The effect of large amplitude motions on the transition frequency redshift in hydrogen bonded complexes: a physical picture.
We describe the vibrational transitions of the donor unit in water dimer with an approach that is based on a three-dimensional local mode model. We perform a perturbative treatment of the intermolecular vibrational modes to improve the transition wavenumber of the hydrogen bonded OH-stretching transition. The model accurately predicts the transition wavenumbers of the vibrations in water dimer compared to experimental values and provides a physical picture that explains the redshift of the hydrogen bonded OH-oscillator. We find that it is unnecessary to include all six intermolecular modes in the vibrational model and that their effect can, to a good approximation, be computed using a potential energy surface calculated at a lower level electronic structure method than that used for the unperturbed model.
Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
Kasper
K
Mackeprang
Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark.
Henrik G
HG
Kjaergaard
Laboratory of Physical Chemistry, Department of Chemistry, P.O. Box 55, A.I. Virtasen aukio 1, FI-00014, University of Helsinki, Helsinki, Finland.
Teemu
T
Salmi
Laboratory of Physical Chemistry, Department of Chemistry, P.O. Box 55, A.I. Virtasen aukio 1, FI-00014, University of Helsinki, Helsinki, Finland.
Vesa
V
Hänninen
Laboratory of Physical Chemistry, Department of Chemistry, P.O. Box 55, A.I. Virtasen aukio 1, FI-00014, University of Helsinki, Helsinki, Finland.
Lauri
L
Halonen