The emission of Si, SiCl, Cl, Cl2, CCl, Cl+, and Cl+ 2has been observed in a CCl4rf discharge in the presence of Si(100) in a plasma etching system. Spectral intensities have been recorded over a wide range of process gas flow rates and rf powers. These data have been analyzed to show that (i) SiCl emission from theA˜ state arises through chemiluminescent reactions of metastable (1S) Si and (ii) the species which leaves the Si surface in the etching process is SiClx(x=0, 1, or 2) rather than SiCl3or SiCl4. To arrive at these conclusions, detailed chemical models are examined and shown quantitatively to reproduce our observed variations of emission with flow and power.