Electric field effect on molecules: Relation between the orientation of the molecule with respect to the field and the vibrational frequency shift observed in IR spectra of molecules adsorbed in zeolites

Abstract

We propose a speculative approach to determine the orientation of a molecule in an electric field. In condensed media, the frequency of an internal vibrational mode is shifted with respect to the gas frequency. The spectra of some small molecules adsorbed in zeolites show that the direction of the shift depends on the mode (stretching or bending) and on the orientation of the molecular axis with respect to the surface. The sign of the shift is related to the direction of the transition dipole moment with respect to the direction of the electric field.