Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, M/S 183-901, Pasadena, California 91109, USA.
J Phys Chem A. 2010 Jul 8;114(26):6983-95. doi: 10.1021/jp912129j.
The self-reactions and cross reactions of the peroxy radicals C2H5O2 and HO2 were monitored using simultaneous independent spectroscopic probes to observe each radical species. Wavelength modulation (WM) near-infrared (NIR) spectroscopy was used to detect HO2, and UV absorption monitored C2H5O2. The temperature dependences of these reactions were investigated over a range of interest to tropospheric chemistry, 221-296 K. The Arrhenius expression determined for the cross reaction, k2(T) = (6.01(-1.47)(+1.95)) x 10(-13) exp((638 +/- 73)/T) cm3 molecules(-1) s(-1) is in agreement with other work from the literature. The measurements of the HO2 self-reaction agreed with previous work from this lab and were not further refined. The C2H5O2 self-reaction is complicated by secondary production of HO2. This experiment performed the first direct measurement of the self-reaction rate constant, as well as the branching fraction to the radical channel, in part by measurement of the secondary HO2. The Arrhenius expression for the self-reaction rate constant is k3(T) = (1.29(-0.27)(+0.34)) x 10(-13)exp((-23 +/- 61)/T) cm3 molecules(-1) s(-1), and the branching fraction value is alpha = 0.28 +/- 0.06, independent of temperature. These values are in disagreement with previous measurements based on end product studies of the branching fraction. The results suggest that better characterization of the products from RO2 self-reactions are required.
过氧自由基 C2H5O2 和 HO2 的自反应和交叉反应使用同时独立的光谱探针进行监测，以观察每种自由基。波长调制（WM）近红外（NIR）光谱用于检测 HO2，UV 吸收监测 C2H5O2。在对大气化学有意义的范围内（221-296 K）研究了这些反应的温度依赖性。交叉反应的 Arrhenius 表达式为 k2(T) = (6.01(-1.47)(+1.95)) x 10(-13) exp((638 +/- 73)/T) cm3 molecules(-1) s(-1)，与文献中的其他工作一致。HO2 自反应的测量结果与本实验室以前的工作一致，没有进一步改进。C2H5O2 自反应由于 HO2 的次级生成而变得复杂。该实验首次直接测量了自反应速率常数以及自由基通道的分支分数，部分通过测量次级 HO2 来实现。自反应速率常数的 Arrhenius 表达式为 k3(T) = (1.29(-0.27)(+0.34)) x 10(-13) exp((-23 +/- 61)/T) cm3 molecules(-1) s(-1)，分支分数值 alpha = 0.28 +/- 0.06，与温度无关。这些值与基于分支分数终产物研究的先前测量值不一致。结果表明，需要更好地表征 RO2 自反应产物。
