Measurements of OH and HO2 yields from the gas phase ozonolysis of isoprene
Other literature type
Malkin, T. L.
Heard, D. E.
Seakins, P. W.
The reactions of ozone with alkenes are an important source of hydroxyl (OH)
radicals; however, quantification of their importance is hindered by
uncertainties in the absolute OH yield. Hydroxyl radical yields for the
gas-phase ozonolysis of isoprene are determined in this paper by four
different methods: (1) The use of cyclohexane as an OH scavenger, and the
production of cyclohexanone, (2) The use of 1,3,5-trimethylbenzene as an OH
tracer, and the diminution in its concentration, (3) A kinetic method in
which the OH yield was obtained by performing a series of pseudo-first-order
experiments in the presence or absence of an OH scavenger (cyclohexane), (4)
The OH and HO<sub>2</sub> yields were determined by fitting the temporal OH and
HO<sub>2</sub> profiles following direct detection of absolute OH and HO<sub>2</sub>
concentrations by laser induced fluorescence at low pressure (Fluorescence
Assay by Gas Expansion- FAGE). The following OH yields for the ozonolysis of
isoprene were obtained, relative to alkene consumed, for each method: (1)
Scavenger (0.25±0.04), (2) Tracer (0.25±0.03), (3) Kinetic
study (0.27±0.02), and (4) Direct observation (0.26±0.02), the
error being one standard deviation. An averaged OH yield of 0.26±0.02
is recommended at room temperature and atmospheric pressure and this result
is compared with recent literature determinations. The HO<sub>2</sub> yield was
directly determined for the first time using FAGE to be 0.26±0.03.