28.7MeV/u的 14，16，18 O+7，9Be反应中的同位素分布研究

用同位旋相关的Boltzmann-Langevin方程研究了在入射能量为28.7MeV/u下,不同弹核^14O,^16O和^18O轰击不同靶核^7Be和^9Be的反应,计算了生成碎片的产生截面,发现用丰中子（缺中子）炮弹或丰中子（缺中子）靶进行反应,所得到的产物均有丰中子（缺中子）的碎片出现。同位素分布宽度和峰位与入射体系密切相关,产生碎片的电荷数越接近入射弹核的电荷数,则同位素分布的宽度越大,峰位偏离β稳定线值越远,其同位旋效应越明显。。     

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.     

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.     

30MeV/u 40Ar+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^6Ni/^7Li的产额比随角度的增加而增加,^6He/^4He和^8Li/^7Li随角度的增加而减少,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。     

40 Ca+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53,100,1506 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,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。     

35MeV/u 36,40Ar+112,124Sn反应中同位旋自由度的弛豫

35MeV/u ^36,40Ar+^112,124Sn反应中,在前角5°和20°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20°处却表现出明显的靶核相关性.     

35MeV/u 40Ar+112Sn/124Sn反应中热核的同位旋对热核发射机制的影响

作为放射性束物理的延伸,热核的同位旋效应引起了理论和实验研究的广泛重视.给出35MeV/u ⁴⁰Ar+¹¹²Sn/¹²⁴Sn实验中,热核的同位旋对热核衰变出射道机制的影响:由于库仑不稳定性和库仑力作用,丰质子热核达到系统平衡前,很容易出现大量有利于增加余核中质比的高能粒子出射(如p.3He、a等);该类轻粒子在热核的衰变链中发射几率较大而且衰变链很长.这样,传统的热核测量量(如能谱斜率温度)将受到测量粒子种类的较大影响.     

25MeV/u6He+9Be反应的轻粒子发射

在25MeV/u ⁶He与⁹Be靶的反应中,107°和128°处明显地观察到了轻粒子发射.粒子能谱形状与平衡热源蒸发相一致,分析得到热源的核温度为完全熔合条件下的5.6MeV或非完全熔合条件下的5.2MeV .实验发现发射氚的数量特别大,这可能与目前广泛研究的⁶He的集团结构和同位旋效应有关.     

30MeV/u 40Ar+ 112,124Sn反应中态布居核温度的同位旋效应

用13单元望远镜探测器阵列测量了30MeV/u ⁴⁰Ar +^112,124Sn反应中小角关联粒子,由两体符合事件提取了αα关联函数.用三体弹道理论模型MENEKA计算本底关联函数,用Monte Carlo方法计算探测效率函数,在扣除本底产额并考虑探测效率的修正后,对不同同位旋反应系统⁴⁰Ar +¹¹²Sn和⁴⁰Ar+¹²⁴Sn提取的相对态布居核温度分别是4.18±0.25 0.21MeV和4.10±0.22 0.20MeV ;考察态布居核温度和粒子能量的关系时,观察到两个系统的发射温度均随着粒子能量的增加而降低,缺中子系统⁴⁰Ar +¹¹²Sn中由低能时的5.13±0.30 0.2 6MeV降低到高能时的3.87±0.37 0.29MeV ,丰中子系统⁴⁰Ar+¹²⁴Sn中由低能时的5.39±0.30 0.26MeV降低到高能时的3.32±0.28 0.23MeV .用激发热核衰变过程的同位旋选择性对这种同位旋相关性进行了解释.     

同位旋相关的Boltzmann-Langevin方程及新核素19Na产生截面的研究

介绍了一种同位旋相关的输运方程,研究了在入射能量为28.7和6 0. 0MeV/u时 12C+ 12C的反应,对模型进行检验,发现计算结果较好地符合实验结果,说明了方程的可靠性. 利用该模型研究了在入射能量为28.7MeV/u下反应系统 17 -20,22Ne+ 12C中核素 19Na的产生截面,发现缺中子核引起的反应,具有更大 19Na的产生截面,为新核素的探测找到了理论依据.     

p+56Fe散裂反应中同位素产生截面的规律现象

提出一个经验公式,预测散裂反应中同位素产生的截面值,并且利用现有GSI-FRS实验测量的300,500,750,1 000和1 500 MeV/u能量下p+56Fe散裂反应产物的实验结果进行验证。发现此经验公式预测的同位素截面值与实验值的符合度比较好,但随着质量数与能量的改变,同位素产生截面的计算值与实验值的差距也在变大。通过引入质量与能量修正可使此经验公式计算出的同位素截面值的精确度更高,与实验值的符合程度更好。An empirical formula is proposed to predict the isotopic cross section in spallation reactions. The measured fragments in the 300, 500, 750, 1 000 and 1 500 MeV/u p+56Fe spallation reactions have been adopted to perform the analysis. The cross sections of isotopes predicted by the proposed empirical formula have been compared to the experimental results, which shows that the empirical formula can predict the results well. But with the change of the mass and incident energy, the difference between the calculated results and experimental data is larger. The proposed empirical formula is found to predict the isotopic cross sections better, by incorporating the incident energy and mass dependents of fragments.     

