The gas phase reaction of the singly positive charged aluminum ion with ethanethiol molecule clusters was investigated by the laser ablation molecular beam method. The cluster ions composed of Al⁺ and 1～6 ethanethiol molecules are produced. Density functional calculations on the structures and energetics of the two isomers Al⁺(C₂H₅SH)_n and HAl⁺SC₂H₅(C₂H₅SH)_n-1 were carried out at B3LYP/6-31+G(d) level to get a qualitative picture of the gross geometries and relative thermodynamic stability of the species. According to the results of our experiment and calculation, it can be presumed that the product ion is Al⁺(C₂H₅SH)_n for n=1. The anomalous increase of the signal for n=2 and 3 stands for a switching regions of the product cluster, and thus these two clusters are both HAl⁺SC₂H₅(C₂H₅SH)_n-1. For n=4, both Al⁺(C₂H₅SH)₄ and HAl⁺SC₂H₅(C₂H₅SH)₃ are produced by our experiment. From n≥5, the cluster ion of Al⁺(C₂H₅SH)_n becomes more and more predominant.

Key words: cluster, ethanethiol, laser ablation-molecule beam