Original scientific paper

The Vibrational Stark Shifts of Sulfate Internal Modes in SO₄2- Doped Potassium, Rubidium and Cesium Selenates. A Quantum Model for Measurement of Crystalline Fields

Ljupčo Pejov ; Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Cyril and Methodius University, P. O. Box. 162, 91001 Skopje, Macedonia
Vladimir M. Petruševski ; Institute of Chemistry, Faculty of Natural Sciences and Mathematics, Cyril and Methodius University, P. O. Box. 162, 91001 Skopje, Macedonia

Abstract

A quantum theoretical basis for the experimentally observed vibrational Stark shifts of the sulfate internal modes in SO₄2- doped K₂SeO₄, Rb₂SeO₄ and Cs₂SeO₄ is presented. Analytical first order perturbation theoretical expressions are derived for the field-dependent wavenumbers of the 1 ← 0 and 2 ← 0 transitions, harmonic wavenumbers, as well as for the Stark tuning rate and the electrostatic field strength at the C_s sites of the host lattices. It is shown that the local field differences are the factor dominating over the differences in the anharmonicities of the guest anions in various host lattices, and are thus responsible for the experimentally observed trends. The proposed method allows calculation of the local crystalline field strength if the anharmonic potential energy parameters of the dopant anions are known. The calculated values for the studied series of matrices range from 229 to 259 V nm-1, which are approximately 3 times larger than those reported for water molecule sites in several clathrate hydrates and for the N₂O adsorbed in the NaA zeolite cavities. The model also successfully explains the greater bond length distortions than the angular ones of the dopant anions observed in ali studied cases.

Keywords

vibrational Stark effect; perturbation theory; sulfate impurities; internal crystalline fields; solid Solutions; isomorphous isolation; mixed crystals

Hrčak ID:

131996

URI

https://hrcak.srce.hr/131996

Publication date:

4.12.2000.

Visits: 911 *