The generation of silicon dioxide-aluminum oxide compound clusters under 308nm XeCl excimer laser ablation of ZSM-5 zeolites with different silicon aluminum mole ratios has been investigated with the time-of -flight mass spectrometry. Two strong AL-containing cluster sequences [(SiO~2)~n~-~1(AlO~2)]^-and [(SiO~2)~nOAl]^- are observed in the negative ion channel. The relationship between the abundance distribution of the cluster sequences and the silicon aluminum ratio of the siliceous material samples and the gtowth mechanism of the[ (SiO~2)~n~-~1(AlO~2)]^- sequence are discussed. The presence of Al atoms in the cluster skeleton makes the [(SiO~2)~n~-~1(AlO~2)]^- sequence more stable than the [(SiO~2)~nO]^- sequence so that the intensity distribution of the two strongest sequences becomes different from that in the all-sillicon siliceous samples. Due to the high electron affinity of AlO~2 compared to (SiO~2)~n, it is considered as the core of growth of the compound cluster [(SiO~2)~n~- ~1(AlO~2)]^-.

Key words: ZEOLITE, TIME-OFF FLIGHT MASS SPECTROMETRY, SILICON OXIDE, ALUMINIUM OXIDE, SILICATE, REACTION MECHANISM