Figure 2. Local structure probes.

(a) XAS spectra of liquid water measured in transmission as function of temperature. The top section shows the difference in absorption cross-section compared with the spectrum measured at 299 K. The difference in absorption cross-section was magnified by a factor of 4, to highlight the spectral changes; the dotted black line denotes no difference. (Adapted from ref. 21). (b) XES spectra in the lone pair 1b₁ region of D₂O liquid water measured at 283 and 363 K. The heavier isotope is used to minimize core hole-induced dynamics. (Adapted from ref. 16). (c) OH-stretch Raman spectrum as a function of temperature with an inset showing the difference spectra (Adapted from refs 38, 39). (d) The Fourier transform of the time-dependent optical Kerr response as a function of temperature. This is directly related to the frequency-dependent spectrum measured in the dynamic light scattering. The contributions of the three slave correlators are reported in the figure as magenta–blue–orange lines. (Adapted from ref. 40). In each figure the dominant spectral contributions interpreted as due to H-bond distorted or tetrahedral character are indicated, showing consistent trends with temperature, NaCl concentration and O–O pair-distribution function (PDF). (e) The normalized probability density function of the asymmetry parameters YA (acceptor) and YD (donor). (Adapted from ref. 50).