X-ray photoelectron spectroscopy and infrared adsorption spectroscopy - correlations

Abstract

Since the early seventies, a correlation has been known to exist between changes in intramolecular bond vibrational frequencies (as measured by IAS) and core level binding energy shifts (as measured by XPS). It is possible to explain such correlations by relating both shifts to the partial atomic charges which exist on the bonding pair of atoms. For a series of related molecules, for example, the charge on a common atom may vary and may be related to the core level shifts on that atom. Equally, Liesegang and Lee have shown that changes in this charge correspond with variations to the bond stretching frequency. This model has also been recently extended to include correlations between XPS shifts and rocking vibrational mode variations. In both applications, however, the elastic properties of bonds (springs) are considered. In the former, spring stretching properties are linked to the partial charges, while in the latter case molecular flexing involving a cantilever-like vibration permits a link with partial charges and their effect on rocking frequency. Experimental data will be presented for comparative purposes to illustrate the predictions of the model.