| Autor: |
Yue H; Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.; Science Island Branch, Graduate School, University of Science and Technology of China, Hefei 230026, China., Zhang C; Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.; Science Island Branch, Graduate School, University of Science and Technology of China, Hefei 230026, China.; Univ. Lille, CNRS, UMR 8522-PC2A-Physicochimie des Processus de Combustion et de I'Atmosphère, F-59000 Lille, France., Lin X; Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China., Wen Z; Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China., Zhang W; Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China., Mostafa S; Univ. Lille, CNRS, UMR 8522-PC2A-Physicochimie des Processus de Combustion et de I'Atmosphère, F-59000 Lille, France., Luo PL; Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan., Zhang Z; Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, CH-5232 Villigen, Switzerland., Hemberger P; Laboratory for Synchrotron Radiation and Femtochemistry, Paul Scherrer Institute, CH-5232 Villigen, Switzerland., Fittschen C; Univ. Lille, CNRS, UMR 8522-PC2A-Physicochimie des Processus de Combustion et de I'Atmosphère, F-59000 Lille, France., Tang X; Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China. |
| Abstrakt: |
Organic peroxy radicals (RO 2 ) as key intermediates in tropospheric chemistry exert a controlling influence on the cycling of atmospheric reactive radicals and the production of secondary pollutants, such as ozone and secondary organic aerosols (SOA). Herein, we present a comprehensive study of the self-reaction of ethyl peroxy radicals (C 2 H 5 O 2 ) by using advanced vacuum ultraviolet (VUV) photoionization mass spectrometry in combination with theoretical calculations. A VUV discharge lamp in Hefei and synchrotron radiation at the Swiss Light Source (SLS) are employed as the photoionization light sources, combined with a microwave discharge fast flow reactor in Hefei and a laser photolysis reactor at the SLS. The dimeric product, C 2 H 5 OOC 2 H 5 , as well as other products, CH 3 CHO, C 2 H 5 OH and C 2 H 5 O, formed from the self-reaction of C 2 H 5 O 2 are clearly observed in the photoionization mass spectra. Two kinds of kinetic experiments have been performed in Hefei by either changing the reaction time or the initial concentration of C 2 H 5 O 2 radicals to confirm the origins of the products and to validate the reaction mechanisms. Based on the fitting of the kinetic data with the theoretically calculated results and the peak area ratios in the photoionization mass spectra, a branching ratio of 10 ± 5% for the pathway leading to the dimeric product C 2 H 5 OOC 2 H 5 is measured. In addition, the adiabatic ionization energy (AIE) of C 2 H 5 OOC 2 H 5 is determined at 8.75 ± 0.05 eV in the photoionization spectrum with the aid of Franck-Condon calculations and its structure is revealed here for the first time. The potential energy surface of the C 2 H 5 O 2 self-reaction has also been theoretically calculated with a high-level of theory to understand the reaction processes in detail. This study provides a new insight into the direct measurement of the elusive dimeric product ROOR and demonstrates its non-negligible branching ratio in the self-reaction of small RO 2 radicals. |
