THE ADSORPTION OF METHYL RADICALS ON OXYGEN-MODIFIED MO(100) STUDIED BY HREELS

The adsorption of methyl radicals on two different oxygen-modified Mo( 100) surfaces at room temperature has been studied using high-resoluti on electron energy-loss spectroscopy (HREELS) and low-energy electron diffraction (LEED). Previous experiments have shown that methyl radica ls adsorbed to these surfaces produce CH4, H-2 and CO as reaction prod ucts. Since the data from this earlier study was inconclusive, vibrati onal spectroscopic evidence was sought in order to obtain a chemical i dentification of the surface species. This study confirms the previous data, which suggested that methyl radicals do not form surface methox y but rather a metal alkyl analog when adsorbed at 300 K. Methyl group s dehydrogenate at room temperature and reveal an O-H stretching vibra tion as well as the CH2 scissor mode. This data is compared to the res ults observed when CH3OH is adsorbed on the same surface. In the latte r case, no O-H vibrations are detected in the spectrum and modes corre sponding to adsorbed methoxy are seen.