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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Cross Section of OH Radical Overtone Transition near 7028 cm(-1) and Measurement of the Rate Constant of the Reaction of OH with HO2 Radicals
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Cross Section of OH Radical Overtone Transition near 7028 cm(-1) and Measurement of the Rate Constant of the Reaction of OH with HO2 Radicals

机译：接近7028 cm（-1）的OH自由基泛音跃迁的截面以及OH与HO2自由基反应的速率常数的测量

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摘要

The absorption cross section of an overtone transition of OH radicals at 7028.831 cm(-1) has been measured using an improved experimental setup coupling laser photolysis to three individual time resolved detection techniques. Time-resolved relative OH radical profiles were measured by laser-induced fluorescence (LIF), and their absolute profiles have been obtained by cw-cavity ring-down spectroscopy (cw-CRDS). HO2 radicals were quantified simultaneously at the well characterized absorption line at 6638.21 cm(-1) by a second cw-CRDS absorption path. Initial OH concentrations and thus their absorption cross sections have been deduced from experiments of 248 nm photolysis of H2O2: OH and HO2 profiles have been fitted to a simple kinetic model using well-known rate constants. The rate constant of the reaction between OH and HO2 radicals turned out to be sensitive to the deduction of the initial OH concentration and has been revisited in this work: OH decays have been observed in the presence of varying excess HO2 concentrations. A rate constant of (1.02 +/- 0.06) x 10(-10) cm(3) s(-1) has been obtained, in good agreement with previous measurements and recent recommendations. An absorption cross section of sigma(OH) = (1.54 +/- 0.1) X 10(-19) cm(2) at a total pressure of 50 Torr helium has been obtained from consistent fitting of OH and HO2 profiles in a large range of concentrations.
机译：OH的泛音跃迁在7028.831 cm（-1）处的吸收截面已使用改进的实验装置将激光光解法与三种独立的时间分辨检测技术耦合在一起进行了测量。通过激光诱导荧光（LIF）测量了时间分辨的相对OH自由基分布，并通过cw-腔衰荡光谱法（cw-CRDS）获得了它们的绝对分布。通过第二个cw-CRDS吸收路径，同时在6638.21 cm（-1）的特征明确的吸收线上同时定量了HO2自由基。初始OH浓度及其吸收截面已从H2O2的248 nm光解实验中推导得出：OH和HO2曲线已使用众所周知的速率常数拟合为简单的动力学模型。事实证明，OH和HO2自由基之间的反应速率常数对初始OH浓度的降低很敏感，并且在这项工作中得到了重新考虑：在存在过量HO2浓度变化的情况下，观察到OH的衰减。已获得（1.02 +/- 0.06）x 10（-10）cm（3）s（-1）的速率常数，与先前的测量结果和最新建议相吻合。通过在大范围内一致地拟合OH和HO2曲线获得在总压力为50 Torr氦气下sigma（OH）=（1.54 +/- 0.1）X 10（-19）cm（2）的吸收截面浓度。

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