Frequency Assignments in Infra-red Spectrum of Water

Abstract

ALTHOUGH the infra-red spectra of water and deuterium oxide vapour have been carefully mapped and satisfactorily analysed, the infra-red spectrum of water in the liquid state possesses many features that are still not clearly understood. As in the case of most liquids, the near-infra-red spectrum of the liquid is characterized by strong bands in the same spectral regions as those in which the strong vibration–rotation bands of the vapour occur. However, in the case of liquid water there are additional weaker near-infra-red bands that have no counterparts in the water-vapour spectrum. This communication offers a tentative assignment of these near-infra-red ‘associational bands’ in terms of monomeric vibrational modes and certain lattice modes reported recently by Draegert et al.¹, who have investigated the far-infra-red spectrum of liquid water between 30 cm⁻¹ and 1,200 cm⁻¹.