The nature of vibrational frequency shifts in weakly bound molecular clusters

Carol A Parish, Purdue University

Abstract

A direct manifestation of weak intermolecular interaction is the shift that occurs in the vibrational transition frequencies of one molecule upon interaction with another. Wide-ranging theoretical investigations of weakly bound complexes have been performed in order to understand the nature of weak bonding and with this knowledge to develop a simple model which accounts for the blue and red shifts in the stretching transition frequencies of diatomic molecules. The fundamental assumption of this model is that the primary electronic structure change upon weak complexation is that associated with electrical polarization. A second important element is the coupling of the intramolecular stretch to the weak mode vibrations. Calculations with this model were carried out for a number of complexes, and comparison with nineteen available experimental values indicates that shifts are predicted with a mean error of 10 cm$\sp{-1}$, excluding one interesting anomalous case, the HF frequency shift in OC-HF. The model is applicable in cases of both blue and red shifts.

Degree

Ph.D.

Advisors

Dykstra, Purdue University.

Subject Area

Chemistry|Molecules|Physics

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