Raman spectra of supercooled H2O from 0 to −21 °C

Abstract

Polarized and depolarized Raman spectra have been obtained from supercooled water down to a temperature of 251 K (−21 °C). The spectral ranges investigated include the intramolecular OH stretch (3000→3800 cm⁻¹) region, the 175 cm⁻¹ region which represents asymmetric stretch of intermolecular hydrogen bonds, and the −1 region which contains information on the hydrogen bond fluctuations and formation of clusters. The results indicate that as the temperature is lowered, the number of hydrogen‐bonded polyhedra of water molecules increase. The Raman intensity change with temperature led to a determination of the enthalpy for hydrogen bonding of 3.1±0.5 kcal/mol. There is also a suggestion of decreased hydrogen bond fluctuation and an increase in the number of larger polyhedra clusters as the temperature is lowered.