Intermolecular Vibrational Coupling A Model Calculation for the Out-of-Plane Vibration of CO3−-in Compounds with the Aragonite Structure

Abstract

¹³CO₃ ^−- substituted compounds with the aragonite structure show a fine structure of the out-of-plane vibration in the infrared spectra. A simple quantum mechanical model of coupled oscillators is developed to describe quantitatively the observed spectra. The spectra can be interpreted in terms of isolated ^12CO ₃ ^−- and ¹³CO₃ ^−- clusters, whose eigenfunctions interact. The heavy ions have localized vibrations, whereas clusters of the light ion with more than one ion show only localized vibrations at small coupling; stronger coupling results in resonant modes. Intensitytransfer from light to heavy ion bands is explained and the consequences of interaction between different clusters are discussed.