The rotational correlation times τ 1,2 were determined by fitting the curves C n=1,2 (t) with the function Ae -t/τ 1,2 in the exponential regime following the initial subpicosecond decay, which is due to the librational motion of the water molecules . These relaxation times have been found to be less affected by finitesize effects compared to the self-diffusion coefficient , and are of interest because they can be measured experimentally using techniques such as NMR or IR spectroscopy.