The photodesorption of CO from Si(100) has been studied using 355 and 266 nm light obtaining time-of-flight spectra detailing the translation energy released. The spectra clearly exhibit two non-thermal desorption channels, of which one is characterized by an offset energy the size of which is remarkably close to the vibrational quantum of CO. Detailed studies of the spectra as function of coverage and laser fluence used prove that both desorption channels originate from a single adsorbed species. It is suggested that the energy offset is due to vibrational to translational energy transfer along the reaction pathway of the desorbing molecule.