Vibrational Spectroscopy of Hydrous Components

Abstract

Water molecules, hydroxide ions and fluid inclusions are important components of many natural systems, and are also prominent in a variety of synthetic minerals and related technological materials. Water and OH ions can be both a major component required by the mineral's stoichiometry and an accidental trace component. The trace hydrous species can have a disproportionately important role in the physical, chemical, rheological, electronic and optical properties of the material. In minerals, hydrogen is most commonly bonded to oxygen. The strongly polar OH groups absorb infrared photons efficiently. Furthermore, if the OH groups are structurally oriented within the host, the amount of incident radiation absorbed can be strongly dependent upon the relative orientation of the OH dipole and the direction of linear polarization of the interrogating light. General discussions of the vibrational spectra of the water molecule and the OH ion are presented in many general spectroscopy texts such as Nakamoto (1978). The topic of the infrared spectroscopy of OH and H_2O in minerals has been reviewed in Farmer (1974) and more recently by Aines and Rossman (1984a).

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