Parameters And Products Measurement Of C₂H₅O₂ Atmospheric Chemical Reaction With Advanced Spectroscopy And Photoionization Mass Spectrometry

Peroxy radicals are important intermediates in atmospheric chemical reactions and play an important role in the atmospheric oxidation process caused by PM2.5 and ozone pollution complex as well as in the atmospheric radical chain reactions.The atmospheric chemical reaction parameters and product composition of peroxy radicals are key information in global air quality model simulation,and are of great scientific and practical significance for understanding the mechanism of air combined pollution and its prevention.Ethane is one of the most abundant non methane hydrocarbons in the atmosphere,and its oxidation reaction generates the ethyl peroxy radical C₂H₅O₂,In low NOx environments,its self-and cross-reaction are very important,but limited by technology,there are still problems such as insufficient reaction rate constants and product information,as well as inconsistent results,which need to be addressed urgently.Peroxy radicals are substances with high reactivity and thus short life time,techniques with high sensitivity are necessary to measure its related reaction parameters and products.The combination of highly sensitive cavity ringdown spectroscopy（CRDS）with near-infrared detecting laser source allows selective and time-resolved quantitive detection of different peroxy radicals,then,reliable reaction rate constants and product branching ratio information are finally determined.Vacuum ultraviolet photoionization mass spectrometry（PIMS）can measure rich product information for reactions,both reactive intermediates,such as radicals,and stable products are able to be obtained simultaneously.Besides,the combination of synchrotron radiation light source and photoelectron spectra with high energy resolution obtained by photoelectron photoion coincidence spectroscopy（PEPICO）allows to distinguish isomeric products and to accurately measure and separate reaction products.Highly sensitive spectroscopy and PIMS have been used in this thesis to detect the reaction parameters and products of C₂H₅O₂ related reaction in low NOx environment,including the self-reaction of C₂H₅O₂,and its cross-reaction with CH₃O₂ peroxy radical.The absorption time kinetic profiles of reactant and product radicals have been meaured with near infrared continuous wave dual-path CRDS,the rate constant and branch ratio of the self-reaction of C₂H₅O₂ and its cross-reaction with CH₃O₂ have been determined.Based on flowtube reactor with PIMS and PEPICO combined with advanced synchrotron radiation light source,the products fromed in peroxy radical reactions were detected,including the detection of the dimer product C₂H₅OOC₂H₅,as well as the detection of further oxidation reaction products of acetaldehyde CH₃CHO,a common product of C₂H₅O₂ self-reaction and C₂H₅O₂+CH₃O₂ cross-reaction.The main contents of this thesis are:1.Measurements of the self-reaction of C₂H₅O₂ by CRDS and PIMS.351 nm pulsed laser photolysis of Cl2/C2H6/O₂ mixture in the reactor to create C₂H₅O₂.The absorption cross-section of the C₂H₅O₂ in the ?←X electronic transition with the peak wavelength at 7596.47 cm-1 has been measured by relative measurement or rate constant measurement,the obtained value was applied to quantitively measure the concentration of C₂H₅O₂.The concentration-time kinetic profiles of HO₂ and C₂H₅O₂ in the near-infrared region have been selectively and quantitively measured at the same time with dual path CRDS,the rate constant and branching ratio of C₂H₅O of the C₂H₅O₂ self-reaction were directly obtained.A microwave discharge flow tube with PIMS were conducted to measure the branching ratio for the dimer product C₂H₅OOC₂H₅.Considering that secondary reactions such as C₂H₅O₂+HO₂/C₂H₅O influence the rate constant and product branching ratio measurements of the C₂H₅O₂ self-reaction,separate experiments were conducted to measure the rate constants of these two reactions.At present,the IUPAC website database has adopted the conclusions of this experiment and updated the recommended values for the rate constant and product branching ratio of C₂H₅O of the C₂H₅O₂ self-reaction.2.Measurements of the cross-reaction of C₂H₅O₂ with CH₃O₂ by CRDS.C₂H₅O₂ and CH₃O₂ were created at the same time by 351 nm pulsed laser photolysis of Cl2/C2H6/CH5/O₂ mixture in the reactor,the absorption-time kinetic profiles of C₂H₅O₂ and CH₃O₂ were relative selectively measured,and the concentration-time kinetic profiles of HO₂ was also measured,with a model to fit the experimental results,the rate constant and branching ratio of radical channel C₂H₅O⁺CH₃O of C₂H₅O₂+CH₃O₂ cross-reaction were obtained.The obtained rate constant in the present thesis is nearly two times faster than the only reported earlier value,but in excellent agreement with an estimated results based on the mean geometric rule.During the measurements,small amount of Cl in the reaction with C₂H₅O₂ and CH₃O₂5 separate experiments were conducted to measure the rate constant and product branching ratio of C₂H₅O₂/CH₃O₂+Cl reaction.The obtained values have been included in the model of C₂H₅O₂+CH₃O₂ cross reaction.3.Measurements of the oxidation reaction of CH₃CHO by PEPICO combined with synchrotron radiation light source.The oxidation of CH₃CHO initiated by F/Cl gives two isomer radicals CH₃CO/CH₂CHO,the photoelectron spectra of two radicals and its reaction products were obtained,the branching ratio of CH₂CHO radical in Cl+CH₃CHO reaction was determined.The oxidation of CH₃CO and CH₂CHO generates peroxy radicals CH₃COO₂ and O₂CH₂CHO.Theoretical calculations in this thesis indicate that CH₃COO₂⁺is unstable,one of the O₂CH₂CHO⁺is stable,while the others are not and will dissociate.Another product of CH₃CO oxidation reaction α-lactone,its ions are unstable and will dissociate,the photoelectron spectra of its fragment ions were measured.