Comment on the classical-trajectory Monte Carlo method for ion-atom collisions

It is shown that the procedure described by Olson and Salop for classical-trajectory Monte Carlo treatment of ion-atom collisions does not provide a uniform statistical distribution of all the parameters defining the initial conditions of a trajectory. Impact-ionization and charge-transfer cross sections for collisions of H⁺ with H at H energies between 25 and 600 keV are recalculated eliminating this failing and compared with those obtained using the procedure of Olson and Salop and with experimental results.