极端条件下原子核性质的研究

近几年来，北京大学重离子物理研究所低能核物理研究组，对极端条件下原子核性质研究取得了一些成果，其中包括原子核的高自旋态，超形变带及远高β稳定线核的性质。     

极端条件下的核结构

本文评述了原子核结构研究的新进展和面临的新挑战。指出当今原子核结构发展方向的基本特点是“极端条件下的核结构”，它的主要内容是高自旋态物理和远离稳定线直至滴线原子核两个方向。     

极端条件下的核结构

本文评述了原子核结构研究的新进展和面临的新挑战．指出当今原子核结构发展方向的基本特点是“极端条件下的核结构”,它的主要内容是高自旋态物理和远离稳定线直至滴线原子核两个方面．而这些新发展方向,有新一代超级γ谱探测器系统和放射性核束加速器的发展和建造做为坚实的技术保证． This paper reviews the new developments and new challenges for the nuclear structure studies. It points out that the developments of the nuclear structure today is characterized by the term u Nuclear Structure in Exotic Conditions",the main contents of which are the high spin physics and physics for the nuclei far from the stability line and up to drip lines.All these new developments are solidly ensured by the developments and the constructions of super γ- ray spe ctrometer...     

奇异核性质的研究

介绍了用放射性核束研究奇异核性质的物理问题, 分析了理论研究的主要方法、模型和现状, 并就对关联、连续态与束缚态的耦合、壳效应和自旋 轨道相互作用、质子晕等问题作了进一步的讨论．We briefly present the physical aspects in the study of exotic nuclei with radioaction nuclear beams and introuduce the main theoretical methods,models and present status. A few theoretical problems,such as....     

现代应用物理系的原子核结构实验研究简介

对近年来清华大学现代应用物理系开展的原子核结构实验研究的情况作了介绍,着重对所研究过的核高自旋态（包括个别核的低自旋态）结构特性进行了简述．The experimental research on nuclear structure in Department of Modern Applied Physics, Tsinghua University has been summarized. The main research results in high spin states of nuclear structure, as well as some low spin states, have been reported.     

转动原子核的对关联变化

利用粒子数守恒方法,在i=11/2壳中精确处理了推转壳模型和粒子转子模型。研究了转动原子核对关联随角动量的变化情况。且通过对上述两种模型给出的对关联、能谱,顺排角动量和seniority结构的分析和比较,还对推转壳模型的可靠性进行了估价。 关键词：     

一种改进的对力形式

通过引进一个关联因子提出了一种改进的对力形式,更合理地反映出短程关联的特点.解释了¹⁵⁷Tm的基态自旋为[411]1/2⁺这一实验事实.     

能量密度泛函中不同对关联处理方式对原子核形变描述影响的探讨

在Skyrme能量密度泛函理论的框架下,研究了不同对关联处理近似,如Hartree-Fock-Bogoliubov(HFB)、Hartree-Fock-Bogoliubov Lipkin-Nogami (HFBLN)及在HFBLN基础上考虑粒子数投影,对于原子核势能曲面计算及基态结合能的影响。同时,也研究了不同对力,如体积对力、表面对力及混合对力对结果的影响。研究的对象为典型的双幻核16O,40Ca,100Sn和208Pb,它们的基态为球形;还有典型的形变核48Cr,也研究了相应的Cr和Fe同位素链的结合能,最后讨论了对超重核298Fl的势能面计算。研究发现,对关联基本不改变形变极小点,但是由于对关联能的引入,对结合能会带来几个MeV的修正能量,HFB、HFBLN及投影计算的修正能量逐渐递增。对关联可以改变位能面最小点附近曲线的软度,使得形变较小点变浅,而在HFBLN基础上考虑粒子数投影,又可以让形变极小点变得更加明显。对关联也降低了位垒高度。在相同对关联处理近似下,混合对力与体积对力计算的势能面结果相接近,表面对力带来了更多的对关联能,对关联的效果更加显著。     

Search for Ring-Like Nuclei under Extreme Conditions

The potential energy surfaces of 24Mg are studied within the adiabatic and diabatic constrained relativistic mean field approaches. The possible ring-like states are searched by analyzing the density distribution. It is found that in 24Mg the ring-like states are energetically favored at the extreme oblate condition ｜β2｜ ≥ 1.54 and a ring-like minimum is obtained with excitation energy Ex = 49.42 MeV and quadrupole deformation β2 = -0.93.     

