Water in the vicinity of solvated ions: modified dynamical and structural water properties resolved by sub-picosecond IR-spectroscopy

Sub-picosecond IR-spectroscopy is applied to aqueous salt solutions with low concentrated HDO acting as a local probe for the H-bonds in the D2O sample. We find a notable lengthening of the OH-lifetime by the presence of the dissolved salt ions by a factor of 2 (LiCl) up to 2.7 (NaCl). Simultaneously the average reorientation of the OH-dipoles slows down to 12 ps (273 K) and 4 ps (343 K, NaCl).