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Study of proton resonances in ^(18)Ne via resonant elastic scattering of ^(17)F+p and its astrophysical implication

Science china(physics,Mechanics & Astronomy) 2011年第S1期54卷 32-36页

作者： HE JianJun1, HU Jun1,2, XU ShiWei1, CHEN ZhiQiang1, ZHANG XueYing1, WANG JianSong1, YU XiangQing1, ZHANG LiYong1,2, LI Long1,2, YANG YanYun1,2, MA Peng1,2, ZHANG XueHeng1, HU ZhengGuo1, GUO ZhongYan1, XU Xing1,2, YUAN XiaoHua1, LU Wan1,2, YU YuHong1, ZANG YongDong1,2, TANG ShuWen1,2, YE RuiPing1,2, CHEN JinDa1,2, JIN ShiLun1,2, DU ChengMing1,2, WANG ShiTao1,2, MA JunBing1,2, LIU LongXiang1,2, BAI Zhen1,2, LEI XiangGuo1, SUN ZhiYu1, ZHANG YuHu1, ZHOU XiaoHong1, XU HuShan1, SU Jun3, LI ErTao3, WANG HongWei4, TIAN WenDong4 & LI XiangQing5 1 Institute of Modern physics (IMP), Chinese Academy of Sciences, Lanzhou 730000, china 2 Graduate university of Chinese Academy of Sciences, beijing 100049, china 3 china Institute of Atomic Energy (CIAE), beijing 102413, china 4 Shanghai Institute of Applied physics (SINAP), Chinese Academy of Sciences, Shanghai 201800, china 5 school of physics and state key laboratory of nuclear physics and technology, peking university, beijing 100871, china 1. Institute of Modern physics (IMP) Chinese Academy of Sciences Lanzhou 730000 China2. Graduate University of Chinese Academy of Sciences Beijing 100049 China3. China Institute of Atomic Energy (CIAE) Beijing 102413 China4. Shanghai Institute of Applied Physics (SINAP) Chinese Academy of Sciences Shanghai 201800 China5. School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871 China

The proton resonant properties in 18Ne, which determine the reaction rate of the key stellar 14O(α,p)17F reaction, have been studied by using a technique of proton resonant elastic scattering of 17F+p. A 4.22 MeV/nucleon 17F radioactive ion (RI) beam was produced via a projectile-fragmentation reaction, and separated by a Radioactive Ion Beam Line in Lanzhou (RIBLL). By bombarding a thick (CH2)n target, the energy spectra of the recoiled protons were measured by two ΔE-E silicon telescopes at the center-of-mass scattering angles of θc.m.≈175°±5°, θc.m.≈152°±8°, respectively. Several proton resonances in 18Ne were ob served clearly. A further R-matrix analysis of the experimental data is under way to determine the resonant parameters. The present work reports the preliminary results briefly.

关键词： resonant reaction reaction rate explosive burning accreting binary systems

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Study of the structure of unstable nuclei through the reaction experiments

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Science china(physics,Mechanics & Astronomy) 2011年第S1期54卷 1-5页

作者： CAO ZhongXin & YE YanLin state key laboratory of nuclear physics and technology, school of physics, peking university, beijing 100871, china 1. state key laboratory of nuclear physics and technology School of Physics Peking University Beijing 100871 China

Along with the development of the radioactive nuclear beam facility, the study of the structure of unstable nuclei has progressed rapidly over the last few decades. Due to the weakly binding property, the structure information of the unstable nuclei comes primarily from the scattering or reaction experiments. Therefore it would be very important to understand clearly the reaction mechanism involved in the experiment. We outlined here the major reaction mechanisms which are adequate to the study of unstable nuclei, with the focus on the new phenomena and methods in comparison with those with traditional stable nucleus beam. Especially emphasized are the breakup and knockout reactions, developed as accurate tools for spectroscopy investigation into the nuclear structure with low intensity secondary beam. Couplings of the breakup channel to the elastic scattering and the fusion and transfer reactions are also reviewed.

关键词： binaries: unstable nuclei nuclear structure breakup reaction knockout reaction fusion reaction transfer reaction

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X-ray flares of γ-ray bursts: Quakes of solid quark stars?

