PRESSURE BEHAVIOR OF INXGA1-XAS/GAAS STRAINED QUANTUM-WELLS WITH DIFFERENT WIDTHS

The photoluminescence of InxGa1-xAs/GaAs strained quantum wells with widths of 30 angstrom to 160 angstrom have been studied at 77 K under hydrostatic pressure up to 60 kbar. It is found that the pressure coefficients of exciton peaks from 1st conduction subband to heavy hole subband increase from 9.74 meV/kbar for a 160 angstrom well to 10.12 meV/kbar for a 30 angstrom well. The calculation based on the Kronig-Penney model indicated that the extension of the electronic wave function to the barrier layer in the narrow wells is one of the reasons for the increase of the pressure coefficients with the decrease of well width. Two peaks related to indirect transitions were observed at pressures higher than 50 kbar.

Tb3+/Yb3+ heavily-doped tellurite glasses with efficient green light emission

Without introducing concentration quenching phenomenon, a few wt% of Tb3+ and Yb3+ ions were doped into a group of easily-fiberized tellurite glasses characterized by loose polyhedron structures and rich interstitial positions. Intense green upconversion emission from Tb3+ ions centered at 539 nm due to transition 5D4→7F5 was observed by direct excitation of Yb3+ ions with a laser diode at 976 nm. Optimizing the concentration ratio of Tb3+/Yb3+, a tellurite glass with composition of 80TeO2-10ZnO-10Na2O (mol%)+1.0wt% Tb2O3+3.0wt% Yb2O3 was found to present the highest green light intensity and therefore is especially suitable for efficient green fiber laser development.

DBHF方法和热力学自洽性

采用Dirac Brueckner-Hartree-Fock理论方法,计算了零温核物质中每核子的结合能、压强和单核子能量,着重讨论了不同的T矩阵协变表示对核物质中Hugenholtz-Van Hove(HVH)定理满足程度的影响．结果表明:不同的协变表示对核子自能各分量的动量相关性和密度依赖性均有重要影响,进而对核介质中HVH定理的满足程度产生重要影响．在完全的膺矢量表示下,HVH定理遭到了相当大程度的破坏,从而体现出基态关联效应对单核子性质的重要性,并与非相对论BHF理论方法得到的结论一致,因而完全的膺矢量表示要优于膺标量表示．

模型及其参数对确定K介子有效质量的影响

分别使用线性和非线性Walecka模型 ,讨论了重子标量密度 ρS 和矢量密度 ρB 的关系 .运用相对论平均场理论给出了不同模型下 ρS ρB 关系曲线 .利用这些结果 ,分析了模型和参数组对核物质中K介子有效质量影响的大小 ,得到了不同参数组下K介子有效质量随核物质密度的变化关系曲线 .同时计算了非对称核物质中K介子有效质量在不同模型和不同参数下的有效质量的曲线 ,并与对称核物质中的情况进行了比较 .

^14C-Ams测年在考古学中的应用

IEECAS SKLLQG

~(23)Al 的β~+延发质子测量

利用ＴＯＦ－ Ｅ和０°注入探测器的方法，鉴别并测量了２３Ａｌβ＋延发质子衰变能谱，通过精密脉冲发生器和计数器测得２３Ａｌ的半衰期 Ｔ１／２＝（４７６±４５）ｍｓ．实验中重现了能量为０．２１６，０．２７８，０．４３８，０．４７９ＭｅＶ的低能衰变质子．另外，还观察到了一个新的β＋延发衰变能级 Ｅｘ＝ ８．９１６ＭｅＶ，并给出了它们的相对强度．

Baryon magnetic moment and beta decay ratio in colored quark cluster model

Baryon magnetic moments of p, n, Sigma(+), Sigma(-), Xi(0), Xi(-) and the beta decay ratios (G(A)/G(V)) of n -> p, Sigma(-) -> n and Xi(0) -> Sigma(+) are calculated in a colored quark cluster model. With SU(3) breaking, the model gives a good fit to the experimental values of those baryon magnetic moments and the beta decay ratios. Our results show that the orbital motion has a significant contribution to the spin and magnetic moments of those baryons and the strange component. in nucleon is small.

DBHF approach and thermodynamic consistency for nuclear matter calculations

Within the framework of Dirac Brueckner-Hartree-Fock (DBHF) approach, we calculate the energy per nucleon, the pressure, the nucleon self-energy, and the single-nucleon energy in the nuclear matter by adopting two different covariant representations for T-matrix. We mainly investigate the influence of different covariant representations on the satisfiable extent of the Hugenholtz-Van Hove (HVH) theorem in the nuclear medium in the framework of DBHF. By adopting the two different covariant representations of T-matrix, the predicted nucleon self-energy shows a quite different momentum and density dependence. Different covariant representations affect remarkably the satisfiable extent of the HVH theorem. By adopting the complete pseudo-vector representation of the T-matrix, HVH theorem is largely violated, which is in agreement with the result in the non-relativistic Brueckner-Hartree-Fock approach and reflects the importance of ground state correlations for single nucleon properties in nuclear medium, whereas by using the pseudoscalar representation, the ground state correlation cannot be shown. It indicates that the complete pseudo-vector presentation is more feasible than the pseudo-scalar one.