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Restricted Validity of the Two-State Model Describing a Vibronic EPR g-Factors Averaging in Cs_{2}Zn(SO_{4})_{2}·6H_{2}O Tutton Salt Crystals Doped with Cu^{2+} Ions

100%
Hoffmann S., Kaszyński R., Augustyniak M., Hilczer W.
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vol. 96
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issue 6
733-740
EN
Single crystals and powder EPR spectra of Cu^{2+} ions in Cs_{2}Zn(SO_{4})_{6}·6H_{2}O were recorded in the temperature range of 4.2-300 K and the g-factor temperature variations were determined. The g_{z} and g_{y} 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(H_{2}O)_{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 Cs_{2}Zn(SO_{4})_{6}·6H_{2}O 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 δ_{12}=318(9) cm^{-1}=3.7 kJ/mol.
2
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Electron Spin Echo Envelope Modulation Analysis of SeO¯_{3} Radical in (NH_{4})_{3}H(SeO_{4})_{2} Single Crystal

88%
Tritt-Goc J., Goslar J., Hilczer W., Hoffmann S., Augustyniak M.
Acta Physica Polonica A
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1993
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vol. 84
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issue 6
1131-1141
EN
A detailed computer analysis of the electron spin echo envelope modulations of SeO_{3} radical in a suitable orientation of (NH_{4})_{3}H(SeO_{4})_{2} single crystal is presented. It was found that the modulations are due to a weak dipolar coupling with nitrogens and protons of the only two neighbouring NH_{4} groups among the five NH_{4} groups surrounding SeO¯_{3} center. Isotropic dipolar coupling constant is 1.7 MHz for nitrogens and 0.9 MHz for protons. It was shown that thermal reorientations of NH_{4} groups observed by NMR have a negligible effect on the electron spin echo envelope modulation pattern but can be responsible for the same value of a^{H}_{iso} for all protons in a NH_{4} group. A good fit obtained between experimental spectra and theoretical calculations assuming nondisturbed crystal geometry indicates a small damage of the crystal by X-rays during the radical center formation.
3
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Modelling and Simulation of 3 Blade Helicopter's Rotor Model

88%
Latalski J., Bocheński M., Warmiński J., Jarzyna W., Augustyniak M.
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vol. 125
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issue 6
1380-1384
EN
Results of model tests of a rotating composite beam with integrated piezoelectric active element are presented in the paper. A proposed electromechanical system is a simplified model of the structure of a modern helicopter rotor blade. Numerical analysis of the considered system is developed by means of the finite element method. In addition, the laboratory setup has been built in order to perform real experimental studies. Selected static and dynamic characteristics of the object are determined by a series of numerical simulations. The results are compared with the outcomes of tests performed on the experimental setup. A very good agreement between numerical simulation and experiment results is observed.
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