Fast-timing measurements in neutron-rich odd-mass zirconium isotopes using LaBr3:Ce detectors coupled with Gammasphere

E R Gamba ,V Vedia,I Burrows,Zs Podolyák,S Lalkovski,J Sethi,T Lauritsen,S Zhu,S Bottoni,J Rohrer,O Yordanov,D Seweryniak,T Daniel,S Ilieva,G Fernández Martínez,P Copp,I Lazarus,Thilo Kroll ,M Rüdigier ,John Simpson ,R S Ilieva ,Laila Gurgi ,G Lotay,D M Cullen ,P H Regan ,M Smoleń ,G J Lane ,V Pucknell,A M Bruce ,J P Greene ,F G Kondev ,M Carmona-Gallardo ,M P Carpenter ,D J Hartley ,M W Reed ,J Anderson ,T Berry ,R V F Janssens ,C Shand ,E A Stefanova ,R Carroll ,A D Ayangeakaa

doi:10.1051/epjconf/201819305004

Abstract

A fast-timing experiment was performed at the Argonne National Laboratory to measure the lifetimes of the lowest lying states of nuclei belonging to the deformed regions around mass number A≃110 and A≃150. These regions were populated via spontaneous fission of 252Cf and the gamma radiation following the decay of excited states in the fission fragments was measured using 51 Gammasphere detectors coupled with 25 LaBr3:Ce detectors. A brief description of the acquisition system and some preliminary results from the fast-timing analysis of the fission fragment 100Zr are presented. The lifetime value of τ = 840(65) ps was found for the 2+ state in 100Zr consistent within one standard deviation of the adopted value with 791 +26 -35ps. This is associated with a quadrupole deformation parameter of 0.36(2) which is within one standard deviation of the literature value of 0.3556+82 -57.

Highlights

The aim of the experiment was to measure the evolution of the quadrupole deformation in nuclei around mass numbers A 110 and A 150
A lifetime value τ = 840(65) ps was obtained for the 2+ state by fitting the time spectrum with an exponential decay function in the region far from the prompt peak, as shown in Fig 4 b). This contribution presents the first lifetime measurement obtained from this data set after two gates on the Gammasphere energy information have been applied. It shows a step forward in the analysis with respect to the results presented in [12], where only one gate on the Gammasphere data was employed and a lifetime of τ = 827(108) ps was obtained using the decay slope fitting method
For the first time the capability of this setup to produce a valid time distribution after a double gate on the energy information from Gammasphere has been shown, and the results are in good agreement with the values given in the literature

Summary

Introduction

The aim of the experiment was to measure the evolution of the quadrupole deformation in nuclei around mass numbers A 110 and A 150. The gamma-ray energy spectra obtained by applying each one of these pairs of gates to the data, have been added together and the sum spectrum is shown in Fig. 2 a).

Results

Conclusion