Structures and formation mechanism of potassium cyanide clusters

Abstract

Formation mechanism of potassium cyanide clusters produced by the laser vaporization of K3 [Fe(CN)3] and K4CFe(CN)6] · 3H2O is studied by use of a linear time-of-flight mass spectrometer. It is found that the positive cluster ions are due to [K(KCN)n]+, n = 0-37,in which magic numbers are n=4,13,22,37,whereas the negative cluster ions are assigned to [(KCN)nCN]-, n = 0-13, in which magic numbers are n=4,13. These magic numbers are identical with those in sodium chloride clusters. This indicates that they have the same structures as 1×3×3(n = 4), 3×3×3(n = 13), 3×3×5(n = 22) and 3×5×5(n=37)0 Thus the formation process of potassium cyanide crystal in the initial stage should also go along the growth course of the rock salt structure. In the plasma produced in laser vaporization, the propagation of clusters from the reactions between positive or negative ions and neutral clusters, the neutralization reactions between positive and negative ions, and the metastable decay of clusters lead to the distribution of the different abundance of clusters. In potassium cyanide clusters the formation of stable structures determines the occurrence of the magic numbers.