Quantification of the Tropospheric Removal of Chloral (CCl3CHO): Rate Coefficient for the Reaction with OH, UV Absorption Cross Sections, and Quantum Yields

Abstract

Rate coefficients for the reaction, OH + CCl3CHO (chloral) → products (k5), were measured over the temperature range 233−415 K using the pulsed laser photolysis-laser-induced fluorescence method, and were determined to be k5(T) = (1.79 ± 0.17) × 10-12 exp[−(240 ± 60)/T] cm3 molecule-1 s-1. The quoted uncertainties are at the 95% confidence level with σA = AσlnA, and include estimated systematic errors. Our results are compared with those from previous work and the differences are discussed. UV absorption cross sections of CCl3CHO were measured between 200 and 345 nm and over the temperature range 240−360 K. These measurements are in good agreement with previously reported values. The quantum yields for O, H, and Cl atoms in CCl3CHO photolysis were measured via atomic resonance fluorescence detection following pulsed excimer photolysis. Upper limits for the O atom quantum yield in CCl3CHO photolysis at 308 and 248 nm were measured to be <0.01 and <0.02, respectively. The H atom quantum yields in CCl3CHO ph...