Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan. Department of Chemistry, National Taiwan University, Taipei 10617, Taiwan.
Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan. Stanford University, Stanford, CA 94305, USA.
Science. 2015 Feb 13;347(6223):751-4. doi: 10.1126/science.1261549. Epub 2015 Jan 1.
Carbonyl oxides, or Criegee intermediates, are important transient species formed in the reactions of unsaturated hydrocarbons with ozone. Although direct detection of Criegee intermediates has recently been realized, the main atmospheric sink of Criegee intermediates remains unclear. We report ultraviolet absorption spectroscopic measurements of the lifetime of the simplest Criegee intermediate, CH2OO, at various relative humidity levels up to 85% at 298 kelvin. An extremely fast decay rate of CH2OO was observed at high humidity. The observed quadratic dependence of the decay rate on water concentration implied a predominant reaction with water dimer. On the basis of the water dimer equilibrium constant, the effective rate coefficient of the CH2OO + (H2O)2 reaction was determined to be 6.5 (±0.8) × 10(-12) cubic centimeters per second. This work would help modelers to better constrain the atmospheric concentrations of CH2OO.
羰基氧化物，或克里格中间体，是在不饱和烃与臭氧反应中形成的重要瞬态物种。尽管最近已经实现了对克里格中间体的直接检测，但克里格中间体的主要大气汇仍不清楚。我们报告了在 298 开尔文下，各种相对湿度水平下最简单的克里格中间体 CH2OO 的寿命的紫外吸收光谱测量结果，最高可达 85%。在高湿度下，观察到 CH2OO 的极快衰减速率。衰减速率与水浓度的二次依赖性表明主要与水二聚体反应。基于水二聚体平衡常数，确定了 CH2OO + (H2O)2 反应的有效速率系数为 6.5（±0.8）×10(-12)立方厘米每秒。这项工作将有助于建模者更好地约束 CH2OO 的大气浓度。
