Investigation Of The Structures Evolution And Collective Properties Of Even-Even N=76 Isotones And Tungsten Isotopes

The shape evolutions and collective natures along the yrast line of even-even N= 76 isotones with 54≤Z≤68 and tungsten isotopes have been investigated using the Total-Routhian Surface(TRS) calculations in this thesis, which is based on the pairing-shape-cranking self-consistent cranked shell model(CSM). The main content of this article are divided into three parts. Firstly, the relevant concepts and calculated methods of the framework of TRS theory are illustrated briefly. Secondly, to analysis of the shape evolution of the even-even 130Xe-144Er (N=76 isotones) and 160-190W isotopes in three-dimensional space (β2,γ,β4). Thirdly, collective nature along the yrast line in even-even tungsten isotopes are investigated by studying the variation of moments of inertia, rotational alignment, E-Gamma Over Spin curves.There are various shape information in even-even nuclei in the rare earth region. The shape of the nuclei determined by the number of nucleons, especially the high-j orbitals near the Fermi surface. They have the different, strong shape driving effect, such as prolate driving effect and oblate driving effect. Note that there are prolate, oblate and triaxial shape coexistence in the nuclei according to the nuclear potential energies curves versus deformation parameters. It should be pointed out that these nuclei in N=76 isotonic chain exhibit triaxiality or y softness in high-spin states as well as ground states. Such instabilities are also supported by the odd-and even-spin level staggering of the observed y bands, S(I), which is usually used to distinguish between y-rigid and y-soft asymmetry. In addition, the similar properties (y unstable) are also found by investigated systematically in W isotopes.The relevant parameters R4/2= E4+/E2+, P= NpNn/(Np+Nn), Es/E(21+)=(E22+ - E41+)/E2+ are applied to describe the evolution of shape to a good extent. It is found that the neutron rotation-alignment is preferred for most of the W isotopes (e.g. in 164-180W), while in 182W the competition between the neutron and proton alignments may occur. However, the proton alignment is favored in the very neutron-deficient nucleus 160W. Then a brief discussion of the moments of inertia with and without the quadrupole pairing in three typical nuclei is given to test the present model. In addition, the shape evolution and transition between vibrational and rotational collective modes along the yrast line are investigated on the basis of the E-GOS (E-Gamma Over Spin) curves, showing the existing disagreement between theory and experiment may be to some extent attributed to a lack of the vibration mechanism in present model.