Product Study of the Photolysis of Ketene and Ethyl Ethynyl Ether at 193.3 nm

Abstract

The product distributions of the excimer laser photolysis of ketene (CH2CO) and ethyl ethynyl ether (C2H5OCCH) at lambda = 193.3 nm (ArF) were studied using a time-of-flight mass spectrometer (TOFMS) as an analytical tool. Ketene was photolyzed in bath gases consisting of mixtures of He and H2/D2 at various mixing ratios at constant total pressures of 4 Torr and temperature of about 300 K. Singlet methylene (1CH2) produced in the photolysis of ketene was almost instantaneously converted either to triplet methylene (3CH2) or to methyl radicals in collisions with He and H2 or D2. By extrapolating the methyl and methylene signals to zero time after photolysis, initial concentrations of these radicals were obtained. Analyzing the initial 3CH2 and CH3 concentrations as functions of hydrogen-to-helium ratios as well as simulating the observed traces of reactant and product species resulted in 1CH2 + CO (66 +/- 8)%, as the main product channel of the ketene photolysis with smaller contributions from HCCO + H (17 +/- 7)% and 3CH2 + CO (6 +/- 9)%. Hydrogen atoms, acetylene, ethylene, ethyl, and ketenyl radicals, and small amounts of ketene were observed as primary products of the ethyl ethynyl ether photolysis. Quantification of C2H2, C2H4, C2H5, and CH2CO product leads to a HCCO yield of (91 +/- 14)%.