Decay Spectroscopy Of Nuclei In The Nuclear Region Near ¹⁸⁶Pb

Shape coexistence is a peculiar phenomenon in atomic nuclei,which involves scientific issues such as the evolution of nuclear shell structure and the origin of nuclear collectivity.It is one of the frontiers in current nuclear physics research.¹⁸⁶Pb is a best-known nucleus for the shape coexistence phenomenon.Three 0⁺states of ¹⁸⁶Pb are prolate,oblate and spherical.It's predicted the existence of a shape isomer island in the nuclear region near ¹⁸⁶Pb.There are many new isomers in the nuclear region that remain to be explored.In this paper,the nuclei in the nuclear regions of Z?82 and N?104 are studied by experimental method.The experiment was done at Argonne National Laboratory in the United States.In the experiment,a 255 Me V ⁵⁰Cr heavy ion beam was used to bombard the ¹⁴²Nd isotope target.Heavy ion fusion evaporation reaction ⁵⁰Cr+¹⁴²Nd?¹⁹²Po^*is used.¹⁹²Po is at high excitation energy.¹⁹²Po will evaporate 3 to4 particles(neutrons,protons,?nuclei)to de-excite,then forming nuclides in the nuclear region of Z?82,N?104.This thesis uses the recoil-decay correlation method to analyze the nuclear decay data.During the analysis,recoil-?-prompt?event,recoil-?-delayed?event and recoil-delayed?event,were searched.The nuclei produced in the experiment are identified based on recoil?-?coincidence relationship.Four nuclei were identified in the recoil-?-prompt?events,they are ¹⁸⁴Pt,¹⁸⁴Os,¹⁸⁸Hg,and ¹⁸⁶Hg.In the recoil-?-delayed?events,two nuclei,¹⁸⁴Au and ¹⁸³W,were found by half-life fitting.In the case of the recoil as the isomer,two known isomers were found,^188mPb with J^?=8^-and ^187mTl with J^?=(25/2^-,27/2⁺,29/2⁺).A new isomer of ¹⁸⁵Au was discovered with a lifetime of 732(23)ns,it may be shape isomer or K isomer.At the same time,a new 295 ke V?-ray was observed.Based on the intensity balance and reduced transition probability,its transition mode may be E1,E2 or M1.The spin parity of this isomer cannot be determined,yet.Through the analysis of the experimental data,the nuclei produced by nuclear reactions were found.Their decay information was obtained.The experimental data results are mutually verified with the existing nuclear decay data.This not only tests the existing nuclear data,but also proves the reliability of the experimental data.A new isomer of ¹⁸⁵Au was found,which filled a gap in the study of isomers related to ¹⁸⁵Au.The study and discussion of the isomer also help to understand the physics related to the isomeric state in this nuclear region.