Neutral mean kinetic energies and the amount of neutral source gas cracking of particles emanating from an electron cyclotron resonance (ECR) plasma source and a radio-frequency inductively coupled plasma (ICP) source are compared as a function of applied power by modulated beam time-of-flight analysis for Ar and N2 gases. For both sources, the source chamber is maintained at 0.07 Pa by a constant flow of either Ar or N2, while the applied power is varied from 50 to 250 W and from 50 to 550 W for the ECR and the ICP sources, respectively. For the Ar plasmas, the neutral Ar mean kinetic energies are similar and range between 0.07 and 0.15 eV, with the ICP being somewhat higher. In the case of the N2 plasmas, the ICP mean energies are also somewhat higher than those found for the ECR source. The mean energies range between 0.02 and 0.26 eV and 0.02 and 0.40 eV for the N2 and N species, respectively. The N:N2 flux ratio for the ICP source increases to a plateau of approximately 0.021±0.002 after an applied power of 250 W is reached, while for the ECR plasmas, the N:N2 flux ratio varies in a more complex fashion with a much higher value of 0.17±0.04. © 1998 American Institute of Physics.