Atmospheric photooxidation and ozonolysis of "3-carene and 3-caronaldehyde: Rate constants and product yields

The oxidation of "3-carene and one of its main oxidation products, caronaldehyde, by the OH radical and O3 was investigated in the atmospheric simulation chamber SAPHIR under atmospheric conditions for NOx mixing ratios below 2ĝ€¯ppbv. Within this study, the rate constants of the reaction of "3-carene with OH and O3 and of the reaction of caronaldehyde with OH were determined to be (8.0±0.5)×10-11ĝ€¯cm3s-1 at 304ĝ€¯K, (4.4±0.2)×10-17ĝ€¯cm3s-1 at 300ĝ€¯K and (4.6±1.6)×10-11ĝ€¯cm3s-1 at 300ĝ€¯K, in agreement with previously published values. The yields of caronaldehyde from the reaction of OH and ozone with "3-carene were determined to be 0.30±0.05 and 0.06±0.02, respectively. Both values are in reasonably good agreement with reported literature values. An organic nitrate (RONO2) yield from the reaction of NO with RO2 derived from "3-carene of 0.25±0.04 was determined from the analysis of the reactive nitrogen species (NOy) in the SAPHIR chamber. The RONO2 yield of the reaction of NO with RO2 derived from the reaction of caronaldehyde with OH was found to be 0.10±0.02. The organic nitrate yields of "3-carene and caronaldehyde oxidation with OH are reported here for the first time in the gas phase. An OH yield of 0.65±0.10 was determined from the ozonolysis of "3-carene. Calculations of production and destruction rates of the sum of hydroxyl and peroxy radicals (ROxCombining double low lineOH+HO2+RO2) demonstrated that there were no unaccounted production or loss processes of radicals in the oxidation of "3-carene for conditions of the chamber experiments. In an OH-free experiment with added OH scavenger, the photolysis frequency of caronaldehyde was obtained from its photolytical decay. The experimental photolysis frequency was a factor of 7 higher than the value calculated from the measured solar actinic flux density, an absorption cross section from the literature and an assumed effective quantum yield of unity for photodissociation.