弱束缚弹核引起的熔合反应

⁶Li, ⁹Be为弱束缚核. 通过弱束缚弹核⁶Li, ⁹Be轰击靶²⁰⁸Pb,²⁰⁸Be的实验熔合激发函数与理论预言的比较, 讨论了弱束缚弹核破裂对熔合过程 的影响. 比较结果显示, 弱束缚弹核与重靶核的完全熔合截面在垒上能区 明显压低. 由部分熔合截面与完全熔合截面之和得到总熔合截面. 研究结果 表明, 破裂对总熔合截面几乎没有影响. 由此可见, 弱束缚核的部分熔合 可能发生在强吸收区域附近. 最后还给出了全熔合截面与部分熔合截面 之间的关系.     

Decay Analysis of Ge Isotopes Formed in Reactions Induced by Tightly and Loosely Bound Projectiles

The dynamical cluster-decay model (DCM) is employed to investigate the decay of ^68,70Ge^* compound nuclei formed respectively via tightly (⁴He) and loosely (⁶He) bound projectiles, using ⁶⁴Zn target. The study is carried out over a wide energy range (E_c.m.~5 MeV to 16 MeV) by including the quadrupole deformations (β2i) and optimum orientations (θ_i^opt) of the decaying fragments. The fusion cross-sections, obtained by adding various evaporation channels show nice agreement with the experimental data for ⁴He+⁶⁴Zn reaction. The contribution from competing compound inelastic scattering channel is also analyzed particularly for ⁶⁸Ge^* nucleus at above barrier energies. On the other hand, the decrement in the fusion cross-sections of ⁷⁰Ge^* nuclear system is addressed by presuming that ⁶⁵Zn ER is formed via two different modes:(i) the αn evaporation of ⁷⁰Ge^* nucleus, and (ii) 1n-evaporation of ⁶⁶Zn^* nuclear system, formed via breakup and 2n-transfer channels due to halo structure of the ⁶He projectile. Besides this, the suppression in 2np evaporation cross-sections suggests the contribution of another breakup and transfer process of ⁶He i.e. ⁴He+⁶⁴Zn. The contribution of breakup+transfer channels for ⁶He+⁶⁴Zn reaction is duly addressed by applying relevant energy corrections due to the breakup of " ⁶He" projectile into 2n and ⁴He. In addition to this, the barrier lowering, angular momentum and energy dependence effects are also explored in view of the dynamics of chosen reactions.     

Survey of deep sub-barrier heavy-ion fusion hindrance phenomenon forpositive and negative Q-value systems using the proximity-type potential

A systematic survey of the accurate measurements of heavy-ion fusion cross sections at extreme sub-barrier energies is performed using the coupled-channels (CC) theory that is based on the proximity formalism. This work theoretically explores the role of the surface energy coefficient and energy-dependent nucleus-nucleus proximity potential in the mechanism of the fusion hindrance of 14 typical colliding systems with negative \begin{document}$Q$\end{document}-values, including ¹¹B+¹⁹⁷Au, ¹²C+¹⁹⁸Pt, ¹⁶O+²⁰⁸Pb, ²⁸Si+⁹⁴Mo, ⁴⁸Ca+⁹⁶Zr, ²⁸Si+⁶⁴Ni, ⁵⁸Ni+⁵⁸Ni, ⁶⁰Ni+⁸⁹Y, ¹²C+²⁰⁴Pb, ³⁶S+⁶⁴Ni, ³⁶S+⁹⁰Zr, ⁴⁰Ca+⁹⁰Zr, ⁴⁰Ca+⁴⁰Ca, and ⁴⁸Ca+⁴⁸Ca, as well as five typical colliding systems with positive \begin{document}$Q$\end{document}-values, including ¹²C+³⁰Si, ²⁴Mg+³⁰Si, ²⁸Si+³⁰Si, ³⁶S+⁴⁸Ca, and ⁴⁰Ca+⁴⁸Ca. It is shown that the outcomes based on the proximity potential along with the above-mentioned physical effects achieve reasonable agreement with the experimentally observed data of the fusion cross sections \begin{document}$\sigma_{\rm{fus}}(E)$\end{document}, astrophysical \begin{document}$S(E)$\end{document} factors, and logarithmic derivatives \begin{document}$L(E)$\end{document} in the energy region far below the Coulomb barrier. A discussion is also presented on the performance of the present theoretical approach in reproducing the experimental fusion barrier distributions for different colliding systems.     

基于双核模型的粒子交换势能面与熔合几率的研究(英文)

研究了基于双核模型的粒子交换势能面.原子核的形变效应对于势能面的形状有较大的影响.在反应过程中,作为反应时间函数的动态形变的变化是显著的.通过求解主方程,对一些基于冷熔合机制的反应道的全熔合几率也进行了讨论. The Potential Energy Surface (PES) for particle exchange in Di nuclear system is studied in detail. It is found that the nuclear deformation effect can change the shape of PES significantly. The dynamical deformation as a function of the reaction time in the reaction process is investigated in a simple model and we found that its variation with time is dramatic. The fusion probabilities P-CN of some reaction channels based on the mechanism of cold fusion are also calculated.     

