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Issue 12, 2018
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High-resolution synchrotron terahertz investigation of the large-amplitude hydrogen bond librational band of (HCN)2

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Abstract

The high-resolution terahertz absorption spectrum of the large-amplitude intermolecular donor librational band ν18 of the homodimer (HCN)2 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 ν18 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 ν0 of 119.11526(60) cm−1 together with values for the excited state rotational constant B′, the excited state quartic centrifugal distortion constant DJ′ and the l-type doubling constant q for the degenerate state associated with the ν18 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−1 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−1 for the dissociation energy D0 of this strictly linear weak intermolecular CH⋯N hydrogen bond.

Graphical abstract: High-resolution synchrotron terahertz investigation of the large-amplitude hydrogen bond librational band of (HCN)2

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Publication details

The article was received on 15 Dec 2017, accepted on 04 Mar 2018 and first published on 12 Mar 2018


Article type: Paper
DOI: 10.1039/C7CP08412A
Citation: Phys. Chem. Chem. Phys., 2018,20, 8241-8246
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    High-resolution synchrotron terahertz investigation of the large-amplitude hydrogen bond librational band of (HCN)2

    D. Mihrin, P. W. Jakobsen, A. Voute, L. Manceron and R. Wugt Larsen, Phys. Chem. Chem. Phys., 2018, 20, 8241
    DOI: 10.1039/C7CP08412A

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