Shape coexistence in 94Zr studied via Coulomb excitation

N Marchini ,Andrea Gozzellino,Giovanni Sighinolfi,D T Doherty ,M Siciliano ,J Sinclair ,L Morrison ,J M Keatings ,F Camera ,M Scheck ,G Pasqualato ,Vincent H Brunet,D Testov ,T Faestermann ,Josè Javier Valiente Dobón ,M Ottanelli ,D Mengoni ,F Recchia ,F Galtarossa ,P Spagnoletti ,D R Napoli ,S Bakes ,A Diaz Varela ,V Bildstein ,M Rocchini ,D Brugnara ,T Berry ,N Gelli ,A Nannini ,G Benzoni ,S Riccetto ,W N Catford ,A Bergmaier ,A Goasduff ,K Wrzosek-Lipska ,A Kennington ,P E Garrett ,D Bazzacco ,M Zielińska ,M Vandebrouck ,A Illana ,H Bidaman ,R Hertenberger ,K Hadyńska-Klȩk ,Matteo De Rizzo,A Gottardo ,I Zanon

doi:10.1051/epjconf/201922301038

Abstract

In recent years, a number of both theoretical and experimental investigations have been performed focusing on the zirconium isotopic chain. In particular, state-of-the-art Monte Carlo shell-model calculations predict shape coexistence in these isotopes. In this context, the 94Zr nucleus, which is believed to possess a nearly spherical ground state, is particularly interesting since the purported deformed structure is basedon the low-lying 02+ state, making it amenable for detailed study. In order to provide definitive conclusionson the shapes of the low-lying states, two complementary experiments to study 94Zr by means of low-energy Coulomb excitation were performed. This data will allow the quadrupole moments of the 21,2+ levels to be extracted as well as for the deformation parameters of the 01,2+ states to be determined and, thus, definitive conclusions to be drawn on the role of shape coexistence in this nucleus for the first time. The first experiment was performed at the INFN Legnaro National Laboratory with the GALILEO-SPIDER setup, which, for the first time, was coupled with 6 lanthanum bromide scintillators (LaBr3:Ce) in order to maximize the γ-ray detection effciency. The second experiment was performed at the Maier-Leibnitz Laboratory (MLL) in Munich and used a Q3D magnetic spectrograph to detect the scattered 12C ions following Coulomb excitation of 94Zr targets.

Highlights

The shape of the nucleus is one of its fundamental properties and is governed by the correlations present among the nucleons and evolves with their number
Some of the most dramatic cases of shape evolution in the ground states of nuclei are encountered along the Sr and Zr isotopic chains. 90Zr, with a closed proton sub-shell at Z = 40 and a closed
Coulomb excitation selectively excites low-lying collective states with cross sections that are a direct measure of the electromagnetic matrix elements

Summary

Introduction

The shape of the nucleus is one of its fundamental properties and is governed by the correlations present among the nucleons and evolves with their number. Coulomb excitation selectively excites low-lying collective states with cross sections that are a direct measure of the electromagnetic matrix elements. Clear shapes, and the implication is that the distinct configurations should be present in neighboring nuclei, they may exist at high excitation energy. The even zirconium isotopes have been studied extensively in the framework of the Monte-Carlo Shell Model (MCSM) [2] that reproduces well the trends of the excitation energies and B(E2) values. These calculations predict a spherical ground state and an oblate deformed structure for the 0+2 state for the 94Zr isotope The goal of the present study is to provide a definitive determination of the shapes involved for the 0+1 and 0+2 states, and for this purpose we employed Coulomb excita-

Experimental details

On-going analysis

Conclusion and further perspectives