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Science china(physics,Mechanics & Astronomy) 2009年第2期52卷 315-320页

作者： XU RenXin1 & LIANG EnWei2 1 school of physics and state key laboratory of nuclear physics and technology, peking university, beijing 100871, china 2 Department of physics, Guangxi university, Nanning 530004, china 1. school of physics and state key laboratory of nuclear physics and technology Peking University Beijing 100871 China 2. Department of physics Guangxi University Nanning 530004 China

A star-quake model is proposed to understand X-ray flares of both long and short γ-ray bursts (GRBs) in a solid quark star regime. Two kinds of central engines for GRBs are available if pulsar-like stars are actually (solid) quark stars, i.e., the SNE-type GRBs and the SGR-type GRBs. It is found that a quark star could be solidified about 103 to 106 s later after its birth if the critical temperature of phase transi- tion is a few Metga-electron-volts, and then a new source of free energy (i.e., elastic and gravitational ones, rather than rotational or magnetic energy) could be possible to power GRB X-ray flares.

关键词： γ-rays bursts: X-rays neutron stars elementary particles

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Recent HERMES Results on DVCS from Proton and nuclear Targets

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原子核物理评论 2009年第S1期26卷 124-128页

作者： YE Hong-xue,MAO Ya-jun (school of physics and state key laboratory of nuclear physics and technology,peking university,beijing 100871,china) school of physics and state key laboratory of nuclear physics and technology Peking UniversityBeijing 100871China

Spin structure is one of the fundamental subjects in the study of nucleon structure. Recently it is found that Generalized Parton Distributions(GPDs) are related to the total angular momentum carried by partons,which offers a possible solution to the spin puzzle in the first time. We get access to certain GPDs by looking at the azimuthal angle asymmetries attributed to the interference between Deeply Virtual Compton Scattering(DVCS) and Bethe-Heilter processes in HERMES experiment. By measuring the asymmetry with respect to transverse target polarization from proton target,a model-dependent constraint on Ju vs Jd is obtained. Another worldwide unique channel is nuclear DVCS. The preliminary results on asymmetries with respect to beam spin and beam charge are reported.

关键词： GPDs DVCS TTSA nuclear DVCS

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Magnetic moments of ^(33)Mg in the time-odd relativistic mean field approach

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Science china(physics,Mechanics & Astronomy) 2009年第10期52卷 1586-1592页

作者： LI Jian1,ZHANG Ying1,YAO JiangMing1 & MENG Jie1,2 1 school of physics,state key laboratory of nuclear physics and technology,peking university,beijing 100871,china 2 school of physics and nuclear Energy Engineering,Beihang university,beijing 100191,china school of physics State Key Laboratory of Nuclear Physics and Technology Peking University Beijing 100871 China school of physics and nuclear Energy Engineering Beihang University Beijing 100191 China

The configuration-fixed deformation constrained relativistic mean field approach with time-odd component has been applied to investigate the ground state properties of 33Mg with effective interaction *** ground state of 33Mg has been found to be prolate deformed,β2=0.23,with the odd neutron in 1/2[330] orbital and the energy -251.85 MeV which is close to the data -252.06 *** magnetic moment -0.9134 μN is obtained with the effective electromagnetic current which well reproduces the data -0.7456 μN self-consistently without introducing any *** energy splittings of time reversal conjugate states,the neutron current,the energy contribution from the nuclear magnetic potential,and the effect of core polarization are discussed in detail.

关键词： magnetic moment binding energy time-odd component configuration-fixed deformation constrained calculation relativistic mean field theory

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β-decay studies of the neutron-rich ^(18,21)N isotopes

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Science china(physics,Mechanics & Astronomy) 2011年第S1期54卷 53-60页

作者： HUA Hui, LI ZhiHuan, YE YanLin, JIANG DongXing, LOU JianLing, LI XiangQing & XU FuRong school of physics and state key laboratory of nuclear physics and technology, peking university, beijing 100871, china 1. school of physics and state key laboratory of nuclear physics and technology Peking University Beijing 100871 China

The β-decay studies of neutron-rich 18,21N isotopes have been performed using β-n, β-γ, and β-n-γ coincidence methods. The 18,21N ions were produced by the fragmentation of the 22Ne and 26Mg beams, respectively, on a thick beryllium target. The time of flight of the emitted neutrons following the β-decay of 18,21N was measured by a neutron detector system with wide energy detection range and low-energy detection threshold. In addition, several clover germanium detectors were used to detect the β-delayed γ-rays. The half-lives of the β-decays of 18N and 21N were determined to be (619±2) ms and (82.9±7.5) ms, respec tively. Several new β-delayed neutron groups were observed with a total branching ratio of (6.98±1.46)% and (90.5±4.2)% for 18N and 21N, respectively. The level schemes of 18O and 21O were deduced. The experimental Gamow-Teller β-decay strengths of 18N and 21N to these levels were compared with the shell model calculations.

