The structure of Ni-39

The geometrical structure of Ni-39 is probed via molecular adsorption of ni trogen on its surface. Nitrogen uptake patterns are determined at various r eaction temperatures, and the results are interpreted in terms of the numbe r and nature of nitrogen binding sites on possible structures. It is found that an adsorbate-induced isomerization occurs at partial nitrogen coverage , but that at saturation a reverse isomerization returns the cluster to its initial structure. The two lowest energy structures calculated by Wetzel a nd DePristo [T. L. Wetzel and A. E. DePristo, J. Chem. Phys. 105, 572 (1996 )] are completely consistent with the observed saturation and isomerization behavior. The structures consist of atom caps packed around a central pent agonal bipyramid, and reflect a marked change from the octahedral structure determined earlier for Ni-38. [S0021-9606(98)70947-X].