Raman spectroscopy of supercooled water

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Abstract
We report Raman spectroscopic measurements on supercooled water down to a temperature of −20 °C. The spectral region investigated is the uncoupled OD stretching vibration (2000–3000 cm−1) from a 5% solution of D2O in H2O. The results are consistent with an interpretation in terms of two categories of OD bonds, those that are hydrogen bonded and those that are essentially free. The fraction of H‐bonded OD bonds varies from 0.9 to 0.95 as the temperature decreases from 0 to −20 °C. We observe that the frequency of the bonded OD component decreases with temperature at a slightly slower rate in the supercooled region than in the normal liquid region. With decreasing temperature, a decrease in width of this component band is observed, and this decrease appears to have a much larger slope in the supercooled region as compared to that observed previously in the normal temperature region.