Investigation Of High-K State In Heavy Nuclei By Using A Particle Number Conserving Method

In recent years,due to the extensive application of radioactive detecting devices in nuclear experiments,we have started to extending the region where detailed spectroscopic data are known towards heavier system.For decades,defining the limits of the stability of the nucleus has been of great interest,while different theoretical approaches yield different regions which depend crucially on the details of the underlying nuclear structure.Of special note in spectroscopy studies are multi-quasiparticle(multi-qp)high-K isomers which can provide a probe into the single-particle structure around the Fermi surface.Such information is vital for determining the nuclear potential that can be used to predict properties of superheavy nuclei.And the ensuing attempts at interpretation,configuration assignments and quantitative analyses of the lifetime stimulated the development of nuclear models.The high-K isomer states in the heavy mass region are investigated systematically by using the cranked shell model(CSM)with the pairing correlations treated by the Particle-number-conserving(PNC)method.Beside we also calculated the rotational band on the top of ground state and high-K states,including even-even nuclei ^238,240U,^240-244Pu,^242-246Cm,^244-248Cf,and ^246-250Fm.The calculated results can reproduce the experimental excited states energy and momnets of inertia well.Then we predicted some other multi-quasiparticle states according to the single particle structure in the mass region.We found that there is a backbending or upbending in the high spins which observed in the U and Pu isotopes.The behavior of backbending is possible due to the high-j intruder orbitals.By analyzing the cranking frequency dependence of the occupation probability of each cranked Nilsson orbital near the Fermi surface and the contributions from high-j orbitals in each major shell,the backbending mechanism is explained clearly.There is a backbending in the ground state band of ²³⁸U and ²⁴⁴Pu,which is attributed to the proton orbital?i_13/2.The backbending disappears with the increasing Z and the moment of inertia increase gradually.There is enough study about ²⁵⁴No,including the experiment and theory.We get some new information about this nucleus recently,thus we investigate its isomer states fully by using the particle number conserving method.According to the calculated excited states energy and moment of inertia,we can assign the states configuration.The high order deformation(?₆)will influence the deformed shell and result in the energy difference.We focus that the pairing reduction have an effect on the moment in the low spins due to the Pauli blocking effect..The experiments about Dy isotopes in neutron-rich nuclei have been carried out in the RIKEN.Two isomers are reported,and they are k^?=6⁺ in ¹⁷⁰Dy and k^?=8^- in ¹⁷²Dy.The configuration are assigned according to the similarities with their isotones.In our calculations,we get the same results about the observed isomers and predicte the other multi-quasiparticle states below 2.5Me V.Based on the PNC-CSM calculations,we get the cranked Nilsson levels at the nertron number N=104 which is focused.We get the pairing strength effect on the isomeric state energy.The ground state rotational band is also reproduced well at low spins and is predicted the behavior at high spins.