Electron and ion reactions with hexamethyldisiloxane and pentamethyldisiloxane

The dissociative recombination of electrons with the hexamethyldisiloxane (HMDSO) cation ((CH3)(3)Si-O-Si(CH3)(3))(+) and the pentamethyldisiloxane cation ((CH3)(3)Si-O-Si(CH2)(2))(+) as well as the ion-molecule reaction between Ar+ and HMDSO have been studied at 300 K using a flowing afterglow Langmuir probe-mass spectrometer apparatus. The rate constants for these reactions, measured directly for the first time, are, respectively, alpha(1)=1.8x10(-6), alpha(2)=3.6x10(-6) cm(3)/s, and k=2.0x10(-9) cm(3)/s with uncertainties of +/- 30%. In addition, the electronic attachment to neutral HMDSO was also studied and an upper limit value of the rate constant was determined to be beta=3.3x10(-11) cm(3)/s. (c) 2007 American Institute of Physics.