New isomers in 125Pd79 and 127Pd81: Competing proton and neutron excitations in neutron-rich palladium nuclides towards the N = 82 shell closure

H Watanabe,S Nishimura,G.D Kim,G Lorusso,A Odahara,K Yoshinaga,G Gey,D Nishimura,A Yagi,J Taprogge,P.-A Söderström,Zs Vajta,J Wu,Y.K Kim,H Baba,T Sumikama,Z Li,K Moschner,Z Patel,N Kurz,I Kojouharov,P Doornenbal,R Gernhäuser,N Fukuda,D Kameda,Zs Podolyák,T Kubo,A Jungclaus,F Naqvi,T Isobe,N Inabe,A Montaner-Pizá,R Orlandi,A Wendt,Y Sun,H Schaffner,F Browne,G Benzoni,Han-Kui Wang ,F G Kondev ,G J Lane ,Hiroshi Suzuki ,Z Y Xu ,H Nıshıbata ,Hiroyuki Takeda ,Y K Kwon ,M Nııkura ,G S Simpson ,Chang-Bum Moon ,F C L Crespi ,H S Jung ,Katja Steiger ,H Sakuraï ,K Y Chae

doi:10.1016/j.physletb.2019.03.053

Abstract

The neutron-rich isotopes of palladium have attracted considerable interest in terms of the evolution of the N=82 neutron shell closure and its influence on the r-process nucleosynthesis. In this Letter, we present the first spectroscopic information on the excited states in 125Pd79 and 127Pd81 studied using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity 238U beam at the RIBF facility. New isomeric states with half-lives of 144(4) ns and 39(6) μs have been assigned spins and parities of (23/2+) and (19/2+) in 125Pd and 127Pd, respectively. The observed level properties are compared to a shell-model calculation, suggesting the competition between proton excitations and neutron excitations in the proton-hole and neutron-hole systems in the vicinity of the doubly magic nucleus 132Sn.

Highlights

41(8) μs 36(9) μs a Relative to the respective (11/2−) states. b Relative to the 757, and 422-keV γ -ray intensities for 125Pd and 127Pd, respectively
The 11/2− state is likely to feed J = 9/2, 11/2, and 13/2 levels in the daughter nucleus, while comparatively low-spin states can be populated in the β decay from the 3/2+ state
As an example of the 125Pd → 125Ag decay, a β-delayed γ -ray spectrum measured within 200 ms after implantation of the 125Pd ions is shown in or 11/2−) the aforementioned 144-ns isomer is built in 125Pd, the correlation between the β-delayed γ rays and the preceding isomeric-decay transitions has been confirmed

Summary

Introduction

41(8) μs 36(9) μs a Relative to the respective (11/2−) states. b Relative to the 757-, and 422-keV γ -ray intensities for 125Pd and 127Pd, respectively.

Results

Conclusion