The phase space density in the weakly ionized D region is calculated by numerically solving the Boltzmann equation and through a Monte Carlo simulation for high power, high frequency radio wave heating under the assumption that the electron collision frequency is much larger than the gyro-frequency. The effects of elastic and inelastic collisions, such as vibrational, rotational and electronic excitation, are taken into account using the best available cross sections. The solutions demonstrate that the distribution function deviates significantly from a Maxwellian distribution, and that even though a temperature can be defined from the second moment of the distribution, it is not sufficient to specify the distribution functions.