a variety of final channels. We found that the cross-section results by the QCTMC-KW method are higher compared with the standard four-body CTMC results and in good agreement with the experimental data, particularly at low energies.
