FT - ICR Study of Chemical Reaction of Silicon Clusters

Chemical reaction of small silicon cluster ions Sin (11 ≤ n ≤ 20) with ethylene was studied with a newly implemented Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Silicon clusters were generated by a pulsed laser-vaporization supersonic-expansion cluster beam source directly connected to FT-ICR spectrometer. Injected and size selected silicon clusters were thermalized to the room temperature by collisions with argon gas. The exposure time of ethylene gas before the mass detection was varied in order to study the reaction kinetics. The reaction rate of chemisorption of first ethylene molecule was generally in good agreement with the ion drift tube experiments. Effect of a hydrogen atom hidden in isotope distribution of mass spectra was clearly determined. Furthermore, the saturated reaction products were summarized. Sin(C2H4)m when n + m = 19 were observed to be remarkably stable. Furthermore, it was found that a hydrogen atom terminated the reaction as an ethylene molecule.