Laser-Induced Fluorescence of the CHClCHO Radical and Reaction of Oxygen Atoms with Halogenated Ethylenes

Abstract

A new laser-induced fluorescence spectrum has been observed in the region 320−360 nm. Since this spectrum is observed when reacting oxygen atoms with chlorinated ethylenes such as CH2CHCl, CH2CCl2, CHClCHCl, and CHClCHF and also when chlorine atoms react with chloroacetaldehyde, the fluorescing molecules are identified as cis- and trans-2 chlorovinoxy radicals (cis- and trans-CHClCHO). From an analysis of the laser-induced single vibronic level fluorescence, some of the vibrational frequencies can be assigned for the ground electronic state (X̃ 2A‘ ‘): ν3(CO str) = 1567, ν4(CH rock.) = 1380, ν5(CH rock.) = 1309, ν6(CC str) = 1060, ν7(CCl str) = 820, ν8(CCO bend.) = 677, and ν9(CCCl bend.) = 220 cm-1 for cis-CHClCHO; ν3 = 1581, ν4 = 1379, ν5 = 1267, ν6 = 1145, ν7 = 942, ν8 = 472, and ν9 = 324 cm-1 for trans-CHClCHO. Some of the vibrational frequencies for the excited B̃2A‘ ‘ state also are assigned. These vibrational assignments are supported by ab initio calculations. The calculated geometries of the cis- and trans-CHClCHO radicals are planar in the ground state and slightly nonplanar in the excited state. Radiative lifetimes of the excited cis- and trans-CHClCHO radicals are also reported. The experimental results showed that the C−C−O skeleton and spectroscopic character of the cis- and trans-CHClCHO are closer to those of CH2CHO than to those of CH2CFO. The mechanisms of the O + halogenated ethylene reactions are discussed.