Scattering and reactions of 14C + 14C and 14C + 14C

We have studied elastic scattering, inelastic scattering and several transfer channels of the systems ¹⁴C + ¹⁴C and ¹⁴C + ¹²C over a wide range of energies up to E_c.m. = 35 eMeV and 32 MeV, respectively. The reaction channels were identified by means of kinematic coincidences between solid-state detectors, γγ coincidences were measured to determine cross sections for mutual inelastic scattering of ¹⁴C + ¹⁴C.Pronounced regular gross structures, similar to those found for ¹⁶O + ¹⁶O, are observed in the elastic excitation function of ¹⁴C + ¹⁴C at θ_c.m. = 90°, The angular distributions measured at the energies of the maxima and an optical-model analysis suggest that one or a few surface partial waves dominate the scattering behaviour. Correlated structure of narrower width is found in the inelastic channels and, to a lesser degree, in the transfer channels which appear with rather small cross sections.In ¹⁴C + ¹²C elastic scattering the gross structures are strongly fragmented, in contrast to ¹⁴C + ¹⁴C but similar to ¹²C + ¹²C. While the ¹²C(2⁺) excitation is very weak, the observed strengths of the ¹⁴C(3^?) excitation and of neutron transfer point to a substantial role of these channels as coupling partners to the elastic configuration and to their influence on the elastic scattering behaviour. A correlated intermediate structure is observed near 23.5 MeV, where a dominance of l = 18 is suggested by the elastic scattering angular distribution. This unexpectedly high l-value exceeds l_graz at this energy by at least two units of ?.     

On the decay of the photo resonance in 14N and 14C nuclei

The decay of the photo resonances in ¹⁴N and ¹⁴C nuclei is analyzed in terms of the shell model with intermediate coupling. Cross sections and branching ratios of nucleon channels are compared with experimental data. Successive decay branches are estimated.     

Charge exchange reaction 14C(6Li, 6He)14N

Angular distributions of the charge exchange reaction ¹⁴C(⁶Li, ⁶He)¹⁴N leading to the 1⁺ ground state and 3.95 MeV 1⁺, and 5.20 MeV 2^? excited states at the 34 MeV incident beam energy were analyzed and measured. The 62 MeV data of Goodman et al. were also reanalyzed. The direct one-step charge exchange caused by the spin-isospin dependent term in the two-body interaction can account well for the observed data. The strength of spin-isospin dependent effective interaction (gaussian form with a range parameter of 1.8 fm) was extracted to be 18.5 MeV.     

Reactions of 14N and 16O ions with light nuclei at Elab = 16–58 MeV

Yield curves for formation of ⁷Be and other radio-nuclides from bombardment of C, Al and Si targets with 16–58 MeV ¹⁴N and ¹⁶O ions were measured. The ⁷Be yields disagree by several orders of magnitude with Hauser-Feshbach and transition-state predictions. The other yields are in order-of-magnitude agreement with nucleon and/or α-particle evapolation calculations.     

Energy levels of 14C

The ⁹Be (⁶Li, p)¹⁴C reaction has been studied using 20 MeV ⁶Li ions and the Penn multiangle spectrograph. Proton groups are reported corresponding to thirty excited states of ¹⁴C with E_x < 18.2 MeV. The total cross section for formation of the six bound excited states, whose J^π are known, is proportional to 2J_f + 1. Possible new spin assignments are suggested for several unbound levels of ¹⁴C, based on the 2J_f + 1 rule and a comparison of the experimental widths and widths predicted from neutron penetration of a centrifugal barrier.     

热熔合反应合成超重核产生截面的同位素依赖性

通过在形成超重核的重离子俘获和熔合过程中引入位垒分布函数的方法对双核模型做了进一步发展. 超重核形成过程中的俘获、熔合和蒸发3个阶段分别采用了半经验的耦合道模型、数值求解主方程和统计蒸发模型的方法来描述. 计算了近年来Dubna小组利用热熔合反应⁴⁸Ca(²⁴³Am, 3n—5n)^288—286115和⁴⁸Ca(²⁴⁸Cm, 3n—5n)^293—291116合成超重新核素的蒸发余核激发函数. 系统分析了⁴⁸Ca轰击锕系元素U,Np,Pu,Am,Cm合成超重核Z=112—116产生截面的同位素依赖性. 给出了合成超重新核素最佳的弹靶组合和入射能量, 即有最大的超重核产生截面. 计算说明, 壳修正能和中子分离能是影响超重核生成截面产生同位素依赖性的主要因素.     

A study of 14N using the 13C(d,n)14N reaction

Absolute differential cross sections for the ¹³C(d, n)¹⁴N reaction were measured at deuteron bombarding energies of 4.5, 5.0 and 5.5 MeV. Spectroscopic factors and statistical compound-nucleus contributions are obtained by treating the observed cross sections as an incoherent sum of distorted-wave Born approximation and compound-nucleus contributions. Energy-averaged spectroscopic factors are derived. An anomaly is observed in the yield for the 2.313 MeV T= 1 state.     

The reaction 14C(6Li, 6He)14N and the distribution of Gamow-Teller strength

We find that the correlation between the L=0 component of the (⁶Li, ⁶He) reaction and the GT matrix element holds down to a very low level of GT strength, and that essentially all (90%) of the GT strength lies in the 3.95 MeV state of ¹⁴N.