Mass spectroscopic study of metal-rich K2-5(KI)n+ nanoclusters

Metal-rich K1-5(KI)n+ (n ∼27) clusters were produced by the supersonic cooling expansion of laser-induced KI plasma. The obtained mass spectroscopic peaks show the unique magic numbers at n=9, 13, and 22 for K1(KI)n; n=8, 12, and 21 for K2(KI)n; n=8, 12, 16, and 21 for K3(KI)n; n=7, 9, 11, and 13 for K4(KI)n; and n=12 and 21 for K5(KI)n. These magic numbers are fairly different from those of other reported metal-rich Na1-9(NaF)n+ and Cs1-5(CsI)n+ clusters. It is interesting to note that K2,3,5(KI)n+ clusters have the same magic numbers at n=12 and 21 and possess structures that are closely related to the 3×3×3 and 3×3×5 cubic structures with the excess electron at the side anion vacancy or the center anion vacancy.