Electron and thermal dissociation of BF3(g)

Electron impact fragmentation studies were performed on the BF3(g) molecule. Appearance potentials for BF+2, BF+, and F+ ions produced in the fragmentation process were 16, 24, and 30 eV, respectively. The appearance potential of BF+2 was found to be only 0.2 eV greater than the I.P. of BF3(g). The fragmentation ratio of the ionic concentrations at 70 eV for BF+3, BF+2, BF+, and F+ is 10/100/8/3. The primary mechanism for the thermal dissociation of BF3(g) is to the lower borofluorides in nearly equal concentrations. Dissociation to the dimeric borofluorides and F atoms is negligible, with F atom concentrations less than 1% of the three borofluorides. Ionization potentials for BF3(g), BF2(g), and BF(g) were 16, 9, and 11 eV (all ±1), respectively. The partial pressures for the isomolecular reaction BF3(g)+BF(g)=2BF2(g) in the temperature range 1780 to 1900 K yielded a ΔH298 of 17.1±0.5 kcal/mol, resulting in a ΔHf298 of BF2(g) of −141.0±0.5 kcal/mol, in good agreement with the photoionization and electron impact values.