High-resolution synchrotron terahertz investigation of the large-amplitude hydrogen bond librational band of (HCN)2Electronic supplementary information (ESI) available: The observed and calculated line positions from the rovibrational analysis are given as electronic supplemental material together with the calculated absolute electronic energies employing the CCSD(T) and CCSD(T)-F12b methodologies with Dunning's augmented correlation-consistent aug-cc-pVXZ (X = D, T, Q, 5, 6) basis sets and the

• Main Authors: Mihrin, D, Jakobsen, P. W, Voute, A, Manceron, L, Wugt Larsen, R
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp08412a

The high-resolution terahertz absorption spectrum of the large-amplitude intermolecular donor librational band ν 1 8 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 ν 1 8 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 0 of 119.11526(60) cm −1 together with values for the excited state rotational constant B ′, the excited state quartic centrifugal distortion constant D J ′ and the l -type doubling constant q for the degenerate state associated with the ν 1 8 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 D 0 of this strictly linear weak intermolecular CH N hydrogen bond. The high-resolution terahertz absorption spectrum of the large-amplitude intermolecular donor librational band ν 1 8 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.