The reaction Mg + 0 2 + Nz was studied by a static-flow technique in which the rate coefficient was determined relative to the diffusion coefficient of Mg('S) atoms in Nz. This yielded k(349K

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.

No abstract

kl is shown in Figure 4. The results indicate that the revised SAR expression largely corrects for the original overestimate of the magnitude of kl. The revised model also accurately predicts the temperature dependence of kl and is thus recommended for extrapolation to higher combustion temperatures. These revised group factors do not significantly affect the temperaturedependent J. Phys. Chem. 1992, 96, 1296-1301 reaction rate predictions for CH,CH,Cl and CH2ClCH2C1.National Acknowledgment. The partial support of this work by the Foundation (Grant CBT 8900750) is Patefully RegistryThis reaction was studied by two techniques. At temperatures below 650 K, where the reaction is extremely slow, a novel static-flow method was used to measure the rate coefficient relative to the diffusion coefficient of Mg('S) atoms in N2 These measurements were complemented at higher temperatures by employing a two-laser pulseprobe technique to determine absolute rate coeficients; Mg atoms were produced in an excess of N20 and N2 bath gas by the pulsed multiphoton (193.3 nm) disoociation of MgO and then monitored by timeresolved laser-indud fluorescence spectroscopy at 285.21 nm (Mg(31P1-31S)). The dependence of the rate coefficient is given by k(382 K 4 T 4 893 K) = (6.8 f 1.6) X lo-" exp[-(39.6 1.0) kJ moI-'/RT] an3 molecule-I s-', where the quoted uncertainty is 2a. This result is discussed in terms of the reaction o c c u h g both adiabatically and via a nonadiabatic spin transition from the 1'A' to the 13A' surface. Lastly, a comparison is made with the analogous reactions of other group 2 metal atoms.

No abstract