Femtosecond mid-infrared spectroscopy of aqueous solvation shells
J. Chem. Phys. , Volume 115 p. 8942- 8948
We use femtosecond two-color mid-infrared spectroscopy to study the dynamics of aqueous solutions of salts in HDO:D2O. We find that the lifetime of the OH stretch vibration of HDO molecules in the solvation shell of the halogenic anions Cl , Br , and I is much longer than the lifetime of the OH stretch vibration of the HDO molecule in bulk D2O solution. This difference in lifetime allows for a clear separation of the response of the solvation shell from that of the bulk liquid. A detailed investigation of the spectral dynamics of the solvating HDO molecules reveals that the hydrogen-bond dynamics of these molecules are much slower than the hydrogen-bond dynamics of bulk liquid water.