一种推广对力模型及在大形变核中的应用

总结了可描述大形变原子核运动的Nilsson平均场加推广的对力相互作用的可解模型.该模型在对力强度较弱的区域仍然以单体和两体相互作用为主.但随着对力强度的增加,高阶相互作用的修正将逐渐变得重要.通过对同位素154—171Yb奇偶质量差的数值拟合显示,该新模型可说明大形变核的运动规律.     

Nucleon Isovector Pairing in Nuclei: Microscopic Approach,Boson Representation,and Collective Model

Nucleon pair correlations in atomic nuclei are analyzed within a nuclear microscopic model with residual isovector pairing forces. These are formulated in the boson representation of fermion operators whereby the collective mode of pair excitations can be isolated without restricting the size of the one-particle basis. This method allows one to analyze the fluctuations in the nonsuperfluid phase of nuclear matter, its phase transition to the superfluid phase, and strong pair correlations. The performance of the method is exemplified by numerical results for the nuclei in the vicinity of the doubly magic ⁵⁶Ni nucleus.     

平均场加邻近轨道相互作用对力模型在大形变核中的应用

利用严格可解的平均场加邻近轨道相互作用对力模型来描述大形变核.将该模型应用于稀土区和超铀区的核素.计算了^158—171Er,^160—178Yb,^170—183Hf,^226—234Th, ^230—240U,及^236—243Pu同位素的结合能和对激发能,并与实验结果进行了比较     

An Interference Approach to Perturbed Angular Correlation Spectroscopy

This paper recalls the formalism of H. J. Leisi, which shows an alternative way to understand Perturbed Angular Correlation Spectroscopy: as a quantum interference effect. This revised version was published online in July 2006 with corrections to the Cover Date.     

描述大形变核中对力的硬核Bose-Hubbard模型

讨论了一种描述大形变偶偶核邻近轨道对力相互作用近似的硬核Ｂｏｓｅ－Ｈｕｂｂａｒｄ模型．利用代数方法得到了该模型对激发谱和相应波函数的严格解．该结果可推广到具有任意自旋和有限格点的硬核Ｂｏｓｅ－Ｈｕｂｂａｒｄ和Ｆｅｒｍｉ－Ｈｕｂ－ｂａｒｄ模型中去．     

Beamline 12.2.2: An Extreme Conditions Beamline at the Advanced Light Source

The Advanced Light Source (ALS) is a 1.9-GeV, third-generation synchrotron optimized for the production of VUV and soft X-rays from undulators. There is also a hard X-ray program at the ALS, which is based around three 6-T superconducting bending magnets [1 Robin, D. Proceedings of the 2002 European Particle Accelerator Conference. Paris, France. pp.215Geneva: EPAC..  [Google Scholar]] that shift the critical energy from 3 keV to 12 keV. The extreme conditions beamline at the ALS is situated on Beamline 12.2.2, which benefits from radiation produced by one of these superbend sources. The beamline is designed for X-ray diffraction, X-ray spectroscopy, and X-ray imaging of samples held in diamond-anvil high-pressure cells (DACs). In a DAC, samples are on the order of 10 to 50 μm in diameter and 10 to 30 μm thick and are contained in a metal gasket of typical inner diameters of 100 to 150 μm. For high-quality diffraction patterns with little or no contamination from diffraction from the gasket, the X-ray beam size needs to be on the order of 10 μm × 10 μm.     

Finite Temperature Self-Consistent Semiclassical Approach to the Incompressibility of Hot Nuclei

The self-consistent semiclassical approach is extended from zero temperature to finite temperatures. The nucleon densities of a hot nucleus at thermal equilibrium are determined. The centroids of isoscalar giant monopole resonances(GMR) are evaluated by making use of these densities with sum rules. The incompressibility of hot nuclei is studied with these centroids. It is found that the incompressibility decrepes as the temperature increases. A non-self-consistent finite temperature semiclassical approach with a Woods-Saxon mean field is also presented and compared with the self-consistent result.     

An Eavesdropping Detecting Approach Based on Mode-Mode Correlation

We find that second-order coherence as well as a Hanbury-Brown-Twiss intensity interferometer may provide an optimal approach for eavesdropping detection in the quantum key distribution based on two-mode squeezed vacuum states. With this approach, eavesdropping can be easily detected without sacrificing extra secret bits as the test key. In addition, the efficiency of the quantum key distribution protocol is enhanced greatly.