Laser Measurements of the H Atom + Ozone Rate Constant at Mesospheric Temperatures

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• 作者：Yingdi Liu ; Jian Peng ; Kelsey Reppert ; Sara Callahan ; Gregory P. Smith
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：June 9, 2016
• 年：2016
• 卷：120
• 期：22
• 页码：3855-3860
• 全文大小：311K
• 年卷期：0
• ISSN：1520-5215

文摘

The exothermic H + O₃ reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We remeasured its rate constant to reduce its uncertainty and extended the measurements to lower mesospheric temperatures using modern laser-induced fluorescence (LIF) techniques. H atoms were produced by pulsed ultraviolet laser trace photolysis of O₃, followed by reaction of O(¹D) with added H₂. A second, delayed, frequency-mixed dye laser measured the reaction decay rate with the remaining ozone using LIF. We monitored either the H atom decay by two photon excitation at 205 nm and detection of red fluorescence, or the OH (v = 9) product time evolution with excitation of the B²Σ⁺–X²Π (0,9) band at 237 nm and emission in the blue B²Σ⁺–A²Σ⁺ (0,7) band. By cooling the enclosed low pressure flow cell we obtained measurements from 140 to 305 K at 20 to 200 Torr in Ar. Small kinetic modeling corrections were made for secondary regeneration of H atoms. The results are consistent with the current NASA JPL recommendation for this rate constant and establish its extrapolation down to the lower temperatures of the mesosphere.