A kinetic investigation of the reaction magnesium (1S) + nitrous oxide over the temperature range 382-893 K

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.

Absolute photolysis cross-sections for NaHCO3 , NaOH, NaO, NaO2and NaO3 : implications for sodium chemistry in the upper mesosphere

“…1), the flow of Na atoms from the heat pipe into the central chamber is balanced by diffusion to the chamber walls of Na (in the absence of reagents) or of NaX. As we have shown previously for this reactor, 12 the steadystate concentration of Na is given by F Na =k diff (Na), where F Na is the flow rate of Na into the chamber from the heat pipe, and k diff (Na) is the first-order loss of Na to the walls of the chamber, which closely approximates to a cylinder of radius r ¼ 3 cm and length l ¼ 6 cm. k diff (Na) is given by…”

Laboratory study of the reactions Mg + O3 and MgO + O3. Implications for the chemistry of magnesium in the upper atmosphere

“…Nevertheless, the presence of a relatively deep energy minimum on the reaction potential energy surface [D0(Mg-03) = 204 kJ mol-', vide infra], is probably one reason why reaction ( 2) is about seven orders of magnitude faster at room temperature than the apparently similar reaction Mg + N 2 0 + MgO + N, . 34 Eqn. (11) demonstrates that reaction (2) proceeds essentially at the collision number, with a very small T-dependence.…”

Kinetic Study of Ca(1S) + N2O and Sr(1S) + N2O Reactions in the Temperature Ranges of, Respectively, 303−1015 and 303−999 K

“…Correlation between Experimental Arrhenius Parameters and Physicochemical Properties of the Reactants. The dynamical aspects of the alkaline earth metal/N 2 O reactions have already been discussed extensively in the literature, ,,,, and only some essential features will be repeated here. As already mentioned, a possible explanation for the observed non-Arrhenius behavior is related to the occurrence of two reaction paths.…”

“…Despite the problems for extracting kinetic parameters by means of the diffusion flame technique, values for the activation barriers derived with this technique are also given in Table . Indeed, it has already been pointed out by several authors that this technique allows us to determine quite well the temperature dependence of the rate constant but not the preexponential factor. − …”

“…[4][5][6][7][8][9][10] A survey of much of the research work concerning metal atom reaction kinetics carried out during the past years has been amply described in ref 11 and more particularly the alkaline earth metal atom/N 2 O reactions. 10 Until now, kinetic data for the Mg( 1 S) atom reaction with N 2 O were obtained by means of quite different techniques [12][13][14] and a fairly good agreement between the rate constants was observed.…”