The gas-phase reactivity of ammonia-methylsilane mixtures has been studied by ion trap mass spectrometry. The mechanisms of ion-molecule reactions have been determined, and their rate constants measured and compared with the corresponding collisional rate constants calculated according to the average dipole orientation theory. The SiCH+n (n = 2-5) and SiH+n (n = 0-3) primary ions react with methylsilane according to the previously reported self-condensation processes. These ions also give the SiNH+n (n = 2-4) and SiCNH+n (n = 5, 6) ionic species in different reactions with NH3. Among them, SiNH+4 and SiCNH+6, which are the most abundant N-Si-containing ions, react further with ammonia to form SiN2H+n (n = 5, 6) and SiCN2H+9 respectively. The most frequent pathways of silicon-containing ions reacting with ammonia correspond to elimination of H2, or H, or adduct formation. Chain propagation proceeds mainly through ions of general formula SixCyH+n in reactions with NH3, while ions containing only silicon, nitrogen and hydrogen give species, such as NH+4 and SiN2H+n (n = 5, 6), which do not react further.
Gas phase ion/molecule reactions in ammonia/methylsilane mixtures studied by ion trapping
OPERTI, Lorenza;RABEZZANA, Roberto;VAGLIO, Gian Angelo;
1996-01-01
Abstract
The gas-phase reactivity of ammonia-methylsilane mixtures has been studied by ion trap mass spectrometry. The mechanisms of ion-molecule reactions have been determined, and their rate constants measured and compared with the corresponding collisional rate constants calculated according to the average dipole orientation theory. The SiCH+n (n = 2-5) and SiH+n (n = 0-3) primary ions react with methylsilane according to the previously reported self-condensation processes. These ions also give the SiNH+n (n = 2-4) and SiCNH+n (n = 5, 6) ionic species in different reactions with NH3. Among them, SiNH+4 and SiCNH+6, which are the most abundant N-Si-containing ions, react further with ammonia to form SiN2H+n (n = 5, 6) and SiCN2H+9 respectively. The most frequent pathways of silicon-containing ions reacting with ammonia correspond to elimination of H2, or H, or adduct formation. Chain propagation proceeds mainly through ions of general formula SixCyH+n in reactions with NH3, while ions containing only silicon, nitrogen and hydrogen give species, such as NH+4 and SiN2H+n (n = 5, 6), which do not react further.
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