35MeV/u?36,40 Ar+112,124Sn反应中同位旋自由度的弛豫

35MeV/u 36 ,40　Ar+ 112 ,12 4Sn反应中 ,在前角 5°和 2 0°观测到丰中子核与稳定核的产额比随粒子出射动能的增加而减小 ,而缺中子核与稳定核的产额比随动能的增加而增加 .对于某种元素 ,随着动能的减小 ,其平均中质比逐渐由弹核N/Z向靶核N/Z过渡 .这些现象表明在这样的入射能量下 ,周边或近周边碰撞过程中同位旋自由度没有完全达到平衡 .这种行为对两个靶核系统是相似的 ,但是同位素产额比的绝对值在 5°没有靶核相关性 ,而在 2 0°处却表现出明显的靶核相关性 .     

30MeV/u40Ar+112,124Sn反应中的同位素产额比与核温度

系统研究了30MeV/u ⁴⁰Ar+^112,124Sn反应中的轻粒子同位素产额比随角度和初始激发能的变化关系.对于两个反应体系,均观察到³He/⁴He和⁶Li/⁷Li的产额比随角度的增加而增加,⁶He/⁴He和⁸Li/⁷Li随角度的增加而减小.统计发射的运动学效应不能完全符合实验结果.各种单同位素产额比与靶核的N/Z比有关,表现出同位旋效应,而由双同位素比提取的核温度几乎没有靶核相关性.     

17N+197Au反应中碎片与中子的符合测量

在3?3?.4MeV/u ¹⁷N束轰击¹⁹⁷Au靶产生的反应中,利用放置于不同角度组合的17个中子探测器(4°—83°)和14个半导体望远镜(2.3°—9.0°)对反应产物碎片与中子进行了符合测量.经对所得实验角分布积分得到Z=3—6元素的同位素产额分布.在参加者-旁观者模型框架下,采用¹⁷N原子核内部的不同密度分布计算了同位素产额分布并与实验数据做比较.     

35MeV/u36Ar+124Sn反应中类弹产物的同位素分布特性

测量了35MeV/u³⁶Ar+¹²⁴Sn反应中5.3°处类弹产物的同位素分布,观察到随着出射动能的增加,产物的平均中质比逐渐减小而接近弹核的平均中质比.同位旋相关的量子分子动力学计算表明,随着反应时间的增加,类弹产物的平均出射动能逐渐减小而平均N/Z值则逐渐增大.另外,碰撞参数也影响类弹产物的同位素组成:随着碰撞参数的减小,类弹产物的平均N/Z值减小.     

50MeV/u 18O离子轰击Be、Cu和Au厚靶的中子产额和中子发射率

用阈探测器中子活化法测量了50MeV/u ¹⁸O离子轰击Be.Cu和Au厚靶的总中子产额和前向中子发射率. 实验结果表明,中子产额对靶核原子序数有一定的依赖性,较轻靶子的中子产额和中子发射率高于较重的靶子;当靶核(Cu)和入射离子单核能(50MeV)相同时,¹⁸O离子的中子产额约为¹²C离子的4倍.     

25MeV/u 40Ar引起的反应中碎片同位素分布的研究

本文描述了25MeV/u ⁴⁰Ar+²⁷Al、⁵⁸Ni、¹¹⁵In反应中在小角区方向测得的出射碎片同位素分布及其产额,给出了出射碎片的中子数与质子数之比(N/Z)和靶核的关系. 并对出射碎片的来源进行了分析.     

46.2MeV/u 12C+64Ni、58Ni反应中发射的轻粒子和复杂碎片

用光二极管读出的CsI(Tl)闪烁探测器和多叠层硅望远镜,测量了46.2MeV/u ¹²C引起各种靶⁶⁴Ni、⁵⁸Ni、¹²C、¹⁹⁷Au、²⁰⁹Bi反应中所发射的轻粒子和中等质量碎片,这些探测器对轻粒子和中等质量碎片有很好的能量分辨和质量分辨.单举的能谱用运动源模型进行了分析,对各种靶在不同角度的中等质量碎片的产额进行了比较.由单举数据推出同位素产额比随靶质量变化的系统性,讨论了N/Z自由度的平衡.     

