Reactivity and photoionization studies of bimetallic cobalt-manganese clusters

The reactivity of selected ConMnm (8 less than or equal to m + n less than or equal to 23) clusters with N-2 and the vertical ionization potentials (I Ps) of selected ConMnm (8 less than or equal to m + n less than or equal to 31) clusters have been measured. No obvious correlation is found between t he reactivities and the IPs. Inferences about cluster structure may be made from the nitrogen uptake data. In particular, whereas pure cobalt clusters tend to adopt structures having bulk packing, incorporation of manganese a toms into the cluster shifts the relative energies of close-lying isomers t o favor an icosahedral growth sequence. For many cluster sizes, the maximum number of nitrogen molecules adsorbed on a cluster at -80 degrees C is equ al to the number of cobalt atoms on the surface of the cluster, thereby giv ing insight into the cluster structure and the locations of the individual cobalt and manganese atoms in these bimetallic species.