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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Improved Shock Tube Measurement of the CH4 + Ar = CH3 + H + Ar Rate Constant using UV Cavity-Enhanced Absorption Spectroscopy of CH3
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Improved Shock Tube Measurement of the CH4 + Ar = CH3 + H + Ar Rate Constant using UV Cavity-Enhanced Absorption Spectroscopy of CH3

机译：使用CH3的紫外腔增强吸收光谱法改进CH4 + Ar = CH3 + H + Ar速率常数的冲击管测量

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摘要

We report an improved measurement for the rate constant of methane dissociation in argon (CH4 + Ar = CH3 + H + Ar) behind reflected shock waves. The experiment was conducted using a sub-parts per million sensitivity CH3 diagnostic recently developed in our laboratory based on ultraviolet cavity-enhanced absorption spectroscopy. The high sensitivity of this diagnostic allowed for measurements of quantitatively resolved CH3 time histories during the initial stage of CH4 pyrolysis, where the reaction system is clean and free from influences of secondary reactions and temperature change. This high sensitivity also allowed extension of our measurement range to much lower temperatures (<1500 K). The current-reflected shock measurements were performed at temperatures between 1487 and 1866 K and pressures near 1.7 atm, resulting in the following Arrhenius rate constant expression for the title reaction: k(1.7 atm) = 3.7 x 10(16) exp(-42 200 KIT) cm(3)/mol.s, with a 2 sigma uncertainty factor of 1.25. The current data are in good consensus with various theoretical and review studies, but at the low temperature end they suggest a slightly higher (up to 35%) rate constant compared to these previous results. A re-evaluation of previous and current experimental data in the falloff region was also performed, yielding updated expressions for both the low-pressure limit and the high-pressure limit rate constants and improved agreement with all existing data.
机译：我们报告了一种改进的测量方法，用于测量反射冲击波后氩气中甲烷的甲烷解离速率常数（CH4 + Ar = CH3 + H + Ar）。实验是使用最近在我们实验室中基于紫外线腔增强吸收光谱法开发的百万分之一灵敏度CH3诊断进行的。此诊断程序的高灵敏度允许在CH4热解的初始阶段测量定量解析的CH3时间历史记录，在该阶段反应系统干净且不受二次反应和温度变化的影响。这种高灵敏度还使我们的测量范围扩展到了更低的温度（<1500 K）。电流反射冲击测量是在1487至1866 K之间的温度和接近1.7 atm的压力下进行的，得出以下标题反应的Arrhenius速率常数表达式：k（1.7 atm）= 3.7 x 10（16）exp（-42） 200 KIT）cm（3）/mol.s，2σ不确定度系数为1.25。目前的数据与各种理论和综述研究都非常一致，但是在低温端，它们建议的速率常数比以前的结果略高（最高35％）。还对衰减区域中的先前和当前实验数据进行了重新评估，从而获得了低压极限和高压极限速率常数的更新表达式，并且与所有现有数据的一致性得到了改善。

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