47MeV/u 12C同133Cs反应碘同位素产额的测定

用放化法测量了47MeV/u ¹²C同¹³³Cs相互作用时碘同位素的产额.发现碘同位素产额分布曲线的峰位在¹²⁴I附近,半宽度为6.5质量单位,最可几产物的质量损失为9.2个质量单位.靶核削裂2个质子的产物¹³¹I的形成截面约0.47—0.87mb,没观察到靶核削裂2个质子,再俘获1个中子的产物¹³²I的活性.     

30MeV/u 40Ar+58,64Ni和115In反应中中等质量碎片的角分布

在5°—140°范围内测量了30MeV/u ⁴⁰Ar束流轰击不同靶核(⁵⁸Ni、⁶⁴Ni、¹¹⁵In)后出射的中等质量碎片(IMF,Z=3—19)的角分布.用指数分布函数dσ/dΩ=N·exp(–θ/α)对出射碎片角分布分角区做了拟合.对3个反应系统分别提取出与相互作用时间有关的衰减因子α和与发射源强度有关的物理量N,讨论了α与N在不同角区与反应系统和出射IMF电荷数的关系.考察了角分布与同位旋自由度和反应系统对称性的关系.     

100,104Sn核在裂变过程中发射的轻粒子多重性

用扩散模型考察了轻的幻核¹⁰⁰Sn在裂变过程中蒸发的轻粒子多重性. 发现壳仅对质子的发射有很强的影响, 而对中子几乎没有影响, 这与¹³²Sn核的情况正好相反. 因此把这种现象归因于系统中质比(N/Z)的影响. 通过比较¹⁰⁴Sn和¹⁰⁰Sn发射的粒子, N/Z的 影响得到了进一步证实. 计算发现高激发能弱化了N/Z效应.     

The 26Mg(14N, 10B)30Si and 26Mg(14N, 11B)29Si reactions

Reactions induced by ¹⁴N on ²⁶Mg at bombarding energies of 60–95 MeV have been studied. Angular distributions for states populated in ²⁹Si by the (¹⁴N, ¹¹B) reaction and in ³⁰Si by the (¹⁴N, ¹⁰B) reaction have been compared with Hauser-Feshbach and DWBA calculations to determine the reaction mechanism and to deduce spectroscopic information. The cross sections for the states populated in ²⁹Si and ³⁰Si are in poor agreement with statistical model calculations, indicating a non-compound nucleus mechanism.     

40Ca+58Fe,58Ni反应中的径向膨胀流研究

利用同位旋相关的Boltzmann-Langevin方程研究了⁴⁰Ca+⁵⁸Fe和⁴⁰Ca+⁵⁸Ni两个反应系统在53,100,150和200MeV/u入射能量下对心碰撞的径向膨胀流.发现对于丰中子系统⁴⁰Ca+⁵⁸Fe的径向膨胀流系统性地小于稳定系统⁴⁰Ca+⁵⁸Ni的径向膨胀流.在假定轰击能量与反应体系的压缩密度呈抛物线关系时,能够解释入射能量和径向膨胀流之间呈现的直线关系.提取了出现径向膨胀流的轰击能量阈值,发现对丰中子系统⁴⁰Ca+⁵⁸Fe得到的能量阈值小于稳定系统⁴⁰Ca+⁵⁸Ni所得到的能量阈值.     

The 12C(18O, α)26Mg and 12C(18O, 8Be)22Ne reaction

Excitation functions for α-emission leading to the ground and first excited states of ²⁶Mg and ⁸Be emission leading to the ground and first and second excited states of ²²Ne have been measured at several forward angles for E_c.m. = 15 to 22.4 MeV. There is little evidence for correlated structure. The angular distribution at 16.5 MeV for the α + ²⁶Mg(g.s.) channel is rather structureless while that for the ⁸Be+²²Ne(g.s.) channel appears to be dominated by a J = 13 contribution. Statistical model calculations indicate that much of the yield for both the α and ⁸Be exit channel is compound nuclear in origin, with some indication of a larger direct contribution for the ⁸Be channel at the lower end of the bombarding energy range.     

Reactions of 40Ar with 159Tb, 142Nd and 144Sm; New α-activities from 189Bi, 173Pt and 177Au

Reactions of ⁴⁰Ar ions with targets of ¹⁵⁹Tb, ¹⁴²Nd, and ¹⁴⁴Sm have been studied at energies below 300 MeV with a helium gas-jet system. Excitation functions for (Ar, xn) reactions, where x = 5–10, were obtained for the radioactive products that decay by α-emission. Based on the characteristics of these excitation functions and on the systematics of α-decay, evidence is presented for the existence of the nuclides ¹⁸⁹Bi with α-particle energy E_α = 6.67±0.01 MeV and half-life < 1.5 sec, and ¹⁷³Pt with E_α = 6.19±0.01 MeV; and for the emission from ¹⁷⁷Au of an α-particle with E_α = 6.15±0.01 MeV.     

