Restricted Validity of the Two-State Model Describing a Vibronic EPR g-Factors Averaging in Cs2Zn(SO4)2·6H2O Tutton Salt Crystals Doped with Cu2+ Ions |
| S.K. Hoffmann, R. Kaszyński, M.A. Augustyniak and W. Hilczer Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland |
| Received: September 16, 1999 |
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| Single crystals and powder EPR spectra of Cu2+ ions in Cs2Zn(SO4)6·6H2O were recorded in the temperature range of 4.2-300 K and the g-factor temperature variations were determined. The gz and gy have the values of 2.443 and 2.134, respectively, at the rigid lattice limit below 20 K, and then continuously tend to an average value on heating. This vibronic averaging produced by reorientations of Cu(H2O)6-complexes between Jahn-Teller distorted octahedral configurations is described in terms of a two-state Silver-Getz model which is known as a good model for diamagnetic non-ammonium Tutton salts. We found, however, that this model is only a crude approximation in Cs2Zn(SO4)6·6H2O below 150 K. Above this temperature the model works better and describes the vibronic dynamics between the two lowest energy potential wells in the adiabatic potential surface differing in the energy of δ12=318(9) cm-1=3.7 kJ/mol. |
| DOI: 10.12693/APhysPolA.96.733 PACS numbers: 63.90.+t, 76.30.-v |