Research on High Spin Structures of N=79 Isotones in A=135 Nuclear Region
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Graphical Abstract
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Abstract
The progress of research on the high spin states at N=79 isotopes 135Ba， 137Ce and 139Nd in A=135 neutrondeficient region by the research group of Tsinghua University has been reviewed. The experiments were carried out by using inbeam γray spectroscopy technology and heavy ion nuclear reactions 130Te(9Be， 4n)， 124Sn(18O， 5n) and 128Te(16O， 5n) at China Institute of Atomic Energy (CIAE). The high spin level schemes of these nuclei have been expanded. The results indicate that the lower spin states of these nuclei originated from νh-111/2 hole state coupling with the neighboring eveneven nucleus cores. All the deformation parameters γ values of these three isotones are larger than 30°， which indicates that they have triaxial deformation with oblate side. The prolateoblate transition in Ba， Ce and Nd isotopic chains indeed happens between N=77 and N=79. Through systematical comparison with the neighboring isotones， the configurations for some middle spin state levels have been assigned. At the high spin states， one oblate band in 137Ce and three ones in 139Nd with γ≈ -60° were discovered. The origination and structural character of these oblate bands have been discussed.
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