25MeV/u 6He在9Be靶上的弹性转移反应研究

报告了25MeV/u ⁶He在⁹Be靶上的弹性散射和弹性转移的实验结果. 用光学模型和一阶DWBA的方法计算了弹性散射和³He集团转移的截面, 计算结果和实验测量基本一致. 计算表明³He在⁹Be中的谱幅度应该明显大于壳模型的理论计算值0.70.     

16O+152Sm、184W准弹和弹性散射的位垒分布

利用¹⁶O束流轰击稳定形变靶¹⁵²Sm和¹⁸⁴W,在背角测量准弹散射和弹性散射激发函数,分别定出准弹和弹性位垒分布D^qel(E)和D^el(E).将结果与从已有的熔合激发函数、自旋分布及其相邻同位素¹⁵⁴Sm和¹⁸⁴W实验得出的位垒分布进行比较,得到相互自洽的结果,同时也用ECIS79程序作了耦合道理论计算.实验表明,靶的变形效应导致位垒分布是非对称的.     

16O+94Zr和16O+116Sn的弹性散射角分布测量

用北京Q3D磁谱仪及其重离子焦面探测器系统测量了两个体系的14个弹性散射角分布,即¹⁶O+⁹⁴Zr体系在52,57,59,62,72,82和92MeV 7个能量点及¹⁶O+¹¹⁶Sn体系在57,59,62,67,72,82和92MeV 7个能量点的弹性散射角分布.用耦合道理论的ECIS计算程序拟合数据,初步观察到了“阈反常”现象.     

89Y(α,p)92Zr反应中的核芯激发和全微观理论分析

测量了⁸⁹Y(α,p)⁹²Zr反应的基态和几个激发态的微分截面及⁸⁹Y(α,α)⁸⁹Y弹性散射微分截面.利用⁸⁹Y、⁹²Zr的壳模型波函数对该反应基态和第一激发态的实验数据进行了完全微观DWBA理论分析.具有核芯激发组态的核波函数明显地改善了不同末态的截面相对强度,而对角分布的形状影响甚微.它表明具有核芯激发组态的⁸⁹Y、⁹²Zr核波函数有较好的实验基础.最后,讨论了⁸⁹Y(α,p)⁹²Zr反应的截面绝对值问题,揭示了α浅势阱的重要性.     

16O+24Mg熔合激发函数和深光学势

基于重离子碰撞中势共振的考虑,在光学模型的框架下,使用深光学势研究了¹⁶O+²⁴Mg全熔合激发函数中所呈现的粗共振结构和弹性散射角分布后角振荡上升的现象,并与核分子轨道模型的计算结果作了比较,对产生粗共振结构的原因进行了讨论.     

近垒及垒下12C+93Nb的蒸发剩余核截面

使用离线γ测量技术在实验室系28.3MeV至45.7MeV的能区首次测量了¹²C+⁹³Nb反应产生的8个核素及同质异能态的激发函数.使用包括非弹性激发和α转移道的简单耦合道模型,结合统计蒸发程序对实验结果进行拟合.计算结果能较好地重现强截面的中子蒸发道(xn)的激发函数.而对于弱的质子(xpyn)特别是α粒子(xαyn)蒸发道的截面,实验测量明显高于模型计算结果.α转移道与入射道耦合作为熔合反应的门庭态使垒下能区重离子熔合截面有很大的加强,实验测量与理论计算的比较表明对于¹²C+⁹³Nb反应系统在垒下能区可能存在着很强的α转移截面.     

核子与镜象核3H和3He弹性散射中电荷对称破环效应

采用微观的动量空间光学势及R.Crespo和J.A.Tostevin建议的处理动量空间库仑作用的方法,计算了500MeV的核子与镜象核³H和³He弹性散射微分截面,截面比r₁,r₂和超比R.理论计算结果r₁,r₂和R均不等于1,显示出由于p–核库仑作用直接引起的电荷对称破坏效应.     

22MeV质子在28Si上弹性及非弹性散射微观分析

通过22MeV质子与²⁸Si的散射实验,测量了质子弹性散射和在21+(1.78MeV)及41+(4.62MeV)激发态上的非弹性散射微分截面.采用动量空间DWBA理论,利用由电子散射实验得到的核结构信息,和低能区的密度依赖、能量依赖的复数有效相互作用对数据进行了分析.在没有任何可调参数和归一因子的情况下,理论计算与实验数据的符合情况是令人满意的.     

12C快中子辐射俘获反应中的共振现象

主要研究中子辐射俘获反应中的共振现象,利用DSD模型计算激发能量在5—25MeV能区的¹²C(n,γ0)反应截面与E_n=9MeV时的角分布.所考虑的反应机制包括复合核俘获、直接和半直接俘获、复弹性和非弹性散射道的辐射俘获.计算表明,矮共振的峰值在激发能量为13MeV处;巨共振的峰值位置在激发能量21MeV处.计算结果与实验符合较好.     

