The Projected Shell Model And Its Applications In The Research Of High Spin Spectroscopy Of Nuclear Physics

The focus of today’s nuclear physics research is to explore the nature of atomic nuclei under extremeconditions. To the nucleus to some extreme state by various means, to the stability limit, to find newphysical phenomena under extreme conditions and to explain or predict these phenomena where thegeneral rules undergoing will remain so for a long time to be the kernel problems and tasks in nuclearphysics. The researching of high spin states is carried out in the seventies of the last century. In thiscontext, our main purpose is to explore the nature of heavy-mass region and deformation unstable ofmedium mass region nuclei shown by the high-spin state, and explained these phenomena theoretically.First of all we summarized the status of the nuclear structure physics, reviewed the history of this,and introduced several cutting-edge issues of today’s nuclear structure studies. Then we expounded thetheoretical knowledge of nuclear structure, gave a brief introduction to several research in nuclearcollective rotation theoretical models, such as particle-rotor model, interacting boson model and thecranked shell model and the newer projected shell model, as well as their respective advantages andshortcomings. Subsequently, the details of the theoretical framework of the projected shell model wereintroduced, under this framework we made the following three aspects of this thesis.First we use the projected shell model to investigate the odd neutron nucleus253No to compared withthe experimental level scheme, we found that our theoretical discription fulfills the experimental datavery well, unless a little discrepancy with experimental result in the high spin region which indicatingthat the cutoff of the current shell model basis and the choices of Hamiltonian used in PSM for theheavy nucleus may not be complete, nevertheless our calculations correctly reproduce the signature splitting of A=247,249,251,153four No isotopes. With the band diagram, we predict that the signaturesplitting will be delayed with the increasing of neutron number as well as the decreasing of the signaturesplitting amplitude.Second we used the projected shell model to calculate the high spin states of of heavy mass nuclei244Pu,242Pu and240Pu. In order to interprete the backbending phenomenon of heavy nuclei244Pucorrectly, we believe that for the proton N=6major shell, the Nilsson parameters κ and μ needed to beadjust to improve the calculation results. We find out that the crossing of three2-quasi-proton bandsat I=26is the cause of back-bending in the244Pu yrast band.. We apply the same improvement on the242Pu and240Pu to test the validity of our adjustment. Due to the fact that the nilsson single-particle levelis the base on which numerous nuclear structure model established, a systematic research of the thenilsson single-particle energy spectra has become necessary.We studied the signature splitting and inversion characteristics of the yrast band of this nucleus. Bythe PSM theory we explain the reasons for this phenomenon. Results showed that with PSMquasi-particle band diagram the signature reversion mechanism can be well qualitatively described.Because of the intense competition between single particle motion and collective motion in thesetransitional odd-odd nuclei, not only the coupling of the quasi-particles but also the shape changes ofnuclei should be considered. If we adopted prolate shape in the low-spin states but oblate shape in thehigh-spin states, we can well reproduce the signature inversion phenomenon, which suggesting that thetriaxial shape consideration is not negligible in the PSM calculation.