COLLISION-INDUCED DISSOCIATION AND CHARGE-TRANSFER REACTIONS OF SIFX+ (X = 1-4) - THERMOCHEMISTRY OF SIFX AND SIFX+

Guided ion beam mass spectrometry is used to measure cross sections as a function of kinetic energy for interaction of SiF3+ (x = 1-4) ions with Xe. Energy dependences of the collision-induced dissociation cross sections are analyzed to yield the following 0 K bond dissociation energies (BDEs): D(SiF3+-F) = 0.85 +/- 0.16 eV, D(SiF2+-F) = 6.29 +/- 0.10 eV, D(SiF+-F) = 3.18 +/- 0.04 eV, and D(Si+-F) = 7.04 +/- 0.06 eV. The ionization energies, IE(SiF2) = 10.84 +/ -0.13 eV and IE(SiF3) = 9.03 +/- 0.05 eV, are also measured from analysis of endothermic charge transfer reactions. From these BDEs and IEs, previous results of Weber and Armentrout [J. Chem. Phys. 1988, 88, 68981, and work in the preceding paper, we derive heats of formation for the silicon fluoride cations and neutrals that provide a self-consistent set of thermochemical data for the silicon fluoride species. In some cases, the thermochemical values determined here are considerably different from available literature values but are in good agreement with theory. The differences are discussed in detail.