Using laser-induced fluorescence spectroscopy dispersed emission spectra of HCO and DCO have been recorded. The formyl radical was produced by the UV photolysis of acetaldehyde (d0 and d4) and detected via the Ã2A ″–X 2A′ transition, with excitation into single vibronic levels of the first excited state. We report, for the first time, emission into the overtone of the C—H stretching frequency, demonstrating the large anharmonic motion of ...