Fine Structure of Mass Spectrum of Sodium Clusters: Giant-Atom Concept
We propose a giant-atom cluster model for sodium clusters, which explains the fine structure of the mass spectra of sodium clusters, that is, the non-shell-closing magic numbers. The giant-atom concept is another aspect of the shell model for alkali-metal clusters. A typical example of the giant atom is Na2, which can be regarded as a giant rare-gas atom because it has a shell-closing electronic structure, (Is)2, in the shell model. An icosahedron of this giant rare-gas atom, (Na2)13, is expected to be stable and corresponds well to the non-shell-closing magic number, 26, in the mass spectrum of sodium clusters. Another example is a giant alkali-metal atom, Na19, which has a spherical core and one s-electron, and the dimer (Na12)2 explains the peak at 38. Some other examples are also enumerated and found to coincide to the mass spectrum of sodium clusters. This fact supports that the reaction of sodium clusters is analogous to that of ordinary atoms, since the cluster reaction at the adiabatic expansion of sodium gas rules the relative abundances of clusters.
KeywordsShell Model Magic Number Electronic Energy Level Sodium Cluster Spherical Core
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