A combined vacuum ultraviolet laser and synchrotron pulsed field ionization study of BCl3.
The pulsed field ionization-photoelectron (PFI-PE) spectrum of boron trichloride (BCl3) in the region of 93 590-95 640 cm(-1) has been measured using vacuum ultraviolet (VUV) laser. At energies 0-1100 cm(-1) above the adiabatic ionization energy (IE) of BCl3, the bending vibration progression of BCl3+ is clearly resolved in the PFI-PE spectrum, whereas the spectrum at energies 1200-1900 cm(-1) above the IE (BCl3) is found to exhibit dense vibrational structure. This observation unambiguously shows that BCl3+ in its ground state has C2v symmetry. Ab initio calculations performed at the CCSD(T)/CBS level with high-level corrections are consistent with this observation, indicating that the BCl3+(X 2B2) ground state has two long and one short B-Cl bonds. Furthermore, the CCSD(T)/CBS calculations predict the existence of two BCl3+ transitional structures with D3h and C2v symmetries lying 800 and 1300 cm(-1), respectively, above the BCl3+ (X 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(-1) above the IE (BCl3). The assignment of the PFI-PE vibrational bands gives the IE (BCl3) = 93 891 +/- 2 cm (11.6410 +/- 0.0003 eV) and the bending frequencies for BCl3+ (X 2B2), v1+ (b2) = 194 cm(-1) and v1+ (a1) = 209 cm We have also examined the dissociative photoionization process BCl3 + hu --> 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 IE (BCl3), 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 CCSD (T, Full)/CBS calculations with high-level corrections are highly reliable for the predictions of IE (BCl3), AE (BCI2+) and D0 (Cl2B(+) -Cl) with error limits of less than 35 meV. However, the CCSD (T, Full)/CBS predictions for deltaH(f0) degrees (BCl3), deltaH(f0) degrees (BCl2+), and deltaH(f0)degrees (BCl3+) are less reliable with discrepancies up to 0.1 eV as compared to the experimental determinations.
Department of Physics and Key Laboratory for Atomic and Molecular Nanosciences, Tsinghua University, Beijing 100084, China.
Jie
J
Yang
Yuxiang
Y
Mo
K C
KC
Lau
Y
Y
Song
X M
XM
Qian
C Y
CY
Ng