The molecular structure of liquid water delivered by absorption spectroscopy in the whole IR region completed with thermodynamics data

摘要

Absorption spectra of liquid water at various temperatures in the whole IR region (0<ν?<4000cm~(-1)) are obtained from ATR spectra recorded in the mid-IR region combined with absorption spectra measured in the FIR region. They can be accurately decomposed over two independent spectra. The spectra of the two kinds of H_2O (D_2O) molecules they suppose are defined as fulfilling spectroscopic constraints and as being in accordance with thermodynamic values. Their enthalpy difference H~e - Hg is found equal to 11.8 kJ mol~(-1) for ordinary water and 12.2 kJ mol-1 for heavy water. H_2O (D_2O) molecules of lower enthalpies Hg, greater than the enthalpy of H _2O or D_2O molecules in ices by 1.3 kJ mol-1, display vibrations that resemble those of H_2O (D_2O) molecules in ice. Molecules with enthalpies He reorient without breaking their H-bonds as He appears greater than the potential barrier for rotations around their symmetry axes.