对三氯化硼的真空紫外激光与同步加速器脉冲场电离联合研究

A combined vacuum ultraviolet laser and synchrotron pulsed field ionization study of BCl3.

作者信息

Yang Jie, Mo Yuxiang, Lau K C, Song Y, Qian X M, Ng C Y

机构信息

Department of Physics and Key Laboratory for Atomic and Molecular Nanosciences, Tsinghua University, Beijing 100084, China.

出版信息

Phys Chem Chem Phys. 2005 Apr 7;7(7):1518-26. doi: 10.1039/b417083k.

DOI:10.1039/b417083k

PMID:19787977

Abstract

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.

摘要

使用真空紫外（VUV）激光测量了三氯化硼（BCl₃）在93590 - 95640 cm⁻¹区域的脉冲场电离光电子（PFI - PE）光谱。在高于BCl₃绝热电离能（IE）0 - 1100 cm⁻¹的能量下，BCl₃⁺的弯曲振动序列在PFI - PE光谱中清晰分辨，而在高于IE（BCl₃）1200 - 1900 cm⁻¹的能量下，光谱呈现出密集的振动结构。这一观察结果明确表明，基态的BCl₃⁺具有C₂ᵥ对称性。在CCSD(T)/CBS水平并进行高级校正的从头算计算与这一观察结果一致，表明BCl₃⁺(X²B₂)基态有两个长的和一个短的B - Cl键。此外，CCSD(T)/CBS计算预测存在两个具有D₃ₕ和C₂ᵥ对称性的BCl₃⁺过渡结构，分别比BCl₃⁺(X²B₂)基态高800和1300 cm⁻¹。这一预测也与在高于IE（BCl₃）1200 - 1900 cm⁻¹区域的PFI - PE光谱中观察到的密集特征一致。PFI - PE振动带的归属给出IE（BCl₃） = 93891 ± 2 cm⁻¹（11.6410 ± 0.0003 eV）以及BCl₃⁺(X²B₂)的弯曲频率，v₁⁺(b₂) = 194 cm⁻¹和v₁⁺(a₁) = 209 cm⁻¹。我们还使用基于同步加速器的PFI - PE - 光离子符合方法研究了离解光电离过程BCl₃ + hν --> BCl₂⁺ + Cl + e⁻，得出该过程的0 K阈值或出现能（AE）为12.495 ± 0.002 eV。结合这个0 K AE值和IE（BCl₃），我们确定Cl₂B⁺ - Cl的0 K键解离能（D₀）为0.854 ± 0.002 eV。这项实验和理论研究表明，进行高级校正的CCSD (T, Full)/CBS计算对于预测IE（BCl₃）、AE（BCI₂⁺）和D₀（Cl₂B⁺ - Cl）高度可靠，误差限小于35 meV。然而，与实验测定相比，CCSD (T, Full)/CBS对ΔH(f0)°（BCl₃）、ΔH(f0)°（BCl₂⁺）和ΔH(f0)°（BCl₃⁺）的预测可靠性较低，差异高达0.1 eV。