The product gas yields for a 30 mTorr C2H2 13.56 MHz glow discharge were measured using mass spectrometry. The volatile products are H2, C4H2, and C6H2. A reaction mechanism has been proposed that accounts quantitatively for the yields of C4H2 and C6H2, and film deposition rate, as a function of discharge power. The product gases C4H2 and C6H2 are depleted at high rates in the plasma by electron collisional dissociation, and by reaction with H atoms and C2H radicals. Under high power conditions suitable for diamondlike carbon deposition it is proposed that the film growth is dominated by the radicals C4H3, C6H3, and C2H. These results are compared with the kinetics of methane rf glow discharges under similar conditions. © 1997 American Institute of Physics.