Research Of High-spin States In Neutron-deficient¹²⁹Xe And Neutron-rich^140,141Xe Nuclei

In the study of nuclear structure,it is of particular interests in the A～130 neutron-deficient transitional mass region that shape coexistence may occur,giving abundant in-formation about the interplay between the single-particle motion and the collective motion in nuclei.And in the other hand,in the A=140 neutron-rich nuclei,the occurrence of the ocutupole deformation released that there is reflection asymmetry in nuclei,is very interesting and important for the understanding of the the violation of fundamental sym-metries in nuclear physics.To have a better understanding of the characteristics of the nuclear structure,nuclear force and so on,we studied the high-spin states of the neutron-deficient¹²⁹Xe,neutron-rich¹⁴⁰Xe and¹⁴¹Xe nuclei.High-spin states in the¹²⁹Xe nucleus were populated with a beam energy of 36 MeV through the fusion-evaporation reaction¹²⁴S n（⁹Be,4n）at the HI-13 Tandem Accelerator,which is at China Institute of Atomic En-ergy（CIAE）.A total of 1.7×10⁷γ-γand higher foldγcoincidence events were collected.High-spin states of¹⁴⁰Xe and¹⁴¹Xe nuclei were populated through the spontaneous fission of²⁵²C f,which was carried out at the Lawrence Berkeley National Laboratory（LBNL）.The promptγrays emitted were detected by the Gammasphere detector array and a total of 5.7×10¹¹triple and higher foldγ-γ-γcoincidence events were collected.The level scheme of¹²⁹Xe is updated and extended significantly with 31 levels and 48γtransitions newly identified and six collective band structures are newly es-tablished.The positive and negative parity bands are proposed to originate respectively fromνd_3/23/2⁺[402]andνh_11/211/2^-[505]configurations through the Nilsson diagram calculation.Based on the total Routhian surface and quasiparticle triaxial rotor model calculations,the negative parity band is interpreted as a triaxially deformed shape withγ≈-30^?,while the positive parity band is associated withγsoftness.Signature splitting is observed both in the positive and negative parity bands and a backbending is observed in the negative-parity band,which originates from the alignments of two h_11/2protons ac-cording to crank shell model calculations.In the high-spin states,three decoupled bands and one oblate band withγ≈-60^?are newly identified.In the study of the neutron-rich¹⁴⁰Xe nucleus using a tripleγcoincidence,the pre-viously observed s=+1 octupole band structure is confirmed and expanded.A new set of the positive and negative parity bands with backbending is observed and we assigned it as the s=-1 octupole band structure.We updated and expanded the s=±i octupole band structures of¹⁴¹Xe significatively through analyzing the triple-and four-foldγco-incidence data.Reflection asymmetric shell model（RASM）calculations have been taken for the s=±i octupole bands in¹⁴¹Xe,which is in good agreement with the experimental data.Thus,two sets of the doublet octupole bands both in¹⁴⁰Xe and¹⁴¹Xe are completed.The characteristics of the octupole bands in both nuclei are discussed through the experi-mental B（E1）/B（E2）branching ratios,the energy difference and so forth.