Magic Numbers in a Mass Spectrum of Lithium Clusters Emitted from a Liquid Metal Ion Source

Abstract

Lithium ion clusters Li n + with n ranging up to 19 have been observed from liquid lithium ion sources by using a magnetic mass analyzer. The ion intensity as a function of cluster size showed local maxima at n=7, 9, 13, and 19. Only n=9 and 19 can be explained by the electronic shell model, which successfully predicts magic numbers of other alkali metal (Na, K) clusters. On the other hand, the geometrical atom packing model explains the observed magic numbers except for n=9.

Coexistence of electronic and atomic shells in microclusters

“…which favor delocalization of the valence electrons in the alkali atoms. Thus, in [2][3][4] electronic shells and shells of atoms coexist within the same cluster-size bracket which is in contradiction to the segregation of the two kinds of shells reported in [1]. Thus, in [2][3][4] electronic shells and shells of atoms coexist within the same cluster-size bracket which is in contradiction to the segregation of the two kinds of shells reported in [1].…”

“…The existence of electronic shells and shells of atoms for alkali clusters has also been reported in [2][3][4] referring to those experimental conditions (temperature, size, etc.) which favor delocalization of the valence electrons in the alkali atoms.…”

“…There, the delocalized electrons form the electronic shells according to the jellium model [5], while the ion cores form the shells of atoms. Such a reinterpretation makes [I] and [2][3][4] consistent. The clarification of this contradiction is the subject of the present paper.…”

Atomic structure and collective excitations of medium size NanKm clusters

“…On the experimental side, N= 13 hast not been detected as particulary abundant in supersonic expansion experiments. However, Saito and coworkers reported the observation of highly stable Li + and Na + clusters produced by the Liquid Metal Ion Source technique (LMIS) [33][34][35], which they have proposed to be indicative of an icosahedral structure. Figure 4a-c give the variation of the different KohnSham one-electron energy eigenvalues as a function of cluster size for NaK u_ 1, Na, K, and Na N_ 1K.…”

General properties of the electronic structure of alkali metal clusters and Ia-IIa mixed clusters

“…First two "magic" numbers (n e = 6, 8) are in agreement with quantum chemical predictions (A2E7, A2E9 large). The further two (n= 13, 19) could be interpreted [22] as due to large stability of compact icosahedric structures.…”