Lifetimes of low-lying excited states in Kr50 3686

J. Henderson, A. Chester, G. C. Ball, R. Caballero-Folch, T. Domingo, T. E. Drake, L. J. Evitts, A. B. Garnsworthy, G. Hackman, S. Hallam, M. Moukaddam, P. Ruotsalainen, J. Smallcombe, J. K. Smith, K. Starosta, C. E. Svensson, J. Williams

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Background: The evolution of nuclear magic numbers at extremes of isospin is a topic at the forefront of contemporary nuclear physics. N=50 is a prime example, with increasing experimental data coming to light on potentially doubly magic Sn100 and Ni78 at the proton-rich and proton-deficient extremes, respectively; however, experimental discrepancies exist in the data for less exotic systems. Purpose: In Kr86 the B(E2;21+→01+) value- A key indicator of shell evolution-has been experimentally determined by two different methodologies, with the results deviating by 3σ. Here, we report on a new high-precision measurement of this value, as well as the first measured lifetimes and hence transition strengths for the 22+ and 3(2)-states in the nucleus. Methods: The Doppler-shift attenuation method was implemented using the TRIUMF-ISAC γ-ray escape-suppressed spectrometer (TIGRESS) γ-ray spectrometer and the TIGRESS integrated plunger device. High-statistics Monte Carlo simulations were utilized to extract lifetimes in accordance with state-of-the-art methodologies. Results: Lifetimes of τ(21+)=336±4(stat.)±20(sys.) fs, τ(22+)=263±9(stat.)±19(sys.) fs, and τ(3(2)-)=73±6(stat.)±32(sys.) fs were extracted. This yields a transition strength for the first-excited state of B(E2;21+→01+)=259±3(stat.)±16(sys.) e2 fm4. Conclusions: The measured lifetime disagrees with the previous Doppler-shift attenuation method measurement by more than 3σ, while agreeing well with a previous value extracted from Coulomb excitation. The newly extracted B(E2;21+→01+) value indicates a more significant reduction in the N=50 isotones approaching Z=40.

Original languageEnglish (US)
Article number044311
JournalPhysical Review C
Volume97
Issue number4
DOIs
StatePublished - Apr 16 2018

Funding

The authors thank the TRIUMF beam delivery group for their efforts in providing high-quality beams. This work has been supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), The Canada Foundation for Innovation, and the British Columbia Knowledge Development Fund. TRIUMF receives federal funding via a contribution agreement through the National Research Council of Canada. The work at LLNL is under Contract No. DE-AC52-07NA27344.

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

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