Mihrin D, Jakobsen P W, Voute A, Manceron L, Wugt Larsen R
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 and Lab. MONARIS, CNRS-UPMC UMR8233, 4 Place Jussieu, 75230 Paris Cedex, France.
Phys Chem Chem Phys. 2018 Mar 28;20(12):8241-8246. doi: 10.1039/c7cp08412a. Epub 2018 Mar 12.
The high-resolution terahertz absorption spectrum of the large-amplitude intermolecular donor librational band ν of the homodimer (HCN) has been recorded by means of long-path static gas-phase Fourier transform spectroscopy at 207 K employing a highly brilliant electron storage ring source. The rovibrational structure of the ν band has the typical appearance of a perpendicular type band of a Σ-Π transition for a linear polyatomic molecule. The generated terahertz spectrum is analyzed employing a standard semi-rigid linear molecule Hamiltonian, yielding a band origin ν of 119.11526(60) cm together with values for the excited state rotational constant B', the excited state quartic centrifugal distortion constant D' and the l-type doubling constant q for the degenerate state associated with the ν mode. The until now missing donor librational band origin enables the determination of an accurate experimental value for the vibrational zero-point energy of 2.50 ± 0.05 kJ mol arising from the entire class of large-amplitude intermolecular modes. The spectroscopic findings are complemented by CCSD(T)-F12b/aug-cc-pV5Z (electronic energies) and CCSD(T)-F12b/aug-cc-pVQZ (force fields) electronic structure calculations, providing a (semi)-experimental value of 17.20 ± 0.20 kJ mol for the dissociation energy D of this strictly linear weak intermolecular CHN hydrogen bond.
利用高亮度电子储存环光源，通过长程静态气相傅里叶变换光谱法，在207K下记录了同二聚体（HCN）的大振幅分子间供体振动带ν的高分辨率太赫兹吸收光谱。ν带的振转结构具有线性多原子分子Σ-Π跃迁垂直型带的典型外观。采用标准的半刚性线性分子哈密顿量对生成的太赫兹光谱进行分析，得到带起源ν为119.11526(60) cm，以及与ν模式相关的简并态的激发态转动常数B'、激发态四次离心畸变常数D'和l型加倍常数q的值。迄今为止缺失的供体振动带起源使得能够确定由整个大振幅分子间模式类产生的振动零点能量的准确实验值为2.50±0.05 kJ/mol。光谱学研究结果通过CCSD(T)-F12b/aug-cc-pV5Z（电子能量）和CCSD(T)-F12b/aug-cc-pVQZ（力场）电子结构计算得到补充，为这种严格线性的弱分子间CHN氢键的解离能D提供了17.20±0.20 kJ/mol的（半）实验值。
