A combined vacuum ultraviolet laser and synchrotron pulsed field ionization study of BCl3Presented at the Bunsen Discussion on Chemical Processes of Ions, Marburg, 15–17 September 2004.

The pulsed field ionization-photoelectron PFI-PE spectrum of boron trichloride BCl3 in the region of 93 590–95 640 cm−1has been measured using vacuum ultraviolet VUV laser. At energies 0–1100 cm−1above the adiabatic ionization energy IE of BCl3, the bending vibration progression of BCl3is clearly resolved in the PFI-PE spectrum, whereas the spectrum at energies 1200–1900 cm−1above the IEBCl3 is found to exhibit dense vibrational structure. This observation unambiguously shows that BCl3in its ground state has C2Vsymmetry. Ab initiocalculations performed at the CCSDTCBS level with high-level corrections are consistent with this observation, indicating that the BCl3X 2B2 ground state has two long and one short B–Cl bonds. Furthermore, the CCSDTCBS calculations predict the existence of two BCl3transitional structures with D3hand C2Vsymmetries lying 800 and 1300 cm−1, respectively, above the BCl3X 2B2 ground state. This prediction is also consistent with the dense features observed in the PFI-PE spectrum in the region of 1200–1900 cm−1above the IEBCl3. The assignment of the PFI-PE vibrational bands gives the IEBCl3 93 891 ± 2 cm−111.6410 ± 0.0003 eV and the bending frequencies for BCl3X 2B2, ν1b2 194 cm−1and ν1a1 209 cm−1. We have also examined the dissociative photoionization process BCl3hν→ BCl2 Cl e−using the synchrotron based PFI-PE-photoion coincidence method, yielding the 0 K threshold or appearance energy AE for this process to be 12.495 ± 0.002 eV. Combining this 0 K AE value and the IEBCl3, we have determined the 0 K bond dissociation energy D0 for Cl2B–Cl as 0.854 ± 0.002 eV. This experimental and theoretical study indicates that the CCSDT, FullCBS calculations with high-level corrections are highly reliable for the predictions of IEBCl3, AEBCl2 and D0Cl2B–Cl with error limits of less than 35 meV. However, the CCSDT, FullCBS predictions for ΔHf0°BCl3, ΔHf0°BCl2, and ΔHf0°BCl3 are less reliable with discrepancies up to 0.1 eV as compared to the experimental determinations.