Cluster molecular structure in neutron-rich nuclei

我们研究了在455 MeV下通过(^7Li，^7Be)电荷交换反应对原子核的异向量激发。大阪大学核物理研究中心的环形回旋加速器提供了一个^7Li^&lt；3+&>束流。我们的研究主要集中在丰中子核的分子结构和由(^7Li，^7Be)电荷交换反应得到的(γ，n)截面。我们得到了两个主要结果。通过测量^7Be粒子与^7Be1的0.43 MeVγ射线符合，(^7Li，^7Be)反应可以提供自旋翻转(ΔS=1)和自旋非翻转(ΔS=0)光谱。^6He、^6Li和^6Be的三核子团簇结构。该结构是由t和/或^3He的三核子团簇组成的类分子结构，是一个二费米子系统。根据测量的衰变粒子的角关联和利用Breit-Wigner公式分析光谱形状，对^1P和^3P共振进行了归属。用(^7Li，^7Be)电荷交换反应推导出光解截面的新途径。我们将该方法应用于^2H(γ，n)和^4He(γ，n)反应。前者表明，利用(^7Li，^7Be)ΔS=1和ΔL=0谱，成功地从类似的B(GT)分布中推导出了用于重离子光解的B(M1)还原矩阵元的分布。后者表明，(^7Li，^7Be)ΔS=0和ΔL=1谱被成功地用来推导出^4He中巨偶极共振的EL光解截面。

We investigated isovector excitations of nuclei via the (^7Li,^7Be) charge exchange reaction at 455 MeV. A ^7Li^<3+> beam was provided from the ring cyclotron of the Research Center for Nuclear Physics, Osaka University. Our research was focused on the molecular structure in neutron-rich nuclei and the (γ,n) cross section deduced with the (^7Li,^7Be) charge exchange reaction. We got tow main results. The (^7Li,^7Be) reaction can provide the spin-flip (ΔS=1) and spin-nonflip (ΔS=0) spectra by measuring the ^7Be particle in coincidence with the 0.43-MeV γ-ray of ^7Be.1. Tri-nucleon cluster structure in ^6He, ^6Li and ^6Be. The structure was found to be a molecular-like structure composed of tri-nucleon clusters of t and/or ^3He, which is a two-fermion system. The ^1P and ^3P resonances were assigned from the measured angular correlations of decay particles and the analysis of the spectral shape by using the Breit-Wigner formula.2. A new approach to the photodisintegration cross section deduced with the (^7Li,^7Be) charge exchange reaction. We applied the method to the ^2H(γ,n) and ^4He(γ,n) reaction. The former showed that the (^7Li,^7Be) ΔS=1 and ΔL=0 spectrum was successfully used to deduce the distribution of the B(M1) reduced matrix elements for the photodisintegration of deuteron from the analogous B(GT) distribution. The latter showed that the (^7Li,^7Be) ΔS=0 and ΔL=1 spectrum was successfully used to deduce the El photodisintegration cross section for the giant dipole resonance in ^4He.