The major constituent in the atmosphere of the Earth at altitudes between 200 and 500km is atomic oxygen.\sp1 Collisions involving atomic oxygen are therefore important in this region of the atmosphere. Due to the difficulty in producing atomic oxygen in the laboratory, there are very few reported measurements of scattering cross sections with an atomic oxygen target.\sp2−6 We have undertaken an experimental program designed to measure absolute differential cross sections for various collision processes involving atomic oxygen. The oxygen atoms are produced through dissociation of O\sb2 in a microwave discharge, producing a target of atomic and molecular oxygen whose densities are inferred from measurements with an electron impact time of flight mass spectrometer.