EVIDENCE FOR ICOSAHEDRAL ATOMIC SHELL STRUCTURE IN NICKEL AND COBALT CLUSTERS - COMPARISON WITH IRON CLUSTERS

For the first time, the mass distribution of nickel, cobalt and iron clusters is analyzed in a large mass range with near threshold photoionization experiments and standard time-of-flight mass spectrometry. In the case of nickel and cobalt, oscillations observed in mass spectra correspond to icosahedral atomic shell structure in the studied mass range (50-800 atoms). For iron clusters, the situation is less clear. The exact location of structures in mass spectra depends on source operating conditions. We have observed the competition between different cluster geometries.