Classical phase-space distributions for atomic hydrogen collisions

A new phase-space distribution is derived for use in the classical trajectory Monte Carlo treatment of ion scattering by hydrogenic atoms. The distribution, which depends only on the energy and is hence stationary, yields exactly the same coordinate distribution as the quantum mechanical wavefunction and provides a good approximation to the momentum distribution. The function is analytic and contains no adjustable parameters. It is possible to obtain cross sections in this representation by transforming existing cross sections obtained with the usual classical microcanonical distribution. Ionisation and charge transfer cross sections in the new representation are compared with microcanonical results and experimental determinations. (author)