Laser-induced fluorescence of the CHFCHO radical and reaction of OH radicals with halogenated ethylenes

摘要

A new laser-induced fluorescence spectrum of the 2-fluorovinoxy (CHFCHO) radical was first observed around 335 nm. The radical was produced in the reaction of an OH radical with 1,2-difluoroethylene (CHF=CHF). A single weak band was observed, which was assigned to the 0(0)(0) band of the (B) over tilde-(X) over tilde transition of the trans-CHFCHO radical. The (B) over tilde <- (X) over tilde electronic transition energy (T-0) for trans-CHFCHO was 29 871 cm(-1), which was just 3 cm(-1) lower than that of its isomer, the 1-fluorovinoxy (CH2CFO) radical. The fluorescence lifetime at 29 871 cm(-1) was shorter than 20 ns. This means that strong predissociation is probable at v' = 0 in the excited (B) over tilde state of trans-CHFCHO. From an analysis of the dispersed fluorescence spectrum, some of the vibrational frequencies can be assigned for the ground electronic state: v(3) =1557 cm(-1) (C-O stretch), v(7) =1162 cm(-1) (C-C stretch), and v(8) = 541 cm(-1) (CCO bend). These vibrational assignments were supported by ab initio calculations. The structure of the C-C-O skeleton and the spectroscopic character of trans-CHFCHO were close to those of CHClCHO and CH2CHO than those of CH2CFO. For the reaction of CH2=CHF with O(P-3), the formation of both the regioisomeric radicals, i.e., 1- and 2-fluorovinoxy radicals, was confirmed. The regioselectivity of the oxygen atom added to the double bond of monofluoroethylene is discussed. Published under license by AIP Publishing.