Laser-induced fluorescence of the CH2CFO radical

Abstract

A new laser-induced fluorescence spectrum has been observed in the region of 307–335 nm. Since this spectrum is observed when reacting oxygen atoms with CH2CHF, or CH2CF2, or CH2CFCl and also by photolysis of CH3CFO, the fluorescing molecule is the CH2CFO (fluoroformyl methyl) radical. From an analysis of the laser-induced single vibronic level fluorescence, some of the vibrational frequencies can be assigned for the ground electronic state ν3=1724 cm−1 (C–O stretch), ν5=1211 cm−1 (C–F stretch), ν6=906 cm−1 (CH2 rock), ν7=847 cm−1 (C–C stretch), ν8=584 cm−1 (FCO bend), and ν9=416 cm−1 (CCO bend), for the excited state ν3=1790, ν5=1253, ν6=911, ν7=874, ν8=537, and ν9=421 cm−1. Ab initio calculations on the CH2CFO radical give a planar geometry with vibrational frequencies that are consistent with the observed fundamental frequencies. The vibrational frequencies show that the structure of the ground state is closer to fluoroformyl methyl (⋅CH2CFO) rather than a vinoxy-type (CH2=CFO⋅) radical. The collision-free radiative lifetimes of the excited state are 49–81 ns depending on excitation energy and vibrational modes. Strong predissociation is observed above v=1, especially in the ν3′ mode.