Photolysis of acetone at 193.3 nm

Abstract

The photodecomposition of acetone by single-pulse excimer laser photolysis at 193 nm has been studied by using end product analysis and time-resolved absorption spectroscopy at 300 and 600 K and as a function of helium pressure. Ethane is the dominant product and the channel producing 2CH/sub 3/ + CO accounts for about 95% of the overall photolysis. It is suggested that the next most important channels produce H + CH/sub 2/COCH/sub 3/ (approx. 3%) and CH/sub 4/ + CH/sub 2/CO (/approx lt/ 2%). Time-resolved experiments failed to detect acetyl radicals on a approx. 1-ms time scale, demonstrating that their yield is < 1% of that of the methyl radical. The ethylene yield increases nonlinearly with laser energy, an observation attributed to secondary photolysis of vibrationally excited methyl radicals to yield CH/sub 2/ + H. The experiments demonstrate that 193-nm laser photolysis is a clean source of methyl radicals.