Procedures are described for the preparation of the d(1) (CDCH3) and d(4) isotopologues of [(mu(2)-CHCH3)-Os-2(CO)(8)] (1) Infrared and Raman spectra for the d(0), d(1), and d(4) molecules are analyzed, in comparison with those of CH3CHCl2 and its deuterium-containing species, in order to characterize the vibrational spectrum of an ethylidene group bonded to metal atoms. Taking into account the effects of the metal-surface selection rule for species adsorbed on metal surfaces, a comparison is made between the interpreted spectra of 1 and a number of vibrational spectra in the literature which may reflect the presence of ethylidene groups. These include electron energy loss spectra (EELS) near 300 K from ethene adsorbed on Pt(111) with coadsorbed potassium or oxygen, and a vibrational inelastic tunneling spectrum (IETS) obtained by hydrogen reduction of CO adsorbed on Rh/Al2O3. Taking into account the limited resolution of the EELS data, the spectra on Pt(111)/K and Pt(111)/O can reasonably be attributed to the ethylidene surface species. A more definitive structural assignment requires higher resolution spectra from the adsorbed species. The agreement between the infrared spectrum of 1 and the IETS spectrum on Rh/Al2O3 is particularly good.