Abstract

The rate constants of the interactions of chromium atoms with molecular oxygen through recombination Cr + O₂ + M → CrO₂ + M (I) and exchange Cr + O₂ → CrO + O (II) were determined by a new method for treatment of experimental data. The results, together with the available literature data, led to the following equations for the rate constants of recombination in the low-pressure limit and of the exchange reaction: \({{k}_{{1,0}}}(300 < T < 2000\,\,{\text{K}}) = {\text{ }}3.7{\text{ }} \times {\text{ }}{{10}^{{18}}}{{\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 1.49}}},\) cm⁶ mol^–2 s^–1, \({{k}_{2}}(700 < T < 4000\,{\text{K}}) = \) \(4.0 \times {{10}^{{14}}}{{\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 0.32}}}exp\left( { - {{4480{\kern 1pt} \,{\text{K}}} \mathord{\left/ {\vphantom {{4480{\kern 1pt} \,{\text{K}}} T}} \right. \kern-0em} T}} \right)\), cm³ mol^‒1 s^‒1. An expression for the rate constant of the reverse reaction was obtained from k₂(T) and the equilibrium constant for reaction (II): \({{k}_{{ - 2}}}(700 < T < 4000\,{\text{K}}) = 3.6 \times {{10}^{{13}}}{{\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 0.64}}}\) cm³ mol^‒1 s^‒1. Modeling within the framework of the RRKM theory shows that calculation of the rate constant k_1,0(T) requires inclusion of not only the ground electronic state of the CrO₂ molecule, but also the low-lying excited electronic states up to the dissociation threshold. A comparison of the experimental and calculated temperature dependences shows that the best agreement between them is achieved at an average portion of energy transferred in deactivating collisions of the excited CrO₂ molecule with diluent gas molecules of ΔE = 2.8 kJ/mol.

中文翻译：

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确定反应 Cr + O2 + M → CrO2 + M 和 Cr + O2 → CrO + O 的速率常数

摘要

通过重组 Cr + O ₂ + M → CrO ₂ + M (I) 和交换 Cr + O ₂ → CrO + O (II)的铬原子与分子氧相互作用的速率常数通过一种新的处理方法确定实验数据。结果，连同可用的文献数据，得出了以下用于低压极限和交换反应中复合速率常数的方程：\({{k}_{{1,0}}}(300 < T < 2000\,\,{\text{K}}) = {\text{ }}3.7{\text{ }} \times {\text{ }}{{10}^{{18}}}{ {\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 1.49}}},\ ) cm ⁶ mol ^–2 s ^–1 ,\({{k}_{2}}(700 < T < 4000\,{\text{K}}) = \) \(4.0 \times {{10}^{{14}}}{{\left ( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 0.32}}}exp\left( { - {{4480{\kern 1pt} \,{\text{K}}} \mathord{\left/ {\vphantom {{4480{\kern 1pt} \,{\text{K}}} T}} \对。\kern-0em} T}} \right)\) , cm ³ mol ^‒1 s ^‒1。由k ₂ ( T ) 和反应 (II) 的平衡常数获得逆反应速率常数的表达式：\({{k}_{{ - 2}}}(700 < T < 4000\, {\text{K}}) = 3.6 \times {{10}^{{13}}}{{\left( {{T \mathord{\left/ {\vphantom {T {1000}}} \right. \kern-0em} {1000}}} \right)}^{{ - 0.64}}}\) cm ³mol ^‒1 s ^‒1 . RRKM 理论框架内的建模表明，速率常数k _1,0 ( T ) 的计算不仅需要包括 CrO ₂分子的基电子态，还需要包括低位激发电子态直至解离阈值。实验和计算温度相关性的比较表明，它们之间的最佳一致性是在激发的 CrO ₂分子与稀释气体分子的失活碰撞中传递的能量的平均部分达到Δ E = 2.8 kJ/mol。