posted on 2021-07-08, 10:05authored byAmira Allani, Yuri Bedjanian, Dimitrios K. Papanastasiou, Manolis N. Romanias
d9-Butanol or 1-butan-d9-ol
(D9B) is often used as an OH radical tracer in atmospheric
chemistry studies to determine OH exposure, a useful universal metric
that describes the extent of OH radical oxidation chemistry. Despite
its frequent application, there is only one study that reports the
rate coefficient of D9B with OH radicals, k1(295 K), which limits its usefulness as an OH tracer for studying
processes at temperatures lower or higher than room temperature. In
this study, two complementary experimental techniques were used to
measure the rate coefficient of D9B with OH radicals, k1(T), at temperatures between 240 and
750 K and at pressures within 2–760 Torr. A thermally regulated
atmospheric simulation chamber was used to determine k1(T) in the temperature range of 263–353
K and at atmospheric pressure using the relative rate method. A low-pressure
(2–10 Torr) discharge flow tube reactor coupled with a mass
spectrometer was used to measure k1(T) at temperatures within 240–750 K, using both the
absolute and relative rate methods. The agreement between the two
experimental aproaches followed in this study was very good, within
6%, in the overlapping temperature range, and k1(295 ± 3 K) was 3.42 ± 0.26 × 10–12 cm3 molecule–1 s–1, where the quoted error is the overall uncertainty of the measurements.
The temperature dependence of the rate coefficient is well described
by the modified Arrhenius expression, k1 = (1.57 ± 0.88) × 10–14 × (T/293)4.60±0.4 × exp(1606 ± 164/T) cm3 molecule–1 s–1 in the range of 240–750 K, where the quoted error represents
the 2σ standard deviation of the fit. The results of the current
study enable an accurate estimation of OH exposure in atmospheric
simulation experiments and expand the applicability of D9B as an OH
radical tracer at temperatures other than room temperature.