讲座题目：Reactivity of Peroxy Radicals studied by Laser photolysis - Cavity Ring Down Spectroscopy

讲座时间：2023年4月27日（星期四）上午 9:30—10:30

讲座地点：图书馆六层报告厅

主讲人：Prof. Christa Fittschen

研究方向：化学动力学、光谱学、过氧自由基的研究

讲座简介：Peroxy radicals, RO₂, are key species in the atmosphere. They are formed from a reaction of OH radicals with hydrocarbons:

RH + OH + O₂→ RO₂+ H₂O

In polluted environments, RO₂radicals react predominantly with NO, leading to formation of NO₂, and eventually through photolysis of NO₂to formation of O₃.

At low NOx concentrations such as in the marine boundary layer or the background troposphere, the lifetime of RO₂radicals increases and other reaction pathways such as self- and cross reaction with other RO₂or with HO₂radicals become competitive. To study these reactions, UV absorption spectroscopy has been employed in the past: this technique gives good sensitivity for peroxy radicals, but poor selectivity as these radicals have broad absorption features in the UV. We have established a technique allowing to follow peroxy radicals with a better selectivity compared to UV, but with still good sensitivity by coupling laser photolysis to cw-Cavity Ring Down Spectroscopy in the near IR.

I will present the experimental technique and results on the recent measurement of the rate constant of the self-reaction of the acetylperoxy radical, CH₃C(O)O₂. Studying this reaction is much complicated due to unavoidable secondary chemistry: the self-reaction leads to formation of CH₃O₂radicals, which in turn react with CH₃C(O)O₂. This reaction has two different paths, one leading to stable products, the other to CH₃O₂and HO₂radicals. The HO₂radicals from this reaction in turn react with both, CH₃C(O)O₂and CH₃O₂radicals, leading also to either stable products or recycling the radicals. Therefore, the branching ratios of both secondary reactions will influence the decay of the acetylperoxy radical and need to be determined.

主讲人简介：

Prof. Christa Fittschen，法国里尔大学“燃烧过程和大气的物理化学”实验室PC2A的研究主任。从事与化学动力学、光谱学、过氧自由基的研究。1986年获得德国哥廷根大学硕士学位，1989年获得德国哥廷根大学博士学位，1989-1991年，任加利福尼亚斯坦福研究所博士后研究员，1991年3月-8月，在哥廷根物理化学研究所担任研究员。1991年9月-1992年9月，在里尔大学担任博士后研究员。1992年10月-1996年9月，在里尔大学担任CNRS初级科学家。1996年10月-2006年9月，担任CNRS高级科学家。2007年10月-2016年9月，担任CNRS二级研究主任，负责PC2A实验室大气化学研究小组。自2016年10月起，担任CNRS一级研究主任。