High-spin States In Odd-odd Nucleus⁹²Nb

This paper describes the establishment of odd-odd nucleus92Nb level scheme andthe study of high spin states. Scmi-Empcrical Shell Model (SESM) and shell modelcalculations (NUSHELLX) have been per formed to interpret the experimental levelscheme of92Nb. A series of methods such as capacitance method, the method to preparevery flat target foil and so on were mastered in the process of building the Plunger.The research on the high-spin states in the nuclei was regarded as one of thefrontiers of fields in nuclear physics, which can provide us with valuable informationabout nuclear shape,nuclear structure,nucleon coupling and so on.In recent years, a variety of nuclear structure phenomena in the A～90massregion have attracted great interest. The study of odd-odd nuclei is most important fordetermining the effective proton-neutron residual interaction between quasi-proton andquasi-neutron, have attracted more and more attention. The level structures of odd–oddnuclei more complicated than even–even and odd A nuclei. It is more difficult toinvestigate the high-spin states of odd–odd nuclei due to their complicated levelstructure are uncertain.In the vicinity of Z=38subshell closure and N=50shell closure，many studiesshowed that the nucleus in this mass region, there are some very interestingphenomena, such as some isotope excited state, the isotope can be maintained for along time before de-excitation to the ground state, the vast majority of the nucleusshow the spherical or near spherical structure and irregular transition energy. Theexcited states are intrinsic single-particle excitations within the fp subspace(2f5/2,2p3/2,2p1/2) proton excitation generated. As the excitation energy increases, N=50neutron closed shell is broken, forming neutrons [(g9/2)-1]/d5/2/g7/2particles-holeconfiguration, called the core excitation. In previous studies previous, the majority oflevel energy are good agree with shell model calculations. In the description of shell model, For the low spin states, the valence protons excitations mainly described theangular momentum of growth and the high spin states attributed to theneutron-particle-hole excitation of the N=50inert core-specifically,the excitation of asingle g9/2neutron across the N=50shell closure into the d5/2/g7/2orbits coupled to thevalence proton states in the Ï€(f5/2, p3/2, p1/2, g9/2) valence space. As the excitationenergy increases, the high spin states might be concern the proton excitation across theZ=38shell gap Ï€(f5/2, p3/2)â†'g9/2and the neutron the neutron excitation within (d5/2,h11/2) shell model orbitals.According to systematic analysis and comparison with neighboring isotonesnuclei, their energy level structures were very similarly. And with the number ofprotons increasing,the corresponding energy of levels decreased,this may due to theincrease in the number of protons, it makes that the excitation energy of protonsdecreased.Systematic comparison in the isotones of N=51region, will help us betterunderstand that the valence nucleon filling mechanisms effect on the energy levelstructure of the nucleus.Due to the similarity of high spin level configuration adjacent valence nucleonfilled orbits,it may be exactly similar to the corresponding the same spin energy levelstructure. According to known nucleus level configuration,we can extract thecorresponding interactions of the valence nucleon orbits,and calculate the other nucleicorresponding configuration energy level, it is important to determine the energy levelof configurations.In present work, excited levels in92Nb were populated using a82Se(14N;4n)92Nbreaction at a beam energy of54MeV. The14N beam was provided by the HI-13tandem accelerator in the China Institute of Atomic Energy(CIAE). The targetconsisted of a0.99mg/cm2foil of82Se(isotopically enriched to96%)evaporated onto a8.27mg/cm2natural Yb backing. The de-excitation rays from the reaction residueswere detected with an array consisting of9Compton-suppressed HPGe detectors and2 planar HPGe detectors. A total of about150×106coincidence events were accumulated.Measurement results of standards in-beam spectroscopy experiments were sortedoffine into a two-dimensional symmetrized E-E coincidence matrix and twoasymmetrized ADO matrices. A total of36new transitions have been identified andplaced in this scheme. positive and negative parity level which have been substantiallyextended up to21+(Ex=9784.9keV) and21-(10738keV).As a conclusion，the level scheme of92Nb has been substantially extended on theprevious level scheme, The Shell Model calculations have been performed performedin the model spaceÏ€(0f5/2,1p3/2,1p1/2,0g9/2) ν(1p1/2,0g9/2,1d5/2,0g7/2) and the results werein line with the experimental results. The systemical analyzes for the isotones of N=51showed that there were some rules for the high spins level structure of nuclei in thisregion.The Recoil Distance Doppler Shift (RDDS) method has been well developed. Aseries of methods such as installation of target and the stopper foil and the delicatemeasurement of the distance between the target and the stopper foil and the steps of inbeam experiment were mastered in the process of building the Plunger. And theapparatus will have a good application for ground. The lifetimes of the excited nuclearstates can be measured and more information of the nuclear structure can be gotten byPlunger.