Gas phase ion chemistry in silane/propane and silane/propene mixtures

The silane/propane and silane/propene gaseous mixtures have been investigated by ion trap mass spectrometry. The variations of ion abundances observed under different partial and total pressures are reported. The mechanisms of ion/molecule reactions have been elucidated by successive isolation steps. Moreover, the rate constants for the main processes have been experimentally measured and compared with the collisional rate constants to determine the reaction efficiencies. A great number of processes have been observed in SiH4/C3H6 leading to the formation of silicon and carbon containing ions with high efficiency, whereas propane and silane give very few ion products with low efficiencies. Chain propagation in the SiH4/C3H6 system gives clusters of increasing size, such as Si2C2H7+ and Si3CH7+, with rather high efficiencies starting from silicon containing ions and neutral propene.