Study Of High Spin States In ¹²⁹Cs

Nuclei in the A=120～130 light rare earth mass region attracted great interest in the research on the high spin states. In this nuclear region , the valence neutrons lying on the high K h11/2 nillsson orbit, drive the nuclear toγ=00 prolate deformation ; and the valence protons lying on the low K h11/2 orbit, drive the nuclear toγ=-600 oblate deformation. Hence the competition between the two different shape driving forces lead the shape coexistence effect, which is common in the low lying states in this nucleus region.. In a word, single-particle movement and collective movement compete strongly at the high lying states, and so many nuclear structure proterties are accumulated in this A=120～130 nuclear region, it is important to pay attention to the study on this region.The first part is introduction. Such as a brief review of the development of nuclear physics history and several commonly used methods method about how to layout nucleus high spin states, such as heavy particle fusion evaporation reaction, heavy particle multiple coulomb excitation, heavy particle induced fission promptγ-spectroscopy etc., and they gave an explanation of the advantages and disadvantages of the method. Because of the experimental conditions, Early research work in the high-spin state have used the radioactive decay process, as well as heavy nucleus neutron capture process methods programe the nucleus high spin states, The results has provided a powerful experimental evidence for the early collective rotational spectrum of nucleus. The advantages of these methods is that a clean objective and very good selectivity has provided, however, its shortcomings is that it cannot programe a higher spin states. It also provide a method called systematic method that often used on analyzing the structure of nucleus. Although strictly speaking, the system is only a study of experience, and not strictly theoretical foundation cannot be completely ruled out a singular nuclear incident (such as the shell effect or association), which also must be approved by the inference and experimental test, but Phylogenetic analysis method as the reasonableness of the method and effectiveness has been fully affirmed and confirmed.The second part is a detailed in-beam gamma spectroscopy. The high-spin states of ¹²⁹Cs were populated through the reaction ¹²²Sn(¹¹B,4n)¹²⁹Cs ,at two beam energy,Elab1=55MeV, Elab2=60MeV,provided by the HI-13 tandem accelerator of CIAE in Beijing. The target was consisted of self-supporting one stacked foil of 122Sn, thickness 5mg/cm2. Theγ-rays emitted from the residuals were detected in promptγ-γcoincidence measurement with a combined detector array. Eleven BGO Compton suppressed HPGe detectors weir used in this experiment. The detectors were placed at angles of 90°to the beam direction. A total of about 1.5×10⁸ coincidence events were accumulated. The experimendal data will be recorded and used as chronological record to the computer. Whenever KODAQ acquisition system received an interrupt signal (TRIG, from multiple logical units) Description detection array detection to a line with the incident, the computer records began, according to TDC in which the order read out to-ray detector, How many time it partitions, and then read out from the ADC-ray energy. TDC is one-to-one with the ADC. The detectors were read after all, the end of an event,wait under an interrupt signal to begin recording a new incident.All of this will be recorded to the accumulation of these events together to form a document stored in the computer in the buffer zone. In order to prevent the emergence of a sudden brownout or detector, electronics accidents such as changes in working conditions, generally a document in the records of the buffer zone stored on the hard drive every tow hours.The third part is about the offline data processing. We inverse the data acquired from the data acquision system, it can be used for the analysis of the symmetry of the Eγ-Eγmatrix and DCO for the analysis of the non-symmetric Eγ-Eγmatrix. Symmetric matrix to the X or Y axis on a projection of the total projection spectrum, By fenestration and analysis we are concerned with the relationship between the-ray spectroscopy. Befor the analysis, We need for the energy calibration and efficiency calibration of various detector and the detection arrays. Energy calibration is acquired by through the selection of the energy generated in the known characteristic peak. The efficiency calibration are standarded by the standard peak of 152Eu. Then we could get the relatively array detection efficiency calibration curve, as a future-ray intensity of the amendment.γ-ray intensity through the peak for the area and the corresponding detection efficiency to determine the peak area for the three main methods. Through a single spectrum for the other a total projection of the spectrum, spectrum-as accurate, but it is simple. The third window for the spectrum, fenestration larger spectral method of error, usually powerless when the former two methods used. In this work, we have adopted a spectral method is fenestration. With the experimental data fitting procedure fitting the peak area of peak area, it is necessary to pay special attention to the background of continuity. After deducting the end, it is necessary to a wide selection of the correct identification to prevent because a lot of energy near-ray single-spectrum brought in the very high, leading to the peak area fitting grave error. Then try to fit the scope of the election wider, as far as possible, includes all the nearby peaks at the peak at the same time fitting, in order to reduce the introduction of errors.The forth part is divided into experimental results and analysis. Based on the work of L.Hildingsson, we extended the level structure of ¹²⁹Cs. A more completely band structure were established. Most of the relative intensity of theγ-rays of ¹²⁹Cs were measured. The linking transitions between band 1 and the g_9/2 band are built fot the first time, which help the assignment of the configuration of band 1. The mixing (Ï€g_7/2/Ï€d_5/2)(?) (Ï…h_11/2)² configuration was assigned to the band 1, the existence of signature splitting indicates the triaxial deformation. In our work the study of band 5 has been observed the second upbend probably for the first time in the (α=-1/2)Ï€h_1/2 rotational band. A coupled band ofÏ€h_1/2 andγ-vibration configuration was assigned to band 7.