High-Resolution Infrared Synchrotron Investigation of (HCN)2 and a Semi-Experimental Determination of the Dissociation Energy D0

D. Mihrin, P. W. Jakobsen, Alexandre Paolo Voute, L. Manceron, R. Wugt Larsen*

*Corresponding author for this work

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The high-resolution infrared absorption spectrum of the donor bending fundamental band ν61 of the homodimer (HCN)2 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 ν61 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 ν0 of 779.05182(50) cm-1 together with spectroscopic parameters for the degenerate excited state. This band origin, blue-shifted by 67.15 cm-1 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-1. 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-1 for the dissociation energy D0 of this prototypical homodimer.
Original languageEnglish
Issue number23
Pages (from-to)3238-3244
Number of pages7
Publication statusPublished - 2019


  • Dissociation energy
  • Hydrogen bonding
  • Infrared synchotron radiation
  • Non-covalent forces
  • Vibrational zero-point energy


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