Critical analysis of the OH fundamental vibrational spectrum of supercooled liquid water

The OH stretching vibrations of liquid H2O have been investigated with Raman Spectroscopic Technique from +65 deg. C down to -20 deg. C. From our experimental results, we suggest in agreement with Yeh et. al., 1932 that in the low temperature region, clusters of tetrabounded water molecules are formed. This will explain the intensity enhancement and the anomalous structure reported by Bosio and coworkers in the supercooled region (Bosio, Teixeira and Stanley, 1981). Based on our measurements, we propose that the 3200 cm-1 spectral component which is absent from the OH vibrational spectrum of HOD (Murphy and Bernstein, 1972) but which prominently appears in the OH stretching vibrational spectrum of liquid H2O in a coupling band. The spectral band centers of both the 3200 cm-1 and the 3400 cm-1 components of the OH stretching vibrations in liquid H2O decrease with decreasing temperature indicating strengthening of hydrogen bonding on the average with decreasing temperature. The rate of decrease of frequency with temperature is greater with the coupling band and this result together with behaviour of the band width leads us to conclude that the coupling band component is the more hydrogen bonded component of the spectrum. The high frequency spectral shoulder at about 3600 cm-1 is found to increase with increasing temperature. (author). 16 refs, 4 figs, 1 tab