Conventional and dynamic actinometric optical emission spectroscopies were used to investigate the composition of discharges of mixtures of tetramethylsilane, sulfur hexafluoride, and helium. Argon was present in a small proportion as an actinometer. Trends in the plasma concentrations of the species H, CH, Si, F, and CF2 were obtained as a function of the proportion of SF6 in the feed, R-s. Dynamic actinometry, which involves monitoring the relative intensities of plasma species following interruption of one of the principal feed gases, gave clues as to the relative importance of gas-phase and plasma/polymer-surface reactions in the production of the measured plasma species. Based on these data, reaction pathways and mechanisms for the production of these species are suggested. (C) 1998 American Vacuum Society.162509513