The generation mechanism of silicon oxide-aluminum oxide compound clustersby laser ablation of siliceous materials

The generation of silicon dioxide-aluminum oxide compound clusters under 30 8 nm XeCl excimer laser ablation of ZSM-5 zeolites with different SiO2/Al2O 3 ratios was studied by time-of-flight mass spectrometry. Two Al-containing cluster sequences [(SiO2)(n-1)(AlO2)] and [(SiO2)(n)OAl](-) are observed i n the negative ion channel. Through the relationship between the abundance distribution of cluster sequences and the silicon aluminum ratio, the growt h mechanism of [(SiO2)(n-1)(AlO2)]. is discussed. Owing to the high electro n affinity of AlO2 compared to small (SiO2)(n) clusters, AlO2 is considered to be the core of growth of the compound cluster [(SiO2)(n-1)(AlO2)](-). ( C) 2000 Elsevier Science B.V. All rights reserved.