  Using Monte Carlo Collisions (MCC) method, we have performed simulations of
ion velocity distribution functions (IVDF) taking into account both elastic
collisions and charge exchange collisions of ions with atoms in uniform
electric fields for argon and helium background gases. The simulation results
are verified by comparison with the experiment data of the ion drift velocities
and the ion transverse diffusion coefficients in argon and helium. The recently
published experimental data for the first seven coefficients of the Legendre
polynomial expansion of the ion energy and angular distribution functions are
used to validate simulation results for IVDF. Good agreements between measured
and simulated IVDFs show that the developed simulation model can be used for
accurate calculations of IVDFs.
