A kinetic study of the reactions of iron oxides and hydroxides relevant to the chemistry of iron in the upper mesosphere
A kinetic study of the reactions of iron oxides and hydroxides relevant to the chemistry of iron in the upper mesosphere
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与上层中间层铁化学相关的铁氧化物和氢氧化物反应的动力学研究
DOI：
10.1039/b211900e
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发表时间：
2003
影响因子：
3.3
通讯作者：
J. Plane
中科院分区：
文献类型：
--
作者：
Daniel E. Self;J. Plane
本文介绍了一些铁的氧化物和氢氧化物与O，H和O3的气相反应的动力学研究。这些反应对于描述地球上层中间层中流星烧蚀铁的化学性质非常重要。用脉冲激光烧蚀纯Fe棒在快流管上游产生Fe原子脉冲，并在下游端用激光诱导荧光（LIF）在248.3nm Fe（x5F05 <$a5D4）处探测到Fe原子脉冲。 含铁反应物物种FeO和FeO 2通过Fe与NO2的顺序反应产生; FeO 3通过亚稳态激发的Fe原子与O2反应形成FeO，然后加入O2; Fe（OH）2通过将H2O加入FeO。通过微波放电N2产生原子O或H
(with添加NO）或H2，并通过用NO2的常规滴定测定它们的绝对浓度。速率系数基本上是相对于以前确定的Fe和FeO的绝对速率系数测量的[J. M. C. Plane和R. J.Rollason，Phys.Chem.Chem.Phys，1999，1，1843; R.罗拉森和J. M. C. Plane，同上，2000，2，2335]，但是使用包括相关物质的流管壁上的扩散损失的全动力学模型提取。获得了以下结果（单位：cm3 molecule − 1 s − 1;引用的不确定度为2 σ）：k（FeO + O → Fe + O2，209 - 381 K）= 4.6 + 2.6 − 1.6 × 10 − 10 e −（350 ± 130）/T; k（FeO 2 + O → FeO + O2，209 - 381 K）= 1.4 + 0.8 − 0.5 × 10 − 10 e −（580 ± 120）/T; k（FeO 3 + O → FeO 2 + O2，610 K）= 8 + 10 − 5 × 10 − 12; k（FeO 2 + O3 → FeO 3 + O2，224 - 298 K）= 4.4 + 6.4 - 2.6 × 10 - 10 e-（170 ± 230）/T; k（FeO3 + H → FeOH + O2，294 K）=（2.0 + 1.2 − 0.6）× 10 − 11，k（FeOH + H →产物，294 K）=（1.3 ± 0.3）× 10 − 11。 在B3LYP/6 - 311 + g（2d，p）水平上的理论计算被用来确定大多数这些反应的相关势能面上的驻点，然后应用统计理论来模拟动力学。 然后讨论了这些结果对火焰和高层大气中铁化学的影响。
This paper describes the kinetic study of a number of gas-phase reactions of iron oxides and hydroxides with O, H and O3. These reactions are important for characterising the chemistry of meteor-ablated iron in the earth's upper mesosphere. Pulses of atomic Fe were produced in the upstream section of a fast flow tube by the pulsed laser ablation of a pure Fe rod, and detected at the downstream end by LIF at 248.3 nm Fe(x5F05 ← a5D4). The Fe-containing reactant species FeO and FeO2 were produced by sequential reaction of Fe with NO2; FeO3 by the reaction of metastable excited Fe atoms with O2 to form FeO, followed by addition of O2; and Fe(OH)2 by the addition of H2O to FeO. Atomic O or H was produced by the microwave discharge of N2
(with addition of NO) or H2, respectively, and their absolute concentrations determined by conventional titration with NO2. Rate coefficients were essentially measured relative to absolute rate coefficients for Fe and FeO determined previously [J. M. C. Plane and R. J. Rollason, Phys. Chem. Chem. Phys, 1999, 1, 1843; R. J. Rollason and J. M. C. Plane, ibid., 2000, 2, 2335], but were extracted using a full kinetic model including diffusive loss on the flow tube walls of the relevant species. The following results were obtained (units: cm3 molecule−1 s−1; quoted uncertainty is 2σ): k(FeO + O → Fe + O2, 209–381 K) = 4.6+2.6−1.6 × 10−10 e−(350±130)/T; k(FeO2 + O → FeO + O2, 209–381 K) = 1.4+0.8−0.5 × 10−10 e−(580±120)/T; k(FeO3 + O → FeO2 + O2, 610 K) = 8+10−5 × 10−12; k(FeO2 + O3 → FeO3 + O2, 224–298 K) = 4.4+6.4−2.6 × 10−10 e−(170±230)/T; k(FeO3 + H → FeOH + O2, 294 K) = (2.0+1.2−0.6) × 10−11, and k(FeOH + H → products, 294 K) = (1.3 ± 0.3) × 10−11 . Theoretical calculations at the B3LYP/6-311 + g(2d,p) level were used to identify the stationary points on the relevant potential energy surfaces for most of these reactions, before applying statistical theories to model the kinetics. The implications of these results for the chemistry of iron in flames and the upper atmosphere are then discussed.