Rate Constants for Reactions of HCCO and HCCCO Radicals with O over the Temperature Range 243-423 K.

A pulsed laser photolysis-photoionization mass spectrometer system has been employed to measure the rate constants of HCCO + O and HCCCO + O over the temperature range 243-423 K in 1.2-8.4 Torr of He or N. Radicals of HCCO and HCCCO were produced by 193 nm ArF laser photolysis of ethyl ethynyl ether and methyl propiolate, respectively. HCCO was photoionized by a Kr resonance lamp with a CaF window (10.03 eV), and HCCCO was ionized by a Xe lamp with a sapphire window (8.44 eV). Both ions were detected as parent ions in a quadrupole mass spectrometer. From analysis of the time profiles of the ion signals for various O concentrations, the overall rate constants at 298 K are represented by the values = (6.3 ± 1.0) × 10 for HCCO + O and = (5.7 ± 0.6) × 10 for HCCCO + O in the units cm molecule s. The rate coefficients for the two reactions can be described by () = (1.5) × 10 exp[-(225 ± 220)/] and () = (1.8) × 10 exp[(343 ± 228)/] in the units cm molecule s over the temperature range 243-423 K.