Actinometric optical emission spectroscopy was used in the investigation of discharges of mixtures of C2H2, O-2, and Ar to determine relative concentrations of the species CH, OH, H, CO, and O, which all increase with increasing proportions of oxygen in the plasma feed, R(ox). The mean electron energy E and the mean electron density rho were probed using Ar and He as actinometers. Additional measurements of the ratio of the intensities of the H-alpha to H-beta lines, I(H-alpha)/I(H-beta), showed that E was not strongly dependent on R(OX). In contrast, rho was found to fall with increasing R(OX). A dynamic form of actinometry was also used to determine temporal trends in the relative concentrations of the above-mentioned species following cutting of either the O-2 or C2H2 hows. On the basis of these data it is concluded that reactions involving oxygen play a major role in the production of the species CH, H, and CO. Plasma-polymer surface reactions contribute significantly to the production of the species H, CH, CO, and OH.