STUDIES ON THE BEHAVIOR OF THE INTERNAL VIBRATIONAL MODES IN (NH4)2TexSn1-xCl6 MIXED CRYSTALS

The behavior of the internal lattice vibrational modes in (NH4)2TexSn1-xCl6 mixed crystals has been investigated by Raman scattering. All of the Raman-active [MX6]2- internal modes show two-mode property in the mixed crystals with compositions from x?=?0 to 1, and apart from the sample with x?=?0.5, their energy positions are composition-independent. Space group calculations including site symmetry considerations and frequency fittings describe a good force field model. It has been demonstrated that the composition-independent two-mode behavior may come from the strong clustering effect, rather than from the character of the gap and local modes of impurities in mixed crystals. For the sample with x?=?0.5, the two component elements seem to form a pseudo-periodic lattice structure.     

液氦输液管的改进

本文介绍了一种不抽真空的实验室使用的小型液氦输液管的基本原理和制作工艺.使用效果表明,这样的输液管不仅性能不比通常杜瓦管差,而且制作简单,不须定期保养.