Mass spectra of the silicon tetrahalides: metastable ions

The mass spectra of SiBr4 and Sil4 are reported for the first time. The mass spectra of SiF4 and SiCl4 are also reported, and compared with those that have appeared in the literature. In addition to the singly and doubly charged fragment ions, evidence for 38 metastable transitions was observed in the silicon tetrahalide spectra and each of these is identified with a specific dissociation process. The time intervals required for observing these metastable peaks are calculated and listed for each dissociation process. Direct and indirect evidence is reported indicating that the complete fragmentation of these tetrahalides occurs both by stepwise and non-stepwise decompositions.