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- High-spin states of 81Br were populated using the 82Se (𝛼,p4𝑛) reaction. One positive-parity band and four negative-parity bands were observed. Based on the experimental characteristics of these bands, a pair of nearly degenerate three-quasiparticle bands with negative parity are interpreted as chiral doublet bands based on the 𝜋(𝑓5/2,𝑝3/2)−5𝜋𝑔2 9/2 configuration. The third three-quasiparticle band is interpreted as a pseudospin partner band, thereby forming pseudospin-chiral triplet bands in 81Br. The interpretation was supported by the relativistic density functional theory and the multiparticle plus rotor model calculations. The present work suggests a new chiral configuration in the nuclear system and reports the first observation of pseudospin-chiral triplet bands with a pure proton configuration.
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- High spin states in 75 As were investigated by using the 74 Ge (𝛼,𝑝2𝑛) reaction. A total of 27 transitions and 15 levels were newly identified in the level scheme. Based on the experimental characteristics of the observed rotational bands, the positive parity bands 2 and 3 are suggested as a signature partner band and a 𝛾 vibrational band of the yrast band 1, respectively. The nearly degenerate negative parity doublet bands 4 and 5 were interpreted as a pair of pseudospin partner bands based on the relativistic density functional theory and the particle plus rotor model calculations. Additionally, evidence of octupole correlations were observed. The present work reports the coexistence of the soft triaxial and soft octupole deformations in atomic nuclei, which shows a diversity of nuclear shapes and collective excitations in this mass region.
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- The spectroscopy of 76 Se has been studied using the 70 Zn (12 C , 𝛼2n)76Se fusion evaporation reaction. The yrast band of 76 Se has been extended to substantially higher spin, allowing observation of the second band crossing. The much-delayed 𝑔9/2 proton-pair alignment is discussed in terms of the cranked shell model and most likely is caused by a shape transition from prolate to oblate along the yrast line occurring in 76 Se. Based on the systematic investigation of the band crossings associated with the 𝑔9/2 quasiparticle alignments and their relationships with the shape evolutions in the even-𝐴 Se and Kr isotopes, a comprehensive picture of shape evolution along with spin and isospin in these nuclei is obtained.
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- 2019| American Physical So...A pair of nearly degenerate positive-parity bands were observed in 82 Br for the first time using the 82 Se(α,p3n) reaction. The positive-parity doublet bands are proposed to be chiral doublet bands based on the triaxial particle rotor model and the potential energy surface calculations. The root-mean-square values of the angular momentum components and their probability distributions are discussed in detail to exhibit the chiral geometry and its evolution in 82 Br.
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