Velocity distributions of NH2 radicals in an NH3 plasma molecular beam

Using spatially and temporally resolved LIF we have measured the velocity distributions of NH2 molecules in an effusive NH3 plasma molecular beam as a function of applied rf plasma power. Monte Carlo simulation methods are used to model spatial profiles of radicals in the molecular beam. The model assumes a Gaussian distribution and calculates time dependent changes in the profiles using Maxwell-Boltzmann distributions. The translational temperature increases with rf power, from 512 ± 8 K at 25 W to 664 ± 35 K at 150 W. Preliminary data on velocity profiles for NH2 radicals scattered from a 300 K Si substrate are presented.