库仑场中束缚光学极化子的温度效应

采用线性组合算符和幺正变换方法研究强弱耦合情形下,库仑场中束缚光学极化子的基态能量、振动频率和平均声子数与温度的关系。对RbCl晶体进行数值计算,结果表明：在强耦合情形下,库仑场中束缚光学极化子的基态能量的绝对值随温度的升高而增大,振动频率、平均声子数随温度升高也增大。     

磁场和温度对束缚磁极化子有效质量的影响

研究强、弱耦合情形下,库仑场中束缚磁极化子的性质.采用改进的线性组合算符方法研究束缚磁极化子的振动频率和有效质量的温度依赖性,对RbCl晶体进行数值计算,结果表明:在强耦合情形下,束缚磁极化子的振动频率随温度的升高和磁场的增强而增加;有效质量随温度的增加而增加,但随磁场的增强而减少.     

温度对抛物量子点中弱耦合束缚磁极化子的影响

采用线性组合算符和幺正变换方法研究温度对量子点中弱耦合束缚磁极化子性质的影响,导出了弱耦合束缚磁极化子的振动频率、基态能量和声子平均数随温度的变化关系。取CdTe晶体为例进行数值计算,结果表明:弱耦合束缚磁极化子的振动频率、基态能量和声子平均数随温度的升高而增大,基态能量随量子点的受限强度的增强而迅速增大。     

量子点中束缚极化子性质的温度依赖性

采用线性组合算符和幺正变换方法研究抛物量子点中弱耦合束缚极化子性质的温度依赖性,导出了弱耦合束缚极化子的振动频率、基态能量和声子平均数随温度的变化关系。取ZnS晶体为例进行数值计算,结果表明:量子点中弱耦合束缚极化子的振动频率、基态能量和声子平均数随温度的升高而增大。     

Ar2-Ne聚合物的三维势能面和束缚态

使用单双激发并对三重激发作微扰处理的耦合簇方法计算了Ar₂-Ne聚合物的三维势能面. 使用的基组是aug-cc-pVqz并包括3s3p2d2f1g中点键函数. 用二维模型势对7个Ar₂键长值的每一个对应的二维格点(R,θ)上的能量进行了拟合. 再将7个二维模型势通过对(r—re) 的六次多项式内插得到三维势能面,并用于随后的振转能级计算,所得到的跃迁频率、光谱常数等与相应的实验结果进行了比较.     

An Isoratio Method to Study Free Energy and Temperature Effects in Intermediate Mass Fragments Produced in Heavy-Ion Collisions

An isoratio method, i.e., the isotopic (isotonic) ratio among three isotopes (isotones), is proposed to study the free energy and temperature effects in the intermediate mass fragments produced in heavy-ion collisions. The parameterizations for the free energy of nucleus at low temperature, which have been proposed in the framework of the density functional theory using the SKM skymre interaction, are adopted to calculate the temperature-dependent free energy of fragment. By analyzing the measured yields of fragments in the 140A MeV ^58,64Ni + ⁹Be reactions, it is verified that the free energy in the isoratio is almost the same for different reactions. A temperature-dependent pairing-energy is introduced into the parameterizations for free energy, which reveals that the weakened pairing energy at the low temperature accounts for the weakened or disappearing odd-even staggering in isoratio.     

线型分子势能函数及第二维里系数计算

本文以两中心的Lennard—Jones（2CLJ）流体为研究对象,通过引入与温度相关的势能参数,提出了改进型的2CLJDQP势能函数模型。应用此模型计算了乙烷（C2H6）、六氟乙烷（C2F6）、氟甲烷（CH3F）、氯甲烷（CH3C1）、1,1,1-三氟乙烷（CH3CF3）、二氟乙烷（CH3CHF2）的第二维里系数,较...     

Asphericity in the Fermi Surface and Fermi Energy of Na-K, Na-Rb and Na-Cs Binary Alloys

Detailed theoretical investigations into asphericity in the Fermi surface (FS) and Fermi energy (FE) ofNa1_xKx, Na1_xRbx, and Na1_xCsx binary solid solutions are carried out for the first time. The alloying behavior ofthe K, Rb, and Cs with the Na generates the Fermi surface distortion (FSD) of bce simple metals. The FS of Na-K,Na-Rb, and Na-Cs solid solution is a distorted sphere with the largest deviation along [110]. We have found that theimpact of local-field correction function on FSD is maximun at [100] point and minimum at [111] point. The exchangeand correlation effect is found to suppress the value of FE.     

