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γ-ray spectroscopy of neutron rich Ag isotopes: πg9/2n × νh11/2m structure and triaxiality

Abstract : The fission process produces neutron-rich nuclides far from stability with comparable excitation energy and relatively high angular momentum. Therefore it is used as an important tool to study the variety of different nuclear structures . The collective band around neutron-rich Ag isotopes have configuration of two intruder orbitals πg9/2n ×νh11/2m which presents triaxiality . The interpretations of these nuclei towards the mid-shell were usually carried out by the deformed basis collective shell models as- suming deformation in the core and few quasi particles. The view from large-scale shell model with spherical basis could bring new perspective in this region, such as unexpected breaking of natural seniority in In arising from proton neutron interaction. The 113-121Ag isotopes which lie at the borderline of spherical and deformed basis shell model calculations were studied by exploiting the prompt γ-ray spectroscopy of the isotopically identified fission fragments using the VAMOS++ spectrometer and the EXOGAM Ge-array at GANIL [5]. Low-lying high-spin states of neutron-rich 113,118-121Ag have been established for the first time [6]. The excited states of both odd-A and even-A isotopes followed the smooth systematics of those in Cd core. A large signature splitting in odd-A isotopes and a signature inversion in even-A isotopes, which is often used as a finger print of triaxial deformation, through out long chain of isotopes in 50 < N < 82 region, is striking. The large-scale shellmodel calculations reproduce the experimental spectra and the signature splitting, revealing their microscopic nature. The natural seniority ordering was broken more severely than In isotopes [4] inducing strong mixed wave functions. The main features of signature splitting are reproduced by crude shell model including only πg9/2 and νh11/2, indicating the yrast band in the Ag isotopes can be essentially understood based on πg9/2n×νh11/2m multiplet, without any particular assumption about the deformation. This simplicity behind the complex structures in the wave function could be owing to the strong contribution from both proton and neutron intruder orbitals with unique parity, which makes the configuration of the band fairly pure. Perspectives of the recent experiment with VAMOS++ and AGATA γ-ray tracking detectors will be discussed.
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Contributor : Michel Lion Connect in order to contact the contributor
Submitted on : Friday, April 7, 2017 - 4:41:14 PM
Last modification on : Wednesday, August 25, 2021 - 11:16:02 AM


  • HAL Id : in2p3-01503856, version 1



Y.H. Kim, S. Biswas, M. Rejmund, A. Navin, A. Lemasson, et al.. γ-ray spectroscopy of neutron rich Ag isotopes: πg9/2n × νh11/2m structure and triaxiality. 6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei, Mar 2017, Chamrousse, France. ⟨in2p3-01503856⟩



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