Ion chemistry in tetramethylsilane (CH3)4Si

The cross sections for simple and dissociative ionization of tetramethylsilane ((CH3)4Si or TMS) by electron impact have been measured using Fourier-transform mass spectrometry. The total ionization cross section is 8.5 x 10−16 cm2 between 30 and 70 eV. The molecular ion is Jahn-Teller unstable, with dissociative ionization to form (CH3)3Si+ dominating the mass spectrum. CH3SiH2+ and CH3Si+ react rapidly with TMS to produce (CH3)3Si+. (CH3)3Si+ does not react with TMS but is slowly hydrated by background water vapor.