抛物量子阱中束缚极化子的极化势和结合能

利用改进的Lee-Low-Pines(LLP)方法,用变分法计算了无限深抛物量子阱中同时考虑与体纵光学声子和界面纵光学声子相互作用的束缚极化子的极化势和结合能.数值计算得出:阱宽较大时极化势很小,阱宽较小时极化势较大,所以对于较窄的抛物阱必须考虑极化势.对于给定阱宽的抛物阱,随着远离阱中心极化势迅速减小,当到达阱的界面附近极化势又开始增大.阱宽较小时,束缚极化子的结合能随着阱宽L的增大而急剧减小;阱宽较大时,结合能减小的非常缓慢,最后接近体材料中的三维值.     

低能重离子诱导反应中轻带电粒子和蒸发剩余物的能谱(英文)

在多源理想气体模型的框架内, 用一个关于末态粒子多重数分布的统一描述, 研究了低能重离子诱导反应中轻带电粒子和蒸发剩余物的能谱。 在同一个激发的复合核中, 每个源对带电粒子和蒸发剩余物均贡献一个指数分布的能谱。 计算结果与158, 170, 180 和 200 MeV 20Ne+12C 反应中, 轻带电粒子和蒸发剩余物能谱的实验结果符合。     

高能诱导核反应中的核碰撞几何与末态粒子的间歇行为

考虑到核碰撞几何,我们推导出高能诱发核反应中二阶阶乘矩与参加反应核子数涨落之间的关系.分析表明,在高能碰撞的射弹碎裂区,强子-核反应末态粒子的间歇性质决定于其强子-强子子过程的间歇特征;而在靶碎裂区,它却主要依赖于参加反应核子数的涨落.推广到核-核反应(B<相似文献   

量热式激光能量计内外表面温差对测量结果的影响

从理论上研究了量热式激光能量计激光照射过程中和激光照射后内外表面温度时间关系．编制了计算机程序计算得到激光照射时间内以及激光停止照射后内外表面温度关系曲线．通过稳定的高温温度场加热试验件模拟激光照射量热式激光能量计内外表面温度的升温过程，通过迅速将试验件移离高温温度场模拟激光停止照射后量热式能量计内外表面温度的变化，并测量了量热式能量内外表面温度时间曲线．实验和理论研究结果相符，结果表明激光停止照射后，内外表面温度迅速趋近，由此引入的测量不确定度小于0．25％．     

Intermediate Energy Reactions Versus Heavy-Ion Fusion: Light Particle Emission and Post-Saddle Friction in the Presence of Deformation Effects *

A decaying nucleus undergoes a change in deformation when it fissions. This affects the particle emission in the fission process. Using the dynamical Langevin model, we investigate the role of deformation in the sensitivity of post-saddle neutrons and light charged particles (LCPs) to the post-saddle friction strength ($beta$) for heavy nuclei $^{240}$Am produced with different initial conditions: (i) a low excitation energy $E^*$ and a large spin $ell$ (provided via a fusion mechanism) and (ii) a high $E^*$ and a large $ell$ as well as a higher $E^*$ but a small $ell$ (provided in peripheral and near-central intermediate energy heavy-ion reactions, respectively). It is shown that deformation obviously enhances the sensitivity of post-saddle neutrons to $beta$ at intermediate-energy peripheral collisions and that for case (i), the drop of LCPs emission due to deformation makes post-saddle LCPs to be almost insensitive to $beta$, but for case (ii) LCPs still have a significant change with $beta$. Furthermore, we find that post-saddle LCPs display a greater sensitivity to $beta$ for near-central collisions than for peripheral collisions. These results suggest that given the deformation effects, to better probe post-saddle dissipation properties with neutrons (LCPs) in experiments, it is best to choose those excited heavy nuclear systems populated in peripheral (near-central) collisions at intermediate energies.     

35MeV/u 40Ar+197Au反应中复合核的激发能与温度

利用大面积位置灵敏气体探测器对35MeV/u ⁴⁰Ar+¹⁹⁷Au反应中形成的裂片进行了符合测量,由此得到了裂变复合核的速度分布.在大质量转移假设下扣除前平衡发射粒子的影响,得到复合核的激发能.另外利用望远镜探测器对反应中出射的轻带电粒子也进行了符合测量,并由后角α,p,d,t的能谱提取了复合核的温度.温度与激发能的关系没有表现出理论预言的相变特征.     

表面极化子光学声子平均数的磁场和温度依赖性

采用变分法、幺正变换和拉格朗日乘子法,研究了有限温度下纯二维晶体中表面磁极化子的性质.讨论了表面光学声子平均数、磁极化子振动频率λ与磁场B、温度T及Lsgrange乘子u之间的关系.对KCl晶体进行了数值计算,结果表明:磁极化子振动频率、表面光学声子平均数均随磁场B的增强而增加,且随温度T升高而增加.当bgrange乘子u超出慢电子范围时磁极化子振动频率、表面光学声子平均数均随u增加而增大且变化越来越显著.