The ablation of cosmic dust particles entering the Earth’s upper atmosphere produces a layer of Ca atoms around 90 km. Here, we present a set of kinetic experiments designed to understand the nature of the Ca molecular reservoirs on the underside of the layer. CaOH was produced by laser ablation of a Ca target in the fast flow tube and detected by non-resonant laser-induced fluorescence, probing the D(²Σ⁺) ← X(²Σ¹) transition at 346.9 nm. The following rate constants were measured (at 298 K): k(CaOH + H → Ca + H₂O) = (1.04 ± 0.24) × 10^–10 cm³ molecule^–1 s^–1, k(CaOH + O → CaO + OH) < 1 × 10^–11 cm³ molecule^–1 s^–1, and k(CaOH + O₂ → O₂CaOH, 1 Torr) = (5.9 ± 1.8) × 10^–11 cm³ molecule^–1 s^–1 (uncertainty at the 2σ level of confidence). The recycling of CaOH from reaction between O₂CaOH and O proceeds with an effective rate constant of k_eff(O₂CaOH + O → CaOH + products, 298 K) = 2.8_–1.2^+2.0 × 10^–10 cm³ molecule^–1 s^–1. Master equation modeling of the CaOH + O₂ kinetics is used to extrapolate to mesospheric temperatures and pressures. The results suggest that the formation of O₂CaOH slows the conversion of CaOH to atomic Ca via reaction with atomic H, and O₂CaOH is likely to be a long-lived reservoir species on the underside of the Ca layer and a building block of meteoric smoke particles.

中文翻译：

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CaOH 与 H 和 O2 以及 O2CaOH 与 O 的反应动力学：对流星钙大气化学的影响

进入地球上层大气的宇宙尘埃粒子消融会在 90 公里左右产生一层钙原子。在这里，我们提出了一组动力学实验，旨在了解层下侧的 Ca 分子储层的性质。CaOH 是通过激光烧蚀快流管中的 Ca 目标产生的，并通过非共振激光诱导荧光检测，在 346.9 nm 处探测 D( ² Σ ⁺ ) ← X( ² Σ ^{1 ) 跃迁。}测量了以下速率常数（在 298 K）：k (CaOH + H → Ca + H ₂ O) = (1.04 ± 0.24) × 10 ^–10 cm ³分子^–1 s ^–1 , k(CaOH + O → CaO + OH) < 1 × 10 ^–11 cm ³分子^–1 s ^–1和k (CaOH + O ₂ → O ₂ CaOH, 1 Torr) = (5.9 ± 1.8) × 10 ^–11 cm ³分子^–1 s ^–1（2σ 置信水平的不确定性）。_{从 O 2} CaOH 和 O之间的反应中回收 CaOH的有效速率常数为k _eff (O ₂ CaOH + O → CaOH + 产物，298 K) = 2.8 _–1.2 ^+2.0 × 10 ^–10 cm ³分子^–1s ^–1。_{CaOH + O 2}动力学的主方程模型用于外推至中间层温度和压力。结果表明，O ₂ CaOH 的形成减缓了 CaOH 通过与原子 H 反应向原子 Ca 的转化，并且 O ₂ CaOH 可能是 Ca 层下侧的长寿命储层物种和流星烟雾粒子。