ION CHEMISTRY IN TETRAMETHYLSILANE (CH3)4SI

The cross sections for simple and dissociative ionization of tetrameth ylsilane ((CH3)4Si or TMS) by electron impact have been measured using Fourier-transform mass spectrometry. The total ionization cross secti on is 8.5 x 10(-16) cm2 between 30 and 70 eV. The molecular ion is Jah n-Teller unstable, with dissociative ionization to form (CH3)3Si+ domi nating the mass spectrum. CH3SiH2+ and CH3Si+ react rapidly with TMS t o produce (CH3)3Si+.(CH3)3Si+ does not react with TMS but is slowly hy drated by background water vapor.