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Dynamics of Formamide Ionic Solutions Investigated by Ultrafast Optical Kerr Effect
journal contribution
posted on 2012-11-15, 00:00 authored by Francesca Palombo, Stephen R. MeechMolecular dynamics of formamide solutions of alkali metal
halide
salts were investigated using the time-resolved ultrafast optical
Kerr effect (OKE) to observe the effects of ion solvation on the dynamics
of a nonaqueous high-permittivity H-bonding solvent. The picosecond
orientational and ultrafast intermolecular dynamics of liquid formamide
as a function of concentration of NaI and KI are compared with the
temperature effect on the pure solvent. The effect of a range of other
salts at fixed concentration is also recorded. Transient OKE and corresponding
low-frequency (THz) Raman spectra of the solutions revealed differences
in the solvent dynamics caused by ion solvation. Increasing concentrations
of NaI and KI have the effect of slowing down the diffusive reorientation
and reducing the librational frequencies of formamide, with cation-related
effects observed on the THz Raman spectrum. These effects are discussed
in terms of an ion perturbation of the H-bonding structure in the
solution. This approach provides a valuable means of investigating
the dynamics, structure, and interactions in complex, interacting
systems.