Raman spectroscopy of isotopically pure and diluted high- and low-density amorphous ices

We present an experimental and theoretical study of Raman spectroscopy of isotopically pure and diluted amorphous as well as crystalline ices at 30 K. Our experiments comprise polarized (VV) and depolarized (VH) spectra in the OH-stretch region, whereas our calculations involve molecular dynamics (MD) simulation of the high- and low-density amorphous ices through vitrification and subsequent formulation of vibrational Hamiltonian of coupled OH oscillators in the hydrogen-bond network of the ices. Our theoretical Raman VV and VH spectra at each isotopic dilution are in good agreement with the experimental data. This allows us not only to carry out detailed spectral assignments for the amorphous and crystalline ices from the viewpoint of vibrational phase, delocalization, and density of states but also to confirm the reliability of the MD simulation in which deeply supercooled liquid water spontaneously separates into high- and low-density fluid phases below a liquid-liquid critical point.

Automated summary

This study presents an investigation of Raman spectroscopy of isotopically pure and diluted amorphous and crystalline ices at 30 K, using both experimental and theoretical approaches. The comparison between experimental and calculated spectra confirms the reliability of the molecular dynamics simulation method and allows for detailed spectral assignments and analysis.