School of Chemistry, University of Leeds, Leeds LS2 9JT, UK.
Phys Chem Chem Phys. 2010 Aug 21;12(31):9094-106. doi: 10.1039/c004451b. Epub 2010 Jun 8.
This paper describes the kinetic study of a number of gas-phase reactions involving neutral Ca-containing species, many of which are important for describing the chemistry of meteor-ablated calcium in the Earth's upper atmosphere. Ca atoms were produced thermally in the upstream section of a fast flow tube, and then converted to the molecular species CaO, CaO(2), CaO(3), CaCO(3) or Ca(OH)(2) by the addition of appropriate reagents. Atomic O or H was added further downstream, and both Ca and CaO were detected at the downstream end of the flow tube by laser-induced fluorescence. The following rate coefficients were determined: k(CaO + O --> Ca + O(2)) = (3.1) x 10(-10) at 300 K and (1.3) x 10(-10) at 203 K; k(CaO(2) + O --> CaO + O(2)) = (2.2) x 10(-11) at 300 K and (1.6) x 10(-11) at 203 K; k(CaO(2) + H --> products, 298 K) = (1.2 +/- 0.6) x 10(-11); k(CaCO(3) + O --> CaO(2) + CO(2), 300 K) < or = 1.0 x 10(-12); k(CaCO(3) + H--> CaOH + CO(2), 298 K) > or = 2.8 x 10(-12) and < or = 3.6 x 10(-11); k(CaO(3) + H--> CaOH + O(2), 298 K) > or = 1.7 x 10(-11); k(Ca(OH)(2) + H --> CaOH + H(2)O, 298 K) > or = 1.1 x 10(-11); k(CaOH + H --> Ca + H(2)O, 298 K) > or = 1.1x 10(-11) cm(3) molecule(-1) s(-1). The kinetics of the reactions of Ca and CaO with NO(2) and N(2)O were also studied, yielding k(Ca + NO(2) --> CaO + NO) = (2.6 +/- 0.3) x 10(-10) at 300 K and (2.0 +/- 0.3) x 10(-10) at 203 K; k(CaO + NO(2) --> CaO(2) + NO) = (8.1 +/- 2.0) x 10(-10) at 300 K and (2.9 +/- 1.0) x 10(-10) at 202 K; k(CaO + N(2)O --> CaO(2) + N(2)) = (4.2 +/- 1.7) x 10(-11) at 300 K and (2.2 +/- 1.2) x 10(-12) at 206 K; k(CaO + H(2) --> Ca + H(2)O, 300 K) = (3.4 +/- 1.3) x 10(-10) cm(3) molecule(-1) s(-1). Electronic structure calculations of the relevant potential energy surfaces were performed to interpret the experimental results, and the atmospheric implications of these measurements are then discussed.
本文描述了一系列气相反应的动力学研究，这些反应涉及中性含 Ca 物种，其中许多对描述地球高层大气中流星撞击钙的化学性质至关重要。Ca 原子在快速流管的上游部分通过热产生，然后通过添加适当的试剂转化为 CaO、CaO(2)、CaO(3)、CaCO(3) 或 Ca(OH)(2)等分子物种。进一步在下游添加原子 O 或 H，然后通过激光诱导荧光在流管的下游端检测到 Ca 和 CaO。确定了以下速率系数：k(CaO + O --> Ca + O(2)) = (3.1) x 10(-10) 在 300 K 和 (1.3) x 10(-10) 在 203 K；k(CaO(2) + O --> CaO + O(2)) = (2.2) x 10(-11) 在 300 K 和 (1.6) x 10(-11) 在 203 K；k(CaO(2) + H --> 产物，298 K) = (1.2 +/- 0.6) x 10(-11)；k(CaCO(3) + O --> CaO(2) + CO(2)，300 K) < or = 1.0 x 10(-12)；k(CaCO(3) + H--> CaOH + CO(2)，298 K) > or = 2.8 x 10(-12) and < or = 3.6 x 10(-11)；k(CaO(3) + H--> CaOH + O(2)，298 K) > or = 1.7 x 10(-11)；k(Ca(OH)(2) + H --> CaOH + H(2)O，298 K) > or = 1.1 x 10(-11)；k(CaOH + H --> Ca + H(2)O，298 K) > or = 1.1x 10(-11) cm(3) molecule(-1) s(-1)。还研究了 Ca 和 CaO 与 NO(2)和 N(2)O 的反应动力学，得到 k(Ca + NO(2) --> CaO + NO) = (2.6 +/- 0.3) x 10(-10) 在 300 K 和 (2.0 +/- 0.3) x 10(-10) 在 203 K；k(CaO + NO(2) --> CaO(2) + NO) = (8.1 +/- 2.0) x 10(-10) 在 300 K 和 (2.9 +/- 1.0) x 10(-10) 在 202 K；k(CaO + N(2)O --> CaO(2) + N(2)) = (4.2 +/- 1.7) x 10(-11) 在 300 K 和 (2.2 +/- 1.2) x 10(-12) 在 206 K；k(CaO + H(2) --> Ca + H(2)O，300 K) = (3.4 +/- 1.3) x 10(-10) cm(3) molecule(-1) s(-1)。通过执行相关势能面的电子结构计算来解释实验结果，然后讨论了这些测量对大气的影响。
Zotero 插件