Atomic antiproton states in 16O, 18O, 32S, 40Ca, 44Ca and 122Sn

Atomic levels for the systems p? plus ¹⁶O, ¹⁸O, ³²S, ⁴⁰Ca, ⁴⁴Ca and ¹²²Sn are calculated in optical potentials based on the N?N interaction of Dover and Richard.     

Statistical fluctuations and compound elastic scattering for 12C(12C, 12C)12C and 16O(16O, 16O)16O

The difference between the observed fluctuations in the elastic excitation functions for carbon-carbon and oxygen-oxygen scattering, just above the Coulomb barrier, is interpreted in terms of the compound nucleus model.     

15N excitation contribution to 48Ca(16O, 15N)49Sc reaction

The effect of ¹⁵N excitation process is studied in the reaction ⁴⁸Ca(¹⁶O, ¹⁵N)⁴⁹Sc. The excitation process is included into a generalized non-local optical potential for a scattersing ¹⁵N-⁴⁹Sc and is found to be responsible for a shift of a grazing peak in the exact finite-range DWBA calculation.     

Spin assignments from the 142Nd(7Li, 6He)143Pm and 144Sm(7Li, 6He)145Eu reactions at 52 MeV

Angular distributions have been measured for transitions to low-lying states in ¹⁴³Pm and ¹⁴⁵Eu populated by the ¹⁴²Nd(⁷Li, ⁶He)¹⁴³ and the ¹⁴⁴Sm(⁷Li, ⁶He)¹⁴⁵Eu reactions at $\text{E(}{}^7\text{Li}\text{) = 52}$ MeV. Elastic scattering of ⁷Li at 52 MeV on ¹⁴²Nd and ¹⁴⁴Sm, and ⁶Li at 46 MeV on ¹⁴²Nd and at 45 MeV on ¹⁴⁴Sm, were measured. Optical-model parameters extracted from fits to the scattering data were used in a finite-range DWBA analysis of the angular distributions for levels below 1.40 MeV excitation energy in ¹⁴³Pm and 1.84 MeV in ¹⁴⁵Eu. The reaction cross sections forward of 6° c.m. allow unambiguous distinction to be made between 2d_{$\text{5}\text{2}$} and 2d_{$\text{3}\text{2}$} final states. Final-state spins have been assigned to d-states in ¹⁴³Pm at 1.40 MeV($\text{3}\text{2}$⁺)and in ¹⁴⁵Eu at 1.042 MeV ($\text{3}\text{2}$⁺). Existing assignments to other levels in both residual nuclei have been confirmed.     

12C1 and 8Be production in 12C + 208Pb collisions

The mechanisms involved in the production of fast α-particles in ¹²C-induced reactions have been studied for the ¹²C + ²⁰⁸Pb system at the bombarding energies of E_12c = 132, 187 and 230 MeV. Absolute cross sections for the reactions ²⁰⁸Pb(¹²C. ¹²C¹→α + ⁸Be), ²⁰⁸Pb(¹²C, ⁸Be(g.s.)) and ²⁰⁸Pb(¹²C, ⁸Be(2.94 MeV)) have been determined by coincidence measurement of two or three correlated α-particles. Inclusive α-particle production cross sections were also measured at E_12c = 187 MeV. It is found that the inelastic process (¹²C, ¹²C¹→α + ⁸Be) does not contribute significantly to fast α-particle production but that the production of ⁸Be by projectile fragmentation is an important source of α-particles. At the highest bombarding energy (230 MeV) it appears that the ¹²C → 3α fragmentation reaction becomes more prominent at the expense of the ¹²C→α + ⁸Be fragmentation channel.     

12C(7Li,t)16O和20Ne(d,6Li)16O反应的研究

本文把用于处理重离子引起的单粒子转移反应的Goldfarb-Buttle方法推广到多粒子转移反应。计算了¹²C(⁷Li,t)¹⁶O和²⁰Ne(d,⁶Li)¹⁶O反应,用了¹⁶O的全相干波函数,考虑了某些反冲因素,并将结果与实验作了比较。