Study on the atmospheric photochemical reaction of CF3 radicals using ultraviolet photoelectron and photoionization mass spectrometer

Abstract

A study of the atmospheric photochemical reaction of CF 3 radical with CO and O 2 was performed by using a homemade ultraviolet photoelectron spectrometer-photoionization mass spectrometer (PES-PIMS). The electronic structures and mechanism of ionization and dissociation of CF 3 OC(O)OOC(O)-OCF 3 were investigated. It was indicated that the two bands on the photoelectron spectrum of CF 3 OC(O)OOC(O)OCF3 are the result of ionization of an electron from a lone pair of oxygen and a fluorine lone pair of CF 3 group. The outermost electrons reside in the oxygen lone pair. The experimental and theoretical first vertical ionization energy is 13.21 and 13.178 eV, respectively, with the PES and OVGF method. They are in good agreement. The photo ionization and dissociation processes were discussed with the help of theoretical calculations and PES-PIMS experiment. After ionization, the parent ions prefer the dissociation of the C-O bond and giving the fragments CF 3 OCO + and CF3 + . It demonstrated that the ultraviolet photoelectron and photoionization mass spectrometer could be applied widely in the study of atmospheric photochemical reaction. photochemical reaction, CF 3 radical, ultraviolet photoelectron and photoionization mass spectroscopy, transient speciesIt is now well established that the chlorofluorocarbons (CFCs) are responsible for the catalytic destruction of the ozone in the atmosphere and global warming [1] . As substitutes for one class of these stable compounds, various hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) are presently being considered. Their degradation takes place in the troposphere through a series of photochemical reactions [2] . At present, it is important to study the mechanism, intermediate, and products in the process of the degradation of HCFCs and HFCs [3,4] . Ultraviolet photoelectron spectroscopy (UPS) is an important method to study gaseous transient species [5,6] . To improve our ability on studying transient species, our group has built up a photoelectron spectrometer-photoionization mass spectrometer (PES-PIMS) [7] . The modification of the spectrometer was based on the HeI photoelectron spectrometer. Using this new apparatus, we can not only obtain a direct measure of electronic structure and energy levels of stable and unstable molecules, but also provide the information on the complicated process of reaction, ionization, and dissociation [8,9] .In this work, we combined a newly-made on-line photochemical reactions apparatus to our homemade PES-PIMS, and studied the application of this new apparatus in the study on the photochemical reactions of CF 3 radicals with CO and O 2 . With the help of quantum chemical calculation, we investigated the electronic

Electron structure and substituent effects in o-, m-, p-IC6H4OCH3 iodoanisoles

“…The UPS spectra were recorded on a double-chamber UPS-II machine [21][22][23] which was built specifically to detect transient species at a resolution of about 30 meV as indicated by the Ar + ( 2 P 2/3 ) photoelectron band. A sample inlet temperature in the range 25-150℃ was employed to obtain sufficient vapor pressure in the ionization region.…”