The unusual adsorption behaviour of benzene on Co(10(1)over-bar0)

Adsorption of benzene on Co(10 (1) over bar 0) leads to formation of an ord ered p(3 x 1) monolayer. ARPES measurements combined with adlayer density c onsiderations indicate that the Co(10 (1) over bar 0)-p(3 x 1) monolayer co nsists of molecules whose symmetry has been reduced to C-1 consistent with a partially dehydrogenated tilted cyclic Ca intermediate (phenyl or C6H4). Desorption measurements in conjunction with ARPES indicate that a stepwise dehydrogenation of the ring occurs with the dehydrogenation step above room temperature at similar to 380 K corresponding to formation of small well-o riented CxHy (x,y = 1 or 2) hydrocarbon fragment(s) (possibly C2H and CH) r esulting from ring opening. Complete dehydrogenation occurs for temperature s above 550 K, leaving a carbonaceous residue. The low dehydrogenation and decomposition temperatures indicate Co(10 (1) over bar 0) to be particularl y active towards both C-H bond scission and ring opening.