摘要
利用激光气化铁氰化钾或亚铁氰化钾并利用飞行时间质谱检测方法对氰化钾团簇的形成机理进行了研究，结果发现：团簇正离子可归属为［Ｋ（ＫＣＮ）＿ｎ］￣＋，ｎ＝０～３７，它们的幻数为ｎ＝４、１３、２２、３７；团族负离子可归属为［（ＫＣＮ）＿ｎＣＮ］￣－＝，ｎ＝０～１３，它们的幻数为ｎ＝４、１３。这些幻数与氯化钠等碱金属卤化物团簇体系完全一致。这表明：它们的团簇结构应该是相同的，即１×３×３（ｎ＝４）、３×３×３（ｎ＝１３）、３×３×５（ｎ＝２２）、３×５×５（ｎ＝３７）结构。因此氰化钾晶体的初期形成过程也应采取ＮａＣｌ型结构的增长途径。在激光气化产生的等离子体中，正、负离子与中性团簇的碰撞增长反应、正离子与负离子的复合反应以及团簇的亚稳态解离反应造成了团簇离子的不同丰度分布。氰化钾团簇中稳定立方体结构的产生决定了幻数的出现。
Formation mechanism of potassium cyanide clusters produced by the laser vaporization of K_3 [Fe(CN)_6]and K_4[Fe (CN)_6]·3H_2O is studied by use of alinear 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) .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.
基金
辽宁省博士科研起动基金
关键词
团簇
激光气化
飞行时间质谱
氰化钾
形成机理
cluster,laser vaporization,time-of-flight mass spectrum,potassium cyanide
