Catherine S.E. Bale

A discharge–flow study of the kinetics of the reactions of IO with CH3O2 and CF3O2

We have determined the rate constants for the reactions IO + CH3O2 --> Products (1) and IO + CF3O2 --> Products (2) using a discharge-flow tube equipped with off-axis cavity-enhanced absorption spectroscopy (CEAS) for the detection of IO. NO2, produced from the titration of RO2 with NO, was also detected using the CEAS system. The rate constants obtained were k1 = (6.0 +/- 1.3) x 10(-11) cm3 molecule(-1) s(-1) and k2 = (3.7 +/- 0.9) x 10(-11) cm3 molecule(-1) s(-1) at T = 295 +/- 2 K and P = 2.5 +/- 0.3 Torr; this is the first determination of these rate constants. The possible products and the atmospheric implications of reaction (1) are discussed.

An experimental study of the gas-phase reaction of the NO3 radical with 1,4-pentadiene, Z-1,3-pentadiene and E-1,3-pentadiene

Relative-rate and absolute techniques have been used to obtain rate coefficients for the reactions between the NO3 radical and 1,4-pentadiene (k1), Z-1,3-pentadiene (k2) and E-1,3-pentadiene (k3). The rate coefficients obtained by the relative-rate method at T = 300 ± 1 K and P = 759 ± 7 Torr are k1 = (2.3 ± 0.3) × 10−14 cm3 molecule−1 s−1, k2 = (2.0 ± 0.3) × 10−12 cm3 molecule−1 s−1 and k3 = (2.4 ± 0.3) × 10−12 cm3 molecule−1 s−1. The rate coefficients determined by the discharge–flow technique at low pressure (P = 1.8–4.5 Torr) and at T = 300 ± 3 K are k1 = (2.3 ± 0.6) × 10−14 cm3 molecule−1 s−1, k2 = (1.4 ± 0.4) × 10−12 cm3 molecule−1 s−1 and k3 = (1.6 ± 0.4) × 10−12 cm3 molecule−1 s−1. The authors suggest the use of the values k1 = (2.3 ± 0.5) × 10−14 cm3 molecule−1 s−1, k2 = (1.7 ± 0.4) × 10−12 cm3 molecule−1 s−1 and k3 = (2.0 ± 0.4) × 10−12 cm3 molecule−1 s−1 for atmospheric calculations.