High-resolution FTIR study of the CO stretching band ν4 of the fluoroformyloxyl radical, FCO2

► High-resolution Fourier transform infrared spectroscopy of FCO2 radical. ► ν4 Fundamental band (CO2 antisymmetric stretching mode) analyzed. ► Accurate set of molecular constants determined. ► Evidence for vibronic coupling of the X˜2B2 ground state with the B˜2A1 state (1.630 eV).