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Optical phonons (k≈0) of the double perovskite NdBaCo2O5+x are calculated in the cases of x = 0, 1 (tetragonal P4/mmm, a = b = ap, c≈2ap) and x = 0.5 (orthorhombic Pmmm, a = ap, b≈2ap, c≈2ap) using the shell model. The calculated modes in the three crystal structures are classified according to their symmetry and frequency. By analyzing the eigenvectors for different modes the most intense bands in the Raman spectra of the complex compound NdBaCo2O5+x are predicted. [ABSTRACT FROM AUTHOR]

The work is dedicated to the theoretical and experimental investigation of the intense H- volume-plasma generation in cesium-hydrogen discharge. A low-voltage (LV) mode of the discharge, a LV arc with a heated cathode, is studied. Theory of the discharge was created. It was shown theoretically that a very high H- density (∼1013 cm-3) may be achieved in the discharge plasma. A comparison between the discharge theory and the experiments was fulfilled. The main plasma parameters were measured by probe method. The H- density in plasma was determined from the experimentally measured absorption of laser radiation due to the photodetachment of electrons from H- ions. The existence of a very high H- density in plasma (∼1013 cm-3) was proved experimentally. Theoretical modeling shows that, with a high electron emission from the cathode (∼10 A/cm2), the maximum H- density is located in the plasma near the anode. It allows extraction of narrow and bright H- beam through a small opening in the anode. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]