Methylidyne, methylene, and methyl fragments have been proposed to be key intermediates in the methanation of CO and H/sub 2/ over Group VIII (groups 8-10) metals, but the direct experimental observation of these species has proven difficult to achieve. Methylidyne and methylene fragments adsorbed on Fe(110) have been observed by electron energy loss spectrometry (EELS) immediately after Fischer-Tropsch synthesis at 1 atm, but on Ru(001) only methylide was detected by EELS after hydrogenation of a predeposited carbide under vacuum conditions. Only methyl fragments have been previously observed by X-ray photoelectron spectroscopy (XPS) after CH/sub 3/Cl decomposition on Ni or Co surfaces between 170 and 200 K. Here static secondary ion mass spectrometry (SIMS) and XPS data on a Ni(111) single crystal immediately after CO + H/sub 2/ reaction at 50-100 torr, 550 K are presented. The data show the formation of all three of the intermediates methyne, methylene, and methyl. 15 references, 1 figure, 1 table.