Azide-water intermolecular coupling measured by two-color two-dimensional infrared spectroscopy

作者：Borek Joanna^*; Perakis Fivos; Klaesi Felix; Garrett Roe Sean; Hamm Peter

来源：Journal of Chemical Physics, 2012, 136(22): 224503.

DOI：10.1063/1.4726407

• deuterium compounds
• excited states
• hydrogen bonds
• infrared spectra
• intermolecular mechanics
• solvation
• water

We utilize two-color two-dimensional infrared spectroscopy to measure the intermolecular coupling between azide ions and their surrounding water molecules in order to gain information about the nature of hydrogen bonding of water to ions. Our findings indicate that the main spectral contribution to the intermolecular cross-peak comes from population transfer between the asymmetric stretch vibration of azide and the OD-stretch vibration of D2O. The azide-bound D2O bleach/stimulated emission signal, which is spectrally much narrower than its linear absorption spectrum, shows that the experiment is selective to solvation shell water molecules for population times up to similar to 500 fs. The waters around the ion are present in an electrostatically better defined environment. Afterwards, similar to 1 ps, the sample thermalizes and selectivity is lost. On the other hand, the excited state absorption signal of the azide-bound D2O is much broader. The asymmetry in spectral width between bleach/stimulated emission versus excited absorption has been observed in very much the same way for isotope-diluted ice Ih, where it has been attributed to the anharmonicity of the OD potential.

• 出版日期2012-6-14