High Spin States In ⁸⁰Rb

In 1896,Bequerel found the radioactivity of nature. People are used to take this as the beginning of nuclear physics. During this century, many scientists have reported several nuclear models and some theories. Of all these nuclear models, nuclear shell model is one of the most successful. It explains that nucleus has shell structure. This induced the establishment of mean field theory. With the development of the theory and the advance of experiment technique, people become to understand the inside nuclear structure more and more clearness, especially for the phenomenon of high spin states. In the recent years, people pay more and more attention to the area of A~80 area.High spin states of 80Rb have been studied using fusion evaporation reactions, 65Cu+19F, 66Zn+18O and 68Zn+16O with beam energies of 75MeV, 76MeV and 80MeV, respectively, at HI-13 Tandem accelerator Beijing and JAERI Japan. These targets 65Cu,66Zn and 68Zn are all self-supported targets, the thickness of them are 560, 620 and 570μg/cm2.We used 9 HPGe-BGO Compton-suppressed spectrometers in CIAE, and 12 in JAERI Japan. We had accumulated 200 × 106 events in CIAE and 300× 105 γ-γ coincidence events in JAERI. The γ - γ coincidence and DCO ratios were measured by the HPGe -BGO detector systems. After the experiment, we have sorted 9 matrixes, they are γ -γcoincidence, DCO ratio,30° ,60° and 90° angles distribution and other matrixes.Compared with the published data of 80Rb, about twenty new y transitions were added to the previously proposed level schem from the present experiments, we also present the intensities of many transitions. Three rotation bands were confirmed and the spins and parities of most levels were assigned from our DCO ratios. They consistent withpublished data of 80Rb. Both positive and negative parity bands were extended from spin 16+ to 20+ and 18- to 22- as well 23- to 25- respectively. The second negative parity band was pushed up from 12-h to 22-h. A band crossing at frequency of 0.50MeV is observed.Evidence has also been found for two hitherto unknown sidebands built on the negative yrast band. Signature splitting in both negative bands and positive bands were observed. Signature inversion occurs at 11+h in the positive bands and 15-h in the yrast negative bands and it is close to that of 78Br. The plots of [E(I)-E(I-1)]/2I vs I were given and compared with its isotones 78Br and 82Y as well as its isotopes 76Rb and 78Rb. From the comparison, we found that with the increase of neutron number, signature splittingduced. The signature splitting phase of both negative bands 80Rb are similar to its isotones. But not to that of their isotopes. In addition, during the data analysis, We also find a new band in 77Kr, compared with the band in 79Kr, it maybe belongs to A I=1 magnetic rotation band.