High-Spin Studies Of N～Z Nuclei In The Mass 70 Region

摘要

High-spin states have been studied in ~(72,73)Kr using ~(40)Ca+~(40)Ca and ~(36)Ar+~(40)Ca reactions at 160, 164 and 145 MeV respectively. The properties and configurations of the bands observed are interpreted with the aid of unpaired cranked Nilsson-Strutinsky/cranked relativistic mean-field calculations and paired total routhian surface and cranked relativistic Hartree-Bogoliubov calculations. to ~(73)Kr the three previously known structures have been extended to a spin of ～30h and a fourth structure, which is believed to be the signature partner to the g_(9/2) band, has been identified. The negative parity bands show evidence for an unusual type of band crossing. It is currently unclear whether this is a consequence of T=0 n-p pairing. At the highest spins the unpaired calculations can reproduce the observed data, suggesting that there is little evidence for pairing correlations in this spin regime. In ~(72)Kr a new band has been identified that has the properties expected from the missing doubly aligned S-band configuration. The properties of this band can be reproduced by the unpaired CNS/ CRMF calculations, again suggesting that the structure has little pairing. However, paired calculations appear to be necessary to reproduce the properties of the previously known structure in this nucleus. The ~(72)Kr results are also compared with projected shell model calculations.