Direct detection of OH formation in the reactions of HO2 with CH3C(O)O2 and other substituted peroxy radicals
This work details the first direct observation of OH as a product from (R1): HO 2 +CH 3 C(O)O 2 →(products), which has generally been considered an atmospheric radi-cal termination process. The technique of pulsed laser pho-tolysis radical generation, coupled to calibrated laser in-duced fluorescence detection was used to measure an OH product yield for (R1) of α 1 (298 K)=(0.5±0.2). This study of (R1) included the measurement of a rate coefficient k 1 (298 K)=(1.4±0.5)×10 −11 cm 3 molecule −1 s −1 , substan-tially reducing the uncertainties in modelling this impor-tant atmospheric reaction. OH was also detected as a prod-uct from the reactions of HO 2 with three other carbonyl-containing peroxy radicals, albeit at smaller yield, e.g. (R2): HO 2 +CH 3 C(O)CH 2 O 2 →(products), α 2 ≈0.15. By contrast, OH was not observed (α<0.06) as a major product from reactions where carbonyl functionality was absent, e.g. HO 2 +HOCH 2 CH 2 O 2 (R8), and HO 2 +CH 3 CH(OH)CH 2 O 2 (R9).