Speaker
Description
The rapid spherical to prolate shape transition at N = 60 in the mid-shell region around Z = 40 has been evidenced from diverse experiments [1-5], and the shape evolution for more neutron-rich nuclei has been of interest because of the emergence of the triaxial degree of freedom. Theoretical predictions suggested further phase transitions such as a shape transition to oblate spheroid [6-8], a transition to triaxial ground shapes [6, 9] and doubly magic behavior at N = 70 [10]. Experimental information for the low-lying states of even-odd nuclei can be the key since they exhibit the properties of orbitals of the un-paired nucleon near the Fermi surface and the orbital configuration is sensitive to the nuclear shape.
The shape and shell evolution for molybdenum nuclei (Mo, Z = 42) with N ≥ 60 have been studied in various experiments [11-16] but the detailed shell structure near the Fermi surface is still unresolved. The excited states of 109Mo were studied through the spontaneous fissions of 248Cm and 252Cf [11, 12], but the recent discovery of an isomeric transition in 109Mo has revealed that previous studies on 109Mo were limited to the excited states above the ground state [16, 17].
In the present study, the low-lying states in 109Mo are investigated from the γ-rays detected following the β decay of 109Nb. The data was collected as part of the EURICA project in RIKEN [18]. Two new isomeric γ-rays are identified together with the known isomeric γ-ray [16, 17]. Their transition multipolarities have been scrutinized considering internal conversion coefficients and recommended upper limits [19]. New excited states including a new first excited state below the isomeric state are assigned. The results of mean-field calculations [20] and intrinsic gyromagnetic moment calculations [21] are considered to assign associated neutron orbitals for the low-lying states. The analysis results for the most likely quasi-particle configurations of the low-lying states including ground band and isomeric band will be presented.
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| Are you a student or postdoc? | yes |
