REACTIONS OF O2+, AR+, NE+, AND HE+ WITH SICL4 - THERMOCHEMISTRY OF SICLX+ (X = 1-3)

Reactions of O2+, Ar+, Ne+, and He+ with SiCl4 are studied by using guided ion beam mass spectrometry. All reactions are found to be fairly efficient with thermal energy rate constants that exceed 66% of the collision rate. The major products observed in the O2+ and Ar+ reactions are SiCl4+ and SiCl3+, while for the Ne+ and He+ reactions, the major product is SiCl+. Thermochemistry derived from these SiCl4 systems includes the determination of DELTA-(f)H(SiCl2+) = 99.8 +/- 1.6 kcal/mol and DELTA-(f)H(OSiCl3+) < 97 kcal/mol from the O2+ system, and DELTA-(f)H(SiCl2+) = 184.9 +/- 2.6 kcal/mol and DELTA-(f)H(SiCl+) = 203.9 +/- 2.5 kcal/mol from the Ar+ system. The ionization energies IE(SiCl3) = 7.65 +/- 0.15 eV, IE(SiCl2) = 9.81 +/- 0.10 eV, and IE(SiCl) = 6.79 +/- 0.24 eV are also derived after consideration of other literature thermochemistry.