The thermal decomposition of formic acid (HCOOH) and acetic acid (CH 3 COOH), two carboxylic acids which play an important role in oxygenate combustion chemistry, were investigated behind reflected shock waves using laser absorption. The rate constants of the primary decomposition pathways of these acids:were measured using simultaneous infrared laser absorption of CO, CO 2 and H 2 O at wavelengths of 4.56, 4.18 and 2.93 microns, respectively. Reaction test conditions covered temperatures from 1230 to 1821 K and pressures from 1.0 to 6.5 atm for dilute mixtures of acids (0.25 -0.6%) in argon. The rate constants of dehydration (R1) and decarboxylation (R2) reactions of formic acid were calculated by fitting exponential functions to the measured CO, CO 2 and H 2 O time-history profiles. These two decomposition channels were found to be in the fall-off region and have a branching ratio, ! ! , of approximately 20 over the range of pressures studied here. The best-fit Arrhenius expressions of the first-order rates of R1 and R2were found to be:! 6.5 atm = 9.12 ×10 !" exp −30275 s -1 (±32%)The rate constants for acetic acid decomposition were obtained by fitting simulated profiles, using an acetic acid pyrolysis mechanism, to the measured species time-histories. The branching ratio, ! ! , was found to be approximately 2. The decarboxylation and dehydration reactions of acetic acid appear to be in the falloff region over the tested pressure range:! 1 atm = 3.18×10 !! ×exp −28679 s -1 (±30%)! 6 atm = 3.51×10 !" ×exp −31330 s -1 (±26%)! 1 atm = 7.9 ×10 !! exp −29056 s -1 (±34%).! 6 atm = 6.34×10 !" ×exp −31330 s -1 (±31%).

13Furans, a class of cyclic ethers, are potential renewable fuels and additives to 14 conventional fuels. High-temperature oxidation of furans is dominated by their reaction 15 with hydroxyl radical. In this work, rate coefficients for the reaction of hydroxyl (OH) with 16 furan ( 1 ), 2-methyl furan ( 2 ) and 2,5-dimethyl furan ( 3 ) were measured behind 17 reflected shock waves over a temperature range of 890 -1388 K and pressures of 1 -2 18 atm. Hydroxyl radicals were generated via the thermal decomposition of tert-butyl-

A flowing microwave post-discharge source sustained at 2.45 GHz in pure nitrogen has been investigated by optical emission spectroscopy (OES) and two-photon absorption laser-induced fluorescence (TALIF) spectroscopy. Variations of the optical emission along the post-discharge (near, pink and late afterglow) have been studied and the gas temperature has been determined. TALIF spectroscopy has been used in the late afterglow to determine the absolute ground-state nitrogen atomic densities using krypton as a reference gas. Measurements show that the microwave flowing post-discharge is an efficient source of N (4S) atoms in late afterglow. In our experimental conditions, the maximum N (4S) density is about 2.2 × 1015 cm−3 for a pressure of 22 Torr, at 300 K. The decay of N (4S) density as a function of the time spent in the quartz tube has been modelled and a wall recombination probability γ of (2.1 ± 0.3) × 10−4 is obtained.

Atmospheric microplasma jets (MPJs) sustained in rare gases have gained increased attention due to their potential to generate highly reactive species. In this paper, we present space- and time-resolved argon metastable densities, Ar(1s5), measured in an atmospheric pressure MPJ operated in Ar and propagating into ambient air using tunable diode laser absorption spectroscopy (1s5 → 2p9 optical transition). The MPJ was produced using a dielectric barrier discharge energized by short duration (230 ns) high-voltage positive pulses (4.2–6.2 kV) at a repetition frequency of 20 kHz. The spectral absorption line profile was recorded and allowed measurements of the absolute metastable Ar(1s5) density integrated in the line-of-sight of the laser beam under various operating conditions of the MPJ. The results reveal a sensitive dependence of the Ar(1s5) density on spatial coordinates, i.e., distance from the exit of the capillary tube of the discharge and from the axis of the argon jet. The highest Ar(1s5) densities of about 3 × 1013 cm−3 were measured at the axis of the argon jet at longitudinal distances between 4 and 5.5 mm downstream from the nozzle of the tube. The temporal distribution of the Ar(1s5) density, which presents three maxima, is thoroughly discussed in this paper. The spatial distribution of the effective Ar(1s5) lifetime (<250 ns) is also reported, giving some insight into the surrounding environment of the argon metastable atoms. The determined spatiotemporal distributions of the Ar(1s5) density can be useful for the optimization of argon MPJs for different applications like surface or biomedical processes.