Investigation Of Structure And Properties Of Be Isotopes From Clustering Picture

In nuclear physics,a lot of theoretical models are developed to understand the struc-ture and properties of nuclei,such as the liquid drop model,Fermi gas model,shell model,etc.Among these models,the cluster model has special advantages in describ-ing the movement of nucleons and plays an important role in understanding the structure and properties of nuclei.However,not much attention has been devoted to the clus-ter models for a long time.Recently,with the discovery of important properties of the clusters in nuclei,the cluster model has become a hot topic again.The Tohsaki-Horiuchi-Schuck-Ropke(THSR)wave function which is based on the non-localised clustering picture,is one of the most successful cluster models[A.Tohsaki et al.,Phys.Rev.Lett.87,192501(2001)].It also provides a good description of the ?-cluster structure in the na nuclei.However,the N?Z nuclei are more common in nuclear physics and have various properties.Thus,we develop models to extend the THSR wave function to these N?Z nuclei.In this paper,we first extend the nonlocalised clustering model and the correspond-ing THSR wave function into the N = Z + 1 nuclei.We establish an extended THSR wave function describing both the ?-clusters and the extra neutron based on the Brink wave function.In this extended THSR wave function,a phase factor eim?R is introduced to obtain an intrinsic negative parity,which makes it very suitable for the study of the ground state of 9Be and its rotational bands with negative parity.We calculate physical properties of the 3/2-ground state of 9Be and its rotational bands.The calculated binding energy agrees very well with the results from the Brink+GCM(Generating Coordinate Method)technique and the molecular orbit model.The calculated excitation energy also fits the experimental value.For all these states in the rotational band,the squared overlaps between the extended THSR wave function and the wave function from Brink+ GCM technique are found to be nearly 96%.This shows that the extended THSR wave function is a good description of the 3/2-ground state of 9Be and its rotational bands.We also calculated the root-mean-square radius of the ground state of 9Be,which agrees with the experimental value.Furthermore,by showing the density distribution of the ground state of 9Be,we found that the ?-orbit structure is naturally reproduced by using this THSR wave func-tion.This reproduction of nuclear molecular orbit structure provides support for our extension of the nonlocalized clustering concept to N ? Z nuclei,and shows the flex-ibility and the potential of this wave function in describing different nuclear structure.Our calculation and analysis also show that the geometric structure between a-clusters and nucleons in nucleus can be determined only by the kinematic reasons,which is a new concept in nuclear cluster models.By putting two extra neutrons of 10Be nucleus in a separate container,we introduce the neutron-neutron correlation in the THSR wave function.This wave function is able to describe the independent motion,paring motion and mixed motion of the two extra neutrons in the 10Be nucleus.With this wave function,we calculate the properties and structure of the 0+ ground state and its rotational band and a 0+ excited state of 10Be.By the calculations of the ground state,we obtain bound energies which fit the experimental values.The excitation energy of the excited states in this band also fits very well with experiments.We also calculate another 0+ excited state of 10Be with parameter m set to be m = 0.The bound energy obtained for this state nears the experimental value for the 02+ state observed.By comparing the THSR wave function with independent particle approximation and the correlated THSR wave function,we prove that the ground state of 10Be can be better described by taking into account of the correlation between extra neutrons.We also calculated the contour map of the energy surface of the binding energy of the 0+ground state and the 0+ excited state of 10Be with the correlated THSR wave function in its parameter space.The analysis of the calculation results show that correlation weekly exists in the ground state while plays an important role for the 0+ excited state where the extra neutrons occupy the s state.These calculations indicate that with the non-localised concept and the container model,the correlation THSR wave function can naturally describe the motion of a-clusters and two extra neutrons in 10Be nucleus and also provides a new picture for the extra pairing nucleons in nuclei.In nuclear physics,the three-body models are also very important for the study of the structure and properties of the nuclei.In this paper,we also investigate the three-body models in neutron rich nuclei and other exotic Coulomb systems with the Quantum Monte Carlo methods.In these three-body calculations,we take into account all the de-grees of freedom such as the movement of the central nucleus and other heavy particles.The calculated results for the Coulomb systems indicate that even with a very simple test wave function,we can still obtain a result close to the experimental value with the Green's Function Monte Carlo method.By calculating the three-body model of some neutron-rich nuclei,we found that the two-neutron binding energy and the root-mean-square radius of the neutron-rich nucleus obtained the Green's Function Monte Carlo Method agree well with the experimental values.Through the above calculations of 9Be,10Be,11Li and other nuclei,we obtain the physical properties and investigate the cluster structure and three-body structure in these nuclei.Especially,the study of the cluster structure of Be isotopes successfully extends the application of the THSR wave function,and provides some new opinions for the cluster model in nuclear physics.