Temperature study of intra‐ and inter‐molecular coupling and Fermi resonance constants in the Raman spectra of liquid water using Fourier deconvolution

Abstract

Abstract The structure of the Raman OH stretching band of water has been investigated from 4 to 90 °C using a Fourier deconvolution technique. The overlapped components in the isotropic and anisotropic spectra have been resolved. The information on the positions of the components in the deconvoluted spectra was used for calculation of the constants for intra‐ and inter‐molecular coupling and Fermi resonance and for an estimation of the component frequencies according to the model presented. For the first time, the value of the asymmetric Fermi resonance constant and the temperature dependences of all coupling constants have been obtained. Their temperature behaviour is in good agreement with the data in the literature concerning the different phases of water. It was established that the intramolecular coupling constant increases and the intermolecular coupling constant decreases as the temperature increases. The Fermi resonance constant for symmetric components tends to decrease with increasing temperature. The decrease in the symmetric Fermi resonance interaction with increasing temperature is due to the increase in the distance between the unperturbed fundamental and overtone band positions. The asymmetric Fermi resonance constant tends to increase with increasing temperature and this determines the strengthening of the asymmetric Fermi resonance interaction, which exhibits a limiting value at high temperatures.