16O+24Mg和20Ne+24Mg弹性散射的机制

本文考虑了两碰撞核间核子结团的转移机制, 解释了象¹⁶O+²⁴Mg和²⁰Ne+²⁴Mg这样一些4N核间的弹性散射微分截面后角振荡上升的反常现象. 在原子核分子轨道模型的理论框架下, 将交换势的强度作为唯一的可调参数, 数值计算较自然地拟合实验结果.     

12C+27Al,12C+209Bi和14N+Pb反应全熔合截面测量

本文叙述了用云母径迹探测器分别探测复合核蒸发余核和裂变碎片的实验,从而测出了¹²C+²⁷Al,¹²C+²⁰⁹Bi和¹⁴N+Pb反应的全熔合截面和激发函数.并用锐截止模型由全熔合截面导出了临界角动量.实验结果和当前有关的理论计算进行了比较,在实验误差范围内基本相符.     

12C+12C核分子共振

本文利用核分子振转模型, 解释了¹²C+¹²C反应系统的中间结构现象.     

14N+58Ni和14N+64Ni深部非弹性反应产物同位素分布的差异

实验测得¹⁴N(93兆电子伏)+⁵⁸Ni、⁶⁴Ni深部非弹性反应产物同位素分布, 发现这两者存在系统性的差异.     

12C+27Al深部非弹性散射研究

用△E-E 计数器望远镜鉴别反应产物,研究71.5兆电子伏的¹²C 离子在²⁷Al 靶子上的深部非弹性散射,得到了产物 B 和 Be 在质心系 E-θ平面的截面等高线图。由图可以看出准弹性散射和深部非弹性散射的一般特征。有两点值得特别指出:第一,从淮弹性峰到深部非弹性散射岭呈现某些精细结构.第二,完全阻尼部份的平均动能不等于终态库伦能.     

(EC/β+) Decay of 130Nd and 140Tb

Isotopes,¹³⁰Nd and ¹⁴⁰Tb were produced using enriched targets ⁹⁶Ru and ¹⁰⁶Cd, respectively,bombarded by ³⁶Ar ion beam. The two nuclides were identified and studied by a He-jet tape transport system in combination with "X-γ" and "γ-γ" coincidence measure- ments. The half-life of ¹³⁰Nd was determined to be (13±2)s. The EC/β⁺ decay scheme of 130Nd was proposed for the first time, and the spins and parties of the ground-state and observed low-lying states in the daughter nucleus ¹³⁰Pr were speculated tentatively. The previous simple EC/β⁺ decay scheme of ¹⁴⁰Tb was revised, and the spin-parity of its groundstate was assigned to be 7⁺.     

(EC+β+) Decay of 133Sm and 1.1s Isomer of 133Pr

By irradiation of an enriched target of ⁹⁶Ru with ⁴⁰Ca and using a helium-jet fast tape transport system in combination with X-γ and γ-γ coincidence measurements,the very neutron deficient isotope ¹³³Sm was produced and studied. A simple(EC+β⁺) decay scheme of Sm is proposed for the first time. A by product ¹³³Pr was produced simultaneously because of the ^98－102Ru contents of the ruthenium target. The half-life of an 11/2^－ low-lying isomeric state in ¹³³Pr has been measured to be (1.1±0.2)s. Using single-particle model,the reduced transition probabilities of the 11/2^－ isomers in ^{131,133,135,137}Pr are extracted from their experimental half-lives and compared with the Weisskopf estimate.     

12C+27Al,40Ca耗散碰撞的扩散模型分析

在扩散模型的框架内, 用假定中间组合系统以一个统计的寿命衰变的方法分析了68MeV¹²C+²⁷Al和68.6MeV¹²C+⁴⁰Ca的耗散碰撞中产生的产物的三重微分截面d²σ/dZdEdθ的一般趋向. 导出了中间组合系统的半衰期及产生全阻尼深部非弹性产物的平均互作用半径. 简单地对计算的角分布及Wilczynski图与实验测量结果进行了比较, 讨论了产生二者之间的差异的可能原因.     

12C+197Au反应中的大质量转移

本文主要介绍了入射离子能量为64和67MeV时,¹²C+¹⁹⁷Au反应中出射的α粒子的能谱和角分布,以及能量为71.5MeV时该反应中出射的α、Be和B等粒子的能谱和角分布。给出了⁶Li粒子的产额和使用α-α粒子符合技术,在相对于东流方向成90°处测得的反应中出射的⁸Be分裂开的α粒子的能谱和产额。反应中出射的各种粒子的最可几能量,随着入射离子能量的降低而降低,角分布都是大约在擦边角附近出现峰值,当入射离子能量从71.5MeV降到64MeV时,其峰位大约从80°移到120°,显示出转移反应的特征。我们对实验结果作了一些简要的分析讨论。     

12C+28Si反应全熔合激发函数测量

我们用ΔE-E计数器望远镜系统测量了入射能E_Lab在43MeV—70.5MeV范围内¹²C+²⁸Si全熔合反应的激发函数. 实验激发函数显示出某种宽振荡结构, 宽度约为2—3MeV. 对其平均行为分别用Glas-Mosel模型和势模型进行了理论拟合. 在E_cm=35—50MeV范围内, 临界距离模型和统计Yrast线模型满意地复现了实验数据.     

