The vacuumhyphen;ultraviolet photolysis of C3O2in the presence of CH4and Ar has been investigated at 25deg;C using the 147 nm Xe resonance line. The principal gaseous reaction products include CO, C2H2, C2H4, and some C2H6. The yield of acetylene decreases with increasing methane or inert gas pressure while the opposite trend is observed in the case of ethylene. Diagnostic experiments with added H2and CO have shown that excess H2effectively suppresses C2H4formation, while excess CO virtually eliminates the production of C2H2. The results are interpreted in terms of the participation of1Dand3Pcarbon atoms and are consistent with recent flash photolysishyphen;kinetic spectroscopy work on the C3O2sol;CH4system. It is proposed that C2H2formation can be attributed entirely to the reactionClpar;1Drpar;plus;CH4rarr;C2H2plus;H2,whereas C2H4results from reaction of methane with ground state C2O(3Sgr;) radicals, producted in a secondary processClpar;3Prpar;plus;COplus;Mrarr;C2Olpar;3Sgr;rpar;plus;M,C2Olpar;3Sgr;rpar;plus;CH4rarr;C2H4plus;CO.Both Ar and CO deactivate C(1D) to C(3P), however, relative to its rate of attack on methane, the deactivation of C(1D) by argon is an inefficient process.
展开▼
