Temperature and pressure dependence of the near infrared absorption bands of liquid water

Near infrared absorption spectra have been obtained as a function of temperature and pressure for the 1.0, 1.2, 1.4, and 1.9 micron bands of water and the OH overtone region (1.4 micron region) for dilute solutions of HDO in D2O. Also, near infrared spectra have been obtained for the 1.4 and 1.9 micron bands of highly supercooled water and the OH overtone region of supercooled HDO in D2O solutions. The results suggest that application of pressures up to 2000 bars does not alter the water structure enough to result in the breaking of hydrogen bonds but does cause a bending of the bonds. This assumption is supported from estimates of the hydrogen bond energy, deltaH, which decreases from 2.50 kcal/mol H-bonds at 1 atmosphere to 2.02 kcal/mol of H-bonds at 2 kbars. These results are in agreement with the findings from Ramon studies and, when coupled with the observed thermodynamic and transport properties of water, lend support to a two-state random network model for the structure of liquid water