Analytic Approximation for Process e++e－→τ++τ－ Cross Section Near Threshold

In the structure function approach,we calculate the threshold behaviours for e⁺+e^－→τ⁺+τ^－,which including QED radiative corrections from initial correction,vacuum polarization effect,Coulomb effect and final state correction.This theoretical prediction for threshold behaviours of τ-pair production is useful for BES new measurement of lepton τ mass.     

Measurement of β+ Delayed α Decay of 20Na

Through the ²⁰Na β^{+ 20}Ne→¹⁶O+α process,the half-life and β⁺ delayed α decay spectrum of ²⁰Na have been measured on the Radioactive Ion Beam Line in Lanzhou(RIBLL). The ²⁰Na was identified through TOF-ΔE method and alpha particle was measured by four Si(Au) surface barrier detectors. The half life of ²⁰ Na is(459±7)ms. Result shows that in addition to nine high excitation energy levels with E_d≥2.688MeV, three low excitation energy levels of ²⁰Na with E_d=0.890 & 1.054,1.991,2.424 & 2.457MeV were observed in the experiment. The relative intensity for 1.991MeV level, a more important energy level in the center of mass system energy region from 1.6 to 2.5MeV obtained in this experiment is much higher than the existed one. We also obtained the relative intensities of the levels of E_d=0.890 & 1.054,2.424 & 2.457MeV.     

12C+64Ni反应中的轻带电粒子能谱分析

报道了入射能量为69和56MeV时对P、D、T、³He和α五种轻粒子产物所测得的角分布、E_c.m-θ_c.m平面双微分截面等高图及在速度表象中的洛仑兹不变截面等高图. 用有两个粒子发射源的运动源模型计算可较成功地拟合质子能谱, 所提取快速度和温度与已发现的系统化规律值相符. 将α、³He和D等组合粒子的测量能谱与结合模型(Coalescence model)的计算进行了比较, 这些产物的非平衡组分可满意地被结合模型解释.     

Three Body Amplitude Analysis of the Process a2(1320)→π+π+π－

We analyze the decay amplitudes of the process a₂(1320)→π⁺π⁺π^－ using the tensor analysis method and show how to obtain three body amplitudes.     

π－核双电荷交换反应核谱因子和26Mg(π+, π－)26Si反应

π^－核双电荷交换反应的强度与反应过程的两核子转移的核谱振幅直接联系着. 本文讨论了这类反应与它们的核谱因子的关系. 并以²⁶Mg(π⁺, π^－)²⁶Si为例, 用两种核结构讨论了它的激发函数和微分截面. 我们所用的理论方法能够解释实验数据.     

核分子12C+12C振转谱的对称性

本文利用U(5)群代数对核分子¹²C+¹²C振转谱进行分类. 结果表明, 利用动力学对称性U(5) U(4) O(3)可以较好地描述¹²C+¹²C核分子振转能级的对称性质.     

Branching Ratios of J/ψ→π03(π+π－)

The decay mode of J/ψ→π⁰3(π⁺π^－) was studied very little before. There are no informations except branching ratios for this channel in PDG book which based on less than 0.2×10⁶J/ψ events of MARKⅠ. Now, BESⅠ has a data sample of 7.8×10⁶J/ψ events, we can make more accurate results than MARKⅠ. Total of 3290±43 J/ψ→π⁰3(π⁺π^－) events including 1275±86 J/ψ→ω²(π⁺π^－) events are selected. J/ψ→π⁰3(π⁺π^－) and J/ψ→ω²(π⁺π^－) events have been generated with MC simulition for calculating events selection efficiency. BESⅠ result is: Br(J/ψ→π⁰3(π⁺π^－))=(2.52±0.06±0.43)% and Br(J/ψ→π⁰3(π⁺π^－))=(1.31±0.09±0.21)%. Meanwhile, we studied the invariant mass of 4π and ωππ to find interesting signals. It seems that there is a peak at about 1.74GeV in the invarianat mass spectrum of 4π, and a enhancement was also found at about 1.9GeV in the invariant mass spectrum of ωππ. It is not clear whether they are from resonances or background. Therefore, more work in detail is still going on.     

790 MeV 136Xe轰击56Fe靶时产生的丰中子同位素54Ti,56V,57V,58Cr

用790MeV¹³⁶Xe轰击⁵⁶Fe靶,测量了类靶碎片的质量数和原子序数。探测且鉴定了四个丰中子同位素⁵⁴Ti,⁵⁶V,⁵⁷V,⁵⁸Cr。同时提供了⁵⁵Ti,⁵⁸V,⁵⁹Cr存在的可能性。使用西德重离子研究中心的磁谱仪和磁分析一起进行了飞行时间和ΔE-E测量,同位素鉴定是可靠的。     

π+-16O弹性散射的微观计算

本文用π核散射的微观描述,计算了T_π^lab=240、343MeV时π⁺-¹⁶O弹性散射微分截面,定性地符合实验。     

6.8MeV/A—5.1MeV/A 14N+59Co, 51V发射α粒子的研究

用ΔE-E半导体望远镜测量了6.8MeV/A—5.1MeV/A的¹⁴N轰击⁵⁹Co和⁵¹V产生的α粒子, 得到了发射α粒子, 得到了发射α粒子的能谱、角分布和E-θ平面上的d²σ/dΩdE等高图, 区分了直接机制α及复合核蒸发α粒子, 并对直接机制α粒子的来源作了讨论.