9Be超核的三体动力学

用α-α-Λ三集团模型和谐振子乘积态为基的展开方法,计算了⁹Be直到15MeV激发能的能谱.通过计算L^π=0⁺,2⁺,1^－三个态的形状密度,确定了⁹Be处于上述三个态时的几何结构.并根据能谱的耦合特征和几何结构对能谱进行了K分类.     

Elastic and inelastic scattering of 16O and 12C by 24Mg near the Coulomb barrier

Angular distributions for ¹⁶O + ²⁴Mg and ¹²C + ²⁴Mg elastic and inelastic (2⁺, 1.37 MeV state in ²⁴Mg) scattering have been measured at energies spanning the Coulomb barrier. Apart from the structure typical of strong destructive Coulomb-nuclear interference, the data exhibit some additional specific features. Coupled channel calculations were performed, along with DWBA calculations to analyse the data using fixed coupling strengths deduced from the results of Coulomb excitation work. The importance of higher-order effects such as reorientation, is demonstrated.     

Atom-surface interaction in inelastic scattering: He/Ag(111)

The amplitude of inelastic He scattering from Rayleigh waves on a Ag(111) surface is calculated in the framework of the distorted wave Born approximation (DWBA) for a two-body exponential potential. Using the potential parameters recently obtained by Bortolani et al. from a quantum mechanical calculation, agreement is obtained with the experimental data. Simple explicit formulas are presented both in the DWBA and in the eikonal approximation. The essential factor in both cases describes an approximate exponential decay of the intensity for increasing parallel momentum transfer.     

Inelastic processes in the 19F(3He,d)20Ne reaction

We have examined the role of inelastic processes in the ¹⁹F(³He, d)²⁰Ne reaction. By coupling three levels in both the entrance and exit channels it was found that the inelastic processes were able to account for both the magnitude and rather flat shape of the angular distribution for the 4.25 MeV 4⁺ level observed in the ¹⁹F(³He, d)²⁰Ne reaction at 16 MeV bombarding energy. In contrast the DWBA could not account for the data. The magnitude of the inelastic processes was found to be quite sensitive to some of the optical model parameters involved. The DWBA predictions for the 0⁺ and 2⁺ cross sections were modified by the inelastic processes requiring some adjustment of the spectroscopic amplitudes to account for the data.     

Microscopic (p,p′) calculations and polarization charges with large basis shell-model wave functions

Techniques have been developed for performing microscopic model DWBA calculations of inelastic nucleon-nucleus scattering using large basis shell-model wave functions to describe the nuclear states involved. For the case of ¹³⁸Ba at a bombarding energy of 30 MeV, we obtain good fits to the data by including the exchange amplitude in the DWBA and assuming a state and multipole independent polarization charge.     

Coulomb-nuclear interference in the scattering of 3He and α-particles by 122,124Te, 124Sn and 114Cd

Angular distributions and excitation functions of the elastic and inelastic scattering of ³He and α-particles by ^122,124Te, ¹²⁴Sn and ¹¹⁴Cd at incident energies around the Coulomb barrier were measured. The experimental results were analyzed in the framework of the optical model and DWBA taking into account the interference between nuclear and Coulomb excitation. Nuclear and charge deformation parameters were deduced.     

Nuclear rainbow in the O + AL system: The role of couplings at energies far above the barrier

High precision elastic and inelastic angular distributions have been measured for the ¹⁶O + ²⁷Al system at a beam energy of 100 MeV. The data analysis confirms a rainbow formation as already predicted by parameter-free Coupled Channel calculations. It also helps to reveal the crucial role of inelastic couplings in the rainbow formation for heavier systems even at energies far above the Coulomb barrier. This feature, well known in atomic/molecular scattering, is experimentally studied for the first time in Nuclear Physics.     

Hexadecapole deformation studies in<Superscript>148,150</Superscript>Nd

Theγ-ray yields from inelastically excited 2⁺ and 4⁺ levels of^{144,146,148,150}Nd nuclei using¹⁶O beam at near barrier energies in coincidence with the back-scattered projectiles were measured. The 2⁺ and 4⁺ level cross-sections were deduced from the measuredγ-ray yields and fitted to the DWBA calculations to obtain the reduced transition matrix elementsM(E4: 0⁺ → 4⁺). The deducedM(E4) values for¹⁴⁸Nd and¹⁵⁰Nd nuclei, 0.16(0.05) and 0.22(0.12) eb², respectively are consistent with theoretical predictions.     

非对称同位素替代分子HD、HT和DT分子与氦原子(E=0.1 eV) 碰撞角分布计算

当入射氦原子能量E=0.1 eV时,用密耦方程(Close Coupling Equation)计算非对称同位素替代分子HD、DH-He碰撞的弹性和非弹性散射的角分布.