Department of Chemistry, Technical University of Denmark, Kemitorvet 206, 2800, Kgs. Lyngby, Denmark.
Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin-BP 48, 91192, Gif-sur-Yvette Cedex, France.
Chemphyschem. 2019 Dec 3;20(23):3238-3244. doi: 10.1002/cphc.201900811. Epub 2019 Nov 8.
The high-resolution infrared absorption spectrum of the donor bending fundamental band ν of the homodimer (HCN) has been collected by long-path static gas-phase Fourier transform spectroscopy at 207 K employing the highly brilliant 2.75 GeV electron storage ring source at Synchrotron SOLEIL. The rovibrational structure of the ν transition has the typical appearance of a perpendicular type band associated with a Σ-Π transition for a linear polyatomic molecule. The total number of 100 assigned transitions are fitted employing a standard semi-rigid linear molecule Hamiltonian, providing the band origin ν of 779.05182(50) cm together with spectroscopic parameters for the degenerate excited state. This band origin, blue-shifted by 67.15 cm relative to the HCN monomer, provides the final significant contribution to the change of intra-molecular vibrational zero-point energy upon HCN dimerization. The combination with the vibrational zero-point energy contribution determined recently for the class of large-amplitude inter-molecular fundamental transitions then enables a complete determination of the total change of vibrational zero-point energy of 3.35±0.30 kJ mol . The new spectroscopic findings together with previously reported benchmark CCSDT(Q)/CBS electronic energies [Hoobler et al. ChemPhysChem. 19, 3257-3265 (2018)] provide the best semi-experimental estimate of 16.48±0.30 kJ mol for the dissociation energy D of this prototypical homodimer.
采用同步辐射光源 SOLEIL 的 2.75GeV 电子储存环源，在 207 K 下通过长路径静态气相傅里叶变换光谱法，收集了同二聚体（HCN）的供体弯曲基频 ν 的高分辨率红外吸收光谱。 ν 跃迁的转动结构具有典型的垂直型带的外观，与线性多原子分子的 Σ-Π 跃迁相关联。采用标准半刚性线性分子哈密顿量拟合了总共 100 个分配跃迁，提供了带原点 ν为 779.05182(50) cm，以及简并激发态的光谱参数。与 HCN 单体相比，该带原点蓝移了 67.15 cm，这是 HCN 二聚化后分子内振动零点能变化的最后一个重要贡献。与最近为大振幅分子间基频跃迁确定的振动零点能贡献相结合，然后可以完整地确定振动零点能的总变化为 3.35±0.30 kJ mol。新的光谱发现以及之前报道的基准 CCSDT(Q)/CBS 电子能量[Hoobler 等人。ChemPhysChem。19，3257-3265 (2018)]为这个典型的同二聚体的离解能 D 提供了 16.48±0.30 kJ mol 的最佳半实验估计值。
