Reactivity of ionic silicon clusters with methylsilane studied by Fourier transform ion cyclotron resonance mass spectrometry.

The rates and product distributions of the reactions of naked gas phase silicon clusters with methylsilane have been investigated using Fourier transform ion cyclotron resonance mass spectrometry (FTMS). Si(+)(n) and Si(-)(n) (n=1-7) clusters are produced by laser evaporation of bulk silicon, trapped, and reacted for as long as a second with methylsilane, a reagent which is known to form silicon-silicon bonds with other reactive silicon centers. Si(+)(1-5) react to form functionalized ionic silicon cluster products; no reactions are seen for Si(+)(6- 7) or Si(-)(1-7). This is the first time that bimolecular reactions rates and product distributions have been measured as a function of cluster size for any clusters larger than a trimer.