We investigated if the Raman spectrum of snow is affected by the highly differentiated snow morphology. The latter is subjected to continuous changes driven by the variation of ambient parameters, mainly temperature and humidity as snow progresses from freshly deposited, to compact, to icy. We measured the Raman spectrum of snow grains of different size and morphology on the temperature interval between −5.5 °C and −0.5 °C approaching the melting point. We found systematic differences with respect to bulk ice Ih in the OH-stretching band of snows with different histories. We attribute the observed spectral differences to the change of the molecular arrangement of water molecules between bulk and surface sites. We investigate this characteristic via molecular dynamics DFT simulations of bulk ice and of three thin slabs cut along specific surfaces. We analysed the simulated Raman spectra and compared their distinguishing features to those of experimental spectra of snow. The Raman features of the OH-stretching band allow to distinguish among layers inside a snowpack, each layer being characterized by a different specific surface area. This is relevant to estimate the mechanical stability of the snowpack itself. The influence of UV-A irradiation on snow is discussed.

The contribution of surfaces to the Raman spectrum of snow

Maggiore E.;Galimberti D. R.;Tommasini M.;Ossi P. M.
2020-01-01

Abstract

We investigated if the Raman spectrum of snow is affected by the highly differentiated snow morphology. The latter is subjected to continuous changes driven by the variation of ambient parameters, mainly temperature and humidity as snow progresses from freshly deposited, to compact, to icy. We measured the Raman spectrum of snow grains of different size and morphology on the temperature interval between −5.5 °C and −0.5 °C approaching the melting point. We found systematic differences with respect to bulk ice Ih in the OH-stretching band of snows with different histories. We attribute the observed spectral differences to the change of the molecular arrangement of water molecules between bulk and surface sites. We investigate this characteristic via molecular dynamics DFT simulations of bulk ice and of three thin slabs cut along specific surfaces. We analysed the simulated Raman spectra and compared their distinguishing features to those of experimental spectra of snow. The Raman features of the OH-stretching band allow to distinguish among layers inside a snowpack, each layer being characterized by a different specific surface area. This is relevant to estimate the mechanical stability of the snowpack itself. The influence of UV-A irradiation on snow is discussed.
2020
AIMD simulations
Ice I
h
OH-stretching
On field Raman Spectroscopy
Snow
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1152284
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