关键词： β-delayed neutron decay 18 21N neutron detector system branching ratio Gamow-Teller strength

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Near-field properties of a shell nanocylinder pair with gain materials

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Chinese physics B 2012年第11期21卷 388-392页

作者：王乔吴世法王晓钢 MOE key laboratory of Materials Modification by Beams School of Physics&Optoelectronic EngineeringDalian University of Technology state key laboratory of nuclear physics and technology School of PhysicsPeking University

We study the near-field response of a shell nanocylinder pair, with its core filled by gain materials, using a two- dimensional finite-difference time-domain method. It is shown that the gain materials in the core of the cylinder can compensate for the intrinsic absorption of the metal shell, leading to local-field enhancement in the gap of the active pair. A linear dependence is found between the field enhancement and the gain coefficient at resonance. The detailed physics is studied by calculating the electrical-field distribution of the shell pair filled with different gain materials. The influence of the gap width and the shell thickness on the interaction of two adjacent active shell cylinders is also investigated.

关键词： shell nanocylinder pair gain material local-field enhancement

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On Hoava-Lifshitz cosmology

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Chinese physics C 2011年第5期35卷 429-435页

作者： CHEN Bin1) Department of physics, and state key laboratory of nuclear physics and technology, peking university, beijing 100871, china Department of physics and State Key Laboratory of Nuclear Physics and Technology Peking University

We give a brief overview of the Horava-Lifshitz-gravity theory, its modifications and its implications in cosmology. In particular, we discuss the various issues on the gravitational scalar mode, including its decoupling, its role as inflaton and its stability. Our analysis shows that the scalar mode could decouple naturally at λ = 1 due to the extra gauge symmetry. On the other hand, the fact that the scalar mode becomes ghost when 1/3 〈 λ 〈 1 is a real challenge to the theory. We try to overcome this problem by modifying the action such that the RG flow lies outside the problematic region. We discuss the cosmological implications of the theory.

关键词： Horava-Lifshitz-gravity cosmology ghost

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Kinetic characteristics of continuous flow polymerase chain reaction chip: A numerical investigation

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Science china(Technological Sciences) 2010年第7期53卷 1967-1972页

作者： WANG ShiYing1 & WANG Wei2,3 1 school of physics, peking university, beijing 100871, china 2 Institute of Microelectronics, peking university, beijing 100871, china 3 National key laboratory of Science and technology on Micro/Nano Fabrication, beijing 100871, china 1. school of physics Peking University Beijing 100871 China2. Institute of Microelectronics Peking University Beijing 100871 China3. National Key Laboratory of Science and Technology on Micro/Nano Fabrication Beijing 100871 China

Continuous flow PCR (polymerase chain reaction) chip holds impressive advantages compared to micro chamber PCR chip. In order to have better understanding of kinetic characteristics of continuous flow PCR chip, a comprehensive mathematical model is presented in this paper, including melting, annealing and extension phases of a typical PCR process which has the essence of a convection-diffusion-reaction system. Using this model, we can simulate the PCR process in series of reaction cycles. Numerical results show that the average sample velocity plays a significant role in affecting the amplification efficiency. Also, appropriate combination of the PCR mixture is important for high-quality DNA amplification. Giving a large initial DNA concentration range, the continuous flow PCR scheme holds excellent real-time detection ability theoretically. The present numerical model bridges the temperature distribution to the real DNA amplification, and thereby is able to successfully predict continuous flow PCR properties which are important for the chip design.

关键词： continuous flow PCR chip numerical simulation convection-diffusion-reaction system

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A note on the discovery of a 2M_⊙ pulsar

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Research in Astronomy and Astrophysics 2011年第6期11卷 687-691页

作者： Xiao-Yu Lai Ren-Xin Xu school of physics and state key laboratory of nuclear physics and technology Peking University Beijing 100871 China

It is conventionally thought that the state equation of dense matter softens and thus cannot result in high maximum mass if pulsars are quark stars and that a recently discovered 2M⊙ pulsar （PSR J1614–2230） may make pulsars unlikely to be quark stars. However, this standard point of view would be revisited and updated if quark clustering could occur in cold quark matter because of the strong coupling be- tween quarks at realistic baryon densities in compact stars. It can be argued that the state equation of clustered quark matter stiffens to support compact stars with maxi- mum mass Mmax 2M⊙. In this brief note, it is demonstrated that large parameter space ranges are allowed for Mmax 2M⊙ in a Lennard-Jones model of clustered quark matter and the newly measured highest mass of PSR J1614–2230 would be meaningful for constraining the number of quarks inside a single quark-cluster to be Nq ≤ 103.

关键词： dense matter — elementary particles — pulsars: general — stars: neutron

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