This paper discusses the existence of ion-acoustic solitary waves and their interaction in a dense quantum electronpositron-ion plasma by using the quantum hydrodynamic equations. The extended Poincaré-Lighthill-Kuo perturbation method is used to derive the Korteweg-de Vries equations for quantum ion-acoustic solitary waves in this plasma. The effects of the ratio of positrons to ions unperturbation number density p and the quantum diffraction parameter He (Hp) on the newly formed wave during interaction, and the phase shift of the colliding solitary waves are studied. It is found that the interaction between two solitary waves fits linear superposition principle and these plasma parameters have significantly influence on the newly formed wave and phase shift of the colliding solitary waves. The investigations should be useful for understanding the propagation and interaction of ion-acoustic solitary waves in dense astrophysical plasmas (such as white dwarfs) as well as in intense laser-solid matter interaction experiments.

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Since LuTaO4 is a scintillator host with the highest density, it is important to investigate the structure and phase transition for its single crystal preparation. The polycrystalline formed by the mixture of Lu2O3:Ta2O5 with the molar ratio 1:1 is prepared by solid state reaction method at different temperatures. The phase transitions and structures of the polycrystalline powders are investigated by X-ray diffraction and Rietveld refinement. The results show that the polycrystalline has a single phase M'-LuTaO4 when sample is prepared at 1740 ℃, it presents a mixture phase of M'-LuTaO4 and M-LuTaO4 at 1800 ℃, and it displays a single phase M-LuTaO4 at 1840 ℃. The sample is melted when the calcined temperature is 2058 ℃, the melt is quenched and the polycrystalline is the mixture of M-LuTaO4, Lu3TaO7 and Ta2O5, whose structural parameters, including the lattice parameters, atomic fraction coordinates, etc. are obtained by Rietveld refinement to their X-ray diffraction pattern, and the results show their weight ratios are 78.1%, 18.9% and 3.0%, respectively. These results are valuable for the single crystal growth of the heavy scintillators with the host LuTaO4.

Rotational transitions in molecular hydrogen collisions are computed. The two most recently developed potential energy surfaces for the H 2 −H 2 system are used from the following works: 1) A. ibid. 112, 4465. Cross sections for rotational transitions 00→20, 22, 40, 42, 44 and corresponding rate coefficients are calculated using a quantum-mechanical approach. Results are compared for a wide range of kinetic temperatures 300 K ≤ T ≤ 3000 K.

In this paper, Nd3+-doped GdTaO4 laser crystal for scintillator with high density is successfully grown by the Czochralski method, and the absorption spectra are measured along the a, b and c directions in a wide wavelength range of 260-2000 nm. The experimental energy levels for Nd3+ are analyzed and identified. The free-ions and crystal-field parameters are fitted by the experimental energy levels with the root mean square deviation of 12.66 cm-1, and 102 Stark energy levels for Nd3+ in GdTaO4 host crystal are assigned. The fitting results of free-ions and crystal-field parameters are compared with those already reported for Nd3+:GdxLu1-xTaO4 (x=0.85) crystal. It indicates that the fitting results of Stark energy levels agree well with the experimental spectra.