Abstract: Photodissociation of acetyl and propionyl radicals at 248nm has been investigated by Time-Resolved Fourier Transform Infrared Emission Spectroscopy.Acetone and acetyl chloride are used as the precursors of acetyl, 3-pentanone is selected as the source of propionyl and butanone is used as the parent moleaule of both acetyl and propiongl. High vibrational products CO(v≤8) are observed.Since the vibrational distribution of CO are nearly the same for all these precursors,the electronic excited acetyl and propionyl radical should have short life times.