On the role of Fermi resonance in the spectrum of water in its condensed phases

Abstract

In this paper we present a theoretical analysis of the intramolecular stretching spectrum of D2O in H2O and H2O in D2O for both ice I and amorphous solid water H2O(as). The model includes the dependence of the harmonic stretching (k r r ) and stretch–stretch interaction (k r r′) force constants on hydrogen bonding as well as Fermi resonance between the stretching fundamentals and the bending overtone. Provided that the width of the bending mode is broadened by intermolecular coupling, then the model reproduces the anomalously large widths and splittings in the stretching spectrum recently reported by Devlin e t a l. for D2O in H2O ice I and H2O(as). The value of the Fermi resonance interaction force constant k 122 required to fit these spectra is accounted for by diagonal harmonic terms in the valence force field representation of the intramolecular potential.