The reaction NO + 0 3 -NO2 + 0 2 has been studied in a 220-m3 spherical stainless steel reactor under stopped-flow conditions below 0.1 mtorr total pressure. Under the conditions used, the mixing time of the reactants was negligible compared with the chemical reaction time. The pseudo-first-order decay of the chemiluminescence owing to the reaction of ozone with a large excess of nitric oxide was measured with an infrared sensitive photomultiplier. One hundred twenty-nine decays a t 18 different temperatures in the range of 283-443 K were evaluated. A weighted least-squares fit to the Arrhenius equation yielded k = (4.3 f 0.6) X exp[-(1598 f 50)/T] cm3/molecule sec (two standard deviations in brackets). The Arrhenius plot showed no curvature within experimental accuracy. Comparison with recent results of Birks and co-workers, however, suggests that a nonlinear fit, as proposed by these authors, is more appropriate over an extended temperature range.
The title reaction (1) was studied at very low total pressures. The activation energy of the chemiluminescent pathway (1a) depends on the wavelength range in which emission is detected. Measurements at 1.27 μ, close to the maximum of the emission spectrum, yield 16.2 kJ mol−1 which presumably equals the activation energy E1a of the chemiluminescence integrated over all wavelengths. The absolute quantum yield at 290 K was determined to be k1a/k1 = 0.20, using the infrared atmospheric band emitted by known concentrations of O2(1Δg) as intensity standard. These results are combined with temperature dependent rate constants of the bulk reaction to yield separate Arrhenius equations, k1a = 2.90 · 10−12 exp(‐1951 K/T) cm3 s−1 for the electronically excited product, and k1b = 2.27 · 10−12 exp(‐1475 K/T) cm3 s−1 for the dark component of reaction (1). The half‐quenching densities of the chemiluminescence were found to be both wavelength‐ and temperature dependent, following approximately a T0.5 dependence for M = N2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.