A kinetic investigation of the reactions sodium + ozone and sodium monoxide + ozone over the temperature range 207-377 K

Abstract

The reaction Na + 0 3 --c NaO + 0 2 was studied by the pulsed photolysis of NaCl in an excess of 03, HCl, and N2 bath gas, followed by time-resolved laser-induced fluorescence spectroscopy of atomic Na at 589.0 nm (Na(32P3,2-32S)). The rate coefficient is given by k(207 K < T < 378 K) = (1.05 f 0.12) X exp[-(963 f 216) J mol-l/RT] cm3 molecule-' s-I. The reaction between NaO and O3 was studied indirectly by the pulsed photolysis of a higher Na oxide to produce NaO in an excess of O3 and N2 bath gas. Ab initio calculations indicate that the precursor oxide, formed from the reaction between NaO2 and 03, was probably Na03. The NaO concentration was then monitored by time-resolved chemiluminescence from the reaction NaO + 0 -Na(,P,,S) + 0 2 , where the 0 atoms were produced by the photolysis of 03. The temperature dependence of the reaction NaO + O3 -Na02 + 0 2 is given by k(206 K < T < 378 K) = (1.1 1 f 0.34) X l t 9 exp[-(4720 f 580) J mol-l/RT] cm3 molecule-' s-'. The quoted uncertainties are all 2a. The results for both reactions, which are in excellent agreement with previous studies employing fast flow tubes, are then compared to the predictions of long-range capture theory. Finally, the impact of these reactions on the chemistry of meteorablated sodium in the upper atmosphere is discussed.

Chapman's airglow mechanism resurrected?

“…As a result, Herschbach et al [1992] have recently invoked the participation of the lowlying A2Z q-electronically excited state of NaO in reactions Although it is true that NaO(A2Z +) is a major initial product of reaction (1) [Shi et al, 1993] [Yamada et al, 1989] is consistent with theoretical predictions of the relative positions of the potential energy curves [Bauschlicher et al, 1993]. In addition, the extensive overlapping of the A25; + and X2yI rovibrational energy level manifolds of NaO (v" =4 lying close in energy to v'=0) should be conducive to reasonably efficient collisional cross relaxation [Plane et al, 1993]. Although its infrared nature will imply reduced transition moments, a lengthening of the radiative lifetime to the magnitude required appears unlikely.…”

“…Discussions have appeared concerning a role for reaction (12) in atmospheric chemistry [Plane et al, 1993]. In the current analysis, NaO concentrations may fall more than two orders of magnitude below that of the initial N20.…”

Mesospheric Na layer at extreme high latitudes in summer

“…The model that we have employed for this study has been described previously [Plane, 1991;Helmer and Plane, 1993], so that only modifications and improvements will be discussed in depth here. It is a one-dimensional model extending between 65 and 110 km that contains a full treatment of the chemistry of sodium, based upon a recent review of laboratory studies of the pertinent gas phase chemistry of this metal [Plane and Helmer, 1994].…”

“…0148-0227/98/96JD-03709509.00 reservoir or sink for sodium on the underside of layer. Several sinks have been proposed, including the deposition of Na and its compounds onto dust particles [Hunten, 1981], the formation of hydrated cluster ions, and, in most recent models [e.g., Helmer and Plane, 1993;McNeil et al, 1995], the formation of stable gas phase molecules such as NaHCO3 which have relatively long lifetimes in the mesosphere. Unlike the first two of these postulated sinks, for which there is in fact little evidence, the reactions shown in Figure 1 which produce NaHCO3 from atomic Na have all been studied in the laboratory at appropriately low temperatures [Plane and Helmer, 1994].…”

Environmental effects of large igneous province magmatism: a Siberian perspective

“…NaO + O 3 . This reaction was studied by Silver and Kolb [1187], Ager et al [15], and Plane et al [1061], who agree on the rate coefficient and branching ratio. This agreement may be fortuitous because Silver and Kolb used an indirect method and an analysis based on their rate coefficient for the Na + O 3 reaction, which is about 1/2 of the recommended value.…”